appendix h innova hazop notes for dftd plant · chazop, 16 april 2004 ... this document was...
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31/24335/171244 Centre for Site Remediation Works Approval Application Supporting Documentation
Appendix H
Innova HAZOP Notes for DFTD Plant
HAZOP, 16 March 2004
CHAZOP, 16 April 2004
HAZOP, 26 July 2005
HAZOP, 2008 (to be provided upon request)
INNOVA SOIL TECHNOLOGY DIRECT HEATED FAST QUENCHED THERMAL DESORPTION FACILITY - HAZOP 16 March 2004 Prepared for: Innova Soil Technology Cnr Gavey and Frith Streets Mayfield NSW 2304 Report by: HLA-Envirosciences Pty Limited ABN: 34 060 204 702 Level 2, 55-65 Grandview Street PO Box 726 Pymble NSW 2073 Australia Ph: +61 2 9988 4422 Fax: +61 2 9988 4441 HLA Ref: S60034_RPTFinal_Rev0_16Mar04
Innova Soil Technology Direct Heated Fast Quenched Thermal Desorption Facility
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DISTRIBUTION Innova Soil Technology Direct Heated Fast Quenched Thermal Desorption Facility HAZOP 16 March 2004 Copies Recipient Copies Recipient 1 (Draft) Nick Ebrill
Innova Soil Technology Cnr Gavey and Frith Streets Mayfield NSW 2304
This document was prepared for the sole use of Innova Soil Technology and the regulatory agencies that are directly involved in this project, the only intended beneficiaries of our work. No other party should rely on the information contained herein without the prior written consent of HLA-Envirosciences Pty Limited and Innova Soil Technology. By HLA-Envirosciences Pty Limited ABN: 34 060 204 702 Level 2, 55-65 Grandview Street PO Box 726 Pymble NSW 2073 Australia ____________________________________ Steve Sylvester Principal – Risk Management Peer Review: Date:
Rui Henriques Principal – Remediation
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CONTENTS
1 INTRODUCTION............................................................................................1
1.1 Background .....................................................................................................1
1.2 Objectives........................................................................................................1
1.3 Scope ..............................................................................................................1
2 SUMMARY AND RECOMMENDED ACTIONS................2
2.1 Summary...................................................................................................2
2.1.1 Brief Description of the Process.......................................................2
2.2 Brief Description of the Methodology.......................................2
2.3 Recommended HAZOP Actions .................................................3
3 BRIEF DESCRIPTION OF THE DFTD FACILITY............................................................................................................10
3.1 Background............................................................................................10
3.2 DFTD Process Components .......................................................10
3.3 Brief Description of Operations..................................................11
3.3.1 Soil Pre-Treatment and Feed.........................................................11
3.3.2 Rotary Drying and Product Management ......................................11
3.3.3 Gas Treatment ...............................................................................11
3.3.4 Ancillary Systems...........................................................................11
4 METHODOLOGY........................................................................................14
4.1 Selected Study Approach .............................................................14
4.2 Hazard and Operability Study (HAZOP) ..............................14
4.3 Workshop Participants, Location and Timing................................................16
4.3.1 HAZOP Study.................................................................................16
5 RESULTS...........................................................................................................17
5.1 Background............................................................................................17
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APPENDICES A HAZOP Minutes B Drawings Used in the HAZOP
List of Tables 2.1 DFTD HAZOP Recommendations 4.1 Guidewords Used in the HAZOP 4.2 Structure of the HAZOP Minutes Recording Table
List of Figures 3.1 Innova DFTD Plant 3.2 DFTD Plant General Arrangement
ABBREVIATIONS
Abbreviation Description
AS Australian Standard
CEMS Continuous Emissions Monitoring System
CO2 Carbon Dioxide
DFTD Direct-heated Fast quenched Thermal Desorption
FD Forced Draft
H2O Water
HAZOP Hazard and Operability Study
HIPAP Hazardous Industry Planning Advisory Paper
ID Inducted Draft
LPG Liquefied Petroleum Gas
Ms milli-seconds
MSDS Material Safety Data Sheets
N2 Nitrogen
OCP Organo-Chloro Pesticides
OH&S Occupational Health and Safety
P&ID Piping and Instrumentation Diagram
PAH Polycyclic Aromatic Hydrocarbons
PLC Programmable Logic Controller
PPE Personal Protective Equipment
SCADA Supervisory Control and Data Acquisition System
SOP Standard Operating Procedure
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1 INTRODUCTION 1.1 Background Innova Soil Technology (Innova) has designed a Direct-heated Fast quenched Thermal Desorption (DFTD) unit which is capable of treating up to 250,000 tonnes per annum of soils impacted with all hydrocarbon contaminants, including petroleum hydrocarbons, polycyclic aromatic hydrocarbons (PAH), organo-chloro pesticides (OCP), dioxins and furans. As part of the design review, the regulatory authorities require the process to undergo a Hazard and Operability Study (HAZOP), conducted by an independent facilitator. Innova has commissioned HLA-Envirosciences (HLA) to facilitate a HAZOP of the DFTD facility.
This proposal details the HAZOP objectives, scope of work, a brief description of the facility, the study methodology and results.
1.2 Objectives The objectives of the study were to:
• facilitate a HAZOP study of the DFTD facility, in accordance with HIPAP No.8, HAZOP Study Guidelines;
• identify hazard and operability issues associated with the plant operations; and
• report on the findings of the study, including HAZOP minutes and actions.
1.3 Scope The scope of work for the HAZOP study of the Innova DFTD Process and Operation will cover the following system components: • Material Feed System;
• Direct Heating and Rotary Desorption Unit;
• Clean Product Discharge Hopper;
• Soil Cooler;
• Conversion Chamber;
• Compressed Air Saltation System and Sluices;
• Energy Recovery Exchangers;
• Dry Gas Quencher;
• Venturi Wet Scrubber with Wetted Fan;
• PLC and Citect Computer System; and
• CEMS.
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2 SUMMARY AND RECOMMENDED ACTIONS 2.1 Summary 2.1.1 Brief Description of the Process The Innova DFTD plant consists of a series of integrated components designed to achieve successful contaminant separation and subsequent conversion, energy recovery, fines reconstitution and product cooling. The DFTD system consists of the following main components: • Material Feed System – providing a regulated flow of contaminated soil to the process;
• Direct Heated Rotary Desorption Unit – gently heating the soil and separating the contaminants from the solid matrix into the gas phase (Note: this is not incineration as the soil character is retained and not destroyed – soil is re-used on site);
• Clean Product Discharge Hopper – controlled removal of clean soil from the rotary desorber unit;
• Soil Cooler – using sluice and scrubber product water for both cooling and dust reconstitution;
• Conversion Chamber – gas phase contaminants are converted to carbon dioxide and water by passing the gas through the converter over a 3-4 second period at above 950oC (up to 1200oC) ,
• Compressed Air Saltation System and Sluices – promotes and collects fine particles within the conversion chamber prior to the heat exchanger bank;
• Energy Recovery Exchangers – pre-heats the incoming air to the combustion chambers;
• Dry Gas Quencher – eliminated contaminant reformation potential;
• Venturi Wet Scrubber with Wetted Fan – cleans the off-gas of particulates and any acid gases;
• PLC and Citect Computer System – process control and continuous monitoring of operations; and
• CEMS – continuous monitoring of gaseous stack emissions, internet capable results display.
2.2 Brief Description of the Methodology The methodology used for the HAZOP is summarised below:
• A team of experienced personnel were assembled to assist with the HAZOP assessment of the facility;
• A brief description of the proposed system operation was given and questions asked of the designers by study participants;
• The study facilitator selected a system line or section and led the team through a series of guidewords to assist in the systematic assessment of the facility;
• Hazard and operability issues, and action requirements, were recorded as study minutes, along with the organisation responsible for completing the required actions;
• HAZOP minute numbers were recorded on the P&ID in a diamond ( ◊ ) against the equipment or location for which the minute was recorded;
• Draft study minutes were issued to the team for comment and corrections made based on the team’s response;
• A draft report was developed and issued to the team for comment; and
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• A final report was completed incorporating the team’s comments.
2.3 Recommended HAZOP Actions During the study, where a potential hazard or operability issue was identified, a HAZOP worksheet was recorded as a minute of the workshop study. These are presented in Appendix A. The study recommendations are summarised in Table 2.1.
TABLE 2.1 DFTD FACILITY - HAZOP RECOMMENDATIONS
HAZOP No.
Action Description and Recommendation
Front End Loader and Load Station
1 It was identified that there is a potential for spill over the sides of the bin and product to be blown into dust by wind. It was recommended that consideration be given to the installation of “hungry” boards on the hopper
Action: Scott Goldrick
1 The potential to overfill the bin was also identified as a spill problem. It was recommended that consideration be given to the installation of weight indication adjacent to the feed hopper so that the front end loader driver can see the weight in the bin
Action: Scott Goldrick
7 It was identified that once established on site, rain and other incidents (spills) may lead to escape of materials offsite. It was recommended that a procedure be developed for the establishment of sites to include site-specific issues such as spill retention (bunds), dust control, noise control, etc.
Action: Nick Ebrill
Feed Screw and Conveyor
12 It was identified that material density may change during the process operation. This may lead to erratic feed rate to the plant and upset conditions. It was recommended that consideration be given to the development of a standard operating procedure (SOP) for the management of material feed to the plant.
Action: Nick Ebrill
18 The study identified that if power is cut (e.g. operation of safety lanyard) to the conveyor, the screw feeder continues to feed soil to the conveyor. This results in spillage at the tail end of the conveyor and the potential for personnel to come into contact with contaminated soil during clean up. It was recommended that consideration be given to the installation of alarms on the conveyor lanyards, which will provide notification of activation of a lanyard (safety issues).
Action: Scott Goldrick
23 It was identified that personnel sampling the soil at the conveyor tail end have the potential to come into contact with the contaminated soil. It was recommended that consideration be given to the development of a sampling procedure for the soil. This sampling procedure should be expanded to cover all sampling throughout the plant.
Action: Nick Ebrill
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TABLE 2.1 DFTD FACILITY - HAZOP RECOMMENDATIONS
HAZOP No.
Action Description and Recommendation
Feed Screw and Rotary Dryer
26 It was identified that in the event of a slow dryer speed and a corresponding high feed rate, there is a potential for soil to build up in the dryer and spill from the feed end of the drum. It was recommended that consideration be given to the installation of dryer drum seals. Consideration should also be given to the monitoring of dryer speeds and feed rates and the development of an optimum window which if exceeded results in alarm. This could be set up in the Citect system.
Action: Nick Ebrill and Scott Goldrick
28a In the event of ID fan failure it was identified that positive pressure may occur in the dryer, resulting in gas escape from the various gaps around the dryer rim. The following action considerations were recommended:
• Check that interlocks operate between the ID Fan (e.g. feed stops when ID fan fails) – Action: Mark Own
• Developing a procedure for ID Fan failure – Action: Nick Ebrill
• Developing a procedure for maintenance and management of the ID fan including:
- Temperature - Balance - Maintenance Action: Scott Goldrick - Vibration - Spares
31 It was identified that in the event of fuel pump failure the plant would shut down, resulting in potentially lengthy downtime. It was recommended that consideration be given to installation of an on-line parallel fuel pump.
Action: Scott Goldrick
32 In the event the FD Fan supplying air to the burners fails, the flame will shut down and incomplete combustion will result. This may lead to carry over of contaminants into the stack discharge. It was recommended that a stack flare be considered in the event critical system failures occur (particularly in sensitive locations)
Action: John Lucas
36 In the event the kiln drive fails, there is a potential for heat to build up unevenly in the kiln casing. This may lead to severe damage to the kiln shell. It was recommended that a system be developed for the management of kiln failures, including methods for maintaining kiln rotation in the event of drive failure (e.g. barring).
Action: Scott Goldrick
38 It was noted that the majority of instruments in the system are “smart” in that they will provide some form of notification in the event of failure. It was also identified that the instruments have all been set-up to be fail-safe. Notwithstanding this it was recommended that consideration be given to the development of an instrument testing schedule, including test period.
Action: Mark Owen
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TABLE 2.1 DFTD FACILITY - HAZOP RECOMMENDATIONS
HAZOP No.
Action Description and Recommendation
39 It was identified that the plant contains a number of confined spaces. Whilst it is recognised that Innova has a confined space entry permit system, it was not clear whether this system complies with the requirements of AS 2865. It was recommended that the Innova Confined Space Entry system be reviewed in light of AS2865 to ensure it complies with this standard.
Action: Scott Goldrick
Drop Out Hopper and Pug Mill
48 In the event too much water is added at the pug-mill it was identified that there is a potential for slurry to spill from the base of the mill onto the ground around the mill area. It was recommended that consideration be given to the installation of a bund around the pug-mill area. This could be included as part of the site establishment procedure.
Action: Nick Ebrill
51 It was identified that in the event of water spray nozzle blockage, the hot soil will be fed onto the conveyor system, damaging the belts. It was recommended that a dual spray system be installed on the pug-mill to minimise the failure potential of water supply to this area.
Action: Scott Goldrick
Converters 1 & 2
70 It was identified that in the event there were too many hydrocarbon contaminants (calorific value) in the soil, there is a potential for high temperature, which may exceed the refractory capacity or build up slag in the converter. It was recommended that consideration be given to the installation of water or air injection points along the converter to reduce the temperature if required.
Action: Nick Ebrill
Scrubber – Gas Side
96 It was identified that scrubbing of acid forming gases could lead to the formation of hydrochloric, Sulphuric and hydrofluoric acid in the scrubber. Whilst the majority of components in the scrubber are stainless steel, it was recommended that consideration be given to the installation of a dosing system for managing chlorinated soil treatment.
Action: Nick Ebrill
It was also recommended that consideration be given to the development of a procedure for the operation of the chemical dosing system, including management of dangerous goods in accordance with the relevant regulations (e.g. NSW DG Regs).
Action: Scott Goldrick
97 It was identified that some soils may contain heavy metals and they may be carried in the gas/soil stream. This could result in discharge of heavy metals via the stack. It was recommended that consideration be given to the development of a consolidated procedure for the set-up of plant, testing of stacks, soils, etc.
Action: Nick Ebrill
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TABLE 2.1 DFTD FACILITY - HAZOP RECOMMENDATIONS
HAZOP No.
Action Description and Recommendation
Pug-Mill Scrubber
103 It was identified that the design operation of the scrubber leads to a low pressure in the scrubber, which results in the extraction of gas from the converter via the tipper valve. To eliminate this it is recommended that:
• a more effective mist elimination system be installed; • a balance flap be installed to prevent high suction pressure at the pug-mill; • a review be conducted in relation to the current method of pressure measurement
at the pug-mill; and • provision of a pressure differential measurement between the scrubber and
converter.
Action: Nick Ebrill
106 In the event of a scrubber sump pump failure or blocked pipework, the sump would fill and overflow. It was recommended that a spill containment method (bund) be included in the site establishment procedure for the pug-mill area.
Action: Nick Ebrill
107 In the event the sump pump fails, there is a potential for failure to remove particulates, resulting in particulate release to the atmosphere. To prevent this it was recommended that consideration be given to increasing the water supply to the pug-mill scrubber and that the pug-mill scrubber sump cone be changed to increase the cone angle to prevent sludge build up in the bottom of the scrubber.
Action: Nick Ebrill
115 It was identified that the scrubber would raise confined space issues if entry were required for maintenance/repair. It was recommended that a register of confined spaces on the plant be established and that all confined spaces be labelled with appropriate signage.
Action: Scott Goldrick
Pug Mill Scrubber – Water Circuit
116 The pug-mill water circuit has been identified to have a limitation in the area of water supply. This may result in failure to effectively scrub the steam generated in the pug-mill. It was recommended that consideration be given to the size of the water lines supplying the pug-mill system, and these be reviewed and increased accordingly.
Action: Nick Ebrill
121 It was identified that the pug-mill scrubber sump pump may block, resulting in pump damage. At this stage, there is no method of detecting this. It is therefore recommended that flow or pressure detection be installed on the pumps to indicate when a potential blockage has occurred. The instruments should be fitted with alarms.
Action: Scott Goldrick
128 It was identified that the sump pump on the pug-mill scrubber was a critical item and that rapid repair after failure was required. Hence, it is recommended that the spares for the pump be reviewed and the appropriate spares be held on site for rapid repairs.
Action: Scott Goldrick
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TABLE 2.1 DFTD FACILITY - HAZOP RECOMMENDATIONS
HAZOP No.
Action Description and Recommendation
Cooling Water System – Water Tank
130 In the event the water supply fails to the cooling water tanks, the tank will eventually empty and water supply to the heat exchangers will fail. This will result in significant damage to the heat exchanger tubes. It was recommended that consideration be given to the installation of a low level switch and alarm on the cooling water tank.
Action: Scott Goldrick
Cooling Water System – Water Circuit (pipework/pumps/etc.)
143 It was identified that a high process gas mass flow, or high temperature, would result in system upset and potential damage to the heat exchanger tubes. It was recommended that consideration be given to the development of a procedure for the response to high temperature in the cooling water circuit, including pump failure and gas flow changes.
Action: Nick Ebrill
146 It was identified that pressure on the discharge side of the heat exchanger was not monitored. However, it is possible that an instrument is fitted but not connected to the Citect system. It was recommended that the heat exchanger discharge side of the cooling system be reviewed to determine whether there is a pressure instrument fitted. If this is the case, connect the system to the Citect controls and use the output for plant monitoring and control.
Action: Scott Goldrick
149 It was identified that heat exchanger tube cleaning would be required from time to time. Without this there is a potential for the tubes to clog or for build up to make tubes inefficient. It was recommended that consideration be given to establishing a tube cleaning procedure and methodology (e.g. chemical clean).
Action: Scott Goldrick
Cooling Water System - Augers
153 In the event of a hose failure on an individual auger, there is a potential for water supply to fail to the specific auger. This could result in significant damage to the auger. It was recommended that consideration be given to the installation of pressure and flow monitoring for the auxiliary (auger) cooling water circuit, including alarms to indicate loss of flow to augers. It was also recommended that a procedure be developed for response to loss of cooling water to the augers.
Action: Scott Goldrick
154 It was identified that in the event of low flow in the auger circuit there is a potential to generate steam in the cooling water lines, resulting in hose failure. It was recommended that consideration be given to the installation of temperature monitoring on the auger cooling water circuit (discharge area).
Action: Scott Goldrick
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TABLE 2.1 DFTD FACILITY - HAZOP RECOMMENDATIONS
HAZOP No.
Action Description and Recommendation
Scrubber Process Water System – Process Water Tank
162 It was identified that the water fill valve may stick closed resulting in the tank emptying. This would lead to in-effective scrubbing and discharge of particulates to the atmosphere. It was recommended that consideration be given to the installation of a low level alarm on the tank to provide pump protection as well as protection against loss of water for scrubbing.
Action: Scott Goldrick
165 It was identified that salts may build up in the scrubber water circuit leading to blocking of spray nozzles. This would result in reduction in scrubbing efficiency and release of particulates to the atmosphere. It was recommended that consideration be given to the method of accessing nozzles during operation and a method of removing nozzles for cleaning during operation be developed.
In addition, it was identified that foreign objects in the tank have the potential to block pump suction, resulting in water loss and pump/scrubbing failure. It was recommended that consideration be given to installing a top on the tank.
Action: Scott Goldrick
Fuel Supply System – Dryer and Converter Burners
205 It was identified that water and sludge may be delivered to the burners from the fuel tank (which in turn was delivered with the fuel). Whilst this is unlikely with commercially available fuels, where a site requires a specific fuel to be used (i.e. waste fuel from the site), there is a potential for the fuel to contain contaminants. It was recommended that consideration be given to the development of a procedure for fuel specification and system, requirements when fuels are changed (could be incorporated into the management of change system).
Action: Nick Ebrill
Main Scrubber – Process Water Pump Circuit
224 In the event the main water spray pump fails, there would be no scrubbing and particulates would be emitted to the atmosphere. This is a critical component and should have some redundancy. It was recommended that consideration be give to the installation of a stand-by (in line) pump.
Action: Scott Goldrick
Main Scrubber – Slurry Return System
234 The slurry pump has been a high wear issue in the plant and the current mono pump is proving unreliable. Innova are currently reviewing the pump design/specification in view of replacing the current pump with a centrifugal type slurry pump. It was recommended that this project continue and the pump be replaced.
Action: Scott Goldrick
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TABLE 2.1 DFTD FACILITY - HAZOP RECOMMENDATIONS
HAZOP No.
Action Description and Recommendation
Dosing System
270 It was identified that the current dosing system has an isolation valve downstream of the dosing pump. In the event this valve was closed, the dosing pump (positive displacement) may be damaged or the line overpressured. The valve may be required to prevent back feed up the line when the dosing pump is not operating. If this is the case, a non return valve (NRV) may be more effective. In addition, consideration should be given to the installation of a dedicated dosing point for the flocculant material.
Action: Scott Goldrick
273 Mixing of flocculant was identified to be a potential problem in that incorrect mixing may lead to coagulation of the material and difficulty in pumping to the plant. It is recommended that consideration be given to the development of an SOP for mixing the flocculant, including MSDS and PPE.
Action: Scott Goldrick
Overview
282 The nature of the DFTD facility is such that it will be dismantled and reconstructed on many occasions, requiring regular commissioning and start-up. It was identified that in the event of loss of operator experience (e.g. staff leave the company) there is a potential for problems in set-up and commissioning of the plant. It was recommended that consideration be given to the formalising of relocation procedures including commissioning and de-commissioning including:
• Proof tests; • Test programme (at start-up and during operations); • Check of interlocks once established and ongoing testing during operation; • Check emergency shut down operation (once established and during ops); • Disposal of un-used chemicals and fuels after campaign has finished.
Action: Nick Ebrill
283 It was identified that continuous plant re-location, and different sites, may lead to slightly different plant configurations. The procedure currently used for plant set-up is basic and may not be flexible enough to cater for different plant configurations. It was recommended that consideration be given to the development of a more flexible set-up/dismantling procedure be developed.
Action: Nick Ebrill
287 In the event of fire on the plant, the facility is fitted with fire extinguishers, which would be effective in minor, localised fires. However, in the event of a larger fire, the first attack fire fighting equipment would be ineffective. Hence, a system would be required for calling the fire brigade and providing the appropriate fire water as required. It was recommended that consideration be given to the inclusion of fire a management plan within the emergency plan. This should also include the set-up of fire fighting services (water supply) near the plant (within 50m) for use by the fire brigade.
Action: Nick Ebrill
290 It was identified that the existing control room has a single entry/egress door. This door faces the plant and, hence, in the event of an incident directly in front of the control room, it may not be possible to safely egress from the area. It is therefore recommended that a second egress door be installed in the control room to provide egress from the rear of the room.
Action: Scott Goldrick
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3 BRIEF DESCRIPTION OF THE DFTD FACILITY 3.1 Background In the field of soil remediation, thermal desorption is quite a well known technology for separating hydrocarbon contaminants from soils. Hydrocarbon contaminants are volatised in a thermal desorber (rotary dryer) and passed to an offgas stream. The contaminant laden stream is then treated in an emissions control system in which the hydrocarbons are either collected as liquid concentrate or converted in a conversion chamber. Innova has developed an advanced mobile thermal desorption system known as Direct-heated fast quenched thermal desorption (DFTD) which is capable of treating up to 250,000 tonnes per annum of soils impacted with all hydrocarbon contaminants including; petroleum hydrocarbons, polycyclic aromatic hydrocarbons (PAH), organo-chloro pesticides (OCP), dioxins and furans. The Innova DFTD process has several innovative improvements and advantages over the traditional thermal desorption systems, whilst at the same time maintaining widely proven and robust engineering components. The process is designed to remediate soil whilst ensuring that all stack gases and particulate emission standards are met. Figure 3.1 shows a picture of the DFTD plant. Piping and Instrumentation Diagrams (P&IDs) are included at Appendix B. Plant design and operation is detailed in the following sections.
3.2 DFTD Process Components The Innova DFTD plant consists of a series of integrated components designed to achieve successful contaminant separation and subsequent conversion, energy recovery, fines reconstitution and product cooling. A typical plant layout is shown at Figure 3.2. The DFTD system consists of the following main components: • Material Feed System – providing a regulated flow of contaminated soil to the process; • Direct Heated Rotary Desorption Unit – gently heating the soil and separating the
contaminants from the solid matrix into the gas phase (Note: this is not incineration as the soil character is retained and not destroyed – soil is re-used on site);
• Clean Product Discharge Hopper – controlled removal of clean soil from the rotary
desorber unit; • Soil Cooler – using sluice and scrubber product water for both cooling and dust
reconstitution; • Conversion Chamber – gas phase contaminants are converted to carbon dioxide and
water by passing the gas through the converter over a 3-4 second period at above 950oC (up to 1200oC) ,
• Compressed Air Saltation System and Sluices – promotes and collects fine particles
within the conversion chamber prior to the heat exchanger bank; • Energy Recovery Exchangers – pre-heats the incoming air to the combustion chambers; • Dry Gas Quencher – eliminated contaminant reformation potential; • Venturi Wet Scrubber with Wetted Fan – cleans the off-gas of particulates and any acid
gases;
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• PLC and Citect Computer System – process control and continuous monitoring of operations; and
• CEMS – continuous monitoring of gaseous stack emissions, internet capable results
display.
3.3 Brief Description of Operations 3.3.1 Soil Pre-Treatment and Feed The contaminated soil is initially crushed and screened to less than 50mm in diameter. The soil is then stockpiled ready for feed to the plant and conveyed to the feed hopper by front end loader. A screw feeder in the base of the feed hopper then feeds the soil to a transfer conveyor, which in turn passes the soil to a hopper/screw feeder arrangement on the rotary dryer. This unit is used to ensure a steady feed is maintained to the rotary dryer and to ensure an atmospheric seal is maintained within the dryer itself. 3.3.2 Rotary Drying and Product Management Once inside the rotary dryer, the soil is progressively heated through radiative and convective heat transfer from a liquid fuelled flame. The contaminants are evolved through vaporisation and mass transfer processes. The clean soil is then fed to a pug-mill for cooling. The pug-mill consists of a cooling chamber, into which cooling water is sprayed, and two screw feeders, which transfer the cooled soil to a product conveyor. The material is then stockpiled for return to the site. 3.3.3 Gas Treatment The contaminant laden gas stream exits the rotary dryer (at about 850oC) and enters the primary combustion chamber, in the converter, where additional bulkhead mounted burners increase the gas temperature to above 950oC, as required (up to 1200oC). Fines are transported through the chamber with a pulsed air saltation system. After a minimum residence time (about 3-4 seconds, which ensures complete contamination conversion) the off-gas product (mainly CO2, H2O and N2) passes through a grit arrestor with venturi sluice, providing phase 1 fines collection. The flue gases are then cooled to 820oC, through an energy recovery (heat exchangers) system, indirectly heating the incoming combustion air. A rapid quench system (heat exchangers) is then used to dry and cool the gases from 820oC to 175oC in less than 30ms, thus eliminating any dioxin formation potential. The cooled gases are then scrubbed via a large capacity, high efficiency, industrial spray scrubber, with wetted fan polishing (phase 2 fines collection). The water products from the sluice collection and the wet scrubber are used for soil cooling and dust reconstitution with the bulk product. 3.3.4 Ancillary Systems Cooling water for the rapid quench system is provided by a closed loop system containing a water tank, circulation pump and fin-fan coolers. The burner systems are fuelled by diesel. This system consists of a tank and fuel pump, which delivers fuel to a ring main pipe system from which the burner fuel supply is drawn. A pilot flame system is installed, which operates from an LPG supply (cylinder).
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FIGURE 3.1
INNOVA DFTD PLANT
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FIGURE 3.2
DFTD PLANT GENERAL ARRANGEMENT
Innova Soil Technology Direct Heated Fast Quenched Thermal Desorption Facility
HAZOP
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4 METHODOLOGY 4.1 Selected Study Approach The selected study approach was based on the HAZOP methodology described in Hazardous Industry Planning Advisory Paper No. 8, HAZOP Guidelines (Ref.1).
4.2 Hazard and Operability Study (HAZOP) HAZOP was originally developed as a workshop-based approach structured particularly for process operations. However, since its early use in the 1960’s/70’s, HAZOP has been further developed to cover a wider range of operations including mechanical, electrical and computer based systems. The approach was particularly suited to the DFTD facility as this system is process based consisting mainly of pipework, pumps, tanks, vessels, burners, rotary dryers, heat exchangers, etc. The study assessed the process using a series of guidewords to assist the study facilitator in structuring the study. Guidewords used in the study are listed in Table 4.1
The basic approach was as follows:
• A drawing(s) of the process was placed in front of the study team and a team member explained the proposed design and operation of the process. Questions were asked at this point for clarification.
• The facilitator then selected a section of the drawing(s) for review (e.g. loading the hoppers, conveying soil to the dryer, cooling the heat exchangers, etc.), this was then highlighted on the drawing to indicate to the team exactly what section of the drawing was being studied.
• The facilitator then selected a guideword (e.g. position, movement, load, temperature, flow, pressure, level, etc.) and questioned the team as to the potential for a deviation from normal operating conditions associated with the guideword.
• Where a deviation from normal operating conditions was identified, a HAZOP minute was recorded noting the minute number, guideword used, cause of the deviation, consequence of the deviation, proposed safeguards and required action to control the identified deviation. To ensure the minute action was completed and followed up, the minute action was allocated to a specific person. Where an operational deviation was not identified or was assessed to have no impact, the guideword was recorded and a note made that no issues were identified or assessed with the selected guideword.
• This process was continued for all operations associated with the DFTD process until all drawings were completed.
• Once the drawings were completed, a HAZOP overview was performed to review the plant as a whole and determine the potential hazards associated with equipment interactions and other issues associated with the project in total.
Innova Soil Technology Direct Heated Fast Quenched Thermal Desorption Facility
HAZOP
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TABLE 4.1 GUIDEWORDS USED IN THE HAZOP
MECHANICAL SYSTEMS GUIDEWORDS (e.g. loaders, conveyors, cranes, stackers, etc.) POSITION Too High, Too Low, Too Far, Misaligned, Wrong Position
MOVEMENT High Speed, Low Speed, No Movement, Reverse Movement, Vibration, Friction, Slip, Obstacles
LOAD High Load, High Flow, Low Load, Low Flow, Loss of Containment
TEMPERATURE Too high, Too low
TIMING Too Late, Too Early, Too Short, Too Long, Incorrect Sequence
SIZE Too Large, Too Small, Too Long, Too Short, Too Wide, Too Narrow
ENERGY(elect., Hydraulic, Steam, Pneumatic, etc.)
Low Energy, High Energy, Energy Failure
QUALITY Wrong concentration, impurities, cross contamination, side reactions, inspection and testing, instrument quality and quantity
CONTROL Response speed, sensor and display location, interlocks, SCADA system security, hardware/ software weak links, system node/ comms failure
ELECTRICAL SAFETY Hazardous area classification (dusts), earthing, lightning protection
MAINTENANCE Access to plant and equipment, purging of gas, inspection and testing.
PROCESS SYSTEMS GUIDEWORDS (e.g. pumps, pipework, tanks, vessels, heat exchangers, etc.) FLOW Too High, Too Low, No Flow, Reverse Flow
LEVEL Too High, Too Low, No Level
PRESSURE Too High Too Low, Vacuum
TEMPERATURE Too high, Too low
QUALITY Wrong concentration, impurities, cross contamination, side reactions, inspection and testing, instrument quality and quantity
INSTRUMENTS &CONTROL Response speed, sensor and display location, interlocks, SCADA system security, hardware/ software weak links, system node/ comms failure
SYSTEM TESTING Sampling, Special Instruments, Analysers
ELECTRICAL SAFETY Hazardous area classification (dusts), earthing, lightning protection
MAINTENANCE Access to plant and equipment, purging of gas, inspection and testing.
OVERVIEW PHYSICAL DAMAGE Impact, dropped objects, transport collision, vibration, corrosion
FIRE/EXPLOSION Prevention systems, detection systems, fire protection, emergency isolation, emergency procedures
ENVIRONMENTAL IMPACT Vapour/gas emissions, dust emissions, effluent, noise, ground seepage, waste minimisation
MATERIALS OF CONSTRUCTION
Pipework, valves, fitting, instruments, filters, gaskets, protective systems and coatings
UTILITIES AND SERVICES Instrument air/gas, compressed air, breathing air, nitrogen, cooling water, process water, steam, fuel gas, electricity, oxygen, lighting
COMMISSIONING Requirements, sequence, procedures
START-UP First time, routine, procedures
SHUT-DOWN Planned, emergency
SAFETY EQUIPMENT Personnel protection, gas monitoring, breathing apparatus, safety showers, barriers and guards
NATURAL HAZARDS Earthquake, Flooding, Thunderstorm, High Winds
PROCEDURES Operations, maintenance, inspection and testing, confined space, emergency, engineering drawings, modification control
QUALITY CONTROL Inspection and Testing, Quality Assurance System
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HAZOP
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Each HAZOP minute point was recorded on a separate line on a copying white board using the formats shown in Tables 4.2. Each event was given a unique identifying number for future reference. The minutes were then transferred to a Lap Top computer for inclusion in the final report.
TABLE 4.2 STRUCTURE OF THE HAZOP MINUTES RECORDING TABLE
No. Guideword Cause Consequence Safeguard Action Responsible Person`
4.3 Workshop Participants, Location and Timing 4.3.1 HAZOP Study The workshop was conducted at the offices of Innova, cnr of Gavey and Frith Streets, Mayfield West, NSW, on Tuesday 9 and Wednesday 10 March 2004. Four study sessions were conducted each of about 3.5 hours duration.
The workshop was attended by the following personnel:
Name Organisation Position
Nick Ebrill (Chemical Eng.) Innova Soil Technology Manager Operations
Scott Goldrick Innova Soil Technology Plant Supervisor
Mark Owen Combustion Instrumentation Electrical/Instruments Engineer
John Lucas (Chemical Eng.) Innova Soil Technology Managing Director
Steve Sylvester HLA-Envirosciences Study Facilitator
Rui Henriques HLA-Envirosciences Principal - Remediation
Innova Soil Technology Direct Heated Fast Quenched Thermal Desorption Facility
HAZOP
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5 RESULTS 5.1 Background The nature of the HAZOP study, results in the discussion of many points that relate to hazard and operability issues associated with the operation of the plant under analysis. The recording of every discussion item, at length, would result in an un-necessarily long workshop, leading to frustration among the HAZOP participants whilst time was wasted recording minor issues requiring no action.
To ensure the most effective recording of results was achieved, for the DFTD Facility HAZOP, the following recording format was adopted:
• Where a discussion issue was identified to result in no hazard or operability issue, an entry into the guideword row was made stating “No issue”, this entry illustrates that the point was discussed and no issues were identified with the potential deviation or that the deviation is not possible (i.e. incorrect position of a delivery chute over a hopper); and
• Where a discussion point was identified to result in a potential hazard/operability issue, a full minute point was recorded, identifying deviation cause, consequence, proposed safeguards and action required to prevent, detect, protect and/or mitigate the hazard/operability consequences.
The main aim of recording results in this manner is to demonstrate that all deviations were identified and discussed, and that appropriate safeguards were developed for the hazard and operability issues identified.
The minutes recorded during workshop session are presented in Appendix A.
There were 292 minute points discussed during the HAZOP study, of these there were 43 points raised for action. A summary of the actions recorded, as a result of the HAZOP, are presented in Section 2.2. The location of recorded minute points was placed on the P&ID’s in a diamond ( ◊ ) to indicate the equipment for which the minute was recorded and to provide an easy future reference when actioning minutes.
Innova Soil Technology Direct Heated Fast Quenched Thermal Desorption Facility
HAZOP
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APPENDIX A
HAZOP MINUTES
Innova Soil Technology Direct Heated Fast Quenched Thermal Desorption Facility
HAZOP
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Front End Loader and Load Station Date: 9 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 1 Position Level too high –
bin overfills Spill over the side of the bin – clean up required by hand
- bin weigher - 2 way radio to control room - level can be seen when full
- Consider installing “hungry” boards on the hopper
- Consider installing a weight display adjacent to the hopper to indicate hopper level to the driver
SG SG
2 Movement No issues raised 3 Size Rocks in the
feed Damage to hoppers - Material screened prior to
feed - Grizzly at bin loading point
No further action
4 Load Cannot overload the bin – no issues 5 Timing Fail to load bin
(operator does not see bin is empty)
Process stability is
affected
- Bin level alarm (weight) - Alarm shown on screen in
control room
No further action
6 Energy No issues raised 7 Contamination - Water (rain)
- Dust
- Increased energy costs
- Contamination run off
- Shed located on site to cover load station & stockpile (Large projects only)
Consider developing a procedure for establishing equipment on site including addressing site specific issues such as bunding and containment, dust control, noise control, etc.
NE
8 Process Control Filling hopper is a manual operation
No further issues
9 Maintenance No issues raised 10 Access People
accessing the front end loader (FEL) operating area
Potential for accident resulting in injury/fatality to persons struck by FEL
Area is fenced off during operations limiting access by non-authorised people Access and interaction with people and vehicles is covered in the site induction
No further action
11 Safety Equipment
Minimum level of PPE required for all personnel and visitors – hard hats, safety boots, safety glasses, long sleeve shirts and long trousers. No further action
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Feed Screw/Conveyor Date: 9 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 12 Position Material change
(density) Erratic feed rate - Restrictor device
- Motor current monitoring - High current alarm
Consider developing a Standard Operating Procedure (SOP) for the management of material feed
NE
13 Movement No issues raised 14 Size No issues raised 15 Load Wind around
the equipment and site
Potential for dust to be generated from conveyor
Conveyor is covered No further action
16 Timing Down stream equipment stops
Feed into upstream equipment continues and blockage occurs
- Interlocks fitted in upstream equipment
- Alarms (audible & on screen)
No further action
17 Energy Power loss Dryer stops rotating – overheat and damage
Back up generator connected to critical equipment
No further action
18 Energy Conveyor trip chord pulled
Power to conveyor is cut – feed continues to the conveyor from hopper
Consider installing conveyor shut down alarm on lanyards – this will alert operators to shut down situation and raise an alarm if someone has pulled the chord due to accident (i.e. person trapped)
SG
19 Contamination No issues raised 20 Process Control No issues raised 21 Maintenance No issues raised 22 Access No issues raised 23 Safety
Equipment Sampling at the tail end of the conveyor
Potential for exposure to contaminated soil
Consider formalising the SOP for sampling at the conveyor area. Should develop an SOP for all sampling operations
NE
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Feed Screw and Rotary Dryer Date: 9 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 24 Flow No issues raised 25 Reverse flow
(gas) Induction fan draws air through the system, always negative pressure – no issues
26 Reverse flow (soil)
Slow dryer speed & feed rate high
Product builds up in dryer shell and spills out at the feed screw end of the dryer
- Chute collection device - Spill area is directly in from
of the operators control room window
- Recommend continue investigation into rotary seals on dryer drum
- Review the potential to monitor speed and feed rates and notify operators of operational windows and potential to overload the dryer
NE SG
27 Level Low Feed stops: - Conveyor fails - Screw feeder fails
High temperature in the dryer
- High Temp Alarm (available on screen)
- High High Temp alarm (shuts down the burner)
No further action
28a Pressure High - ID Fan fails
Positive pressure in the dryer – gas and dust release
Auto feed shut down - Check that the interlock operates between feed and ID fan (i.e. Feed stops when ID fan shuts down)
- Consider developing a procedure for ID fan failure
- Consider developing a procedure for maintenance and management of the ID fan including the following: Temperature Balance Maintenance Vibration Maintenance Spares
MO NE SG
28b Pressure High - Fan “puff” (rapid localised explosion of materials)
Instantaneous/short term release of gas & dust
Blending Continue investigation into the installation of seals on the rotary dryer drum –0 this should prevent air ingress and the potential for “puff” explosions
NE
29 Pressure low Physically not possible to generate sufficient vacuum to damage the unit – no issues raised 30 Temperature
High High volatiles content in soil and high air content on dryer
Excessive localised burning in the dryer
- High Temp Alarm (available on screen)
- High High Temp alarm (shuts down the burner)
No further action recommended
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Feed Screw and Rotary Dryer Date: 9 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 31 Temperature
Low Burner shuts down due to: - Fuel supply failure - trip
- Incomplete treatment of soil
- Incomplete product combustion
Carry over of contaminants into discharge area
- Low pressure alarm on fuel supply
- Flame trip alarms
Consider a spare in-line fuel pump for fuel supply
SG
32 Temperature Low
FD Fan on air supply fails
Flame shuts down - Incomplete
treatment of soil - Incomplete product
combustion Carry over of contaminants into discharge area
Maintenance Review the need for a flare system to cover critical failures where contaminants may be released in a sensitive location.
JL
33 Change in composition
Change in calorific value of the feed
- Kiln “puff” & temp. increase
- Unstable operations - Trip ID Fan
(See Min No,26)
34 Contamination Chlorine and sulphur in feed
No issues for dryer
35 Loss of Containment
No new issues
36 Instruments & Control
- Speed/Control of rotation of dryer
- Fail to drive
Potential to damage the kiln body – over temperature
Consider a method of managing failures of the kiln drive (e.g. barring the kiln, spares, etc.)
SG
37 Electrical Systems
No new issued raised
38 System Testing Instrument failure No back up instruments, potential for loss of control of specific sections of plant
- “Smart” instruments installed
- Instruments are fail safe
Recommend the establishment of a calibration procedure and schedule for instrument testing
MO
39 Maintenance Confined space Potential for access issues with the confined space
Confined space procedure available on the plant
Review the confined space procedure and determine whether it complies with the requirements of AS2865
SG
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HAZOP
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Drop Out Hopper & Pug Mill Date: 9 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 40 Flow High No issues raised 41 Flow Low
42 Rev Flow (soil) No issues raised 43 Level No issues raised 44 Pressure High Tipper valve
sticks open - Air into the system –
increase in dust carry over, grit hoppers & scrubber leading to high work load
- ID Fan overload
- Position indicator on the valve - Trend on valve position
No further action
45 Pressure Low No possible due to configuration of the system 46 Temperature
High Kiln speed too high – low residence time
Potential for incomplete treatment of soil
Temperature gauge and monitoring
No further action
47 Temperature Low
No issues for the pug mill
48 Change in Composition
Too much water Water/slurry spills from base of pug mill
Consider bunding and containment in the pug mill area (possible inclusion of pug mill bunding in overall site establishment plan
NE
49 Contamination No new issues 50 Loss of
Containment No new issues
51 Instruments and Control
Loss of water to pug mill – blocked nozzles
- High soil temp. - Belt damage - Dust emissions
- Temp alarm high - Manual hose available - Access to nozzles available
Consider installing dual nozzles in the pug mill
SG
52 Electrical Systems
No new issues raised
53 Systems Testing No new issues raised 54 Maintenance No new issues raised
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Product Conveyor and Soil Removal Date: 9 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 55 Position Front end
loader (FEL) Potential for FEL to strike product conveyor resulting in equipment damage
- Trained drivers - Stockpile prevents FEL from
getting too close to the conveyor
- Induction training
No further action
56 Movement Constant speed conveyor
No further issues raised
57 Size No issued raised 58 Load No issued raised 59 Timing No issued raised 60 Energy Area is cordoned off with “bunting” to prevent access – no further action 61 Contamination Hot solids Potential to burn belts Issues covered in pug mill section 62 Process Control Limited process control equipment, conveyor is continuous operation with little control intervention – no issues raised 63 Access/Maint. No issued raised
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Converters 1 & 2 Date: 9 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 64 Flow High No issues 65 Flow Low/No Auger fails Dust/particles not
removed from the converter – potential to block augers
- Can run down & cool system without significant impact on the process
- Sufficient time to manage the failure
No further action
66 Reverse Flow No new issues 67 Level (see flow issues above) 68 High Pressure ID Fan fails Gas build up in the
converter – ignition and explosion
- Explosion is minor and localised
- Explosion doors fitted to the converter
No further action
69 Low Pressure System configuration prevents a vacuum being drawn on the unit, low pressure cannot occur – no issues 70 High
Temperature Too many contaminants (high calorific value)
- Exceed design capacity of refractory – damage
- Slag build up
- Blending - Sampling of soil (same as minute no.30)
Review the possibility of water or air injection points to reduce the temperature
NE
71 Low Temperature
Burner fails: - Fuel failure - Air supply
fails
(see minutes 31 & 32)
72 Change in Composition/ contamination
No new issues
73 Loss of Containment
No new issues
74 Instruments and Control
No new issues
75 Electrical Systems
No new issues
76 System testing No new issues 77 Maintenance No new issues
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Heat Exchanger – Gas Section Date: 9 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 78 Flow High/Low No new issues raised 79 Reverse Flow No new issues raised 80 Level No new issues raised 81 High Pressure No new issues raised 82 Low Pressure Fines build up Restricted flow
through the heat exchanger - Pressure differential
rises - Inefficient
operations
- dP measurement & trending - Temperature element and
alarm
No further action
83 Temperature No new issues raised 84 Change in
Composition/ Contamination
Split tube – air/ water
- Air into the gas - Water into gas
- Large failure required before problems occur
- Tubes can be alternated (turn front to back) to share load
No further action
85 Loss of Containment
No new issues raised
86 Instruments and Control
Critical variables (temperature, pressure) are monitored - No further action
87 Electrical Systems
No new issues raised
88 Systems Testing No new issues raised 89 Maintenance No new issues raised
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Scrubber – Gas Side Date: 9 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 90 Flow Low Fan ails/slow Loss of venturi effect –
particulates up the stack
dP alarms on the scrubber No further action
91 Reverse Flow Not possible 92 Level Low (see water side minutes) 93 Pressure Low Blockage in
conical section No issues for the scrubber
94 Pressure High Fan fails No issues for the scrubber (impacts assessed in other sections of the plant) 95 Temperature Heat exchanger
water supply fails
High temp. in scrubber- Scrubber water
cools gas – no impact on scrubber
- Large qty of steam downstream
- High temperature alarm - Controlled shut down can be
performed
96 Change in Composition
Formation of HCl, H2SO4, HF (acids)
- Potential for equipment corrosion
- Environmental emissions
- Stainless steel system - Preliminary soil analysis
and system control based on results
- Consider installing a dosing system for controlling chlorinated soil treatment
- Procedure required for management and operation of the chemical dosing system
NE SG
97 Contamination Heavy metals in the operational stream
Potential to discharge heavy metals via the stack
- Preliminary soil analysis and system control based on results
- Stack testing
Consider developing a consolidated procedure for set-up of plant, testing stacks, soils, etc.
NE
98 Loss of Containment
No new issues raised
99 Instruments and Control
No new issues raised
100 Electrical Systems
No new issues raised
101 Systems Testing No new issues raised 102 Maintenance No new issues raised
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HAZOP
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Pugmill Scrubber Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 103 Flow high Correct (flow)
operation of scrubber results in low pressure
Dryer offgas drawn out of converter – potential emissions at scrubber stack
- Provide more effective mist elimination - Consider pressure balance flap to
prevent high suction pressure at pub mill
- Review current method of pressure measurement on the scrubber
- Provide pressure measurement of pressure differential (scrubber-converter)
NE NE NE NE
104 Flow Low - Fan fails - Power fails
Steam escape at the pub mil (need to adjust flows and bring plant down for maint./repair)
- By-pass ducts into converter (provides %age of operation)
- No immediate action required
No further action
105 Reverse Flow No new issues raised 106 High Level - Instrument fails
- Pump fails Sump fills in scrubber and overflows into the area under the plant
Level alarm in sump Include the requirement to bund the pug mill area in the plant set-up procedure and site containment design
NE
107 Low Level - Instrument fails - Pump fails
- Pump runs dry – damage
- Particulates released from stack
- Level alarm (low) - Scrubber viewing window
- Consider increasing the water supply to the scrubber
- Change the bottom of the scrubber cone to create a greater angle (reduces slurry build up on low angle surfaces)
108 Pressure No new issues raised 109 Temperature Hot soil and steam
in scrubber Potential damage to fan motor (plant must shut down)
(see minute 103)
110 Change in Composition/ Contamination
No new issues raised
111 Loss of Containment
No new issues raised
112 Instruments and Controls
No new issues raised
113 Electrical Systems
No new issues raised
114 Systems Testing No new issues raised
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Pugmill Scrubber Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 115 Maintenance Confined space
issues Potential confined space incident with personnel entering the scrubber
Confined Space Entry
procedure
Consider installing signs on all confined spaces. This will require the identification and registering of all confined spaces in a plant confined space register (this should be developed as part of an Safety Management System)
SG
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Pug Mill Scrubber Water Circuit Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 116 Low Flow Water pressure
fails (result of adj. Facility use)
Reduction in scrubber capacity - Solids build up in
scrubber - Solids in steam,
stack emissions
Not a serious emissions issue Review the size of the water supply lines to
the plant and the pug mill. Line size
increase may provide additional water flow
NE
117 Low Flow No issues raised 118 Flow High Pump operates
at maximum speed
Low level in the sump Low level alarm No action
119 Reverse Flow No issues raised 120 Level No issues raised 121 Pressure Line blocked Pump dead heads –
resulting in damage to pump
Consider flow detection on the pump, could be pressure switch, low motor current, etc.
SG
122 Temperature No issues raised 123 Change in
Composition/ Contamination
No issues raised
124 Loss of Containment
No issues raised
125 Instruments & Control
No issues raised
126 Electrical Systems
No issues raised
127 Systems Testing No issues raised 128 Maintenance Component
fails Pump out for repair for extended period – pant is shut down
Review the spare parts required on hand to effect rapid for repairs. May need to increase spares holdings
SG
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Cooling Water System - Storage Tank Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 129 Level High - Valve sticks
open - Ball falls off
float arm
Tank overfills – fresh water spill around base of tank
- Water Treatment chemicals are suitable for discharge to sewer
- Development of site bunding will contain spills
No further action
130 Level Low Water supply fails (valve sticks closed, town water supply stops)
Fail to supply cooling to heat exchanger – major tube damage
Consider level switch on the cooling water tank to alarm at tank low level
SG
131 Pressure Atmospheric tank – no issues 132 Temperature No issues raised 133 Change in
Composition/ Contamination
Scale formation in the system
No issues for the tank
134 Loss of Containment
No issues raised
135 Instruments and Controls
No issues raised
136 Electrical Systems
No issues raised
137 System Testing No issues raised 138 Maintenance Confined space Confined space entry
incident – potential injury/fatality
Confined space entry procedures used at the plant (to be reviewed for compliance with AS2865)
No further action
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Cooling Water System – Water Circuit (pipework/pumps, etc.) Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 139 Flow High Pump operates
at set speed No issues raised
140 Flow Low/No - Pump Fails - Valve closed
in the line
Flow s halved as two pumps operate in parallel
- Second pump on line - Spares carried for the pump
No further action
141 Reverse Flow NRVs installed – No further action 142 Pressure Both discharge
valves in pumps closed
No flow of water to heat exchangers – potential tube damage
Pressure switch and alarm installed
No further action
143 Temperature - High
- High process gas mass flow
- High temperature gas
System upset and potential tube damage in heat exchangers
Temperature alarms installed on heat exchangers and water circuit
Consider a procedure for response to high temperature in the cooling water circuit, including pump failure & gas flow changes
NE
144 Change in Composition/ Contamination
Scale in the water flow
Potential tube blockage leading to localised tube overheating
- Scale inhibitors added to water circuit
- pH monitoring of the water (samples)
No further action
145 Loss of Containment
No new issues
146 Instruments and Controls
Pressure on the discharge side of the heat exchanger
Currently not monitored by the CITEC but an instrument may be fitted
Review the heat exchanger discharge side of the cooling water circuit to determine whether there is a pressure instrument fitted in this area – connect to the CITEC if this is the case.
SG
147 Electrical Systems
No issues raised
148 Systems Testing No issues raised 149 Maintenance Tube bundle
access for inspection and cleaning
Potential for tube damage if tubes are not regularly inspected and cleaned
Consider establishing a maintenance regime for the heat exchanger tubes and set up a cleaning methodology (e.g. chemical clean)
SG
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Cooling Water System – Water Supply to Augers Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 150 Flow Low One pump fails Flow is halved –
potential damage to the augers after a period of time
Second pump provides sufficient water to allow plant to be shut down in a controlled manner
No further action
151 Flow No Power supply fails
Immediate damage to the augers
Cooling water pumps are on the emergency power back up system (diesel generator)
No further action
152 Reverse Flow NRVs installed on each pump discharge – No further action 153 Pressure Low Hose failure Potential for water
supply to an individual auger to fail – auger damage
- Consider pressure and flow monitoring for the auxiliary (auger) water circuit, including alarms to indicate loss of flow to augers
- Develop a procedure for response to loss of flow in the auxiliary water circuit
SG SG
154 Temperature Low flow due to pump failure, supply water low, etc.
Potential to generate steam in the lines resulting in hose overpressure and failure
Consider temperature monitoring of auger circuit discharge temperatures
SG
155 Change in Composition/ Contamination
No issues raised
156 Loss of Containment
No issues raised
157 Instruments and Controls
No issues raised
158 Electrical Systems
No issues raised
159 Systems Testing No issues raised 160 Maintenance No issues raised
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Scrubber Process Water System – Process Water Tank Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 161 Level High - Valve sticks
- Ball falls off float
Tank fills and overflows
- Area will be bunded as part of plant set-up and establishment procedure
- The tank is in direct view of the control room operator
No further action
162 Level Low - Top up valve sticks closed
- Town water supply fails
Scrubbing fails – emissions to the atmosphere
Town water system is alarmed at low pressure
Consider installing a low level alarm on the tank to provide pump protection and indicate wether tank filling valve may have failed
SG
163 Pressure Atmospheric tank – No issues raised 164 Temperature Maximum temperature that tank can reach is 100oC – no issues for the tank of process 165 Change in
Composition/ Contamination
- Acidic gases scrubbed
- Clarifier carry
over - Increased salts - Foreign objects
in the tank
- Acidic water build up over time – potential for corrosion
- Slurry in the tank – potential for pump damage
- Blocked nozzles from scale build-up
- Pump suction
blocks or nozzles become blocked
- Batch sampling conducted for water pH
- Initial soil samples taken - Stainless steel equipment
used throughout scrubber system
- Tungsten carbide seals used on the pumps
- No further action (on acidic water) - No further action (on slurry in tank) - Consider redesign of nozzles so that the
nozzles can be accessed individually for cleaning or removal/replacement during operations
- Consider a top on the tank to limit the potential for foreign objects to find their way into the system
SG SG
166 Loss of Containment
No issues raised
167 Instruments and Controls
No issues raised
168 Electrical Systems
No issues raised
169 Systems Testing No issues raised 170 Maintenance No issues raised
Innova Soil Technology Direct Heated Fast Quenched Thermal Desorption Facility
HAZOP
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Burner System – Air Supply Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 171 Flow Lo Fan fails Burners shut down –
no hating for system Issues addressed in the converter/dryer section – no new issues raised
172 Flow High Fan fails Burners shut down – no hating for system
Issues addressed in the converter/dryer section – no new issues raised
173 Pressure Low Fan fails Burners shut down – no hating for system
Issues addressed in the converter/dryer section – no new issues raised
174 Temperature Low
No issues raised
175 Temperature High
No issues raised
176 Change in Composition/ Contamination
No issues raised
177 Loss of Containment
Leaks from ducts – air only – No issues raised
178 Instruments and Controls
Pressure instrument fails
Fan backs off – no air supply and burner shuts down
Air supply loss raises alarm and operator can respond
No further action
179 Electrical Systems
No issues raised
180 Systems Testing No issues raised 181 Maintenance No issues raised
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HAZOP
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Burner System – Atomising Air Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 182 Flow Low - Compressor fails
- Air leak Burner shuts down – no heating to converter only
- Air loss alarm - Sufficient time to respond
and bring plant down safely for repairs
- Hire compressor can be installed as required
No further action
183 Flow High No issues raised 184 Pressure No issues raised 184 Temperature No issues raised 186 Change in
Composition/ Contamination
No issues raised
187 Loss of Containment
No issues raised
188 Instruments and Controls
Burner management system has been installed in accordance with the Australian Standard
189 Electrical Systems
No issues raised
190 Systems Testing No issues raised 191 Maintenance Compressor is under an Atlas Copco maintenance contract – stand by (hire) compressor can be connected to plant as required
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Fuel Supply to Burners – Fuel Tank Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 192 Level High Overfill tank Spill into the bunded
area - Tank dips during operations
and before fill - Operator present during fill
operation
No further action
193 Level Low Fail to order fuel
Plant shuts down (no burners)
- Tank dips during shifts - Fuel use (trend and rates) on
the CITEC – indicates when fuel is required
No further action
194 Pressure Atmospheric Tank – no issues raised 195 Temperature Operates at ambient, sufficient distance from plant to limit heat impact – no further issues 196 Change in
Composition/ Contamination
Water/sludge Potential burner problems
Burners can burn up to 20% water content
No action
197 Loss of Containment
Tank leaks Soil to bund No further action
198 Instruments and Controls
Fully manual fill and check system – no issues raised with this type of operation, considering the temporary nature of the plant
199 Electrical Systems
Ignition sources in electrical systems near the tank
Potential ignition and fire
There are no electrical systems in the bunded area or on the tank
No further action
200 Systems Testing No issues raised 201 Maintenance Tank is supplied under contract by Shell, maintenance conducted under this contract – no further issues
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HAZOP
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Fuel Supply System – Dryer and Converter Burners Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 202 Flow Pump fails No new issues (see dryer minutes) 203 Pressure Valve closed Pump dead heads
(positive displacement pump)
Pump has internal relief Pump has internal pressure relief system – no further action
204 Temperature No issues raised 205 Change in
Composition/ Contamination
Water/sludge delivered from tank
No major impact on the burner with commercial grade diesel fuel Potential for problems with non-commercial fuels
Consider developing a procedure for fuel specification and system requirements when fuels are changed. Could be incorporated as part of the change management system.
NE
206 Loss of Containment
Leak and spray onto hot equipment
Fire potential (low likelihood as hot surfaces are well below auto-ignition temperature (≈200oC)
Fire extinguishers located around the plant Leak tests performed on all equipment (i.e. during commissioning) prior to use
No further action
207 Instruments and Controls
Burner management system installed as per Australian Standard – no further action
208 Electrical Systems
No further action
209 Systems Testing No further action 210 Maintenance No further action
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HAZOP
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Burner Systems – Burner Pilot Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 211 Flow Low - Gas supply
empty - Valve fails
closed
Burner fails to start - Burner management system installed
- No gas in the burner system until pilot starts
- UV Cell awaits flame ignition before allowing gas into the burner
No further action
212 Flow High System has multiple regulators & overpressure protection – no further action 213 Reverse Flow Flash back arrestors fitted in the pipework – no further action 214 Pressure No issues raised (see flow above) 215 Temperature
High System operates at ambient – no further issues raised
216 Temperature Low
High pressure drop across regulator
Potential for Joule-Thompson effect leading to frozen valves
Multiple regulators limit the pressure drop – no freezing potential
No further action
217 Change in Composition/ Contamination
Gas only supplied from cylinder – no further issues
218 Loss of Containment
Leak from gas line
Minor release, ignition and fire
- Plant is located in open space - Small bore pipework only - Max gas qty – 45kg - Gas fitting used on the
system (e.g. no gaskets)
(Low incident probability)
No further action
219 Instruments and Controls
Burner management system installed to Australian Standards – no further action
220 Electrical Systems
No issues raised
221 Systems Testing No issues raised 222 Maintenance Leak tests conducted prior to use (i.e. during commissioning)
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Main Scrubber – Process Water Pump Circuit Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 223 Flow High No issues raised 224 Flow Low/No - Blocked
sprays - Pump fails
- Ineffective scrubbing
- Potential to emit particles via stack
- Redundancy in sprays - Pressure monitoring on line
(with alarms)
Consider installing a back up pump (in-line) in the event of pump failure. System is critical in preventing particulate release from the stack.
SG
225 Reverse Flow No issues raised 226 Pressure No issues raised 227 Temperature No issues raised 228 Change in
Composition/ Contamination
No issues raised (covered in the tank minutes)
229 Loss of Containment
No issues raised
230 Instruments and Controls
No issues raised
231 Electrical Systems
No issues raised
232 Systems Testing No issues raised 233 Maintenance No issues raised
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HAZOP
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Main Scrubber – Slurry Return System Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 234 Flow High - Pump failure
(wear is a major issue)
- Blockage in lines
- Potential overflow of sump (i.e. slurry not pumped out)
- Cooling water problems (no water to thickener and subsequently pub-mill)
Continue with the project to change pump
design from mono pump to centrifugal
slurry pump
SG
235 Flow Low/No Level instrument fails
Tank empties and pumps runs dry
Pressure alarm installed on the pump circuit
No further action
236 Reverse Flow No issues raised 237 Pressure Continuous speed centrifugal pump – no issues raised 238 Temperature No issues raised – maximum possible temperature 100oC 239 Change in
Composition/ Contamination
- Slurry thickness
- Acidic water
- Pump blockage - Corrosion
- Pump is designed for slurry - Stainless steel impeller used
No further action
240 Loss of Containment
No new issues raised
241 Instruments and Controls
No new issues raised
242 Electrical Systems
No new issues raised
243 Systems Testing No new issues raised 244 Maintenance No new issues raised
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Main Scrubber System - Thickener Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 245 Level High - Pump fails
- Closed valve No new issues raised – see process water tank minutes
246 Level Low Slurry return pump fails and slurry pump continues
Slurry pump runs dry – low pressure in pump
High temperature at pug-mill is alarmed (almost immediately)
No further action
247 Pressure No new issues raised 248 Temperature No new issues raised (maximum possible temperature is 100oC) 249 Change in
Composition/ Contamination
No new issues raised (pump is designed for slurry with density much higher than in the clarifier)
250 Loss of Containment
No new issues raised
251 Instruments and Controls
No new issues raised
252 Electrical Systems
No new issues raised
253 Systems Testing No new issues raised 254 Maintenance No new issues raised
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Main Scrubber System – Slurry Pump Circuit Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 255 Flow High No new issues raised 256 Flow Low/No - Pump fails
- Pipework blockage
(see process water tank minutes)
257 Reverse Flow No new issues raised 258 Pressure Blocked nozzle – no issues for the pump (require many nozzles to be blocked before issues arise) 259 Temperature No new issues raised (maximum possible temperature is 100oC 260 Change in
Composition/ Contamination
No new issues raised
261 Loss of Containment
Hose fails Spill of slurry to ground around the base of scrubber
- Area is bunded (site set up) - Area is directly visible from
plant control room
No further action
262 Instruments and Controls
No new issues raised
263 Electrical Systems
No new issues raised
264 Systems Testing No new issues raised 265 Maintenance No new issues raised
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HAZOP
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: Dosing System Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 266 Level High Manual fill –
potential to overflow tank
Batch fill performed by operator when in attendance
No issues raised
267 Level Low Tank not filled during operation (error)
Diaphragm dosing pump used – minimal damage (if any)
No further action
268 Flow High Small diaphragm pump used – very low flow rate (max flow is no issue) 269 Flow Low/No (see minute 267) 270 Pressure High Valve closed
upstream of pump
Potential to damage the pump as diaphragm pump is positive displacement
Consider removing the isolation valve downstream of the dosing pump and replace the line with a proper injection port
SG
271 Pressure Low Pump fails - No dosing and no flocculation
- Dirty water in process water tank
Time is available to respond before failure creates problems
No action required
272 Temperature No issues 273 Change in
Composition/ Contamination
Floc material does is incorrect
Difficult to pump floc material is mix is high in floc material
Procedure for mixing is placed on side of tank
Consider a written SOP for mixing the floc, including MSDS and PPE
SG
274 Loss of Containment
Material is slippery but falls in a non-traffic area (i.e. to ground)
275 Instruments and Controls
Fully manual mixing operation, with pre-set dose rate – no issues raised
276 Electrical Systems
No new issues raised
277 Systems Testing No new issues raised 278 Maintenance No new issues raised
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HAZOP
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: OVERVIEW Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 279 Materials of
Construction No new issues identified, materials of construction covered in detail during main HAZOP review
280 Physical Damage
No new physical damage areas identified
281 Utilities and Services
Main services are Power & Water, which were assessed in detail during the main HAZOP discussions
282 Commissioning Start up by experienced operators/ engineers
Loss of experience may cause problems in start up
Consider formalising relocation procedures including commissioning & decommissioning: - Proof tests - Test programme (at start up & during
operations) - Check of interlocks once established - Check emergency shut down systems - Disposal of un-used chemicals and fuels
NE
283 Start Up Plant reconfiguration at a new site
Difficult set-up may eventuate
Basic procedure developed Review the existing start-up/shut-down procedure and update to be more flexible
NE
284 Shut Down AS above 285 Noise Noise tests performed – plant is below required noise levels at boundary 286 Environmental
Impact No new issues identified with environmental impact assessment (EIS will be required for each new site)
287 Fire/Explosion Fire in the plant (gas, solids, etc.)
Fire is larger than can be managed with extinguishers
Fire brigade will be close to sites in which the plant will be located
Consider inclusion of fire management within the Emergency Response Plan (ERP) and inclusion of liaison with fire fighting services (Fire Brigades)
NE
288 Hazardous Substances
No hazardous/Dangerous Goods on site (Diesel fuel is a combustible liquid and not a DG.
289 Natural Hazards No new issues raised 290 Safety Systems Incident occurs
on the plant Incident may be directly in front of the control room, trapping the operator in the “container”
Consider installing a second egress door from the control room (containers) to enable operators to escape directly to the rear of the control room
SG
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HAZOP STUDY MINUTES Plant: Innova DFTD Section: OVERVIEW Date: 10 March 2004 No. Guideword Cause Consequence Safeguard Action Respons 291 Procedures Limited
procedures Potential problems if staff change – loss of experience
Review all procedures in the plant and identify where upgrades and new procedures are required. Consider the development of a Safety Management System (SMS) to assist in the correct management of the facility
NE
292 QA Order of equipment and incorrect material is supplied
Potential for premature system failure
Informal QA procedure used (i.e.records maintained for all equipment but not formalised
Consider establishing a QA system for inclusion in the SMS
NE
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APPENDIX B
DRAWINGS USED IN THE HAZOP
Drawing Number Drawing Description Revision No. SRP-01-P-01 Dryer & Converter P&ID - SRP01-P-02 Heat Exchanger & Scrubber P&ID - SRP-01-P-03 Drier Burner P&ID - SRP-01-P-04 Converter Burners P&ID -
Innova Soil Technology Direct Heated Fast Quenched Thermal Desorption Facility
HAZOP
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Direct Heated Fast Quenched Thermal Desorption Process Computer HAZOP Study 16 April 2004 Prepared for: INNOVA Soil Technology cnr Gavey & Frith Streets, Mayfield NSW 2304 Report by: HLA-Envirosciences Pty Limited ABN: 34 060 204 702 Level 2, 55-65 Grandview Street PO Box 726 Pymble NSW 2073 Australia Ph: +61 2 9988 4422 Fax: +61 2 9988 4441 HLA Ref: S6003402_RPTDraftRevA_13Apr04.doc
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DISTRIBUTION Direct Heated Fast Quench Thermal Desorption Process Computer HAZOP Study 16 April 2004 Copies Recipient Copies Recipient 1 (Draft) Dr Nick Ebrill
Manager Operations INNOVA Soil Technology Cnr Gavey & Frith Streets Mayfield NSW 2304
This document was prepared for the sole use of INNOVA oil Technology and the regulatory agencies that are directly involved in this project, the only intended beneficiaries of our work. No other party should rely on the information contained herein without the prior written consent of HLA-Envirosciences Pty Limited and INNOVA oil Technology. By HLA-Envirosciences Pty Limited ABN: 34 060 204 702 Level 2, 55-65 Grandview Street PO Box 726 Pymble NSW 2073 Australia ____________________________________ Steve Sylvester Principal - Risk Management
Peer Review: Date:
Rui Henriques Principal – Remediation
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CONTENTS
1 INTRODUCTION....................................................................................1
1.1 Background .....................................................................................................1
1.2 Objectives........................................................................................................1
1.3 Scope of Work .................................................................................................1
2 SUMMARY AND RECOMMENDED ACTIONS .....................................2
2.1 Summary .........................................................................................................2
2.1.1 Brief Description of the Process.......................................................2
2.2 Brief Description of the Methodology ..............................................................2
2.3 Recommended CHAZOP Actions ...................................................................3
3 BRIEF DESCRIPTION OF THE CONTROL SYSTEM...........................6
3.1 Control System Overview................................................................................6
3.2 Brief Description of System Components .......................................................6
4 METHODOLOGY.................................................................................10
4.1 CHAZOP Background ...................................................................................10
4.2 CHAZOP Study Approach.............................................................................10
4.3 Workshop Participants, Location and Timing................................................12
4.3.1 HAZOP Study.................................................................................12
5 STUDY RESULTS................................................................................13 APPENDICES A CHAZOP Minutes B Drawings Used in the CHAZOP C CHAZOP Action Sheets LIST OF TABLES 2.1 DFTD Facility – CAZOP Recommendations 4.1 Structure of the CHAZOP Minutes Recording Table 4.2 CHAZOP Guidewords Used in the Study LIST OF FIGURES 3.1 DFTD Control System Architecture Schematic 3.2 Citect Mimic Screen – Converter
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ABBREVIATIONS
Abbreviation Description CEMS [Hold]
CHAZOP ComputerHazard and Operability Study
DFTD Direct Heated Fast Quenched Thermal Desorption
DIPNR Department of Infrastructure, Planning and Natural Resources
HAZOP Hazard and Operability Study
HT High Temperature
I/O Input/Output
ID Identification
kPa kilo Pascals
LAN Local Area Network
LCD Liquid Crystal Display
mA milli Amps
PC Personal Computer
PLC Programmable Logic Controller
PMI Person machine Interface
SCADA Supervisory Control and Data Acquisition
UPS Un-interruptable Power Supply
VSD Variable Speed Drive
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1 INTRODUCTION
1.1 Background In early March 2004, HLA-Envirosciences (HLA) conducted a HAZOP of the Innova Soil Technology (Innova) Direct-heated Fast quenched Thermal Desorption (DFTD) unit. During this study it was identified that the DFTD process is controlled by a Supervisory Control and Data Acquisition (SCADA) system, incorporating a Programmable Logic Controller (PLC). HAZOP is not an efficient vehicle for assessing such studies and, hence, it was recommended that consideration be given to conducting a Computer HAZOP (CHAZOP) study of the DFTD control system. Innova commissioned HLA Envirosciences to conduct the CHAZOP and to report on the findings of the study. This document details the CHAZOP objectives, scope of work, brief description of the control system, the methodology and study results.
1.2 Objectives The objectives of the CHAZOP of the Innova DFTD Process and operation were to: • conduct a CHAZOP study of the DFTD Process and operation using, as a basis,
the HAZOP methodology published by the Department of Infrastructure, Planning and Natural Resources (DIPNR) in Hazardous Industry Planning Advisory Paper (HIPAP) No.8, “HAZOP Guidelines” [Note: DIPNR does not have a guideline specifically dedicated to CHAZOP, hence, the principles of HIPAP No.8 were used for the CHAZOP study, with focus on CHAZOP guidewords, and approach];
• provide CHAZOP minutes and action sheets on completion of the study; and
• provide a brief report on the CHAZOP study process and outcomes.
1.3 Scope of Work The scope of work for the CHAZOP study of the Innova DFTD Process and Operation will cover the control systems associated with the following system components: • Material Feed System;
• Direct Heating and Rotary Desorption Unit;
• Clean Product Discharge Hopper;
• Soil Cooler;
• Conversion Chamber;
• Compressed Air Saltation System and Sluices;
• Energy Recovery Exchangers;
• Dry Gas Quencher;
• Venturi Wet Scrubber with Wetted Fan;
• PLC and Citect Computer System; and
• CEMS.
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2 SUMMARY AND RECOMMENDED ACTIONS
2.1 Summary 2.1.1 Brief Description of the Process The Innova DFTD plant consists of a series of integrated components designed to achieve successful contaminant separation and subsequent conversion, energy recovery, fines reconstitution and product cooling. The system is controlled using a mix of automatic and manual systems. The automatic control system consists of the following main components: • Person Machine Interface (PMI) – consisting of a personal computer, keyboard, screen
and control software(Citect).
• Engineering PMI – consisting of a LapTop computer for the sole use of updating software and maintaining the control system program.
• Ethernet and Ethernet Hub – communication links between the PMI and the Programmable Logic Controller (PLC).
• PLC – the main control computer which contains and executes the software for plant control.
• Devicenet Trunk Cable and Devicenet Hub- communications link between the PLC and the various input/output devices in the system.
• Variable Speed Drives (VSDs) –self contained units, each with its own PLC and internal control system for the speed control of specific electric motors in the plant.
• I/O – racks containing I/O cards for transfer of communication between the Devicenet Trunk Cable and the control loop.
Whilst a number of plant components are automatically controlled (e.g. variable speed drives), a reasonable proportion of the plant still required manual control and input. Loading of the feed hopper at the front of the plant is an example of this. Whilst the feed to the rotary dryer and converter is automatically controlled, the feed to the hopper is controlled by the operator using a front end loader. A number of other areas within the plant also require similar operator input to start/stop pumps, conveyors, etc. The control of this equipment is managed by the operator based on control system output on the Citect screen (PMI).
2.2 Brief Description of the Methodology The methodology used for the CHAZOP is summarised below:
• A team of experienced personnel were assembled to assist with the CHAZOP assessment of the facility;
• A brief description of the proposed control system operation was given and questions asked of the designers by study participants;
• The study facilitator selected a control system component and led the team through a series of guidewords to assist in the systematic assessment of the facility;
• Computer/control hazard and operability issues, and action requirements, were recorded as study minutes, along with the person responsible for completing the required actions;
• CHAZOP minute numbers were recorded on the control system architecture schematic in
a diamond ( ◊ ) against the equipment or location for which the minute was recorded;
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• Draft study minutes were issued to the team for comment and corrections made based on the team’s response;
• A draft report was developed and issued to the team for comment; and
• A final report was completed incorporating the team’s comments.
2.3 Recommended CHAZOP Actions During the study, where a potential hazard or operability issue was identified, a CHAZOP worksheet was recorded as a minute of the workshop study. The recorded workshop results are presented in Appendix A and the study recommendations are summarised in Table 2.1. Detailed action sheets with space to record the action taken are presented in Appendix C.
TABLE 2.1 DFTD FACILITY - CHAZOP RECOMMENDATIONS
CHAZOP No.
Action Description and Recommendation
Person Machine Interface (Personal Computer in the Control Room)
2 It was identified that there is a potential for a hard drive failure on the PC used as the Person-Machine Interface (PMI) in the control room. In the current plant control set up and configuration, this would lead to plant shut down and potential emissions and damage. It was recommended that a review of the current plant control configuration be conducted to consider plant operations continuing in the event of PC failure in the control room. This would allow the operations staff to bring the plant down manually in a more controlled manner.
Action: Mark Owen
2 As a result of the hard drive failure detailed above, it was also recommended that consideration be given to the installation of a “back-up” computer (not on-lpine_ but with Citect installed so that this computer could be quickly brought on line as the operational unit if required.
Action: Nick Ebrill
2 As a result of the hard drive failure detailed above, it was also recommended that an alarm be raised in the event of PC failure.
Action: Mark Owen
6 It was identified that dust in the control room has the potential to contaminate the UPS resulting in plant shut down due to UPS failure. It was recommended that a procedure for regular cleaning of UPS units be considered including addition to the plant weekly start-up and maintenance checklists.
Action: Nick Ebrill
11 It was identified that MS windows software is generally accessible from the PMI keyboard, which may result in operators using windows for other purposesd than plant control, whilst the Citect system was operational. This may lead to Citect system and windows interface “corruption” and plant shut down. It was therefore recommended that a password be installed on the windows operating system to minimise access to this area of the PC.
Action: Nick Ebrill and Mark Owen.
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TABLE 2.1 DFTD FACILITY - CHAZOP RECOMMENDATIONS
CHAZOP No.
Action Description and Recommendation
Ethernet Link between PC and PLC
14 It was identified that the Ethernet cable or hub could be damaged due to maintenance work in the control room/switchroom. This would result in comms loss and plant shut down (i.e. the comms loss is seen as a PC failure (as in Minute 2 above). To minimise the impact for plant shut down it is recommended that the actions recommended in Minute 2 be implemented and that a trouble shooting guide be developed to indicate the appearance of a PC screen during certain failure modes (e.g. ### is shown in all fields when comms is lost).
Action: Nick Ebrill
PLC
25 In the event of PLC failure, the plant will immediately commence shut down as all control functions are lost. It was identified that this would result in emissions from the plant and potential plant damage. It was therefore recommended that a procedure be considered for failure response and how to bring the plant dwown safely after a major control system failure.
Action: Nick Ebrill
34 It was identified that PLC/Citect programming and other systems maintenance would be required from time to time. This would mean changes to the system, both hardware and software. Incorrect changes or changes not correctly reviewed may lead to hazard introduction. It was therefore recommended that a modification control procedure be developed for the plant which includes software and control system modifications.
Action: Nick Ebrill
Devicenet Trunk Cable
41 It was identified that the Devicenet Trunk Cable may be vulnerable to physical damage and/or impact in the area outside the switchroom. Whilst the cable is installed in cable trays in most areas, there are some vulnerable locations near operating equipment. It was therefore recommended that consideration be given to the guarding of the Devicenet Trunk Cable in specific location around the plant. This will require a review of the areas around the plant and identification of vulnerable locations.
Action: Scott Goldrick
46 It was identified that Devicenet Trunk Cable connectors throughout the plant have the potential to become loose, resulting in loss of communications either to local equipment or between the PLC and the plant. This would manifest itself as a cable failure with the potential to shut down the plant. It was recommended that a procedure be developed for the regular checking of connectors (i.e. during the weekly plant start up or maintenance checks.
Action: Nick Ebrill
Drives
51 It was identified that during transport from site to site there is a potential for the Variable Speed Drives (VSDs) to become damaged, resulting in failure of the drive to operate when required. It was recommended that a pre-transport procedure (and checklist) be developed for preparing the plant for transport, including VSD preparation for transport.
Action: Nick Ebrill
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TABLE 2.1 DFTD FACILITY - CHAZOP RECOMMENDATIONS
CHAZOP No.
Action Description and Recommendation
53 It was identified that dust or water (condensation) may have an impact on VSD operation and start. This could lead to premature VSD failure. It was recommended that a pre-start checklist be developed for all VSDs. This could be included in the maintenance checklist for pre-start of the plant.
Action: Nick Ebrill
54 It was identified that in the event of mains power supply failure, emergency power would be required from the emergency generator. However, the emergency generator does not have sufficient power to drive all equipment on the plant. It was recommended that a list of critical equipment be developed and used as the emergency power list. Further, an order of priority would be assigned within the critical equipment list.
Action: Nick Ebrill
Weigher Control Loop
62 It was identified that in the event of weigher instrument failure, the plant would could enter a high feed rate operation. Whilst the incident would be alarmed at low hopper level it was recommended that a procedure be developed to cater for manual operation until repair of the automatic system can be completed.
Action: Nick Ebrill
Combustion Air Pressure Control Loop
72 It was identified that the combustion air pressure measuring instrument may drift, resulting in a low reading when the reading is actually higher. Whilst a pre-start check and instrument zeroing is performed, it was recommended that regular calibration of this instrument be performed (say once every 6 months) due to the criticality of the measurement in overall plant control. This would also require a maintenance and calibration procedure.
Action: Nick Ebrill
Converter Oxygen Instrument Control Loop
90 It was identified that in the event the parameters in the oxygen analyser software required review and change, the existing parameters were not recorded externally to the unit. Hence, in the event of loss of the parameters due to any reason, it would not be easy to re-load the existing data. Hence, it was recommended that the parameters for the oxygen analyser be included in a chart for analyser input. This should form part of a procedure for re-loading of parameter values for all instruments on the plant.
Action: Nick Ebrill
93 It was identified that the oxygen analyser may be left fitted to the plant after operations cease. This will lead to corrosion of the element and failure at the next start-up. It was therefore recommended that a procedure and checklist be developed for instrument removal, clean and storage after shut-down is complete.
Action: Nick Ebrill
Converter Off-Gas Temperature Loop
154 It was identified that the temperature instrument (thermocouple), used to measure the converter off-gas temperature may drift, resulting in the burners backing off. Whilst this was recognised to be a minor impact, it was recommended that consideration be given to the practicality of installing a low temperature alarm on this control loop – this may be required as part of EPA licensing.
Action: Nick Ebrill
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3 BRIEF DESCRIPTION OF THE CONTROL SYSTEM
3.1 Control System Overview Figure 3.1 shows the control system schematic for the DFTD process. The control philosophy behind the control system on the DFTD plant is a mixture of automatic and manual control operations. The plant is operated basically by a programmable logic controller (PLC), which is monitored by a Supervisory Control and Data Acquisition (SCADA) system. The SCADA system is used to input set points and parameters within set operational ranges. The software is “loaded” to the PLC via an engineering terminal (LapTop) which is only connected during the download process. Changes to the PLC program may only be performed using the engineering computer. The communications links between the various components in the system is conducted via an Ethernet and Devicenet Trunk Cable system. Various input/output (I/O) cards are located within the plant itself (i.e. in the field). These cards direct the communications to the various field components within the system.
3.2 Brief Description of System Components The control system installed on the DFTD plant consists of the following components: • Person Machine Interface (PMI) – The PMI is used as a communication device between
the operations staff and the PLC. The control software is developed by Citect, a specialist control software organization, which is basically the industry standard for this type of operation. The software produces “mimic” screens, on the PMI screen, showing the specific plant section layout and the various operating parameters and real time values on screen. A copy of an example Citect “mimic” screen is shown at Figure 3.2. Operators can access the plant operation set points to change as required, however, set point ranges may only be changed within the software using the engineering PMI. The PMI is used to start the plant, which is performed by a single input to the PLC from the PMI. The plant software starts and ramps components as required. Set points are then established and controlled by the operator as required. The PMI is located in the plant control room.
• Engineering PMI – The engineering PMI is not normally connected to the system and is used purely for the maintenance and update of system software. The PLC code is written in ladder logic, the normal programming code for PLC units. Once written the code is compiled and downloaded to the PLC via the engineering terminal. The code is not accessible for alteration or change via the control PMI. The Innova instruments and controls engineer is the only person with access to the engineering PMI. The engineering PMI is normally connected to the system in the control room.
• Ethernet and Ethernet Hub – This is a simple cable connection and hub unit between the PMI and PLC. The cables and hub are located between the PMI in the main control room and the PLC in adjacent switchroom, where the main control systems (hardware) is located.
• PLC – The PLC is located in the switchroom, adjacent to the main control room. This unit is located on a “rack” alongside other I/O for the digital and analogue communications. The PLC selected for this application is an Allen Bradley SLC5/05. As detailed above, the PLC code’ s ladder logic, which is written and compiled prior to installation in the PLC. The PLC monitors critical variables and controls the plant based on set points established by the operator. Critical variables are recorded and alarmed when exceeded. Alarms are raised both audibly (siren) and visually on the Citect screen (PMI).
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• Devicenet Trunk Cable and Devicenet Hub- like the Ethernet, the Devicenet Trunk Cable is a communication connection between the PLC and the various I/O in the field. The cable starts in the switchroom (adjacent to the control room) and is fed to the various field I/O devices on a cable tray within the plant. Each set of I/O devices (see Figure 3.12) is located in a “rack”, which contains the I/O cards. Each card contains the specific “switching” equipment between the communications cable and the control loop (i.e. cable to the specific control device – pressure transducer, flow switch, etc.).
Key components within the DFTD system are the variable speed drives (VFDs). These units provide the basic soil, gas and liquid flow control around the system. The drive communications are connected to the Devicenet Trunk Cable via an auxiliary cable to an 8 port Devicenet Hub. The hub directs the various communication commands to and from the specific VSD as required.
• Variable Speed Drives (VSDs) – The VSDs are self contained units, each with its own PLC and internal control system. The speed set point is delivered to the drive unit via the Devicenet Trunk Cable. The speed command is then processed by the VSD PLC, which provides control of the varying current supply for speed control. Each VSD control unit is fitted with its own liquid crystal display (LCD) screen and control panel, to enable an operator to manually control the VSDs as required.
• I/O – As indicated above, each I/O is contained in a “rack” within the plant switchroom or in the field. “Racks” contain I/O cards which are fitted with the various control and communication components to direct the communications commands to the specific equipment attached to that “rack”.
Whilst a number of plant components are automatically controlled (e.g. variable speed drives), a reasonable proportion of the plant still required manual control and input. Loading of the feed hopper at the front of the plant is an example of this. Whilst the feed to the rotary dryer and converter is automatically controlled, the feed to the hopper is controlled by the operator using a front end loader. A number of other areas within the plant also require similar operator input to start/stop pumps, conveyors, etc. The control of this equipment is managed by the operator based on control system output on the Citect screen (PMI).
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FIGURE 3.1 DFTD CONTROL SYSTEM ARCHITECTURE SCHEMATIC
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FIGURE 3.2
CITECT MIMIC SCREEN - CONVERTER
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4 METHODOLOGY
4.1 CHAZOP Background The HAZOP study methodology was originally developed in the mid-1960s and was successfully applied to plants with limited automated control systems. As time progressed, control systems in plants became more sophisticated, using sophisticated automated controls to monitor and operate plants with limited operator intervention. In more recent time, computer and PLC controls have been incorporated into plant control system design, bringing their own level of complexity to the control philosophy.
Whilst HAZOP had been successfully applied to identify hazard and operability problems with relatively simple control systems, it became evident, with time, that the HAZOP process was not successful in identifying problems with the interface between plants and complex control systems. In particular the general HAZOP process was not very successful in identifying problems with the automated control operator interface. As automated control systems were becoming more prevalent in industry, it was recognised that a new approach was required to identify potential problems.
In order to provide a more applicable approach to the study of complex control systems, the Computer HAZOP study was developed (CHAZOP). The HAZOP study previously looked at the various deviations from normal plant operation and how the plant responded in controlling the deviation (either directly or via operator notification and intervention). Guidewords were used to aid in the study process and study minutes were recorded. The CHAZOP study uses a different approach, whilst still using the systematic analysis, guidewords and recording techniques. The CHAZOP looks at the overall computer control system and each critical instrument loop and control component in turn and identifies the effects on plant operation of deviations from normal control. A dedicated set of CHAZOP guidewords are used for this process, which are distinct from the normal guidewords used in HAZOP (eg. level, pressure, flow etc.).
The CHAZOP can be conducted at various levels of the control system under study. A high level approach can be used to determine the effectiveness of interfaces between various components and elements of the system (i.e. distributed control system and LAN for electronic control systems). Alternatively, the study can be performed at a detailed level taking each loop in turn and assessing the influences of external and internal controls and signals on the loop (i.e. for detailed design systems).
A mixture of the two processes was used for this study. A high level approach was used to identify areas where control problems may arise in the computer/control interface with the facilities and a detailed analysis was conducted for each critical control loop on the plant.
4.2 CHAZOP Study Approach The study approach was particularly suited to the DFTD Process and Operation. The study assessed the process using a series of guidewords to assist the study facilitator in structuring the study.
The basic approach was as follows:
• A drawing of the control system configuration was placed in front of the study team and a team member explained the proposed design and operation of the controls. Questions were asked at this point for clarification.
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• The facilitator then selected a section of the controls for review (e.g. machine interface, network, hub, PLC, etc.).
• The facilitator then selected a guideword (e.g. hardware failure, software failure, critical device error, communications failure, etc.) and questioned the team as to the potential for a deviation from normal operating conditions associated with the guideword. A list of guidewords used in the study is shown at Table 4.2
• Where a deviation from normal operating conditions was identified, a CHAZOP minute was recorded noting the minute number, guideword used, cause of the deviation, consequence of the deviation, proposed safeguards and required action to control the identified deviation. To ensure the minute action is completed and followed up, the minute action was allocated to a member of the team.
• This process was continued for all operational sequences and system components on the drawing until the drawing was completed.
• Once all drawings were completed, a CHAZOP overview is normally completed. However, as the HAZOP study was performed recently, and as an Overview study was completed for this assessment, the CHAZOP overview was not conducted.
Each CHAZOP minute point was recorded on a separate line on a copying white board using the format shown in Table 4.1. Each event was given a unique identifying number for future reference.
TABLE 4.1 STRUCTURE OF THE CHAZOP MINUTES RECORDING TABLE
No. Guideword Cause Consequence Safeguard Action Responsible Person`
On completion of the study a draft report was developed incorporating the following: - Introduction;
- Objectives;
- Scope of Work;
- Brief Description of the Process;
- Methodology;
- Study Results and Actions (included as an Appendix);
- Control system layout used in the study (drawing included as an appendix). The draft report was issued to Innova for review and comment. Comments on the draft report were then incorporated and a final report issued.
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TABLE 4.2
CHAZOP GUIDEWORDS USED IN THE STUDY
Logic Error (Code failure)
Device Error (instrument/cable failure)
Bad Measurement
− Loss of signal (abnormal)
− Full scale signal (abnormal)
− Signal Drift (incorrect signal)
− Intermittent signal
Frequent/past problems
Failure detection (communications loss)
Contamination
− switching surges
− static
− frequency variation
− signal corruption
Contamination Physical
- Oil, water, dust
Abnormal Operations
− start up
− shutdown
− emergency shutdown
System Maintenance and Code Security
4.3 Workshop Participants, Location and Timing 4.3.1 CHAZOP Study The workshop was conducted at the offices of Innova, cnr of Gavey and Frith Streets, Mayfield West, NSW, on Tuesday 6 April 2004. Two study sessions were conducted each of about 3.5 hours duration.
The workshop was attended by the following personnel:
Name Organisation Position
Nick Ebrill (Chemical Eng.) Innova Soil Technology Manager Operations
Scott Goldrick Innova Soil Technology Plant Supervisor
Mark Owen Combustion Instrumentation Electrical/Instruments Engineer
Steve Sylvester HLA-Envirosciences Study Facilitator
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5 STUDY RESULTS
The nature of the CHAZOP study results in the discussion of many points that relate to computer/control hazard and operability issues associated with the control systems operation of the plant under analysis. The recording of every discussion item, at length, would result in an un-necessarily long workshop, leading to frustration among the CHAZOP participants whilst time was wasted recording minor issues requiring no action.
To ensure the most effective recording of results was achieved, for the DFTD Facility CHAZOP, the following recording format was adopted:
• Where a discussion issue was identified to result in no computer/control hazard or operability issue, an entry into the guideword row was made stating “No issue”, this entry illustrates that the point was discussed and no issues were identified with the potential deviation or that the deviation is not possible (i.e. code security – access to code not possible due to the requirement for the engineering PMI, which is not connected to the plant until required and is only available to the instruments/control engineer); and
• Where a discussion point was identified to result in a potential computer/control hazard or operability issue, a full minute point was recorded, identifying deviation cause, consequence, proposed safeguards and action required to prevent, detect, protect and/or mitigate the computer/control hazard-operability consequences.
The main aim of recording results in this manner is to demonstrate that all deviations were identified and discussed, and that appropriate safeguards were developed for the computer/control hazard and operability issues identified.
The minutes recorded during workshop session are presented in Appendix A.
There were 164 minute points discussed during the CHAZOP study, of these there were 17 points raised for action. A summary of the actions recorded, as a result of the CHAZOP, are presented in Section 2.2. The location of recorded minute points was placed on the system architecture schematic in a diamond ( ◊ ) to indicate the equipment for which the minute was recorded and to provide an easy future reference when actioning minutes.
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APPENDIX A
CHAZOP MINUTES
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CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Personal Computers (Man Machine Interface) Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 1 Communications
Failure No issues raised
2 Critical Device Error
Hard Drive failure
Plant shuts down: - emissions - damaged plant
- Review the current method of plant shut down when critical device failure occurs (e.g. failure that causes shut down). Consider continuing the plant operations, where possible and then instigate a procedure to ramp the plant down manually
- Consider a “back-up” (not on line) PC with Citect installed
- Consider raising an alarm when critical device error occurs
MO NE MO
3 Device Failure No issues raised (covered in 2 above) 4 Contamination
Electrical Power sources Potential to shut down
the plant UPS No further action
5 Contamination Physical
Dust in the UPS UPS fails and plant shuts down
Consider a procedure for blowing dust out of UPS as a regular process (Note: add to plant start up checklist and checklist for weekly maintenance)
NE (SS)
6 High Temperature
Hot control room
Temperature is too high for the electrical control equipment & system shuts down
Control room is air conditioned
No further action
7 Software No issues (Citect System installed) 8 Service Failure UPS fails Plant shuts down as in
the current configuration the UPS supplies both the PC and PLC
UPS Fail Alarm Consider installing an additional UPS to provide separate power supplies for the PC and PLC reduces comment element failure mode)
NE
9 Abnormal Operations
No issues raised
10 Maintenance No issues raised
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CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Personal Computers (Man Machine Interface) Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 11 Code Security Access
windows whilst system is operating
Windows programs may corrupt Citect system
Consider installing a security password on access to windows
NE MO
12 Code Security Virus introduced by external disk use (i.e. 3.5” floppy disk)
PC shuts down and currently brings the plant down
Minute 2 recommendations negates the impact of the virus by permitting continued operation
No further action
CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Ethernet Link between the PC and PLC Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 13 Communications
Failure Corrupt data Potential control
malfunction Parity bit used on all data steams
No further action
14 Critical Device Error
Cable/Ethernet hub is physically damaged
Comms lost – current configuration results in plant shut down
- Recommend implementation of actions in Minute Point 2
- Need to include a trouble shooting procedure that indicates what screen appearance results from certain failure/ error modes (e.g. # is shown in all fields when comms is lost)
NE (SS)
15 Device Failure No issues raised 16 Contamination
Electrical Welding close to the comms links
Potential for electrical contamination resulting in data corruption
Cable is shielded No further action
17 Contamination Physical
No issues raised (the cable is installed in the control room)
18 High Temperature
No issues raised
19 Software Links and hub do not have any software – N/A 20 Service Failure UPS – see Minute Point 8 21 Abnormal
Operations No issues raised
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CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Ethernet Link between the PC and PLC Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 22 Maintenance No issues raised 23 Code Security No issues raised
CHAZOP STUDY MINUTES Plant: Innova DFTD Section: PLC Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 24 Communications
Failure Internal I/O comms fails
Loss of individual I/O # shown on Citect screen for specific failure component
- PLC can be interrogated using the engineering terminal
- Fail safe logic
No further action
25 Critical Device Error
PLC internal component failure
All outputs turn off – PLC shuts down and plant shuts down
- PLC fail alarm - Manual override
available to bring plant down to a safe state
Consider a procedure for PLC failure response (i.e. how to bring the plant down safely)
NE (SS)
26 Device Failure Software overload (maths overload error)
PLC locks up - Software is compiled limiting device error
- Software is tested prior to use
- Internal watchdogs installed
(as per Minute 25)
27 Contamination Electrical
No issues raised
28 Contamination Physical
No issued raised
29 High Temperature
Air conditioning unit fails
Temperature rise in the control room – PLC shuts down (eventually)
Temperature sensor in the PLC cabinet - alarm
No further action
30 Software No issues raised 31 Service Failure See minute No.8 32 Abnormal
Operations No issues raised
33 Maintenance PLC Fails Cannot repair PLC quickly
PLC available at suppliers warehouse
No further action
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CHAZOP STUDY MINUTES Plant: Innova DFTD Section: PLC Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 34 Maintenance Program
maintenance Changes made to the program impact the operations adversely
Consider the development of a modification control procedure – this needs to include a software modification component
NE (SS)
35 Code Security Cannot access PLC code unless engineering computer is used (requires a password) – no further action.
CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Trunk Cable Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 36 Communications
Failure Devicenet Cable cut
Same as PLC failure - Devicenet …[Hold]… protocol
- Parity checking - Can operate equipment
manually (local)
(as per Minute No.2)
37 Communications Failure
Individual cable cut from devicenet cable to equipment
Equipment shut down – remaining equipment continues to operate
- Can start equipment manually
- Equipment failure alarms
Recommend a procedure as per Minute No.2 NE (SS)
38 Critical Device Error
No issues raised
39 Device Failure No issues raised 40 Contamination
Electrical Noise Potential to corrupt
communications and shut down system
- Noise resistant system design
- System installed to manufacturers specification limiting noise impact
No further action
41 Contamination Physical
Impact on cable in plant areas
Cable is cut and plant shuts down
Cable is hard rubber coated and robust
Consider guarding the cable in specific locations around the plant – need to review the cable run and select areas where guarding and additional protection is required
SG
42 High Temperature
No issues raised
43 Software No issues raised 44 Service Failure As per Minute No.8
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CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Trunk Cable Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 45 Abnormal
Operations No issues raised
46 Maintenance Loose connectors
Cable “cut” by connector coming apart – plant shuts down
Include a connector check in the weekly checklist
NE (SS)
47 Code Security No software – N/A
CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Drives Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 48 Communications
Failure No new issues raised
49 Critical Device Error
Input revs not reached on the motor (i.e. overload current)
Full output not reached
- LCD on drive panel indicates error
- Spare drive (11kW and under) held on plant
Covered in the HAZOP study – no new action
50 Device Failure Drive component fails
The specific motor fails, critical drives are:
- ID Fan - Dryer Rotation
Covered in the HAZOP study – no new action
51 Device Failure Transport of equipment
Drives damaged during transport – plant wont operate when required
Consider pre-transport procedure for equipment protection during transport
NE (SS)
52 Contamination Electrical
No issues raised
53 Contamination Physical
Dust/water Drives overheat and fail
Need to include check of all VSDs in the maintenance checklist for pre-start
NE (SS)
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CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Drives Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 54 High
Temperature Air conditioning fails
Temperature rise in the switchroom
- Alarm on HT - Other means of
reducing temperature (e.g. fans, open doors, etc.)
Include procedure for managing A/C failure & temperature rise in the control room
NE (SS)
55 Software No issues raised 56 Service Failure Power supply
fails Moors shut down – ID fan shits down leading to emissions
Back up generator for critical drives
Need to develop a procedure for emergency power use (i.e. a list of critical equipment that is on the emergency power list)
NE (SS)
57 Abnormal Operations
Nom issues raised
58 Maintenance No issues raised 59 Code Security Code can only be accessed via the engineering computer
CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Weigher Control Loop Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 60 Communications
Failure No issues raised
61 Critical Device Error
Drift on the instrument
High or low feed - Regular calibration - Cleaning around the
load cell
Covered in the HAZOP – no further action
62 Device Failure Instrument fails High feed rate - Alarm (low hopper level)
- Manual feed can be operated
Consider developing a procedure for manual operation
NE (SS)
63 Contamination Electrical
No issues raised
64 Contamination Physical
No issues raised
65 High Temperature
No issues raised
66 Software No issues raised 67 Service Failure No issues raised
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CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Weigher Control Loop Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 68 Abnormal
Operations No issues raised
69 Maintenance No issues raised 70 Code Security No issues raised
CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Combustion Air Pressure Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 71 Communications
Failure No issues raised
72 Critical Device Error
Drift 3kPa reading when 2kPa is actual pressure
Pre-start checklist used to zero instruments
Recommend a regular calibration of the instrument – say once per 6 months – maintenance procedure required
NE (SS)
73 Device Failure Cell fails or loop fails
Zero amps – alarm and ramp up fan
Alarm No action
74 Contamination Electrical
No issues raised
75 Contamination Physical
No issues raised
76 High Temperature
No issues raised
77 Software No issues raised 78 Service Failure No issues raised 79 Abnormal
Operations No issues raised
80 Maintenance No issues raised 81 Code Security No issues raised
CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Converter Oxygen Instrument Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 82 Communications
Failure No issues raised
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CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Converter Oxygen Instrument Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 83 Critical Device
Error Polluted cell Wrong oxygen reading - Self check & calibration
- Alarm on incorrect check
No further action
84 Critical Device Error
Lack of calibration air – air hose fails (crimped, split, etc.)
Wrong oxygen reading Alarm on incorrect check (i.e. air loss)
No action
85 Device Failure Heater fails (i.e. pre-start heater)
Oxygen reading is suspect
Alarm on heater failure No action
86 Device Failure Analyser “box” fails
No oxygen reading Alarm on signal loss No action
87 Contamination Electrical
No issues raised
88 Contamination Physical
No issues raised
89 High Temperature
No issues raised
90 Software Need to review and change the parameters in the analyser
Existing parameters not recorded externally to the analyser
Recommend that parameters be included in a chart for analyser inputs (forms part of a procedure)
NE (SS)
91 Service Failure No issues raised 92 Abnormal
Operations No issues raised
93 Maintenance Instrument is left installed on the converter after shut down
Element corrodes and fails at next start up
Instrument is normally removed after operation
Recommend that the requirement for removal of the oxygen instrument be included in the shut down checklist (e.g. removal procedure)
NE (SS)
94 Code Security No issues raised – Cannot access code
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CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Dryer Off Gas Temperature Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 95 Communications
Failure No issues raised
96 Critical Device Error
Drift Minor temperature drifts
No issues
97 Device Failure Instrument fails Zero mA output – reverts to burner minimum output
- Fail safe instrument and loop
- Failure alarm
No further action
98 Contamination Electrical
No issues raised
99 Contamination Physical
No issues raised
100 High Temperature
No issues raised
101 Software No issues raised 102 Service Failure No issues raised 103 Abnormal
Operations No issues raised
104 Maintenance No issues raised 105 Code Security No issues raised
CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Weigher Control Loop Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 106 Communications
Failure No issues raised
107 Critical Device Error
Drift towards zero pressure
Fan speed up – causes inefficient operations
No hazard issues
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CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Weigher Control Loop Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 108 Critical Device
Error Drift towards higher vacuum
Fan slows and actual pressure approaches zero and potential positive pressure resulting in emissions
- Pressure monitoring is possible from other instruments
- Operators in the control room monitoring all parameters
- Can control ID fan manually
- Hand held pressure instrument available
No further action
109 Device Failure Instrument fails to zero mA
Fan runs at 100% - fan normally operates at close to 100% so little change in operation is detected
No further action
110 Contamination Electrical
No issues raised
111 Contamination Physical
No issues raised
112 High Temperature
No issues raised
113 Software No issues raised 114 Service Failure No issues raised 115 Abnormal
Operations No issues raised
116 Maintenance No issues raised 117 Code Security No issues raised
CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Main Scrubber Sump Level Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 118 Communications
Failure No issues raised
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CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Main Scrubber Sump Level Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 119 Critical Device
Error Drift High pressure drift
when actual low pressure is in the line – pump continues to run & pumps sum dry
- Pump is “run dry” protected by design
- Process water tank may overflow – operator will see overflow
No further action
120 Critical Device Error
Drift or pump failure
Low pressure drift – high level and overflow of sump (pump stops)
Operator sees overflow from scrubber sump and responds accordingly (note area is bunded)
No further action
121 Device Failure No new issues 122 Contamination
Electrical No issues raised
123 Contamination Physical
No issues raised
124 High Temperature
No issues raised
125 Software No issues raised 126 Service Failure No issues raised 127 Abnormal
Operations No issues raised
128 Maintenance No issues raised 129 Code Security No issues raised
CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Scrubber Inlet Temperature Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 130 Communications
Failure No issues raised
131 Critical Device Error
Drift Low Temperature is higher than actual indicated – no equipment damage at minor drift [Inefficient operation only]
- Manual temperature checks can be made
No action recommended
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CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Scrubber Inlet Temperature Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 132 Device Failure Instrument fails
to zero mA No plant impact - Screen indicates “#” on
temperature value for scrubber inlet
No further action
133 Contamination Electrical
No issues raised
134 Contamination Physical
No issues raised
135 High Temperature
No issues raised
136 Software No issues raised 137 Service Failure No issues raised 138 Abnormal
Operations No issues raised
139 Maintenance No issues raised 140 Code Security No issues raised
CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Quench Heat Outlet Temperature – 3 Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 141 Communications
Failure Loss of communication link to PLC
High temperature indicated – all fin fans start
SCADA shows all fans started
No further action
142 Critical Device Error
Temperature drift - high
Fin fans start early Other temperatures give indication of Temp-3 validity
No further action
143 Critical Device Error
Temperature drift - low
Fin fans shut down early
Alarm from high temp. on other thermo couples
No further action
144 Device Failure Internal thermo couple component failure
Temperature high indicated – all fans start
- Screen indicates “#” on temperature value for Temp-3
No further action
145 Contamination Electrical
No issues raised
146 Contamination Physical
No issues raised
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
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CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Quench Heat Outlet Temperature – 3 Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 147 High
Temperature No issues raised
148 Software No issues raised 149 Service Failure No issues raised 150 Abnormal
Operations No issues raised
151 Maintenance No issues raised 152 Code Security No issues raised
CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Coverter Off Gas Temperature Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 153 Communications
Failure Loss of link High temperature
indicated – burners go to low fire
- Alarm - Can shut down system
(sufficient time available before impact)
No further action
154 Critical Device Error
Drift to higher temperature
Backs the burners off – minor impact (if any)
- Other indicating temperatures
- Redundant thermo-couples indicating same temp.
Consider practicality of low temperature alarm in this location
NE
155 Critical Device Error
Drift to lower temperature
Burners ramp up- higher temperature in the converter – potential damage
- Redundant thermo couples – alarms
No further action
156 Device Failure Fails to full scale
Burner backs off See Minute No.153
157 Contamination Electrical
No issues raised
158 Contamination Physical
No issues raised
159 High Temperature
No issues raised
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CHAZOP STUDY MINUTES Plant: Innova DFTD Section: Coverter Off Gas Temperature Date: 6 April 2004 No. Guideword Cause Consequence Safeguard Action Respons 160 Software No issues raised 161 Service Failure No issues raised 162 Abnormal
Operations No issues raised
163 Maintenance No issues raised 164 Code Security No issues raised
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
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APPENDIX A
DRAWINGS USED IN THE CHAZOP
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
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Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
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APPENDIX C
CHAZOP ACTION SHEETS
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
S6003402_RPTDraftRevA_13Apr04(NE review).docS6003402_RPTDraftRevA_13Apr04.doc 32
CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
2
PMI:
It was identified that there is a potential for a hard drive failure on the PC used as the Person-Machine Interface (PMI) in the control room. In the current plant control set up and configuration, this would lead to plant shut down and potential emissions and damage. It was recommended that a review of the current plant control configuration be conducted to consider plant operations continuing in the event of PC failure in the control room. This would allow the operations staff to bring the plant down manually in a more controlled manner.
Mark Owen
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
S6003402_RPTDraftRevA_13Apr04(NE review).docS6003402_RPTDraftRevA_13Apr04.doc 33
CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
2
PMI: As a result of the hard drive failure detailed above, it was also recommended that consideration be given to the installation of a “back-up” computer (not on-pine_ but with Citect installed so that this computer could be quickly brought on line as the operational unit if required.
Nick Ebrill
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
S6003402_RPTDraftRevA_13Apr04(NE review).docS6003402_RPTDraftRevA_13Apr04.doc 34
CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
2
PMI: As a result of the hard drive failure detailed above, it was also recommended that an alarm be raised in the event of PC failure.
Mark Owen
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
S6003402_RPTDraftRevA_13Apr04(NE review).docS6003402_RPTDraftRevA_13Apr04.doc 35
CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
6
PMI: It was identified that dust in the control room has the potential to contaminate the UPS resulting in plant shut down due to UPS failure. It was recommended that a procedure for regular cleaning of UPS units be considered including addition to the plant weekly start-up and maintenance checklists.
Nick Ebrill
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
S6003402_RPTDraftRevA_13Apr04(NE review).docS6003402_RPTDraftRevA_13Apr04.doc 36
CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
11
PMI: It was identified that windows is generally accessible from the PMI keyboard, which may result in operators using windows for other purposed than plant control, whilst the Citect system was operational. This may lead to Citect system and windows interface “corruption” and plant shut down. It was therefore recommended that a password be installed on the windows operating system o minimise access to this area of the PC.
Nick Ebrill & Mark Owen
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
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CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
14
Ethernet Link Between PC & PLC: It was identified that the Ethernet cable or hub could be damaged due to maintenance work in the control room/switchroom. This would result in comms loss and plant shut down (i.e. the comms loss is seen as a PC failure (as in Minute 2 above). To minimise the impact for plant shut down it is recommended that the actions recommended in Minute 2 be implemented and that a trouble shooting guide be developed to indicate the appearance of a PC screen during certain failure modes (e.g. ### is shown in all fields when comms is lost).
Nick Ebrill
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
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CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
25
PLC: In the event of PLC failure, the plant will immediately commence shut down as all control functions are lost. It was identified that this would result in emissions from the plant and potential plant damage. It was therefore recommended that a procedure be considered for failure response and how to bring the plant down safely after a major control system failure.
Nick Ebrill
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
S6003402_RPTDraftRevA_13Apr04(NE review).docS6003402_RPTDraftRevA_13Apr04.doc 39
CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
34
PLC: It was identified that PLC/Citect programming and other systems maintenance would be required from time to time. This would mean changes to the system, both hardware and software. Incorrect changes or changes not correctly reviewed may lead to hazard introduction. It was therefore recommended that a modification control procedure be developed for the plant which includes software and control system modifications.
Nick Ebrill
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
S6003402_RPTDraftRevA_13Apr04(NE review).docS6003402_RPTDraftRevA_13Apr04.doc 40
CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
41
Devicenet Trunk Cable: It was identified that the Devicenet Trunk Cable may be vulnerable to physical damage and/or impact in the area outside the switchroom. Whilst the cable is installed in cable trays in most areas, there are some vulnerable locations near operating equipment. It was therefore recommended that consideration be given to the guarding of the Devicenet Trunk Cable in specific location around the plant. This will require a review of the areas around the plant and identification of vulnerable locations.
Scott Goldrick
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
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CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
46
Devicenet Trunk cable: It was identified that Devicenet Trunk Cable connectors throughout the plant have the potential to become loose, resulting in loss of communications either to local equipment or between the PLC and the plant. This would manifest itself as a cable failure with the potential to shut down the plant. It was recommended that a procedure be developed for the regular checking of connectors (i.e. during the weekly plant start up or maintenance checks.
Nick Ebrill
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
S6003402_RPTDraftRevA_13Apr04(NE review).docS6003402_RPTDraftRevA_13Apr04.doc 42
CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
51
Drives: It was identified that during transport from site to site there is a potential for the Variable Speed Drives (VSDs) to become damaged, resulting in failure of the drive to operate when required. It was recommended that a pre-transport procedure (and checklist) be developed for preparing the plant for transport, including VSD preparation for transport.
Nick Ebrill
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
S6003402_RPTDraftRevA_13Apr04(NE review).docS6003402_RPTDraftRevA_13Apr04.doc 43
CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
53
Drives: It was identified that dust or water (condensation) may have an impact on VSD operation and start. This could lead to premature VSD failure. It was recommended that a pre-start checklist be developed for all VSDs. This could be included in the maintenance checklist for pre-start of the plant.
Nick Ebrill
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
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CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
54
Drives: It was identified that in the event of power supply failure, emergency power would be required from the emergency generator. However, the emergency generator does not have sufficient power to drive all equipment on the plant. It was recommended that a list of critical equipment be developed and used as the emergency power list.
Nick Ebrill
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
S6003402_RPTDraftRevA_13Apr04(NE review).docS6003402_RPTDraftRevA_13Apr04.doc 45
CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
62
Drives: It was identified that in the event of weigher instrument failure, the plant would enter a high feed rate operation. Whilst the incident would be alarmed at low hopper level it was recommended that a procedure be developed to cater for manual operation until repair of the automatic system can be completed.
Nick Ebrill
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
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CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
72
Combustion Air Pressure Control Loop: It was identified that the combustion air pressure measuring instrument may drift, resulting in a low reading when the reading is actually higher. Whilst a pre-start check and instrument zeroing is performed, it was recommended that regular calibration of this instrument be performed (say once every 6 months) due to the criticality of the measurement in overall pant control. This would also require a maintenance and calibration procedure.
Nick Ebrill
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
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CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
90
Converter Oxygen Instrument Control Loop: It was identified that in the event the parameters in the oxygen analyser software required review and change, the existing parameters were not recorded externally to the unit. Hence, in the event of loss of the parameters due to any reason, it would not be easy to re-load the existing data. Hence, it was recommended that the parameters for the oxygen analyser be included in a chart for analyser input. This should form part of a procedure for re-loading of parameter values.
Nick Ebrill
Direct Heated Fast Quench Thermal Desorption ProcessComputer HAZOP Study
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CHAZOP ACTION SHEET
Min. No.
Action Recommended Person Responsible
Action Taken Date Actioned
93
Converter Oxygen Instrument Control Loop: It was identified that the oxygen analyser may be left fitted to the plant after operations cease. This will lead to corrosion of the element and failure at the next start-up. It was therefore recommended that a procedure and checklist be developed for instrument removal after shut-down is complete.
Innova Soil Technology HAZOP Record Sheet
Project: 2005 Plant Modifications
Plant: Innova DFTD
Section: Feed Train: FEL & Feed station
HAZOP Team Members:
Ben Willis (Process engineer)
Nick Ebril (Operations manager)
Andrew Michalopoulos (Plant supervisor)
Scott Goldrick (Plant supervisor)
Ryan Flanagan (Student Engineer)
Date: Tuesday 26th
July 2005
Page: 1 of X
No. Guideword Cause Consequence Safeguard Action Who Done
Free flowing soil
- Too much soil fed to
plant
- Adjustable flow
restrictor
- Alarm on high feed rate BW/MO High Flow
Incorrect flow rate from
weigh feeder
- Too much soil fed to
plant
- Feeder to be regularly
calibrated
- Alarm on weigh feeder
if an error occurs
Soil not flowing - Too little soil fed to
plant
- Inconsistent feed rate-
plant instability
- Chopper auger to break
up sticky materials
- Operator monitors feed
rate
- Alarm on Low feed rate BW/MO Low Flow
Incorrect flow rate from
weigh feeder
- Too little soil fed to
plant
- Feeder to be regularly
calibrated
- Alarm on weigh feeder
if an error occurs
Failure of feed screws - Feed to plant stops - Alarm on trip of feed
motor
No Flow
See low level
Reverse Flow N/A
High level FEL operator overloads
hopper
- Hopper overflow - Trained FEL operator
- High level in hopper
visible from FEL
- Hungry boards
- Weigh cells on feeder
Low Level FEL operator fails to load
hopper
- Run out of feed to plant - Low level alarm on
hopper weight
- 2-way radio
communications
between loader and
control room
High pressure N/A
Low pressure N/A
High
temperature
N/A
Low
temperature
N/A
Low
concentration
N/A for load station (see
dryer)
High
concentration
Soil high in contaminant
concentration
- Potential exposure of
operations personnel
- Soil tested prior to
operations.
- PPE provided.
Contaminants
(oversize)
Large objects in soil - Potential damage to
plant
- Soil screened prior to
operation
Contaminants
(Metallic)
Metallic objects in soil - Potential damage to
plant
- Soil screened prior to
operation
Contaminants
(other
hazardous)
Presence of other
hazardous materials in soil
- Operators exposed to
hazardous materials
- Soil tested prior to
operations
- Trained operators
- Appropriate PPE
provided
Overfilling/missing
hopper
- Qualified FEL operators
Operation of load screws
without downstream soil
transport
- Cascaded control of
plant
Loss of
containment
Misalignment of transfer
- Manual cleanup of
spills
- Conveyors “Fit” into Ensure load procedure has BW
from hopper to conveyor
(perhaps due to FEL
impact)
position.
- Correct operation
checked during
commissioning
- Qualified FEL operators
instruction to check feed
operation after any
impact.
High flow (see high flow) - As for high flow
Instruments
and control
N/A
Electrical No special requirements - Electrical installation
conducted by qualified
personnel
System and
testing
N/A
Maintenance N/A
Safety equipment - PPE provided Others
Pedestrian access - FEL traffic areas fenced
off. No pedestrian
access to this area
Project: 2005 Plant Modifications
Plant: Innova DFTD
Section: Feed Train: Weigh feeder, feed
conveyors, magnetic separator, vibrating screen
HAZOP Team Members:
Ben Willis (Process engineer)
Nick Ebril (Operations manager)
Andrew Michalopoulos (Plant supervisor)
Scott Goldrick (Plant supervisor)
Ryan Flanagan (Student Engineer)
Date: Tuesday 26th
July 2005
Page: 1 of X
No. Guideword Cause Consequence Safeguard Action Who Done
Feed too fast - Overflow of conveyors
- Too much feed to plant
- Soil feed rate control
Incorrect flow rate from
weigh feeder
- Too much soil fed to
plant
- Feeder to be regularly
calibrated
- Alarm on weigh feeder
if an error occurs
High Flow
Fuel flow without
combustion
- Fuel pumped into
converter
- UV detector will sense
no flame and control
system will shut off fuel
Feed too slow - Low feed to plant - Soil feed rate control
Incorrect flow rate from
weigh feeder
- Reduced soil feed rate - Feeder to be regularly
calibrated
- Alarm on weigh feeder
if an error occurs
Blockage of vibrating
screen
- Undersize objects
removed from feed train
- Soil screened prior to
operation
- Regular checks of
vibrating screen
Low Flow
Excessive buildup on
magnetic separator
- Restricted flow of soil
and overflow of
conveyor
- Entrainment of
potentially damaging
metal objects with soil
- Regular inspection and
cleaning of magnetic
separator
Failure of any
downstream soil transport
equipment
- No feed to plant
- Overflow from
upstream equipment
- Cascaded control of soil
transport system
- Alarm on electrical
failure of equipment
No Flow
As per low flow
Reverse Flow N/A
High level N/A
Low Level N/A
High pressure N/A
Low pressure N/A
High
temperature
N/A
Low
temperature
N/A
Low
concentration
N/A
High
concentration
See feed station
Contaminants
(oversize)
Large objects in soil - Potential damage to
plant
- Vibrating screen in feed
train
Metallic objects in soil - Potential damage to
plant
- Magnetic separator in
feed train
Contaminants
(Metallic)
Magnetic separator not in
position
- Potential damage to
plant
- Soil screened prior to
feed to plant
- Vibrating screen in feed
train will remove large
metallic objects
Blockage of conveyor - See no flow & low flow Loss of
containment Dust from conveyors - Dust complaints
- Exposure of personnel
to dust
- Conveyors are covered
Instruments
and control
Weigh feeder failure - Erratic, incorrect or no
flow
- Alarm on weigh feeder
faults
Electrical No special requirements - Electrical installation
conducted by qualified
personnel
System and
testing
N/A
Maintenance N/A
Others Safety - Guarding
- PPE
- Emergency
stops/lanyards
- Conveyors covered
- PPE supplied
- Emergency stops and
lanyards installed
- Assess guarding
requirements for feed
train
BW
Project: 2005 Plant Modifications
Plant: Innova DFTD
Section: Converter burner: Fuel train
HAZOP Team Members:
Ben Willis (Process engineer)
Nick Ebril (Operations manager)
Andrew Michalopoulos (Plant supervisor)
Scott Goldrick (Plant supervisor)
Ryan Flanagan (Student Engineer)
Date: Tuesday 26th
July 2005
Page: 1 of X
No. Guideword Cause Consequence Safeguard Action Who Done
Fuel pressure high:
- Faulty regulator
High Flow
Fuel control valve fault
- Inefficient combustion - Flow meter on fuel train
- Position indicator on
fuel control valve
- Fuel pressure
transmitter & alarm
Fuel pressure low:
- Faulty regulator
- Insufficient fuel supply
- Air in fuel line
- Fuel line blocked
- Strainer blocked
- Run out of fuel
- Leak in pipe
Low Flow
Fuel control valve fault
- Low temperature in
converter
- Incomplete combustion
of soil contaminants-
emissions
- Flow meter on fuel train
- Position indicator on
fuel control valve
- Fuel pressure
transmitter & alarm
- Emissions monitoring
equipment
No fuel - UV detector alarm and
control
Blocked pipe
No Flow
Fuel control valve failure
No combustion (as for low
flow)
Reverse flow N/A
High level N/A
Low level N/A
High pressure Dead head pump - None- pump has
internal pressure relief
valve
Low pressure See low flow
High
temperature
N/A
Low
temperature
Cold weather Difficulty in starting
burners
- Consider effects of low
temperature on fuel
properties before
operations
Composition
change
Alternate fuels - Low calorific value
- Viscosity changes
- Chemical resistance of
components
- Issues due to physical
or chemical properties
- Possible use of Class 3
liquids in fuel
- Alternate fuels to be
assessed prior to use
Contaminants Water/sludge in fuel - Sludge blockage of fuel
strainers
- When using commercial
fuels no issues with
water
- Checks of strainer
Loss of
containment
Leaks or sprays on hot
equipment
- Fire potential- likely
hood is low as
temperatures are well
below auto ignition
May need further
consideration with
flammable fuels
Instruments
and control
Compliant with Australian
standards
Electrical No special requirements
for inflammable fuels
May need further
consideration with
flammable fuels
Testing N/A
Maintenance N/A
Other N/A
Project: 2005 Plant Modifications
Plant: Innova DFTD
Section: Converter burner: Combustion air
HAZOP Team Members:
Ben Willis (Process engineer)
Nick Ebril (Operations manager)
Andrew Michalopoulos (Plant supervisor)
Scott Goldrick (Plant supervisor)
Ryan Flanagan (Student Engineer)
Date: Tuesday 26th
July 2005
Page: 1 of X
No. Guideword Cause Consequence Safeguard Action Who Done
Fan speed set too high - None High Flow
Faulty air control valve
- Excess air added to
burner- additional
energy required to heat
excess air
- Position feedback from
valve
Fan speed set too low - Converter temperature
monitored
Faulty air control valve - Position feedback from
valve
Low Flow
Air leak
- Inefficient combustion-
possible emissions
- Air pressure switch
- Plant inspections
Fan turned off No combustion - Feedback on fan
operation
- Air pressure switch
No Flow
Valve shut/pipe blockage
or rupture
- Position feedback on
valve
- Air pressure switch
- Plant inspections
- Inlet to fan gaurded
Reverse flow Fan spins backwards - Qualified person to
install motor
- Direction tested after
installation
- Investigate disabling
reverse on VSD
- Pressure switch on air
line
High level N/A
Low level N/A
High pressure See high flow
Low pressure See low flow
High
temperature
N/A
Low
temperature
N/A
Composition
change
N/A
Contaminants N/A
Loss of
containment
N/A
Instruments
and control
Compliant with Australian
standards
Electrical No special requirements
for inflammable fuels
May need further
consideration with
flammable fuels
Testing N/A
Maintenance N/A
Other
Project: 2005 Plant Modifications
Plant: Innova DFTD
Section: Converter burner: atomizing air
HAZOP Team Members:
Ben Willis (Process engineer)
Nick Ebril (Operations manager)
Andrew Michalopoulos (Plant supervisor)
Scott Goldrick (Plant supervisor)
Ryan Flanagan (Student Engineer)
Date: Tuesday 26th
July 2005
Page: 1 of X
No. Guideword Cause Consequence Safeguard Action Who Done
High Flow See combustion air
See combustion air Low Flow
Fan set too low for
operation at full open flow
- Fan set to operate at
speeds providing
sufficient air for
maximum air flow
Damper valve set
incorrectly
- Reduced atomization of
fuel
- Valve has locking
device to prevent
accidental changes
No Flow See low flow
Reverse flow See combustion air
High level N/A
Low level N/A
High pressure N/A
Low pressure N/A
High
temperature
N/A
Low
temperature
N/A
Composition
change
N/A
Contaminants N/A
Loss of
containment
N/A
Instruments
and control
Compliant with Australian
standards
Electrical No special requirements
for inflammable fuels
Testing N/A
Maintenance N/A
Other N/A
Project: 2005 Plant Modifications
Plant: Innova DFTD
Section: Converter burner: Pilot burner
HAZOP Team Members:
Ben Willis (Process engineer)
Nick Ebril (Operations manager)
Andrew Michalopoulos (Plant supervisor)
Scott Goldrick (Plant supervisor)
Ryan Flanagan (Student Engineer)
Date: Tuesday 26th
July 2005
Page: 1 of X
No. Guideword Cause Consequence Safeguard Action Who Done
High Flow Pilot gas doesn’t turn off Pilot burner will continue
to burn
Unlikely to occur
Low gas flow
Low Flow
Low air flow Pilot may not start
If pilot light does not
ignite control system cuts
off gas supply and alarms
No Flow See low flow
Reverse flow N/A
High level N/A
Low level N/A
High pressure N/A
Low pressure N/A
High
temperature
N/A
Low
temperature
N/A
Composition
change
N/A
Contaminants N/A
Loss of
containment
Gas leak Possible fire Plant in open space
Small bore pipe work only
Maximum gas quantity
45kg
Gas approved fittings
ussed
Instruments
and control
Electrical No special requirements
Testing N/A
Maintenance N/A
Other N/A
Project: 2005 Plant Modifications
Plant: Innova DFTD
Section: Bag house
HAZOP Team Members:
Ben Willis (Process engineer)
Nick Ebril (Operations manager)
Andrew Michalopoulos (Plant supervisor)
Scott Goldrick (Plant supervisor)
Ryan Flanagan (Student Engineer)
Mark Bennet (Student engineer)
Date: Tuesday 26th
July 2005
Page: 1 of X
No. Guideword Cause Consequence Safeguard Action Who Done
High Flow ID fan too high - ID fan unable to cause
high flow causing
problems
ID fan too low Low Flow
Low plant feed
- Low throughput in bag
house leading to cooling
of gas below dew point
- Temperature monitoring
before and after bag
house
Fan stopped - ID fan is monitored
- Pressure monitoring:
- Converter
- Bag house
Isolation Valve closed - Valve limit switches
(alarm on closed)
- Thermal relief valve to
relieve pressure
Bags fouled - Alarm on pulse failure
- Bag house DP
monitoring
Process blockage - Pressure monitoring:
- Converter
- Bag house
No Flow
Hopper too full
- Positive pressure
upstream- No
particulate removal
- Auger motors have
feedback
- Investigate necessity of
dust level sensors
BW
during commissioning
Reverse flow Fan in reverse - Possible to damage bags
- Process failure during
commissioning
- Qualified person to
install motor
- Direction tested after
installation
- Investigate if damage is
likely
- Investigate disabling
reverse on VSD
BW
High level Failure/ plugging of
augers
- See no flow hopper too
full
Low level N/A
High pressure As per low flow
Low pressure Broken bags - Dust emissions - Broken bag detector
- Pressure alarms
High
temperature
Process over temp
- Bags damaged - Process gas cooling
- Isolation valve
- Process temperature
monitoring and alarms
(duplicate sensors)
- Valve to be actuated
both ways
- Automated water
injection nozzle prior to
bag house
BW
Low
temperature
Process under temp Condensation inside bag
house (plugging)
Temperature monitoring
and alarms
Insulated bag house
High dust
Abrasive dust
Wear on bughouse and
bags
Dust emissions
Reduced plant throughput
Bag house has knockout
spiral to remove excess
dust
Investigation of soil prior
to operations
Regular inspection of bag
house during operations
High acid Wear on bughouse and
bags
Emissions
CEMS alerts to high acid
content
Composition
change
High moisture Potential damage to bags Investigations prior to
commencing operations
Fuel in off gas
Burner not tuned
Potential
contamination/clogging of
bags
Burners to be
commissioned with bag
house isolated and thermal
relief vent open
Contaminants
Heavy metals/asbestos Exposure of personnel to
dangerous materials
Analysis of soil prior to
operations
Appropriate PPE
Loss of
containment
Bag failure Dust emissions Broken bag detector
Pipe/structural failure Emissions of dust
Reduced plant capacity
Oxygen measured in
emissions
Pressure monitoring
Visual observation
Instruments
and control
Pulse control failure Checks for valve
operation
Alarm on pulse board
failure (won’t detect valve
failure)
Pressure gauge in on blow
tube manifold
BW
Electrical N/A
Testing System operation Tested during
commissioning for each
project
Maintenance N/A
Other
Project: 2005 Plant Modifications
Plant: Innova DFTD
Section: Grit augers
HAZOP Team Members:
Ben Willis (Process engineer)
Nick Ebril (Operations manager)
Andrew Michalopoulos (Plant supervisor)
Scott Goldrick (Plant supervisor)
Ryan Flanagan (Student Engineer)
Date: Tuesday 26th
July 2005
Page: 1 of X
No. Guideword Cause Consequence Safeguard Action Who Done
High Flow Excessive dust loading Buildup of dust in
converters
Buildup of dust in pug
mill
Un-likely to generate
sufficient dust to overload
augers
Low Flow N/A
Auger blockage Buildup of dust in
converters
Feedback on auger motors
to alert operator to
problems.
Unlikely to get
sufficiently large dust to
block augers
Temperature control
prevents the formation of
slag which may block
augers
No Flow
Auger failure Feedback on motor
operation
Plant inspections
Reverse flow N/A
High level See low flow/no flow
Low level N/A
High pressure N/A
Low pressure Cooling water low
pressure
See high temperature
High
temperature
High converter
temperature
Slag may form and cause
auger blockage
Temperature is controlled
to prevent slag formation
Soil is tested prior to
operations to determine if
slag formation is probable
Water injection to reduce
temperature if unable to
control temperature
Cooling water failure to
augers
Augers may get hot and
warp.
Pressure gauge on pipe
work
Do we need pressure
transmitter and alarm?
Low
temperature
N/A
Composition
change
N/A
Contaminants N/A
Loss of
containment
N/A
Instruments
and control
N/A
Electrical N/A
Testing N/A
Maintenance Hot access to augers Personnel exposed to hot
environment
No access required during
normal operation
Short term exposure for
minor repairs OK. Risk
assessment must be
completed prior to starting
work.
Other
Project: 2005 Plant Modifications
Plant: Innova DFTD
Section: Pug mill to bag house duct
HAZOP Team Members:
Ben Willis (Process engineer)
Nick Ebril (Operations manager)
Andrew Michalopoulos (Plant supervisor)
Scott Goldrick (Plant supervisor)
Ryan Flanagan (Student Engineer)
Date: Tuesday 26th
July 2005
Page: 1 of X
No. Guideword Cause Consequence Safeguard Action Who Done
High Flow High feed rate or high soil
exit temperature
Could generate too much
steam leading to steam
leaking from pug mill
To be considered during
project commissioning.
Low Flow Insufficient pressure drop
between bag house duct
and pug mill
Steam leaking from pug
mill
Pressure monitoring and
alarms in pug mill
System to periodically
clean duct
No Flow Plugging of pipe See low flow
Reverse flow Positive pressure
differential between bag
house duct and
High level N/A
Low level N/A
High pressure High pressure in bag
house duct
No issues
Low pressure Low pressure in bag
house duct
See low flow
High
temperature
N/A
Low
temperature
Heat loss from duct Condensation of water in
duct
Temperature monitoring
in pug mill hood
Composition
change
High water or dust loading Increased plugging in duct
Contaminants N/A
Loss of
containment
Pipe failure
Instruments
and control
N/A
Electrical N/A
Testing Inspection for dust
buildup
Dust buildup to be
monitored during
shutdown
Maintenance N/A
Other
Project: 2005 Plant Modifications
Plant: Innova DFTD
Section: Radial stacking conveyor
HAZOP Team Members:
Ben Willis (Process engineer)
Nick Ebril (Operations manager)
Andrew Michalopoulos (Plant supervisor)
Scott Goldrick (Plant supervisor)
Ryan Flanagan (Student Engineer)
Date: Tuesday 26th
July 2005
Page: 1 of X
No. Guideword Cause Consequence Safeguard Action Who Done
High Flow Plant feed rate too high Overflow of conveyor Plant feed is controlled
Low Flow N/A
No Flow N/A
Reverse flow N/A
High level Stack under conveyor too
high
Conveyor movement
automated
Low level N/A
High pressure N/A
Low pressure N/A
High
temperature
Product soil temperature
too high
Damage to belt Temperature monitoring
of soil temperature
Alarm on high soil
temperature
Low
temperature
N/A
Composition
change
N/A
Contaminants N/A
Belt overflow See high flow Loss of
containment Dust dust Belt is covered
Spray at end of belt to
reduce dust
Instruments
and control
Radial movement May dump soil in
incorrect position
Limit switch located
before limit of operation
Inspection of plant
Electrical N/A
Testing N/A
Maintenance N/A
Other Access Personnel may access area
under moving stacker
Area to be barricaded and
access restricted.
Note the barricade also
forms the restricted are for
FEL operation. Before
pedestrian entry personnel
must stop automatic
movement of the
conveyor and ensure FEL
can not access the area