hazop
DESCRIPTION
hazopTRANSCRIPT
Prepared by: Karin Nilsson
14 July 2009
Prepared for: Eraring Energy
Document Number: ERAPOW\12-B177
Revision B
PO Box 248 Berowra Heights NSW 2082 Telephone: [02] 9985 1056 Facsimile: [02] 9427 7851
Email: [email protected]
HAZOP STUDY REPORT OF THE
TURBINE HYDRAULIC POWER UNIT,
BOILER UPGRADE AND LOW NOX
BURNERS AS PART OF THE ERARING
ENERGY POWER STATION UPGRADE
PROJECT
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Acknowledgment
The author would like to thank the HAZOP review team and in particular Ian O’Brian, Phil Fenney, Steve Shawcross, Graeme Hankin and Frank Mieszala for organising the HAZOP Studies and providing input and reviews of minutes and report.
Disclaimer
This report was prepared by Planager Pty Ltd (Planager) as an account of work for Eraring Energy. The material in it reflects Planager's best judgement in the light of the information available to it at the time of preparation. However, as Planager cannot control the conditions under which this report may be used, Planager and its related corporations will not be responsible for damages of any nature resulting from use of or reliance upon this report. Planager's responsibility for advice given is subject to the terms of engagement with Eraring Energy.
HAZOP Study Report of the Turbine Hydraulic Power Unit, Boiler Upgrade and Low NOx Burners as Part of
the Eraring Energy Power Station Upgrade Project
Rev Date Description Prepared By Authorised By
A 19/06/2009 Draft for Comment Karin Nilsson Frank Mieszala
B 14/07/2009 Final Report Karin Nilsson Frank Mieszala
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CONTENTS
1 INTRODUCTION .............................................................................................. 6
1.1 Background ...................................................................................... 6
1.2 Aim of This Report .......................................................................... 6
1.3 Location of EPS ............................................................................... 7
1.4 Project Description .......................................................................... 7
1.5 Scope of HAZOP Study ................................................................... 7
1.5.1 Boiler Upgrade ................................................................................... 8
1.5.2 Turbine Hydraulic Power Supply ....................................................... 8
1.5.3 Low NOx Burners ............................................................................... 8
2 METHODOLOGY ............................................................................................. 9
2.1 Introduction ...................................................................................... 9
2.2 Details of the HAZOP Study Procedure ......................................... 9
2.3 HAZOP Study Guidewords ........................................................... 10
2.4 Risk Ranking Tools ....................................................................... 12
3 RESULTS AND RECOMMENDATIONS ............................................................... 13
3.1 Presentation of Risk Results ........................................................ 13
3.2 Risk Levels of the Boilers Design ................................................ 14
3.2.1 Level 4 Risks Boilers ....................................................................... 14
3.2.2 Level 3 Risks Boilers ....................................................................... 15
3.2.3 Level 2 and Level 1 Risks Boilers .................................................... 18
3.3 Risk Levels of the Turbine Hydraulic Power Unit Design .......... 18
3.3.1 Level 4 Risks Hydraulic Power Unit ................................................. 18
3.3.2 Level 3 Risks Hydraulic Power Unit ................................................. 18
3.3.3 Level 2 and Level 1 Risks Hydraulic Power Unit ............................. 19
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3.4 Risk Levels of the Low NOx Burner Design ................................. 19
3.4.1 Level 4 Risks Low NOx Burners ....................................................... 19
3.4.2 Level 3 Risks Low NOx Burners ....................................................... 19
3.4.3 Level 2 and Level Low NOx Burners ................................................ 19
3.5 Risk Profile of Plant Assuming HAZOP Recommendations in Place ........................................................................................................ 20
4 CONCLUSION............................................................................................... 21
5 REFERENCES ............................................................................................ 222
LIST OF APPENDICES
Appendix 1 – HAZOP Study Minutes
Appendix 2 – Approval as HAZOP Leader
Appendix 3 – Eraring Energy Risk Tools
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REPORT
PROJECT TITLE: Power Station Upgrade Project
LOCATION: Eraring Energy Power Station.
HAZOP MINUTES: Appendix 1
HAZOP Leaders: Karin Nilsson (DoP Approved)
Mark Wyburn (Eraring Energy, second half day of Boiler HAZOP. Methodology used and outcome reviewed by Karin Nilsson)
HAZOP SCOPE AND DATES FOR STUDY:
- Boiler Upgrade 8 April and 5 May 2009 (1½ days)
- Turbine Hydraulic Power Supply 23 March 2009 (one day)
- Low NOx Burners 22 April 2009 (one day)
RECORD OF ATTENDANCE
Name Company Position
Boiler Upgrade
Ian O’Brian Eraring Energy Project Manager, Boiler Upgrade Project
Ray Ansell Eraring Energy Senior Tradesman
Chris Brucki Eraring Energy Boiler Team Leader and Asset Management
Shaun Edwards Eraring Energy Project Change Manager
Gary Craig Eraring Energy Project Manager, CCP Project
Phil Fenney Eraring Energy Project Manager, Low NOx Burners
Mark Wyburn (part time)
Eraring Energy Chemical Asset Team Leader
Charlie Grima Aurecon Boiler Operations Consultant
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RECORD OF ATTENDANCE
Turbine Hydraulic Power Unit
Steve Shawcross Eraring Energy Project Manager Turbine Upgrade Project
Graham Hankin Eraring Energy Turbine Asset
Phil McWilliam PPI – DPPA Rep Project Manager
Daniel McNally Eraring Energy E&I Technician
Keith Clark Eraring Energy Operator
Ian Dawson Eraring Energy Projects Engineer
Steve Wheeler Eraring Energy Operations Team Leader
Steve Gambrill (part time)
Eraring Energy Environment
Gemma Keith Eraring Energy Secretarial Support
Low NOx Burner
Phil Fenney Eraring Energy Project Manager, Low NOx Burners
Steve Wheeler Eraring Energy Operations Engineer
Chris Brucki Eraring Energy Boiler Team Leader and Asset Management
John Harris Eraring Energy Plant Owner
Tarkel Larson Siemens Field Services Manager
Kenneth Tichy Siemens Project Manager, Low NOx Burners
Meg Trewhella Eraring Energy Secretarial support
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1 INTRODUCTION
1.1 BACKGROUND
The Energy Directions Green Paper (Ref 1) prepared by the NSW Government identified that if the current trend of increased electricity demand continues, additional generation capacity or demand management would be required by 2010.
Eraring Energy (EE), one of three State-Owned Corporations that manages a diverse set of electricity-generating assets located throughout NSW operates a coal-fired power station (at Eraring), known as Eraring Power Station (EPS).
EE has put forward a proposal to undertake capacity increase and performance improvements to the existing EPS to increase the capacity of each of the four 660 MW generating units (which are capable of generating at an equivalent rating of around 700 MW) to enable the units to operate up to a maximum continuous rating of 750 MW.
EE has obtained Project Approval, subject to a number of Consent Conditions, for the capacity increase project under section 75J of the EP&A Act in accordance with the provisions of Part 3A of the EP&A Act. The Minister for Planning is the approval authority for the application.
One of these Consent Conditions requires a HAZOP Study to be undertaken for the proposed development, as follows:
.....a Hazard and Operability Study (HAZOP) for the power station upgrade, chaired by an independent, qualified person or team. The independent person or team shall be approved by the Director-General. The Study shall be carried out in accordance with the Department’s publication Hazardous Industry Planning Advisory Paper No. 8 – HAZOP report. If the Proponent intends to defer the implementation of a recommendation, justification must be included.
1.2 AIM OF THIS REPORT
Eraring Energy has commissioned Planager Pty Ltd to lead a multidisciplinary team through the HAZOP Study of a number of sub-projects which form part of the EPS’ Upgrade Project.
Planager’s principal risk engineer, Karin Nilsson, has received approval from the Department of Planning to lead the HAZOP Study. The letter of approval for Karin Nilsson as HAZOP study leader is included in Appendix 2.
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The aim of the HAZOP study is to review a design of a technological system to identify hazards or significant obstacles to operability, which could arise, particularly through deviations from the design intent.
1.3 LOCATION OF EPS
EPS’s site comprises approximately 1,200 hectares of land and is located in a natural dip on the western shore of Lake Macquarie. The site falls within the Lake Macquarie Local Government Area, near the township of Dora Creek, within the Morisset Planning District. The power station and associated infrastructure covers a footprint of approximately 150 hectares, with the remaining area including the CCP management facility, water canals, and ancillary power station facilities.
The surrounds of the EPS consist largely of natural vegetated areas with development dedicated primarily to the extractive industries, such as coal mining. Some semi-rural areas exist to the south on the shores of Lake Macquarie.
1.4 PROJECT DESCRIPTION
The key objective of the project is to upgrade the infrastructure at EPS. By replacing existing aging components of plant and equipment within the EPS operating units, EE would be able to maintain operational capacity and the replacement/renewal program would enable improved efficiency of operations and the environmental and safety performance of EPS.
The upgrade would allow the four existing 660 MW generating units to operate at a MCR of up to 750MW. This improved performance would be used to meet the increasing demands of the NEM, particularly during peak periods.
Aged components of the Boiler and Turbine Generating Plant would be refurbished to achieve a MCR of 750 MW generated at a Power Factor of 0.9 at rated conditions (Generator 833 MVA rating). This would include:
“Steam Path Upgrade” of high pressure, intermediate pressure and low pressure stages of the turbine;
Upgrade of generator;
Upgrade of generator transformer cooling system;
Additional tubing inside boiler;
Replacement of 28 boiler burners with low NOx burners; and
Other miscellaneous work.
1.5 SCOPE OF HAZOP STUDY
EE has identified the following three operations which would benefit from a HAZOP Study:
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Boiler Upgrade
Turbine Hydraulic Power Supply
Low NOx Burners
The HAZOP study sessions were all carried out By Difference with the existing plant operation, i.e. the HAZOP focussed on the implication of the changes to plants and processes which result from the proposed changes to boilers, hydraulic unit and burners. As such, the HAZOP did not attempt to cover the whole of the Power Station operation and design. The scope of each HAZOP study is as follows:
1.5.1 Boiler Upgrade
Included: The scope of the Boiler HAZOP includes the design and operation of the actual boilers.
Excluded: The scope excludes the new (Low NOx Burners, see below), including the burner management, flame stability and wind box.
1.5.2 Turbine Hydraulic Power Supply
Included: The scope includes the design and operation of pumps, fans, piping, valving, instrumentation etc. which form part of the hydraulic power unit.
Excluded: The scope excludes the control system and the main oil pump and the auxiliary pump. The Emergency Trip Device is also outside the scope of this HAZOP. Further, outside the scope is the extractor relay dump valve operation, the Turbine protection and control module, the mechanical steam path upgrade.
Note that at the time of the HAZOP the exact composition of the hydraulic oil was not known (it was believed to be some type of phosphate ester). The HAZOP team took into account that it could be potentially hazardous to people handling the material. As such the HAZOP of the turbine hydraulic power unit is regarded as a Preliminary HAZOP and further engineering investigation will be required (whether it be in the form of supplementary HAZOP studies or other risk management techniques).
1.5.3 Low NOx Burners
Included: The scope of the Burner HAZOP included the new Low NOx Burners, including burner management, flame stability and wind box.
Excluded: The control system was not part of the scope of this HAZOP.
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2 METHODOLOGY
2.1 INTRODUCTION
The HAZOP study is based on engineering line diagrams (P&ID's) and outline operating procedures. The consequences and deviations are identified, the existing safeguards are highlighted and, where necessary, appropriate corrective actions initiated.
A HAZOP study is a form of design review which concentrates on how the plant will cope with abnormal conditions, rather than on how it will perform under normal conditions. The study comprises consideration of each process line and vessel, examining for each the possible causes and consequences of a wide range of process abnormalities. While some of the postulated abnormalities may be inapplicable for a particular process line, they are all probed with the objective of identifying any significant route to a process upset, operating problem or hazardous incident. It is, in effect, a very thorough but mainly qualitative approach.
HAZOP is the method recommended for identifying hazards and problems which prevent efficient operation of a processing plant. It is a technique which provides opportunities for people to think creatively and examine all possible ways in which hazards or operating problems might arise. To reduce the chance that something is missed it is done in a systematic way - each pipeline and each type of hazard being considered in turn. The study is carried out by a team so that they can stimulate each other and build on each other’s ideas.
The results of a HAZOP depend more upon the experience and attitudes of the participants and on the leadership style adopted, than on the procedures themselves. The participants were selected to provide the necessary experience, knowledge, skills and authority to approve the actions decided upon. The Study leader needs to be very experienced in HAZOP studies and Hazard Analysis techniques and capable of performing as an independent and unbiased leader. This person needs to be familiar with other related techniques and to know when other techniques would be beneficial compared to the HAZOP technique.
2.2 DETAILS OF THE HAZOP STUDY PROCEDURE
The HAZOP study was conducted according to ICI's traditional HAZOP methodology, corresponding to established engineering practices. The study of each step in the operation of the plant followed the pattern outlined below:
A brief outline of the purpose of the step in the operation and of the lines involved with the operation is provided by one of the team members (usually by the designer). The lines are highlighted on the P&ID with dotted lines using a transparent coloured felt pen.
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The purpose, design features, operating conditions, fittings, etc, are explained.
Any general questions about the lines are then answered.
The detailed "line by line" study commences at this point. The discussion leader takes the group through a series of guide words set out in a book (see Section 2.3). Each card has a guide word or prompt on it, such as "FLOW - HIGH", which identifies a deviation from normal operating conditions. This is used to prompt discussion of the possible effects of flow at an undesirably slow speed, and of the possible causes. If in the opinion of the meeting, the combination of the consequences and the likelihood of occurrence are sufficient to warrant action, then the combination is regarded as a "problem" and minuted as such. Potential incidents with severe consequences where the team judges that the risk management techniques already designed into the process are sufficient are also minuted in order to provide a record of the safeguards to be installed. Further, if a particular item was subject to discussions then it would be minuted to record the outcomes of these discussions.
For major risk areas the need for action is assessed quantitatively. For less important risks the need for action can be based on experience and judgement. The person responsible for defining the corrective action is also nominated.
It should always be remembered that the main aim of the meeting is to find problems needing solution, rather than determine actual solutions. If the group becomes tied down by trying to resolve a problem it is better to continue the discussion at a later date and proceed with the study.
When each guide word requires no more consideration, the chairperson turns that card down revealing the next guide word.
Discussion for each guide word is confined to the line marked, the vessels or other major equipment at each end and any equipment such as pumps or heat exchangers in between. Any changes agreed at the meeting are minuted, and where possible, marked on the P&I diagram or layout with red pen.
When all guide words have been covered, the line is fully highlighted (instead of with a dotted line) to show that it has been covered, and the next line is chosen.
When all the lines in a plant sub-section have been reviewed, additional guide words are used for review (overview) of the P&ID as a whole (see below).
2.3 HAZOP STUDY GUIDEWORDS
The guidewords applicable for continuous operations were used for the most of the designs under review. If the operation has critical sequencing conditions,
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such as for the Low NOx Burner project, then the continuous operation guidewords were complemented with batch guidewords as listed below.
Line-By-Line Guidewords - Continuous Process
High Level / High Flow
Low Level / Low Flow
Zero Flow / Empty
Reverse Flow
High Pressure - Venting, relief rate
Low Pressure - Venting, relief rate
High Temperature
Low Temperature
Impurities - gaseous, liquid, solid
Change in concentration / Change in composition / Two phase flow / Reactions
Testing - equipment / product
Plant Items - operable / maintainable
Instruments - sufficient for control / too many / correct location
Overview Guidewords
Toxicity
Commissioning
Start-up
Shutdown (isolation, purging)
Breakdown (including services failure)
Effluent
Fire and Explosion
Safety Equipment
Noise
Materials of Construction
Services required
Electrical: area classification / isolation / earthing
Quality and Consistency
Output - reliability and bottlenecks
Efficiency – losses
Simplicity
Line-By-Line Guidewords - Batch Process
Timing – start too early/late; stop too early/late
Flow High / Low
Level High / Low
Zero Flow / Empty
Reverse Flow
None
Pressure High / Low
Temperature High / Low
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Density High / Low
Viscosity High / Low
Static
Effects on Existing Equipment
Concentration High / Low
Contamination / Extra Phase
Duration – Delayed / Omitted
Out of Sequence / Wrong Operation
Not Complete
Duplication
Testing - equipment / product
Plant Items - operable / maintainable
Instruments - sufficient for control / too many / correct location
Overview Guidewords
Operator Health
Environment
Electrical
Services
Materials of Construction
Non-routine Conditions - Start-up/ Shutdown / Maintenance / Cleaning / Commissioning
Fire and Explosion
Safety Equipment
Quality and Consistency
Output - reliability and bottlenecks
Simplicity & Efficiency
2.4 RISK RANKING TOOLS
The HAZOP Study was complemented with a formal risk ranking of each scenario using Eraring Energy’s risk ranking tool (Ref 2) presented in Appendix 3. This is as per Eraring Energy’s requirements for risk reviews of their projects.
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3 RESULTS AND RECOMMENDATIONS
3.1 PRESENTATION OF RISK RESULTS
Items were recorded on the HAZOP Study Record Sheets, which may be seen in Appendix 1. The 3.5 days HAZOP generated a total of 115 issues and recommendations.
As per the methodology, entries were made on the record sheets as follows:
Where a hazard or an operational problem was recognised as requiring further risk or operations controls;
Where the potential consequences of an incident were severe even though the management of the risk considered acceptable.
Where a particular item was discussed in detail during the study and hence required minuting to record the final outcome of these discussions.
HAZOPs are focussed on the engineering design of a particular plant or equipment. Hence, trip, slip and fall type incidents were not recorded nor were they discussed. These are better discussed in a Job Safety Assessment (or similar) type forum.
The table in Appendix 1 shows the following columns:
Risk Number,
Guideword,
Causes,
Consequences
Controls in place (a listing of the controls currently in place and approved as part of the present project),
Current risk rating (rating of the risk with the controls which are currently in place or approved),
Mitigating actions (further risk reduction recommendations aiming to reduce the risk to ALARP1 levels),
Residual risk rating (the risk rating of the scenario with the recommended mitigating actions (above) in place,
Below is provided a listing of Levels 4 and 4 risk scenarios as identified and evaluated for the existing design. The resultant risk level once the recommendations arising out of the HAZOP Study have been implemented is also discussed for each scenario. The table in Section 3.5 below presents the
1 As Low As Reasonably Practicable
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risk profile of the systems under study assuming all recommendations have been implemented successfully.
3.2 RISK LEVELS OF THE BOILERS DESIGN
Below are listed the risk scenarios for each Risk Level (as per Eraring Risk definition) for the Boiler Design. These risk levels are as per current design without the additional risk reduction recommendations arising from the HAZOP implemented.
3.2.1 Level 4 Risks Boilers
A. Risk of increased copper transportation (Scenario 5)
Increased copper transportation has largely got a financial effect to EE. Copper would eventually carry-over through to turbine blades, reducing the efficiency of the turbine operation and hence output capacity. It may cause flow restrictions in superheater tubes and lead to a decreased life on low pressure heaters. The copper transportation issue will require a change in the manner in which maintenance is carried out on the superheaters and turbine rotors.
Current controls include ongoing routine copper transportation survey; a Strategy Review which is being conducted on the merits of chemically cleaning the superheaters versus foam clean of turbine; a review of the procedures for boiler tube repairs have been reviewed; and new boiler chemical controls being installed to reduce copper transportation from LP heaters.
Recommended additional controls are as follows:
Option a: Successful chemical clean carried out on super heaters which will be carried out there-after as required need to review sliding pressure operation. This would reduce the consequences of this event resulting in reducing the overall risk level to a Level 3 risk.
Option b: Replacement of LP heaters to allow oxygenated treatment of the boiler feed water. This would reduce the risk level to 1.
NB: Eraring Energy has engaged a contractor to complete superheater tube cleaning commencing with unit four in November 2009.
B. Insufficient power supplies or access for operation during construction (Scenarios 51 and 52)
Insufficient power supplies for construction purposes and insufficient access for operations such as cranage due to other works (e.g. bottom ash hopper crushing plant and boiler upgrade crane location) would lead to delays in meeting program. The likelihood of such delays is seen as Very High leading to a Level 4 risk.
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It is recommended to place these risk scenarios on the Electrical Project Teams (#51) and Site Operations Managers (#51 and #52) agenda. This would reduce the risk to a Level 1 and Level 2 for scenarios 51 and 52 respectively.
3.2.2 Level 3 Risks Boilers
A. Flow accelerated corrosion due to increase in normal operational flow (Scenario 1)
Flow accelerated corrosion (FAC) is a temperature dependent corrosion mechanism normally occurring after a bend or in a straight pipe after a flow disturbance e.g. thermocouple probe, orifice plate etc. It may lead to pipe failure and loss of containment of high pressure water, injury from burns, possible fatalities. Existing controls are confirmation of adequate thickness of piping etc. (thickness survey already conducted); planned thickness surveys 4 years after start up and the fact that there is no change in geometry as a result of the project.
Further recommendations are to determine high risk areas in terms of FAC and to perform thickness survey at targeted areas at first Combined Maintenance Outage Program (CMOP2) outage on units 4 and 2 and correlate to the duration above the original design flow. It is also recommended to record the extent of flow above the original design (for use in thickness survey mentioned above) and to confirm that FAC study by contractor has been completed and is valid for current design.
Implementation of these recommendations would reduce the likelihood from a Moderate to a Low. It would however not reduce the overall risk rating, which remains a Level 3 risk due to the relatively High consequence rating.
B. Failure of new pressure parts (Scenarios 7, 15, 19, 26, 50)
Failure of new pressure parts for a number of reasons may lead to pipe failure and loss of containment of high pressure steam / water, injury from burns, and possible fatalities.
Current and approved controls include the fact that the design and construction will adhere to Australian Standards including inspection; 100% radiography on all site tube welds; all other site welds to be NDT in compliance with Australian Standards; testing, including Non Destructive Testing (NDT); Asset Strategy defined field test for creep life of welds.
Provided that these controls are successfully implemented and maintained the team concluded that the risk of these scenarios are As Low As Reasonably
2 A term generally used for planned generating unit maintenance and often associated with
the phrase CMOP outage.
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Practicable (ALARP) and no further risk control measures were identified. The risk scenarios remain however at Level 3 risk due to the relatively High consequence should they occur even though the likelihood is considered as low as reasonably practicable.
C. Increased maximum flow exceeds maximum capacity of superheater safety valves (Scenario 14)
An increase in the maximum flow may exceed the maximum relieving capacity of superheater safety valves. This would result in over pressurisation of the superheater leading to pipe failure and loss of containment of high pressure water, injury from burns, possible fatalities.
Current controls include the review carried out by contractors in this regards which provides advice on the safe operation of safety valves.
Recommendations are to establish actual flows for overload and revise plant control limits if necessary and to include (in the amended plant operating manuals) the established plant limitation. This would have the effect of minimising the likelihood of this event. However, due to the relatively High consequence of the scenario the risk level remains 3.
NB: Review of flow rates from boiler designer indicates that operation to 750 MW will be achievable with installed safety valves. It is not expected that safety valve replacement will be required however it will be assessed post upgrade.
D. Increase of velocities (Scenario 36)
Boiler operation at higher loads increases average flue gas velocity which increases grit erosion. This could lead to tube failures and reduced boiler tube life and would increase maintenance/costs.
Current and approved controls include Combined Maintenance Outage Program (CMOP) inspections and shielding, as identified in surveys for current known high wear area; existing baffling along the wall sections; and acoustic detectors to minimise damage in the event of a failure. Further, tube wall thickness design takes into account exposure to erosion and new economiser panels have all bends enclosed out of gas flow.
Further recommendations from the HAZOP are for the design process to evaluate the need for baffling, shielding and soot blower locations in primary superheater and Reheater backpasses; the review to include rear wall penetration and seal boxes as now in an area of historical high risk. Prior to warranty expiration (12 months) take unit out of service for grit erosion survey on new design items; cold air flow testing and smoke bombs to identify high velocity areas and record high flow areas for targeted inspection - adjust baffling or shielding as required; perform inspections on previously un exposed areas while elements are removed during upgrade; and modify the boiler strategy to reflect concerns and learnings from inspections.
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Provided these recommendations are implemented the risk level of this scenario is reduced to a Level 2.
E. Higher gas temperatures in the backpass (superheater and Reheater passes) (Scenario 42)
Higher flue gas temperatures after the air heater exit and attemperation point will cause fabric filter bag failures due to excessive shrinkage. This could lead to cell isolations and potential breach of the environmental licence if EPS load not reduced. The failure may require long time to implement repairs if a stock holding of replacement bags is not available due to long lead time (3-6 months) on bags.
The risk exposure exists until 2015 when all PAN filter bags would have been replaced. Currently EPS has excellent bag life with 6 to 7 year bag replacement cycle.
Current and approved safeguards are using experience with this potential risk (which exists also in the existing plant); the new attemperating air system which initiates at 125 deg C, a High Alarm at 135 deg C and a High High Alarm at 140 deg C - for load reduction. Boiler flue gas design brief is 135 deg C at air heater exit at 720 MW with a 32 degree ambient air temperature. Fabric filter bag supply contract requires 8 cells of bags on site
Further recommendation are for documentation to be produced to implement an operating limit of 135 deg C to manage bag life, with a nominal operating target of less than 130 deg C; adjustment of operating limit down on subsequent units if rapid multi cell failures occur; evaluating the need of attemperating air spray system if operating need exists; stock holding costs versus risk to be assessed; and investigation of stock holding limits with contracted supplier.
If the recommendation above are implemented the risk is reduced to a Level 2 (possibly to a Level 1 depending on the rigour of implementation).
F. Poor Access To Bottom Bank Reheater Tubes (Scenario 46)
Poor access to bottom bank Reheater tubes may mean that in the event of a tube failure the outage may need to be extended to gain access to carry out repairs.
There are currently no controls for this scenario (apart from a trained workforce with adequate operating procedures and PPE).
Recommendation is if for a review to achieve workable access for maintenance. Provided this is workable access is achieved adequately the risk of this scenario is reduced to a Level 2.
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G. Change in boiler components (Scenario 53)
Change in boiler components would result in change in load distribution.
Currently structural review is being undertaken by contractor which also includes earthquake and wind load code compliance. Further action is to ensure that action resulting from design study to reflect latest Australian Standards and Codes. This would result in a Level 1 risk scenario.
H. Changes to existing job sheets for boiler start up and shut down (Scenario 56 and 57)
Changes to existing job sheets for boiler start up and shut down leading to plant damage or injury. Current controls are that boiler project team work scope includes procedural review. A tight control of the completion of plant modification process would result in a Level 1 risk.
3.2.3 Level 2 and Level 1 Risks Boilers
There are a number Level 2 and Level 1 risks that were identified. These are detailed in Appendix 1.
3.3 RISK LEVELS OF THE TURBINE HYDRAULIC POWER UNIT DESIGN
3.3.1 Level 4 Risks Hydraulic Power Unit
There are not Level 4 risks identified.
3.3.2 Level 3 Risks Hydraulic Power Unit
A. Removal of Pump MRP
Removal of Pump MRP causes Safety issue with 11MPa. Current controls are primary isolation valve and the pressure gauge.
Recommended further controls are to ensure positive isolation to allow stand-by pump removal and to ensure the main isolation valves can be locked out. Provided these recommendations are implemented the risk level for this scenario is reduced to a Level 2 risk.
B. Impact on fluid trip drain from valves back to tank causes pinching
Impact on fluid trip drain from valves back to tank causes pinching resulting in an inability to trip turbine. This may, in adverse operating conditions, cause a burst of drain pipe over 1.4MPa with injury potential to personnel from high pressure event.
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Current and approved controls are the appropriate layout of piping (very short pipe) and protection of pipe between structures.
Further recommendations are to review the layout of drainpipe to rule out impact; consult with contractor as to implications of a blocked drain line on operation; and to ensure EE field surveillance officer approves pipe line layout with attention to mechanical damage and weld inspection. The target is to ensure that this scenario becomes incredible.
3.3.3 Level 2 and Level 1 Risks Hydraulic Power Unit
There are a number Level 2 and Level 1 risks that were identified. These are detailed in Appendix 1.
3.4 RISK LEVELS OF THE LOW NOX BURNER DESIGN
3.4.1 Level 4 Risks Low NOx Burners
There are not Level 4 risks identified.
3.4.2 Level 3 Risks Low NOx Burners
A. Pressure controller has been disabled or the Atomising air pressure is high (Scenario 12)
If the pressure controller has been disabled or the atomising air pressure is high while atomising air to the ignitor it is possible for the unit to fail to ignite causing an operational upset and loss of power generation. Note that this is not a safety concern.
It is recommended to review air pressure requirements with designers and respond appropriately. This would reduce the risk of this scenario to a Level 2.
B. Inability to remove oil gun and spark rod on D level (Scenario 13)
New burner layout may result in an inability to remove oil gun and spark rod on D level.
Provided the design change to relocate oil gun to allow removal this scenario is reduced to a Level 1 risk.
3.4.3 Level 2 and Level Low NOx Burners
There are a number Level 2 and Level 1 risks that were identified. These are detailed in Appendix 1.
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3.5 RISK PROFILE
The risk profile of the part of the plant assessed, assuming that the risk reduction measures recommended during the HAZOP Studies are all implemented successfully, is as follows:
Table 1 – Levels of Risk With HAZOP Recommendations Implemented
Risk Level Risk Scenario
Boilers
Level 4 No scenarios identified remain at Level 4
Level 3 FAC due to increase in normal operational flow (scenario 1)
Financial effect only: Risk of increased copper transportation (scenario 5). Reduced to a Level 1 based on feasibility study.
Failure of new pressure parts (scenario 7, 15, 19, 26, 50)
Increased maximum flow exceeds maximum capacity of superheater safety valves (Scenario 14). Reduced to a Level 1 based on commissioning data and plant control settings.
Level 2 Detailed in HAZOP Minute sheets in Appendix 1
Level 1 Detailed in HAZOP Minute sheets in Appendix 1
Turbine Hydraulic Power Unit
Level 4 No scenarios identified remain at Level 4
Level 3 No scenarios identified remain at Level 3
Level 2 Detailed in HAZOP Minute sheets in Appendix 1
Level 1 Detailed in HAZOP Minute sheets in Appendix 1
Low NOx Burners
Level 4 No scenarios identified remain at Level 4
Level 3 No scenarios identified remain at Level 3
Level 2 Detailed in HAZOP Minute sheets in Appendix 1
Level 1 Detailed in HAZOP Minute sheets in Appendix 1
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4 CONCLUSION
The formal HAZOP review process for major project is part of EE’s multilevel risk management strategy and represents a clear commitment by EE as to the management of risks for the business and for safety, health and environment.
This type of process allows for input by a number of experienced and senior representatives from operations, design, maintenance, safety etc. at a defined number of stages throughout the life of the project, from early conception through to detailed design and to final operation.
It provides an opportunity for a multidisciplinary team to formally review a proposal and to use their experience and corporate memory to improve this proposal and wherever possible avoid any repeat of errors or issues that may have occurred in the past.
The team that took part in the HAZOP reviews which are presented in the present report participated freely and with a high degree of expertise.
This is apparent from the results from these HAZOP Study reviews which provides for a solid understanding as to the risks associated with the projects.
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A1.1 HAZOP Study Report Of The Turbine Hydraulic Power Unit, Boiler Upgrade And Low Nox Burners As Part Of The Eraring Energy Power Station
Upgrade Project
Appendix 1
HAZOP Minutes
Burner HAZOP
Turbine Hydraulic Power HAZOP
Low NOx Burner HAZOP
HAZOP Study Report of the Turbine Hydraulic
Power Unit, Boiler Upgrade and Low NOx Burners
as Part of the Eraring Energy Power Station
Upgrade Project
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BOILER HAZOP
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1 General - -
Line: Feedwater from economiser inlet through to drum and furnace.
2 High Flow FAC due to increase in normal operational flow.
May lead to pipe failure and loss of containment of high pressure water, injury from burns, possible fatalities
Thickness survey already conducted. Planned thickness survey 4 years after start up, No change in geometry
4 2 3 a. Determine high risk areas in terms of FAC. Perform Thickness survey at targeted areas at first CMOP outage on units 4 and 2 and correlate to duration above original design flow. b. Record the extent of flow above original design (for use in thickness survey mentioned in action 1a above) c. Confirm that FAC study by CW has been completed and is valid for current design.
4 1 3
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3 High Flow Inability of drum to effectively separate water from steam at higher flow rates of upgraded design.
If drum unable to effectively separate water form steam, the possibility of carryover of water to superheater. Deposition of chemicals and erosion of turbine blades
Design 2 2 2 Perform carry over test at commissioning of unit 4 and if carryover found engineer out (i.e. replacement separators)
1 1 1
4 High Flow Increased maximum flow exceeds maximum capacity of drum safety valves.
Over pressurisation of drum may cause failure. May lead to pipe failure and loss of containment of high pressure water, injury from burns, possible fatalities.
Design review carried out by Connell Wagner and the safety valves on the drum have been confirmed to be adequate. (10% margin above 750MW flow rate.) With this safeguard in place this scenario has effectively been eliminated.
1 1 1 No further action identified. 1 1 1
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5 High Pressure
Risk of increased copper transportation
Eventually carry-over of copper through to turbine blades. Copper affects the efficiency of the turbine and may cause blockage in superheater tubes. The copper transportation issue will also require a change in manner of which maintenance is carried out on superheaters. Decrease life on LP heaters.
Ongoing routine copper transportation survey. Strategy Review being conducted on merits of chemically cleaning the superheaters versus foam clean of turbine. Procedures for boiler tube repairs have been reviewed. New boiler chemical controls are being installed to reduce copper transportation from LP heaters. Improved start up and shut down procedures.
4 4 4 a. Successful chemical clean carried out on super heaters and turbine. Carry out routinely if cannot stop copper transportation. brevier sliding pressure characteristic. c. Replacement of LP heaters to allow oxygenated treatment (this option is being considered).
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6 Low Flow Imbalance of flow between front and back pass economisers
Flow may be too low in front pass encroaching in steaming margin. May cause pipe damage and level stability issues in drum (so called drum swell). Mixing at T-piece may be unstable.
Design review carried out. Regular operational inspections to confirm design review outcomes. Hazard warning through noise.
1 1 1 Install thermocouples on each outlet header of economisers.
1 1 1
7 Low Flow Failure of new pressure parts
May lead to pipe failure and loss of containment of high pressure water, injury from burns, possible fatalities.
Design and constructed to standards including inspection, testing and NDT.
4 1 3 No further action identified. 4 1 3
8 Low Temperature
Design will lower economiser duty by 35%
Lowering of the feedwater temperature to the drum which leads to higher gas flows and increased risk of erosion.
Parameters have been given to designers as part of design scope and outcomes have been reviewed and accepted by Eraring.
1 1 1 No further action identified. 1 1 1
9 Impurities Construction debris left in system.
Blockages, tube starvation and failure. Financial effect. Impact on human Safety low.
Construction methodology including flush processes. Visual inspections, ITP's
2 2 2 No further action identified. 2 2 2
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10 Reaction Cooler temperatures in economiser
Possible reduced effectiveness of chemical dosing regime (particularly at start up)
Tube samples at outages. Continuous chemical monitoring. Upgrade of Chemical Control Room (CCR) with respect to instrumentation.
1 2 1 Issue to be reviewed by Chemical Team.
1 1 1
11 Operability New operating parameters
Potential mal operation impacting life and viability of equipment.
Training requirements 1 2 1 New performance data sheets to be compiled.
1 1 1
12 Operability/maintaina-bility
Obstruction to galleries from new economiser feed pipe to drum.
Poor access around and into boiler
Ensure adequate access around boiler
1 1 1 No further action identified. 1 1 1
13 Instrumenta-tion
inadequate information of plant condition
Failure to understand plant condition
Existing instrumentation will be a guide to requirements for new equipment.
1 1 1 Refer to action No.6 w.r.t. thermocouples
1 1 1
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Line: Steam from the Heat Recovery Area outlet header through the Superheaters to the Main Steam Outlet
14 High Flow Increased maximum flow exceeds maximum capacity of superheater safety valves.
Over pressurisation of superheater may cause failure. May lead to pipe failure and loss of containment of high pressure water, injury from burns, possible fatalities.
Designer review carried out by CW. Relieving capacity reduced from IHI design of 155.6 to 139.4 kg/s. Minimum Aust Standard code requirements (20% of steam flow relieving) equates to max steam flow rate of 695kg/s, hence steady state 750MW flow conditions of 624kg/s within this margin. Original design assessment allowed for discharging 25% of steam flow rate through superheaters and under this basis 622 kg/s is maximum steam flow under original IHI design or 557 kg/s under revised CW capacity.
4 2 3 a. Establish actual flows at commissioning for overload and revise plant limits if necessary b. Plant limitation to be included in amended plant operating manuals. c. Based on findings in (a) determine need to install larger size safety valves to allow achievement of additional overload above 633 kg/sec (being 22% of the revised CW relieving capacity).
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15 Low Flow Failure of new pressure parts
May lead to pipe failure and loss of containment of high pressure water, injury from burns, possible fatalities.
Design and constructed to standards including inspection, testing and NDT.
4 1 3 No further action identified. 4 1 3
16 High Temperature
Higher steam temperatures resulting in more frequent use of spray water
Potential for thermal fatigue failure of spray water system
Original design and material selection. 12-yearly inspections of spray water systems.
3 2 2 Increase frequency of inspections of spray water system (currently 12-yearly).
3 1 2
17 High Temperature
Insufficient capacity of spray water to control superheater steam temperatures.
Accelerated creep life usage. Material Failure.
Design parameter reviewed and accepted by Eraring Energy. Metal temperature operational limits and alarms (except SSH).
1 1 1 No further action identified. 1 1 1
18 High Temperature
Accelerated creep life consumption of headers
Reduced life of headers
Software system to monitor header life (ODAS). Field testing - replication of headers
2 2 2 Update/improve ODAS 2 1 1
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19 High Temperature
Reduced creep life of welds
Pressure part weld failure. Loss of containment of steam internal of boiler, could be external to boiler. Burns.
Asset Strategy defined field test for creep life of welds
4 1 3 No further action identified. 4 1 3
20 High Temperature
Burner replacement
Higher or lower temperatures
To be covered in burner HAZOP
- - - To be covered in burner HAZOP
- - -
21 High Temperature
Increased primary superheater surface area
Higher steam temperature for stages 1,2 and 3 resulting in higher metal temperatures causing metallurgical failure.
Design review has indicated that materials are suitable for duty
1 1 1 No further action identified. 1 1 1
22 Impurities Increased flow rate increases demand on polishing plant, particularly during periods of salt leaks
Salt leak tolerance reduced due to lack of polishing plant capacity. Load reduction, boiler damage
Reduce load as operating procedure. Polishing plant capacity review is carried out by CW
1 3 2 a. Implement actions from CW review on polishing plant capacity. OR b. Review the turbine condenser life strategy
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23 Impurities Increased exfoliation of internal stable oxide layer due to the increase flow rate and heat fluxes
Blocked super heater tubes or solid particle erosion of HP turbine
Not an issue at current operating conditions.
2 2 2 Desk top review of superheater metallurgy and susceptibility to the phenomena
2 1 1
24 Instrumentation
Inadequate information of plant condition
Failure to understand plant condition
TBA 1 1 1 Review instrumentation when it becomes available from designers
1 1 1
Line: Steam from superheater outlet valve through the Reheater to IP Turbine
25 High Flow Increased maximum flow exceeds maximum capacity of Reheater safety valves.
Over pressurisation of Reheater may cause failure. See No. 1 above.
Design review carried out and confirmed. Maximum Reheater flowrate of 646kg/s for existing safety valves. Hence superheater safety valves are the first high flow limitation with respect to boiler safety valves.
1 1 1 No further action identified. 1 1 1
High Flow Increased design flow and additional surface area increases DP across the Reheater
Reduced IP turbine inlet pressure which may lead to reduced output
Boiler turbine matching review completed with outcome for boiler designer to advise of Reheater DP
1 3 2 No further action identified. 1 3 2
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26 Low Flow Failure of new pressure parts
May lead to pipe failure and loss of containment of high pressure water, injury from burns, possible fatalities.
Design and constructed to standards including inspection, testing and NDT.
4 1 3 No further action identified. 4 1 3
27 High Temperature
Increased surface area enabling Reheater to exceed design temperatures
Metallurgical failure of tubing resulting in loss of generation and revenue. Reduced Creep life on hot Reheater header.
Temperature control with back pass dampers. ODAS system for creep life monitoring. Field replications as per strategy. Note: Existing spray water is decommissioned
2 2 2 Implement alarms on hot reheat steam outlet temperature. Implement appropriate training.
2 1 1
28 High Temperature
Tube failure of hot Reheater elements due to achieving design temperatures
Tube failure unit out of service, loss of revenue
Material review carried out by designers
1 1 1 No further action identified. 1 1 1
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Line: Furnace Area/gas side - from Ash hopper throat to furnace rear wall screen tubes.
29 High Flow Increased firing Increased gas flow causing increased vibration/movement on superheater pendants leading to tube failure.
Outage inspections/condition monitoring, acoustic detectors will limit the impact.
2 2 2 No further actions 2 2 2
30 High Flow No erosion issues identified
- - - No further actions - - -
31 High Pressure Upgrade not affecting existing
- - - No further actions - - -
32 Low Pressure Upgrade not affecting existing
- - - No further actions - - -
33 High Temperature
Refer to Low NOx Burner HAZOP Slagging
No further actions
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34 High Temperature
Increased time at higher metal temperatures on superheaters.
Increased rate of creep life consumption requiring early replacement.
CMOP inspection for gap between pendants and nose
1 1 1 Furnace flue gas temperature measurements to confirm design expectations. Consider metal temperature instrumentation on SSH if flue gas temperatures high.
1 1 1
35 High Temperature
Increased temperatures on superheaters leading to increased metal temperatures
Increased rate of creep life consumption requiring early replacement.
CMOP inspection for gap between pendants and nose
1 1 1 As per 6. 1 1 1
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Line: Backpass (superheater and Reheater passes)
36 High Flow Overall average velocity increases with reduced bias from front to rear pass - specifically higher flow in the superheater compared to previously. High flow causes grit erosion
Tube failures, increased maintenance/costs, shorter life
CMOP inspections and shielding as identified in surveys for current known high wear areas. Existing baffling along the wall sections. Acoustic detectors to minimise damage in the event of a failure. Tube wall thickness design takes into account exposure to erosion. New economiser panels have all bends enclosed out of gas flow.
3 3 3 a) Design process to consider baffling, shielding and soot blower locations in primary superheater and Reheater. b) Review to include rear wall penetration and seal boxes as now in an area of historical high risk. c) Prior to warranty expiration (12 months) take unit out of service for grit erosion survey on new design items. d) Cold air flow testing and smoke bombs to identify high velocity areas and record high flow areas for targeted inspection - adjust baffling or shielding as required. e) Perform inspections on previously un exposed areas while elements are removed during upgrade. f) Modify the boiler strategy to reflect concerns and learnings from inspections.
2 2 2
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37 High Flow Overall average velocity increases with reduced bias from front to rear pass - specifically higher flow in the superheater compared to previously. High flow causes grit erosion
Possible increased grit erosion on dampers, with increased maintenance costs - damper failure loss of temperature control
CMOP inspections to confirm if problem has increased from current
1 1 1 Inspect at 12 month warranty survey
1 1 1
38 Low Pressure Higher DP across finned economiser.
ID fan capacity margin is reduced which may lead to forced load limitation particularly in summer.
Soot Blowing
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2 2 Review ID fan cut back set point with regards to the risk of duct implosion limits.
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39 Low Pressure Higher DP across finned economiser.
More soot blowing to control dust build up in finn tubes, potentially causing higher rates of soot blower steam erosion on tubes leading to tube failure.
Shield soot blower steam impact areas.
2 1 1 No further actions 2 1 1
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40 High Temperature
Higher gas temperatures.
Affects uncooled metal on backpass including baffles, soot blower openings and nose sealing causing metallurgical degradation including plastic deformation and exfoliation leading to early replacement of items.
CMOP inspections 1 3 2 Review material selection
1 2 1
41 High Temperature
Higher gas temperatures.
Increased soot blowing to prevent air heater seizing (365 C max).
Existing plant limits and alarms, soot blowing
1 2 1 No further actions 1 2 1
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42 High Temperature
Higher gas temperatures.
Fabric filter bag failures due to excessive shrinkage leading to cell isolations and potential environmental licence accidence if load not reduced. Long time to implement repairs due to long lead time (3-6 months) on bags. Risk exposure exists until 2015 when all PAN filter bags would have been replaced. Currently Eraring has excellent bag life with 6 to 7 year bag replacement cycle.
Using PAN/PPS bags since 2008 to increase operating temperature range from 125 to 135. Attemperating air system initiates at 125 deg C. High Alarm at 135 deg C with High High alarm at 140 degree - for load reduction Doosan Design brief basis is 135 C at air heater exit at 720 MW with a 32 degree ambient air temperature. Fabric filter bag supply contract requires 8 cells of bags on site
4 2 3 a) Documentation to be produced to implement an operating limit of 135 C to manage bag life, with a nominal operating target of less than 130 deg C.. b) Adjust operating limit down on subsequent units if rapid multi cell failures occur. c) Consideration of attemperating air spray system if operating need exists. d) Stock holding costs versus risk to be assessed. e) Investigate stock holding limits with contracted supplier.
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43 Low Temperature
Actual low load operation
Modelling indicates insufficient heat available for hot primary air at 300MW load resulting in mill outlet temperature drop of 10 deg C to 70 deg C during winter at 300MW - poor burner performance. Refer to Low NOx Burner HAZOP.
Has not been an issue at Eraring. Existing temperature Ok hence model accuracy at low load may be less precise than the design brief control range of 500MW +.
1 1 1 Additional baskets in air heater if required. If identified as an operational issue bid unit higher.
1 1 1
44 Low Temperature
Actual low load operation
Air heater cold end acid attack and plugging due to dew point resulting in additional maintenance outages and reduced life of air heater baskets.
Boiler modelling study indicates acceptable minimum temperature. SAH bypass allows regulation in winter at low load.
1 1 1 No further actions 1 1 1
45 Impurities Excessive tube fouling due to improper soot blower locations
High boiler back end temperatures leading to issues above for high temperature.
Review of boiler design with regard to soot blower locations. Performance guarantee statement in boiler contract.
2 2 2 a) Review operational performance. b) Use contract to pursue performance short falls.
2 2 2
c:\erapow\12-b177\HAZOP Report Upgrade Project Rev B.Doc Revision B 14 July 2009 A1.19 HAZOP Study Report Of The Turbine Hydraulic Power Unit, Boiler Upgrade And Low Nox Burners As Part Of The Eraring Energy Power Station Upgrade Project
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46 Plant Items Poor access to bottom bank Reheater tubes
In the event of a tube failure the outage may need to be extended to gain access to carry out repairs
None 3 3 3 Currently being discussed in design review to achieve workable access for maintenance
2 2 2
47 Plant Items Poor access to economiser feed main and Reheater inlet pipework
Difficult access for operators and maintainers leading to possible injuries or extensions of outage periods.
None 2 3 2 Currently being discussed in design review to achieve workable access for maintenance
1 1 1
48 Instruments Changed conditions
Primary superheater temperatures hotter due to larger surface area meaning redefinition of plant limits.
None 1 2 1 Review alarm limits after initial operation or during commissioning.
1 1 1
Line: Overview
49 Materials for construction
Poor quality or incorrect materials due to manufacture or transportation
Tube failure or shortened life
QA system, warranty, third party inspector and inspections. Experienced boiler manufacturer.
2 1 1 No further actions 2 1 1
50 Construction Site weld failing Tube failure and injury
100% radiography on all site tube welds, all other site welds to be NDT in compliance with Australian standards.
4 1 3 No further actions 4 1 3
c:\erapow\12-b177\HAZOP Report Upgrade Project Rev B.Doc Revision B 14 July 2009 A1.20 HAZOP Study Report Of The Turbine Hydraulic Power Unit, Boiler Upgrade And Low Nox Burners As Part Of The Eraring Energy Power Station Upgrade Project
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51 Construction Insufficient power supplies for construction purposes
Delays in meeting program
None 3 4 4 Place on Electrical project teams and Site Operations Managers agenda
1 1 1
52 Construction Insufficient access for operations such as cranage due to other works eg bottom ash hopper crushing plant and boiler upgrade crane location
Delays in meeting program
None 3 4 4 Place on Site Operations Managers agenda
2 2 2
53 Loads on structures
Change in boiler components
Change in load distribution
Separate structural review being undertaken by Aurecon which also includes earthquake and wind load code compliance.
4 2 3 Action resulting from design study to reflect latest Australian Standards and Codes
1 1 1
54 Commissioning New Plant Operators not aware of issues or performance of new plant
Training of operators. Contractor to provide expected performance data sheets. Eraring Energy commissioning team to communicate change boiler performance.
3 2 2 Confirm designer actively involved and present at commissioning.
1 1 1
c:\erapow\12-b177\HAZOP Report Upgrade Project Rev B.Doc Revision B 14 July 2009 A1.21 HAZOP Study Report Of The Turbine Hydraulic Power Unit, Boiler Upgrade And Low Nox Burners As Part Of The Eraring Energy Power Station Upgrade Project
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55 Commissioning New Plant Superheater control system requires retuning to suit new plant to prevent header design material limits being exceeded and poor operational performance
Existing control will provide initial safe operation. Eraring Energy commissioning team to communicate change boiler performance.
1 3 2 Post commissioning optimisation tuning
1 1 1
56 Start Up New Plant Changes to existing job sheets for boiler start up leading to plant damage or injury
Boiler project team work scope includes procedural review
4 2 3 Completion of plant modification process
2 1 1
57 Shut down New Plant Changes to existing job sheets for boiler shut down leading to plant damage or injury
Boiler project team work scope includes procedural review
4 2 3 Completion of plant modification process
2 1 1
58 Breakdown New Plant Unidentified tube leaks causing extensive failure due to incorrect location of acoustic detectors.
None 3 2 2 Locations being considered as part of design review
2 1 1
59 Breakdown New Plant DNB leading to water wall failure
Modelling indicates DNB is not an issue at 750 MW. Money budgeted to purchase heat flux probes.
2 1 1 Install heat flux probes and alarm package to ICMS
1 1 1
c:\erapow\12-b177\HAZOP Report Upgrade Project Rev B.Doc Revision B 14 July 2009 A1.22 HAZOP Study Report Of The Turbine Hydraulic Power Unit, Boiler Upgrade And Low Nox Burners As Part Of The Eraring Energy Power Station Upgrade Project
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60 Safety Crane operation and lifting
Injuries Boiler Upgrade Risk Review Stage 2 - conducted 24th September 2008 TRIM doc09/15023 covers this issue.
No further actions
61 Safety Equipment
Installation of new plant
Injuries to personnel existing safeguards under OHS legislation and corporate policy
No further actions
62 Output Higher firing rate Increased air demand
Has been reviewed - FD and ID confirmed with suitable margin.
1 2 1 Review plant performance during and after commissioning.
1 1 1
63 Output Higher firing rate Capacity of hoppers and resultant overflow to air heaters increasing DP and causing potential load restrictions
Current operating regime for emptying hoppers
2 3 2 Review plant performance during and after commissioning.
1 1 1
64 Output Higher firing rate Insufficient milling capacity resulting in load restriction
Modelling indicates marginal capacity if one mill unavailable for overload above 720 MW
2 2 2 Review plant performance during and after commissioning. Review classifier revised design if marginal.
1 2 1
c:\erapow\12-b177\HAZOP Report Upgrade Project Rev B.Doc Revision B 14 July 2009 A1.23 HAZOP Study Report Of The Turbine Hydraulic Power Unit, Boiler Upgrade And Low Nox Burners As Part Of The Eraring Energy Power Station Upgrade Project
TURBINE HYDRAULIC POWER UNIT HAZOP
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1 General Location of HPU (cleaning aspects, fire from nearby facilities/equipment, potential energy - impact from items dropping from above, welding etc. etc.)
Security and integrity of operations
To be determined - - - Location of HPU to be reviewed against security and integrity (cleaning aspects, fire from nearby facilities/equipment, potential energy - impact from items dropping from above, welding etc. etc.) Compliance with the Fire Safety Report to be checked
- - -
Line: Fluid Actuator Supply (FAS)
2 High Pressure
Pump fails to cut out
Pump dead heading, Pipe failure, pump failure, Unit out of service. Loss of electricity generation. Financial impact.
Relief valve FV-3 back to tank; Pressure sensors (x3) on manifold.
2 1 1 a) Provide detection and alarm for high pressure situation on manifold. b) Provide Eraring tag names on contractor's drawings.
2 1 1
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3 General Work on actuators
Injury to personnel Permit to Work system
3 2 2 a) Ensure lines are depressurised b) Ensure PPE is used when contact with hydraulic fluid is possible
3 2 1
4 Low pressure Blocked inlet to pipe, or blocked strainer
Loss of pressure to unit, inability to open valves. Loss of electricity generation. Financial impact.
Stand-by pump cut-in on low pressure; trip on low pressure; system to close valves; pressure switch across strainer with alarm.
2 1 1 No further improvements identified. 2 1 1
5 Low pressure Stand-by pump set on manual
Loss of pressure to unit, inability to open valves. Loss of electricity generation. Financial impact.
Alarm entry trip on low pressure; system to close valves
2 3 2 Provide adequate logic to ensure stand-by pump is available to cut in automatically on low pressure.
2 1 1
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6 Low pressure Pipe broken due to mechanical damage or fatigue
Loss of containment of ester, oil would escape (small spray failure through to large loss); environmental damage; possibly operator injury from high pressure and from harmful properties; unit shut-down. Financial effect.
Stainless Steel and welded pipework; Low level alarm and trip on tank.
3 2 2 a) More detail on pipe selection (is it seamless?) b) Request MSDS for ester. c) Ensure layout of all pipework associated with the HPU prevents impact from moving machinery. d) Dangerous Goods and Hazardous substances assessment to be implemented in accordance with the Codes e) Provide identification on Stainless steel lines eg coloured labels with directional symbols. f) Site installation to comply with AS4861. g) Provide rate of change alarm on oil tank to indicate an unusual (unscheduled) loss of oil supply.
3 1 2
7 Low Pressure
Loss of pressure through failure of NRV on the out-of-service pump
Loss of pressure to unit; Inability to open valves. Loss of electricity generation. Financial impact.
Alarm trip on low pressure; System to close valves; Contractor to supply a maintenance regime in OP and Maint manuals
2 1 1 No further action recommended 2 1 1
8 Low Pressure
Stand-by pump switched on but fails to operate.
Loss of pressure to unit, inability to open valves. Shut-down of Unit. Financial impact.
Pressure switches 280A and 280B; Pump start switches and running switches.
2 2 2 ICMS logic to prevent shut-down of running pump before confirmation of adequate running of stand-by pump
2 1 1
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9 Low pressure Low level in tank due to drain valve left open or hole in tank
Loss of oil to valves, unit shut-down. Loss of electricity generation. Financial impact.
Low level alarm, Contaminated water drain captures spill.
2 2 2 a) Ensure appropriate job sheeting, PRIs. b) Training and documentation to define criticality of system c) Containment of fluid required to prevent entry into contaminated drains
2 1 1
10 Reverse Flow
Malfunction of servo leading to excessive flow to one server.
Loss of system pressure possibly leading to trip on low pressure. Loss of electricity generation. Financial impact.
Unknown 2 ? ? Ask contractor if the failure is possible and what are the safeguards
2 ? ?
11 High Temperature
High Temperature of oil piping due to failure of cooling system
Possible burns if system temperature increases above normal; Shorten service life of equipment; Possible degradation of oil and seals; System malfunction. Loss of electricity generation. Financial impact.
Maximum temperature 49 degrees before automatic switch on of cooling system, High temperature alarm above 66 degrees.
2 2 2 No further improvements identified.
12 Low Temperature
Low oil temperature after outage
Low flow, unpredictable operation.
Low temperature protection on start; Ability to heat oil
1 2 1 a) Contractor to advise minimum oil temperature interlock before starting after outage. B) Job sheets for cold start flow chart.
1 1 1
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13 Impurities Contamination during maintenance, construction Filters not maintained; Equipment failure. Hydroscopic nature of ester - water in oil
Valves stuck, high wear, unpredictable operation, possible shut-down. Loss of electricity generation. Financial impact.
Automatic and continuous polishing filter; Sealed system except for opening for dryer; Maintenance for regime as per contractor specifications; A number of trips and alarms for system malfunction (e.g. Low pressure trips).
2 2 2 a) Routine oil sampling. b) Determine spare parts requirements. c) Routine maintenance as per OEM recommendations. D) How long can unit continue operating without the continuous polishing filter? - Check with contractor.
2 1 1
14 Testing Failure to maintain equipment redundancy - failure of plant items.
Loss of redundancy. Shut-down. Loss of electricity generation. Financial impact.
Routine Testing of Stand-by Plant
2 1 1 a) Set up routine testing in accordance with contractor's recommendations.
2 1 1
15 Testing Failure of protective devices
Plant damage or shut-downs. Loss of electricity generation. Financial impact.
Routine Testing of protection devices. Fault tolerances. Redundancies for critical items.
2 1 1 a) Set up routine testing in accordance with contractor's recommendations. B) Routine calibrations of instrumentation.
2 1 1
16 Operability Maintena-bility
Visibility of instrumentation
Failed ability to troubleshoot. Restricted access unless safety rail.
n/a 2 2 2 a) Ensure all instrumentation can be easily read from ground level.
2 1 1
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17 Operability Maintena-bility
Filters and other items requiring access for maintenance.
Unable to easily access filters while complying to OHS guidelines.
n/a 2 2 2 a) Review design to optimise ease of access for items that require maintenance eg filters
2 1 1
18 Instruments No secondary isolation provided on pressure gauges PI-280A, B, C
Inability to isolate pressure gauge for removal in case of failure of primary isolation valve. Risk of injury during the removal of blanking plug. Injury to personnel
Primary isolation valve
3 2 2 a) Consult with Eraring to provide additional isolation and venting for instrument testing. b) the design is to be reviewed once the equipment has arrived on site
3 1 2
19 Operability Maintenance
Removal of Pump MRP
Safety issue with high pressure (11 Map)
Primary isolation valve. Pressure gauge. (Non-return valve)
3 3 3 A) Ensure positive isolation to allow stand-by pump removal. (As per Eraring Energy requirements- EPS to mark drawings) B) Ensure main isolation valves can be locked out.
3 1 2
Line: two parallel FAS supply from tank - BY DIFFERENCE WITH ABOVE HAZOP OF FAS
No additional scenarios identified
Line: fluid emergency trip supply from tank through ETD towards valves (Hasp ETD as graybox) - BY DIFFERENCE WITH ABOVE HAZOP OF FAS
No additional scenarios identified
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Line: fluid trip drain from valves back to tank
20 High pressure
Impact on line causes pinching
Inability to trip turbine. Burst of drain pipe. Injury to personnel
Appropriate layout of piping (very short pipe). Protection of pipe between structures.
4 1 3 A) Review layout of drainpipe to rule out impact. B) Consult with contractor as to implications of a blocked drain line on operation. C) Ensure EE field surveillance officer approves pipe line layout with attention to mechanical damage and weld inspection D)EE emergency procedures to be implemented to contain hydraulic fluid
3 1 2
Line: fluid drain - BY DIFFERENCE WITH ABOVE HAZOP OF FAS
21 High pressure
Impact on line causes pinching
Inability to position valve. Burst of drain pipe. Injury to personnel
Appropriate layout of piping. Self draining.
3 1 2 A) Review layout of drainpipe to rule out impact. B) Consult with contractor as to implications of a blocked drain line on operation. C) Ensure EE field surveillance officer approves pipe line layout with attention to mechanical damage and weld inspection. D)EE emergency procedures to be implemented to contain hydraulic fluid E) Review material selection of drain line to handle full system pressure in the event of a blockage (current design is 1.4 MPa versus supply pipe all pipework which is 11MPa)
3 1 2
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Line: Oil circulation loop through transfer and filtering pump, conditioning filter and polishing filter.
22 High pressure
Blocked filter Thermal overload on transfer pump motor
Pressure relief valve, discharges into tank. Routine filter maintenance. Local pressure gauges
1 2 1 Refer action number 13d) regarding how long unit can operate without polishing system.
1 2 1
23 Low pressure Mal-operation of valves or valve leak eg drain valve FV-79 or sample valve FV-75 or valve FV-78 or FV-80
Potentially drain the tank and trip unit on low oil tank level and/or low oil pressure. Loss of containment, environmental pollution.
Protection devices. Drain directed to contaminated water system.
2 2 2 a) Proper job sheeting b) Training c) Ensure ICMS logic trips transfer pump on tank low level and tank high high. Also refer to action 6g) regarding alarming on rate of change.
2 1 1
24 Low flow Pump failure Failure to polish. . Loss of electricity generation. Financial impact.
Operator rounds 2 1 1 a) Refer action regarding how long unit can operate without polishing system b) Set-up operator routine to inspect oil system operations.
2 1 1
25 Impurities Filters in series rather than parallel
Functional spec refers to filters in parallel
- - - - a) Specifications calls for filters in parallel. Drawing shows filters in series - Contractor to clarify.
- - -
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26 Testing Failure to test oil in tank
Blockages and oil degradation. Maintenance problems leading to needing to overhaul all servos. Loss of electricity generation. Financial impact.
Condition monitoring group exists on site
2 1 1 a) Communication required with condition monitoring group b) Query whether phosphate ester is subject to organic growth
2 1 1
27 Operable and maintainable
Access to conditioning filter
Inability to maintain filters. Injury risk from fall from heights.
Work from heights procedure. PTW.
2 3 2 No further action required 2 3 2
28 Operable and maintainable
Poor maintenance of oil conditioning system
Safety and operability. Possibility of draining oil out of tank. Environmental pollution. Loss of electricity generation. Financial impact.
Isolation valves exist. Drain directed to contaminated water system where it is contained.
2 2 2 a) Adequate PRIs b) Lockable isolation valves and switches to conform with EE standards.
2 1 2
29 Electrical Location of emergency stop
Unable to operate and stop HPU locally
Not yet defined 2 2 2 a) Determine EE requirements and advise contractor with respect to location of start and stop buttons.
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Line: Oil addition from drum through transfer and filtering pump, conditioning filter and polishing filter (BY DIFFERENCE)
30 Reverse flow FV -70 open during drum transfer or leaky FV-70
Reverse flow of oil back to drum unloading area. Environmental pollution.
Operator vigilance. Contain spill
2 1 1 a) Additional check valve down stream of FV-78 b) Hydraulic fluid containment required
2 1 1
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31 Impurities Contaminated oil, wrong oil, dirty hose
Overwhelmed filter, stop polishing unit, degradation of fluid, total hydraulic oil system shut-down, damage to hydraulic components. Loss of electricity generation. Financial impact.
Labelling of drums. 2 2 2 a) Filling and draining procedures required. b) Quality control of oil supply.
2 1 1
32 Operability and Maintaina-bility
Leakage of oil from tank valving, field devices, drums, servos
Slippery surface, environmental pollution, loss of oil requiring more top-ups, hazardous substance (?)
Housekeeping 2 2 2 a) Oil containment mitigation methods to be investigated. b) Implement emergency response procedures
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Line: Cooling and heating systems
33 Low Flow Blocked Hydraulic fluid cooler
High oil temperature. Degradation of oil. Increase in oil pressure. Loss of electricity generation. Financial impact.
Pressure relief valve FV-34. High temperature alarm. Duty stand-by cooler.
2 1 1 a) Fix up drawing referring to TS-2808 (temperature switch no longer there)
2 1 1
34 Reverse flow Failure of the solenoid
Leads to excessive cooling
Automatic shut-down of heating and cooling pump. Temperature transmitter.
1 1 1 a) Ensure manual override of solenoid valve.
1 1 1
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35 Reverse flow Solenoid valve stuck in energised position
Overheating leading to degradation of oil. Loss of electricity generation. Financial impact.
High temperature alarm. Duty stand-by cooler.
2 1 1 No action. Refer to action regarding how long the Unit can run without the polishing.
2 1 1
36 Low pressure Failure of flexible connection
Oil spill, trip on low pressure or on low tank level.
Trips. 2 2 2 a) Routine inspections and replacements. Refer to action rate of change 6g).
2 1 1
37 Low pressure Pump failure Inability to cool or heat
Duty stand-by. Temperature alarm.
2 1 1 a) Provide pump failure alarm (general for all pumps)
2 1 1
38 High temperature
Failure of cooling fan
Overheating leading to degradation of oil. Loss of electricity generation. Financial impact.
Duty stand-by cooler. Temperature alarm.
1 2 1 a) Routine test operation of stand-by system. B) Suggest routine switchover of duty-stand-by systems.
1 1 1
Overview
39 Commissioning
Commissioning program and ITP
Commissioning program and ITP required to ensure safe and smooth commissioning
- - - - a) Contractors to supply commissioning program and ITP for EE approval.
- - -
40 Start-up and shut-down
Start up after outage and start-up of new unfamiliar plant. Routine Shutdown
Damage to plant. Personnel hazard
Contractors responsible for commissioning and handover. Plan is 50% of operators will be trained prior to first start-up. Plant modification checklist completed.
- - - Job sheets to be completed by the first start-up.
- - -
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41 Commissio-ning
Construction, commissioning and handover of new plant items.
Procedures required. EE required to carry out checks.
- - - - a) EE to review procedures for construction, commissioning and handover of new plant items. B) EE to carry out 100% interlock and protection testing
- - -
42 Breakdown Power failure Plant failure, possible unit shutdown
Redundant power supply to HPU.
- - - a) EE and contractor to finalise electrical schematics to ensure redundancy and fault tolerance
- - -
43 Breakdown Vents Blockages and oil degradation.
Routine replacement
- - - No further improvements identified. - - -
44 Breakdown ICMS failure Logic error - 2 2 2 Enquire about CHAZOP or other review of control logic.
2 1 target
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45 Fire and explosion
Combustible nature of Esther unknown (it is not a flammable material)
Fire damage. - 2 2 2 Contractor to supply details of hydraulic fluid
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46 Extreme limitation
a) Flexible hoses b) Servos contamination of fluid
Scenarios identified above. No new scenarios identified here.
Scenarios identified above. No new scenarios identified here.
- - - No further improvements identified. - - -
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LOW NOX BOILER HAZOP
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c:\erapow\12-b177\HAZOP Report Upgrade Project Rev B.Doc Revision B 14 July, 2009 A3.1 HAZOP Study Report Of The Turbine Hydraulic Power Unit, Boiler Upgrade And Low Nox Burners As Part Of The Eraring Energy Power Station Upgrade Project
Appendix 2
Report of the Preliminary HAZOP Study for the Hydrogen Circuit at the New Hydrogen Plant at Eraring Energy, Eraring, NSW
Approval for HAZOP Leader
HAZOP Study Report of the Turbine Hydraulic
Power Unit, Boiler Upgrade and Low NOx Burners
as Part of the Eraring Energy Power Station
Upgrade Project
c:\erapow\12-b177\HAZOP Report Upgrade Project Rev B.Doc Revision B 14 July, 2009 A3.2 HAZOP Study Report Of The Turbine Hydraulic Power Unit, Boiler Upgrade And Low Nox Burners As Part Of The Eraring Energy Power Station Upgrade Project
Phone: 02 9228 6108
Fax: 02 9228 6433
Email: [email protected]
Ms Karin Nilsson Planager Pty Ltd PO Box 248 Berowra Heights NSW 2082
Our ref:
Your ref:
File: Eraring power station upgrade HAZOP Chair.doc
4 May 2009
Dear Ms Nilsson
Subject: Eraring Eneregy Power Station Upgrade HAZOP
I refer to your letter, dated 27 April 2009, seeking approval for you to lead the HAZOP for the above project.
On the basis of the information previously supplied on your qualifications and experience, you are approved to conduct the HAZOP. You should note that the approval is specific to the current project and that separate approvals will need to be sought for any future HAZOPs.
If you have any further queries, please don’t hesitate to contact me.
Yours sincerely
Dr Derek Mullins Director, Major Hazards
c:\erapow\12-b177\HAZOP Report Upgrade Project Rev B.Doc Revision B 14 July, 2009 A3.1 HAZOP Study Report Of The Turbine Hydraulic Power Unit, Boiler Upgrade And Low Nox Burners As Part Of The Eraring Energy Power Station Upgrade Project
Appendix 3
Report of the Preliminary HAZOP Study for the Hydrogen Circuit at the New Hydrogen Plant at Eraring Energy, Eraring, NSW
Eraring Energy Risk Tool
c:\erapow\12-b177\HAZOP Report Upgrade Project Rev B.Doc Revision B 14 July, 2009 A3.2 HAZOP Study Report Of The Turbine Hydraulic Power Unit, Boiler Upgrade And Low Nox Burners As Part Of The Eraring Energy Power Station Upgrade Project
Overall Risk Rating
CONSEQUENCES
Low 1
Medium 2
High 3
Very High 4
Very High 4
3
3 4
4
High 3
2 2 3 4
Medium 2
1 2 2 3
Low 1
1 1 2 3
Table 2 –Risk Rating Classification
Risk Rating of 3
Risk Rating of 4
Risks rated 3 and 4 are defined as “material” and are summarised in the Project Management Plan, Form PMF2-1 for presented to the Sponsor and the Steering Committee.
Risk Rating of 1
Risk Rating of 2
Risks rated 1 and 2 should be identified and included in the Risk Register worksheet of the Risk Management Plan, Form PMF2-4 to allow appropriate monitoring.
Table 3 – Likelihood and Frequency Rating
Low
1 Medium
2 High
3 Very High
4
Probability of occurrence
10% 30% 60% 90%
Likelihood of occurrence
Remote Unlikely to occur
Possible Could occur
Probable Likely to occur
Almost Certain Almost certain
to occur
HAZOP Study Report of the Turbine Hydraulic
Power Unit, Boiler Upgrade and Low NOx Burners
as Part of the Eraring Energy Power Station
Upgrade Project
LIK
EL
IHO
OD
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Table 4 – Consequence Rating
Corporate Risk Category
DRAFT Indicative project risks that fall under this corporate category
Low 1
Medium 2
High 3
Very High 4
Operating Profit Budget overruns Forecasted benefit shortages Contractor insolvency Inaccurate estimates Procurement delays Insurance claims
Impacts operating profit between $0.5m - $2m
Impacts operating profit between $2m - $5m
Impacts operating profit in between $5m - $10m
Impacts operating profit in excess of $10m
Trading - Gross Margin
Impacts energy trading gross margin between 0.5% - 2.0% (between $2.4 and $9.5 million) of budgeted annual gross margin
Impacts energy trading gross margin between 2.0% - 5.0% (between $9.5 and $23.8 million) of budgeted annual gross margin
Impacts energy trading gross margin between 5.0% - 10.0% (between $23.8 and $47.5 million) of budgeted
Impacts energy trading gross margin by more than 10% (greater than $47.5 million) of budgeted annual gross margin
Generation Operations
Unscheduled outages Delays in plant completion
Minimal impact on achieving operational objectives Short term Minor loss of plant function with minor impact on production
Moderate impact on achieving operational objectives Generation capacity reduced by 1 unit for less than 7 days or MW/hr equivalent OR Loss of Kangaroo Valley Units for less than 7 days
Significant impact on achieving operational objectives Generation capacity reduced by 1 unit for more than 7 days or MW/hr equivalent or loss of 2 or more units simultaneously. OR Loss of Kangaroo Valley Units for more than 7 days
Detrimental impact on achieving operational objectives Generation capacity reduced for more than 14 days or MW/hr equivalent or the loss of 3 or more units simultaneously.
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Corporate Risk Category
DRAFT Indicative project risks that fall under this corporate category
Low 1
Medium 2
High 3
Very High 4
IT Systems System outages Loss of data
Short term loss of critical applications with minor business operational impact
Loss of critical IT Systems having a business operational impact for < 1 day
Loss of critical IT Systems having a business operational impact for > 1 day but < 2 days
Loss of critical IT Systems having a business operational impact for > 2 days
Telecommunications Short term loss of telecommunication services with little impact as alternative service capability is available
Loss of telecommunication services for <1 day having a minimal operational business impact.
Loss of telecommunication services having a business operational impact for >1 day but <2 days.
Loss of telecommunication services having a business operational impact for >2 days.
Media Minimal complaints. Readily respond to local forums
Several complaints. Local media coverage.
Multiple complaints State media coverage Significant impact to relationship with Eraring Energy major stakeholders
Multiple serious complaints National media coverage Significant impact to relationships with multiple Eraring Energy major stakeholders
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Corporate Risk Category
DRAFT Indicative project risks that fall under this corporate category
Low 1
Medium 2
High 3
Very High 4
Environment Spills Waste disposal Contractor practices Environmental breaches (e.g. oil/chemical/noise)
Nuisance / Localised impact
Short term issue, reportable to DECC but no environmental impact. Minor compliance issue or improvement notice issued
Medium term/environmental impact issue, reportable to DECC. Possible emergency response by external services required Definite prosecution or fine < $100,000
Long term/serious environmental incident, DECC involvement Emergency response required from external services Definite prosecution or fine > $100,000
Safety Risk of injuries Workcover claims
Minor injury – first aid required / Medical treatment injury (MTI) No lost time
Loss Time Injury (LTI) < 7 days
WorkCover (WC) Notifiable Event LTI Incident > 7 days
WorkCover (WC) Prosecution Serious injury or fatality or multiple injured persons.
Regulatory and Legislative requirements
Changes in legislative requirements
Minor breach not required to be reported to Regulator
Breach requiring non-compliance to be reported to Regulator Incident involving investigation by Regulator Sanctions (eg.) fines possible
Prosecution by Regulator Sanctions (eg fines) imposed by Regulator
Prosecution by Regulator or regulators involving multiple persons Sanctions (eg fines) imposed by Regulator on multiple persons
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HAZOP Study Report Of The Turbine Hydraulic Power Unit, Boiler Upgrade And Low Nox Burners As Part Of The Eraring Energy Power Station Upgrade Project
5 REFERENCES
1 NSW Government, Energy Directions Green Paper, December 2004
2 J Gaillard, Project Management Risk Assessment Guidelines, Guideline PMF2-4a, Eraring Energy, 8 May 2009