swp534v2 cleaning repairing & dismantling tanks

SWP – 534 Ver2 Revision 0

ENVIRONMENTAL, SAFETY, AND HEALTH

WORK PRACTICES

534: TANK CLEANING,

REPAIRING AND DISMANTLING


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Revision Log

Revision No.

Date By Approved

Reason for Revision

Section Change

0 31 May 2010 TBFD All New Version

Tank Cleaning, Repairing, and Dismantling PRACTICE

534

Chevron Products Company SWP – 513 Ver2 Revision 0

534:i Environmental, Safety, and Health Work Practices May 2010

Table of Contents

ABSTRACT .............................................................................................................................. 1 SECTION 1 – PURPOSE .......................................................................................................... 2 SECTION 2 – REFERENCES ................................................................................................... 2 SECTION 3 – DEFINITIONS ................................................................................................... 3 SECTION 4 – HAZARDS OF CLEANING, REPAIRING, AND DISMANTLING TANKS 4 SECTION 5 – JOB PLANNING ............................................................................................... 6 5.1 – Work Permits .................................................................................................................... 6 5.2 – Preparing for the Job ......................................................................................................... 9 5.3 – Emptying the Tank .......................................................................................................... 11 5.4 – Vacuum Trucks ............................................................................................................... 12 SECTION 6 - ROOF STABILIZATION ................................................................................ 13 6.1 – Standard Procedure for Steel Floating Roof Stabilization .............................................. 17 6.2 – Cribbing Floating Roofs ................................................................................................. 18 6.3 – Jacking Floating Roofs ................................................................................................... 20 6.4 – Jacking Fixed Roof Columns .......................................................................................... 20 SECTION 7 – TANK ISOLATION AND STATIC DISCHARGE HAZARDS .................... 22 7.1 – Cathodic Protection Systems and Static Discharge ........................................................ 22 SECTION 8 – TANK CLEANING ......................................................................................... 23 8.1 – Testing the Tank Atmosphere ......................................................................................... 23 8.2 – Personal Protective Equipment ....................................................................................... 25 8.3 – Cleaning Tanks Containing Organic Lead ...................................................................... 25 8.4 – Vapor and Gas Freeing Tanks ......................................................................................... 26 8.5 – Handling Hazardous Waste ............................................................................................. 28 8.6 – Using Agents ................................................................................................................... 29 SECTION 9 – TANK MAINTENANCE ................................................................................ 30 9.1 – Door sheet Removal and Reinstallation .......................................................................... 30 9.2 – General Tank Repairs ..................................................................................................... 33 9.3 – Tank-bottom Repairs ...................................................................................................... 34 9.4 – Dismantling Tanks .......................................................................................................... 35 SECTION 10 – RETURNING THE TANK TO SERVICE .................................................... 36 10.1 – Initial Fill ...................................................................................................................... 36 Appendix A ............................................................................................................................. 38

PRACTICE 534

Tank Cleaning, Repairing, and Dismantling


534:ii Environmental, Safety, and Health Work Practices May 2010



534


534:1 Environmental, Safety, and Health Work Practices May 2010

ABSTRACT

Overview of Practice 534

Environmental, Safety, and Health Work Practice 534: Tank Cleaning, Repairing, and Dismantling describes the precautions necessary to safely clean, repair, and/or dismantle atmospheric storage tanks. This Practice references several Environmental, Safety, and Health Practices that must be followed while performing work on tanks. Good judgment must be used when discrepancies occur between this Practice and other ESH work practices.

Regulatory requirements prevail

This ESH work practice attempts to incorporate state and Federal requirements. If any provision in this or other referenced ESH work practice conflicts with any regulatory requirement, the regulation shall apply.

Contents This Practice covers the following information:

References for information about working in and around tanks Relevant terms and definitions Hazards associated with cleaning, repairing, and dismantling tanks Job planning, including permits/form, preparation, and tank emptying Tank isolation and static discharge Tank isolation and roof stabilization Tank cleaning Tank maintenance Returning a tank to service

PRACTICE 534




SECTION 1 – PURPOSE

Purpose of Practice 534

Environmental, Safety, and Health Work Practice 534: Tank Cleaning, Repairing, and Dismantling describes the precautions and steps necessary to safely clean, repair, and/or dismantle atmospheric storage tanks. This Practice is used hand-in-hand with SWP 513 Confined Space Entry and references several other Safe Work Practice Standards. Its purpose is to ensure that Company personnel understand how to perform these tasks effectively and safely.

SECTION 2 – REFERENCES

References For additional and detailed information about working in and around tanks,

refer to the following documents:

Document Number Title API 2207 Preparing Tank Bottoms for Hot Work API 2015 Safe Entry and Cleaning of Petroleum Storage Tanks API 2016 Guidelines and Procedures for Entering and Cleaning

Petroleum Storage Tanks API 2217 Guidelines for Confined Space Entry in the

Petroleum Industry 29 CFR 1910.146, and appendices

Permit Required Confined Spaces

TES-TK-101 Braces of Floating Roofs in Pre-cleaned Tanks TES-TK-102 Entry Requirements under Floating Roofs after

Tanks have been Gas-Freed or Cleaned SCAQMD Rule 1149

Storage Tank Cleaning and Degassing

BAAQMD Standard 8-5-328

Tank Cleaning Requirements

GD SWP Procedure Assessing Hazards and Managing Risk Procedure ESH-506 Breaking Lines, Isolating, and Release of Equipment ESH-507 General Work Permit ESH-508 Hot Work ESH-509 Isolation of Hazardous Energy (Lockout/Tagout) ESH-511 Personal Protective Equipment ESH-512 Gas Testing ESH-513 Confined Space Entry ESH-517 Respiratory Protection


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SECTION 3 – DEFINITIONS

Relevant Terms The following table lists relevant terms and their definitions:

Term Definition Anti-rotation device

Device that prevents rotation of a floating pan or roof. Can include ladders, gauge poles, or devices specified in TES-TK-101, Terminal Engineering Standards.

API 2015 Certified Tank Entry Supervisor

Also called a “TES”. A person who successfully completed an API 2015 Tank Entry Supervisor course and who has a valid certificate.

Cathodic protection

Systems designed to prevent rusting of piping and tanks through use of impressed current and/or sacrificial anodes.

Class I, Division II, Group D

Electrical classification designating volatile, flammable liquids that are handled but normally kept in closed containers or systems. “Group D” designates gasoline and other volatile liquids.

Confined Space Entry Form

Form used in conjunction with a General Work Permit for entering a confined space.

Cribbing Framework to support a floating roof. Degassing Venting a storage tank through a control device. The device

controls fugitive emissions by adsorption onto activated carbon, or catalytic combustion.

Job Loss Analysis

Systematic method that outlines job steps, hazards, and safeguards needed to safely perform the task without loss.

Leg bracing 4 x 4 wood bracing used to support floating roof legs. LFL/LEL Lower Flammability Level/Lower Explosive Limit. Multi-gas meters

Devices that measure vapor concentrations of flammable and toxic gases. Usually read flammability (LFL or LEL), oxygen, carbon monoxide, and hydrogen sulfide, or sulfur dioxide.

Oxidizing agent

Agent that reacts exothermically (explosively) with hydrocarbons. Examples include potassium permanganate and hydrogen peroxide.

Oxygen deficient

Less than 19.5 percent oxygen.

Rim space blocks

Blocks used to prevent lateral motion of a floating roof or pan.

PRACTICE 534




SECTION 4 – HAZARDS OF CLEANING, REPAIRING, AND DISMANTLING TANKS

Introduction Tanks that have been in hydrocarbon service including tanks removed

from service and cleaned pose risks to workers. These risks include: Fire and explosion Toxic vapors (hydrocarbons, benzene, MTBE, organic

lead) Oxygen deficiency or enrichment Physical hazards Dust and fumes Painting vapors corrosion

This section summarizes these risks.

Fire and explosion

The following create fire and/or explosion hazards: Mixtures of hydrocarbon vapor and air can ignite if the

fuel-to-air ratio is within flammable or explosive limits. Sludge, if disturbed, can release hydrocarbon vapor.

Toxic vapors The following substances encountered in tank work, alone or acting together,

may have a detrimental effect when inhaled: Gasoline Ethanol Diesel fuel Jet fuel Aviation gas Additives Coatings Grit used to clean tanks Welding Fumes Paint Vapors

Continued on next page


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SECTION 4 – HAZARDS OF CLEANING, REPAIRING, AND DISMANTLING TANKS, Continued

MSDSs and toxic vapors

Material Safety Data Sheets (MSDSs) for specific products contain the following information about those products:

Signs and symptoms of harmful exposure to substances in the product

Information on selection and use of personal protective equipment when using the product

First aid procedures Allowable worker exposure limits Fire fighting requirements Emergencies response

Oxygen deficiency

The following can cause oxygen deficiency during tank work: Presence of gases such as carbon dioxide (used for

inerting pipelines prior to hot work) or argon (used in welding) that can displace oxygen in confined spaces

Corrosion of iron

Oxygen enrichment

Oxygen enrichment can occur if oxygen bottles or hoses used for hot work leak.

Physical hazards

The following may present physical hazards to persons cleaning, repairing, or dismantling tanks:

Hazardous aspects of the tank’s design or condition Floating roofs, sumps, floating suctions, and other

appurtenances Weather warm enough to cause heat stress Inadequate lighting Falling tools Slips and trips Discharge of products into an improperly isolated tank Welding, grinding, or use of hand tools that cause high

noise levels inside tanks Work at height

The above hazards should be considered during development of the Tank Entry Plan, Worker Exposure Control Plan and Emargency Action Plan.


PRACTICE 534




SECTION 4 – HAZARDS OF CLEANING, REPAIRING, AND DISMANTLING TANKS, Continued

Dust and fumes The following can expose workers to fumes, dust, and inorganic lead:

Welding Abrasive blasting Grinding Abrasive blasting of lead-based paints

Many Countries have established safe exposure limits to dust, welding fumes, and lead.

In addition to worker exposure issues, abrasive blasting can generate dust that migrates off site. There may air agency restrictions for abrasive blasting that require controls such as wet blasting or use of specific blasting agents.

Consult with your OE/HES Specialist during the job planning phase to determine if dust controls are required and to assist in determining safe exposure levels.

SECTION 5 – JOB PLANNING

Introduction Good job planning can prevent costly and time-consuming delays, as well as

short-cutting. It can also increase worker safety and productivity. Performing a Job Loss Analysis or using a generic pre-

written work plan, reviewed for applicability, is critical for safely executing tank work.

A Pre-job Conference and Contractor Safety Review checklist, contained in the SWP Standard 515, Contractor Safety Performance, must be reviewed before beginning work.

Job planning also includes work permits, job preparation, review of contractor medical evaluations, developing rescue plans and tank emptying.

5.1 – Work Permits

Use of work permits

Work permits provide a means to communicate and authorize activities within the terminal. Often, work permits are required and referenced in local, state, or Federal regulations.



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5.1 – Work Permits, Continued

Mandatory Global Marketing Managing Safe Work Practices requirements

It is mandatory that GM MSWP requirements be followed when issuing the following permits:

Permit/Form GM SWP Standard Requirements General Work Permit 507 – General Work Permit Hot Work Form 508 – Hot Work Confined Space Entry Form

513 – Confined Space Entry

General Work Permits

You must obtain a General Work Permit before initiating non-routine work in the terminal.

Hot Work Forms

Hot Work Forms are used in conjunction with a valid General Work Permit to control and manage ignition sources within the terminal.

Ignition sources Ignition sources within the terminal include:

Sparking tools, both electric and pneumatic Vehicles, including vacuum trucks and cranes Welding equipment Cathodic protection systems Static discharge caused by transfer of water, steam, air,

product, or sludge Temporary lights Lightning Motors

Preventing ignitions

Care must be taken to permit and control ignition sources. The following table gives sources of potential ignitions and precautions for preventing ignition from these sources:


PRACTICE 534





Ignition Source Precautions

Electrical equipment Until an area is free from flammable vapors, use only lighting, adapters, extension cords, and portable equipment approved for the area classification.

Transfer pumps Use air-diaphragm or piston-type portable pumps for transferring liquids.

Portable electrical equipment in the tank

Use ground-fault circuit interrupters on portable electrical equipment used inside the tank.

Electrical storms Stop work during electrical storms. Potential Fuel Sources

The liquid fuel products that can remain in various void spaces in the tank equipment can be potential source of ignitable fuels. Check the following void spaces in a tank for flammable liquid before authorizing hot work permits:

Roof legs Roof drains Pontoons Between tank seals Floating suctions internal hoses.

Discharge flammable liquids and vapors at least 50 feet away from ignition sources and in a safe direction (downwind of workers).

Two types of entries

Two types of entries used in terminals: Permit Required Confined Space Entry - A Confined Space Entry form is

used in conjunction with a General Work Permit for entry into confined spaces that have limited egress and the potential to contain hazardous atmospheres. General Entry - A General Work Permit is issued for entry into a “Non-

Permit required” space that has no potential to contain a hazardous atmosphere.



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Typical uses of entry permits

Typically, a tank undergoing cleaning and maintenance is permitted as a Confined Space during initial entry for cleaning and roof stabilization and requires both a General Work Permit and a Confined Space Entry Form for entry. Once the tank has been degassed, or gas freed, and certified as clean or gas free, and there is no other potential to generate a hazardous atmosphere (e.g. welding, painting, sand blasting, etc.) than entry can be permitted with a General Work Permit and does not required a Confined Space Entry Form.

It is important to account for atmospheric hazards that can be generated by the planned work activities when determining if a Confined Space Entry form is required. Once a door sheet is removed from the tank, if the entrance and exit is no longer limited based on the door sheet removed and the tank is not required to be permitted as a Confined Space. However in some cases, when the door sheet removed is small and entrance / exit is still limited, if the tank may still need to be permitted as a confined space for entry.

5.2 – Preparing for the Job

Job preparation

Preparing to clean, repair, or dismantle a tank requires a series of steps before the tank is taken out of service.

Procedure Make the following preparations before taking a tank out of service:

Step Action 1 Prepare a safety and work plan for tank isolation, entry, and

cleaning. 2 Review tank configuration, piping, and site layout. 3 Review information about products contained in the tank and

previous historical repairs data of the tank. 4 Establish a schedule for the job.


PRACTICE 534




5.2 – Preparing for the Job, Continued

Procedure (continued)

Step Action 5 Identify hazards, including, but not limited to the following:

Leaking tank bottom Faulty tank roof Congested work site Vehicle traffic access

6 Determine if unique hazards are present, including the following: Leaded gasoline Lead-based paint

7 Confirm that equipment meets Class I, Division II, Group D stds. 8 Identify equipment required for job, including the following:

Pumps Ventilation equipment Vacuum trucks Lighting Hazardous waste receptacles

9 Determine need for personal protective equipment. 10 Determine how remaining product will be removed from tank. 11 Determine how to remove and handle sludge in tank. 12 Check roof integrity prior to walking on roof. Follow confined-

space entry procedures while lowering legs. 13 Lower legs on floating roof tank while tank is in service and

preferably while full. Check pontoons for product/water when setting legs. If any measurable depth is found, make plans on how to drain before landing roof on low legs.

Note: Aluminum IFR legs should not be lowered while in service. The aluminum IFR should be taken out service and tank must be filled with water prior to lowering the legs. The Terminal Manager will make the decision, based on risk, as to how much water should be used to refloat the roof before accessing it.

14 Check the following void spaces in a tank for flammable liquid before authorizing work permits:

Roof legs and drains Pontoons Tank seals internal pipelines floating suction

15 Check integrity of roof legs, if possible. Close-ended legs may retain product after tank has been emptied and cleaned.



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5.3 – Emptying the Tank

Remove product

Product must be removed from the tank before the tank is isolated.

Procedure Follow these steps to remove product from tanks before isolating them:

Step Action 1 Verify that legs on floating roof tanks have been lowered. 2 Remove product from tank using existing lines and pumps.

Continue until pump loses suction. 3 If possible, reduce transfer rate while landing floating roof. 4 Consider adding water to tank to return product level to above

pump suction. Floating product on this water minimizes use of temporary pumps and hoses to transfer product to other tanks. CAUTION: Never splash-fill a tank. Static discharge can occur. (Note: In case of Ethanol storage, do not use water ).

5 When using temporary pumps and hoses, verify that they are rated for discharge pressure plus head pressure of tank into which you are transferring product. CAUTION: Do not use compressed air to purge lines or clear hoses. The potential to release significant amounts of energy exists if a line fails while pressurized with air.

6 Install check valves on temporary hoses or piping at tank into which you are transferring product.

7 Ensure that temporary pump meets Class I, Division II, Group D electrical classification. (See ESH-508: Hot Work.)

8 Hook pump to satisfactory tank nozzles (for example, water draw). 9 Electrically bond and ground temporary equipment. 10 Flush tank with water to remove residual products and sludge. If

possible, remove all sludge and water from tank prior to opening tank, using vacuum truck or other enclosed system (for example, underground storage tanks).

11 Only under the following circumstances should you remove the man-way and install a temporary suction hose to pump out residual products:

Tank lacks an adequate low-point drain. Sludge build-up has rendered low-point drain useless.

In such circumstances, ensure that suction hose has been bonded to tank. Gasoline vapors may pose a hazard to workers and should be addressed in Job Safety Analysis or other work procedure.

PRACTICE 534




5.4 – Vacuum Trucks

Vacuum truck hazards

Vacuum trucks used to remove liquid can produce the following hazards: The engine is a source of ignition. The vacuum process can generate vapors.

The vacuum process can generate static charges.

Precautions Take the precautions listed in the following table, when using a vacuum

truck:

Permits and Equipment Precaution Permits A Hot Work Permit is needed when using a

vacuum truck. Truck engines Must be fitted with a spark-arresting system

and a spark-arresting muffler. Vacuum pump discharge Must be fitted with a hose that discharges

vapors at least 50 feet away from the closest ignition source and away from workers.

Vacuum hoses Must be electrically continuous or conductive.

Any hose or string of hoses must have resistance of not more than 10 ohms when measured with a volt-ohm meter.

Hoses and couplings must be physically connected to assure conductivity. (Can be achieved by attaching couplings to reinforcing wire would within hose fabric.

Do not use hoses with longitudinal ridges, corroded or broken wires, damaged covers, or exposed wires.

Wire or zip tie camlock fittings Do not used compressed air to clear line

blockages or excess liquid. Bonding wire Must be attached from vacuum truck to tank.


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SECTION 6 - ROOF STABILIZATION

Introduction This section discusses the stabilization of floating roofs to facilitate tank entry

for cleaning and repair, as documented in the drawing series “Tank Maintenance and Repair Alliance Standard Technical Drawings” included in Appendix A.

This Safe Work Practice does not cover requirements for confined space entry. For these requirements, consult Safe Work Practice Standard 513: Confined Space Entry.

The “Standard Procedure for Floating Roof Cribbing” chart in Appendix A defines the overall requirements for safe entry beneath a floating roof. It is a summary chart designed for use with three sub-charts which each deal in detail with a different aspect of floating roof stabilization. All of these aspects must be addressed individually to ensure safe entry beneath the floating roof.

After addressing the three aspects of floating roof stabilization (Lateral Stability, Anti-Rotation and Vertical Collapse) the results of those verifications are then used to answer the questions on the Summary Chart. If all requirements are met on the Summary Chart, the chart will lead the evaluation team to the Floating Roof is Properly Secured result. If any one of the verifications does not pass, the Summary Chart will lead the evaluation team to the Install Roof Cribbing result.

General training requirements

Ensure that all entrants are: Trained on principals of roof collapse Trained on methods and devices used to stabilize roofs Familiar with use of jacking devices

General bracing requirements

Ensure that all leg bracing is: 4 x 4 treated timbers Strapped to the roof legs at both top and bottom in a

manner that prevents timber movement


PRACTICE 534




SECTION 6 – ROOF STABILIZATION, Continued

General floating roof stabilization requirements

1. Cribbing:

a. A least one crib stack shall always be used. b. If only one crib stack is being used it shall be located adjacent

to the man-way such that it provides an exit path in the event of a roof collapse.

c. If the floating roof does not pass the verification process then cribbing stacks shall be installed beneath every 2nd floating roof bulkhead.

2. Leg Bracing: a. Leg bracing shall consist of 4x4 treated timbers. b. Timbers shall be strapped to the roof legs at both top and

bottom in a manner that prevents their movement. c. The maximum gap between the blocking timber and the roof

shall be 2”. (Timber lengths shall be within 2” of the roof height; sufficient length so as to reach from the floor to within 2” of the roof.)

Note: The 4 x 4 timbers are designed to support the roof at a point should a leg collapse. They are not intended to support the leg itself. It is critical that timbers be fitted as close to the floating roof and tank floor as possible; they should never be more than 2” shorter than the distance from the floor to the roof. The gaps between the top of the timber and the floating roof and the bottom of the timber and the tank floor define the distance that the roof will drop in the event of a leg failure. The farther that distance becomes, the higher the impact load on the timber and the greater the chance for failure of the timber to “catch” the weight of the roof.

3. Rim Wedges: a. A minimum of 4 equally spaced rim wedges are required in all

cases. In larger tanks (above 65’ in diameter) additional wedges should be installed at 50’ intervals measured around the roof perimeter (see below). (For example a 94’ tank would require (94’ x 3.14) / 50 = 6 Rim Wedges. For a 50’ diameter tank this calculation calls for only 3 rim wedges but the minimum of 4 must be installed instead.)

b. If seal is severely damaged or degraded, it may be necessary to take more extensive measures. (Check with Engineering.)



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General floating roof stabilization requirements (continued)

4. Radial Beams: a. The use of radial beams is required in case of severe

deterioration or complete lack of a floating roof seal. The radial beams should be positioned exactly as the requirement for the rim wedges above.

b. A minimum of 4 equally spaced radial beams are required if seal condition warrants their use. In larger tanks (above 65’ in diameter) additional radial beams should be installed at 50’ intervals measured around the roof perimeter. (For example a 150’ tank would require (150’ x 3.14) / 50 = 9 Radial Beams. For a 50’ diameter tank this calculation calls for only 3 Radial Beams but the minimum of 4 must be installed instead.) and 7.2.


PRACTICE 534





General floating roof stabilization requirements (continued)

5. Roof Loads:

a. Water or Product found on the roof or in any compartments must be removed to the point that no more than residual load (less than ¼ inch of water) remains.

b. Static loading by equipment and material shall not exceed 500 lbs in a single group or 1,500 lbs total across the entire roof.

c. No more than 5 people should be on top of the floating roof at any time.

d. No one shall be allowed to work beneath a floating roof if any one (or more) of conditions 3a, 3b or 3c exist.

Planning

Plan in advance for the above requirements when bracing floating roofs. You should be able to determine what type of seal is present and what type and perhaps the condition of anti-rotation device is in the tank for example. Based on these a preliminary plan can be set which can then be modified as necessary.

1. Review the concerns determined by the “Standard Procedure for Floating Roof Cribbing” and the 3 sub-charts.

2. Prepare a job-site specific procedure to address the requirements determined by following the Summary Chart.

3. In general: Minimize entry into the tank, whether on or below the floating

roof. Do not bring metal objects into the tank (other than rings or

personal jewelry.)


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6.1 – Standard Procedure for Steel Floating Roof Stabilization

Introduction This sub-section discusses the stabilization of steel floating roofs to facilitate

tank entry for cleaning and repair, as documented in the “Standard Procedure for Floating Roof Cribbing” Flow Charts in Appendix A.

Procedure Prior to anyone entering beneath the floating roof the following steps must be

accomplished:

Step Action 1 Make an external inspection from above the roof to verify that:

No standing liquid is on the roof. All roof legs are pinned in the same high position. Anti-rotation devices are present and installed at the top of

the tank. Primary and secondary seals are present and in good

condition; determine the type(s) of seals. 2 Make an inspection below the roof to verify that:

Anti-rotation devices are present and securely mounted near the bottom of the tank.

Existence, type, and condition of the primary seal. Existence and condition of the roof legs.

3 Install roof rim wedges and attach a 36” reflective tag to each rim wedge such that each tag is visible from the man-way.

4 Check for liquid loads on roof: Water or product on the roof deck Water or product in the pontoons

5 There shall be no entry beneath the floating roof until liquid found on the roof or in the pontoons is removed to a level of less than ½”. (2.6 lb / sq. ft.)

6 After the above are accomplished, enter the tank to install the leg bracing timbers.

Brace the 3 legs closest to the point of entry and the legs closest to the rim wedges.

Consult engineering on legs identified during inspection as being unstable or of questionable integrity.

Block up roof legs as follows: o Pan Roof – Half of all available legs. o Pontoon or Double Deck Roof – 8 evenly spaced legs.


PRACTICE 534




6.1 – Standard Procedure for Steel Floating Roof Stabilization, Continued

Caution: 4 x 4 timbers will not stabilize a roof alone. Care must be taken to leave anti-rotation devices and rim wedges in place.

6.2 – Cribbing Floating Roofs

Scope The scope of this procedure is the safe use of cribbing.

Cribbing is a generic name typically referring to 4” x 4” or 6” x 6” timbers.

This procedure applies to stacks used for storing cribbing and stacks of cribbing used to support loads.

This procedure is written to assure that cribbing is stacked in a stable manner and that potential hazards associated with the use of cribbing are addressed.

General Safety Issues

Cribbing stacks are critical components of many procedures used to jack roofs and support loads.

It is essential that cribbing be stacked in a manner that minimizes susceptibility to fall or tumble over.

All procedures listed apply to cribbing that is either stored or being used to support a load.

Cribbing Material

Cribbing typically uses timber made of Southern Yellow Pine or Douglas Fir. Cribbing timbers of #1 grade can be used to insure consistent strength characteristics.

Cribbing shall be treated for exposure to the elements to insure acceptable service life.

Timbers shall not be painted except on the ends of the timber as needed for identification purposes. Timbers rely on friction between each layer and painting the entire timber may make them more susceptible to slipping.



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Chevron Products Company SWP – 5 13 Ver2 Revision 0


6.2 – Cribbing Floating Roofs, Continued

Inspection The primary use of cribbing timber is crush resistance. Evaluate timbers to insure they can withstand crushing forces without failure. Timbers shall be inspected during the placement of the timber cribbing stack. Cracks, physical or chemical are indications of damage that should be further evaluated. All timber has some degree of cracking.

Stacking The cribbing stack shall never exceed a height to width ratio of 2 to 1 All cribbing stacks shall be stacked with each successive layer being rotated

90 degrees.

Cribbing stacks shall always be placed on level surfaces that will uniformly support the applied load.

Any leaning cribbing stacks shall be immediately disassembled and the source of the leaning shall be corrected before re-assembling the stack.

When erecting a load bearing cribbing stack each layer shall be stacked so that the ends of the cribbing timbers extend past the lower supporting layer by the nominal dimension of the timbers. For example a 4” x 4” timber should be installed to extend 4” beyond the layer below it (see below).


PRACTICE 534




6.2 – Cribbing Floating Roofs, Continued

Timbers that are in layers, which are parallel, shall be aligned with each other.

This insures that the timber stack capacity can develop the full crush resistance of the timbers. Misaligned timbers can cause shear and bending failure.

6.3 – Jacking Floating Roofs

Procedure for jacking floating roofs

Follow these steps when jacking floating roofs:

Step Action

1 Visually inspect all temporary support systems prior to, during, and after jacking any part of a floating roof.

2 Visually inspect adjacent support legs to ensure that they remain plumb.

3 Jack stands must be vertical. Re-plumb as necessary. 4 Verify with carpenter’s level as necessary.

6.4 – Jacking Fixed Roof Columns

Introduction Any jacking on columns shall have tank-specific written procedures. The

Standards Engineer or Terminal Engineer must approve the procedure.



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6.4 – Jacking Fixed Roof Columns, Continued

Inspection Before jacking fixed roof columns, an inspection must be made.

Procedure for inspecting fixed roof columns before jacking

Follow the procedure below to inspect fixed roof columns before jacking:

Step Action 1 To verify that the weights established in the procedure are

accurate, the following must be verified: Thickness of roof plates Number and size of rafters, girders, or other structural

members Presence of other loads, such as fiberglass coatings and

piping. 2 For built-up columns, examine each stitch weld or member-joining

weld from column bottom to a height of 6 feet, to ensure that it is not severely corroded or cracked.

3 Verify that bottom of column is not welded to bottom plates. 4 Establish amount of uniform corrosion as a percentage of nominal

thickness. Use UT testing to establish column thickness. 5 Inspect all jacking equipment in accordance with manufacturer’s

recommendations. 6 The column must be plumb to within 5 degrees of vertical.

Consult Engineering for instructions if the column is not plumb. 7 Inspect column for existing damage. Report any defects to the

Terminal Engineer. Jacking requirements

The following requirements apply when jacking fixed roof columns: There must be two diametrically opposite jacking lugs to prevent

significant eccentricity in the column during loading. Lugs must be properly sized for the load. Lugs shall be welded to both columns on built-up columns with

approximately half of the welding on each member. The bottom 6 inches of built-up members shall be continuously welded

together. No column shall be jacked in excess of 6 inches without a structural

analysis stamped by a registered professional structural engineer.

PRACTICE 534




SECTION 7 – TANK ISOLATION AND STATIC DISCHARGE HAZARDS

Introduction Before performing any type of maintenance or inspection activity on a tank,

you must isolate the tank. This section discusses the hazard of static discharges during tank isolation.

Safe entry procedures

Follow procedures in the GM SWP Standard for Lockout/Tagout and Confined Space Entry for safe entry into a tank. This includes entry onto a floating roof while the tank is in service, to inspect tank seals.

7.1 – Cathodic Protection Systems and Static Discharge

Arcing during isolation

Cathodic protection systems or static electricity can induce arcing between flanges during isolation. Often, flammable liquid or vapors are present while valves, gaskets, or dropout spools are being removed.

Procedure to prevent ignition

Take the following steps to prevent ignition of flammable liquid or vapors that may be present while valves, gaskets, or dropout spools are being removed:

Step Action

1 Drain and clean lines to and from tank. 2 Inspect all tank ground cables and cable clamps to ensure

grounding and bonding integrity. 3 Turn off and isolate cathode protection system. If terminal is co-

located with other terminals, consider turning off adjacent systems as well. NOTE: Cathodic protection should be shut off 24 hours in advance to allow dissipation of charge.

4 Install a bond wire from tank to piping (across valve, dropout spool, or gasket).

5 Remove valve, dropout spool, or gasket. 6 Remove bond wire after either:

Establishing an adequate gap Installing a plate blind and re-establishing

the electrical bond 7 Turn on cathodic protection system.


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SECTION 8 – TANK CLEANING

Introduction The need to clean tanks is determined by maintenance requirements, PIRT

issues, or the need to perform routine and non-routine inspections. Hazardous waste, worker exposure to chemicals, and other safety and environmental issues must be addressed before and during tank-cleaning operations.

Tanks are hazardous until proven safe

In general, treat all tanks as if they contain a hazardous substance and a flammable atmosphere until adequate testing is performed to demonstrate a safe, hazard-free tank.

8.1 – Testing the Tank Atmosphere

When to test Testing the atmosphere inside a tank is required prior to obtaining a Confined

Space Permit or a Hot Work Form. If testing of the complete tank cannot be done from the outside, a separate Confined Space Entry form is required for the initial entry to conduct gas testing.

Information sources

You will find information on the use of gas-testing equipment and interpreting test results in the following documents:

508: Hot Work 512: Gas Detection 513: Confined Space Entry

Equipment classification

Equipment used to test the atmosphere should be classified as intrinsically safe for Class I, Division I areas.

Qualified gas-tester

A qualified gas tester knowledgeable in the use of gas-testing equipment and in interpreting gas-testing results must conduct the gas testing in accordance with the GM MSWP Standard for Gas Detection.


PRACTICE 534




8.1 – Testing the Tank Atmosphere, Continued

Gas-testing precautions

The following precautions must be taken when gas-testing tank atmospheres: All ventilation equipment must be shut off for 15 minutes prior to

testing a tank for entry. If entry is required during initial testing, the qualified individual must

wear an air-supplied respirator operated in positive-pressure mode. Appropriate protective clothing must also be worn if entering the

tank.

Sludge hazards Disturbing sludge often liberates additional hydrocarbon vapors. For this

reason, continuous gas monitoring may be necessary during initial tank entry to verify that flammable vapors remain below 10 percent LEL/LFL.

Reviewing results

Multi-gas meters rely on the presence of oxygen to accurately measure flammability ranges. Because of this, test results must be reviewed in the following order: 1. Oxygen 2. Flammability 3. Toxic vapors

Organic lead hazards

Organic lead can remain in sludge indefinitely. Tanks that have stored aviation gasoline or leaded gasoline without being cleaned may contain organic lead. Special safety precautions must be used when cleaning these tanks. See Section 8.3.

Hazards from benzene and aromatics

Gasoline contains less than 4.9-weight percent benzene. Direct reading instruments are available to test for benzene, as well as “length of stain” detector tubes. Benzene, aromatics, and poly-nuclear aromatics (found in diesel fuel) can present a health hazard for employees cleaning tanks.

Supplemental-air respirators

Multi-gas meters cannot adequately measure low concentrations of total hydrocarbon vapors or Benzene to determine the risk of adversely affecting the health of workers. For this reason, workers entering confined spaces exceeding 0% LFL, in the absence of definitive toxic vapor monitoring results must use respiratory protection.


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8.2 – Personal Protective Equipment

Introduction Employees entering tanks must wear personal protective equipment (PPE)

adequate to protect them from the hazards they are likely to encounter.

PPE selection considerations

Consider the following when selecting PPE: Do you need impervious clothing? Should you select light-colored clothing to enhance

worker visibility and/or to identify contaminated clothing?

Do you need hard hats, gloves, boots, goggles, welding clothing, etc.?

Have you selected an appropriate respirator? Have you selected a harness and lifelines for confined

space entry? For top-entry tanks, have you selected a device to

extract incapacitated workers?

Respirator guidelines

Respirator guidelines are found in SWP - 517: Respiratory Protection. Supplied-air respirators are required whenever workers enter a tank that hasn’t been adequately tested for benzene, aromatics, total hydrocarbons, and organic lead. Air purifying respirators are allowed only after the space has been adequately tested and a qualified individual has selected the appropriate respirator.

Respiratory program

Employers are responsible for establishing a respiratory protection program for employees that includes training and access to respirators.

8.3 – Cleaning Tanks Containing Organic Lead

Presence of organic lead

Organic lead is present in leaded gasoline and aviation gasoline and can remain in sludge indefinitely. Cleaning tanks containing organic lead requires special precautions.


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8.3 – Cleaning Tanks Containing Organic Lead, Continued

Respirators Supplied-air respirators are mandatory. They must be operated in positive-

pressure mode.

Impermeable gloves, clothing

You must wear impermeable gloves (nitrile, PVC, or Viton) and impermeable clothing.

Contaminated clothing

Remove and decontaminate clothing when it becomes contaminated. Shower and put on clean clothing before resuming work. Disposable coveralls such as Tyvek are recommended.

Procedure for cleaning tank containing organic lead

Follow these steps when cleaning a tank containing organic lead:

Step Action

1 Clean tank. 2 Dry tank. 3 Test for lead contamination before commencing additional

maintenance activities. A qualified individual must perform lead-in-air analysis.

8.4 – Vapor and Gas Freeing Tanks

Purpose Vapor and gas freeing is performed because entry into tanks cannot occur

until the flammable atmosphere in the tank drops to below 10 percent of the LEL/LFL.

Control-device requirements

Local, state, or Federal rules may prohibit vapor freeing without the use of a control device. Facility permits may also contain conditions that require use of control devices for degassing tanks. Terminals in Los Angeles, Phoenix, and the San Francisco Bay area are subject to these requirements. Consult with the TESH Specialist in your area for specific guidance on the use of control devices while degassing tanks.



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8.4 – Vapor and Gas Freeing Tanks, Continued

Methods of purging vapors

Tanks must be purged of flammable vapors through either natural or mechanical ventilation.

Natural ventilation

Natural ventilation is an undesirable method of purging tanks of flammable vapors, due to the length of time it takes to adequately vapor-free the tank. Using natural ventilation to purge a tank allows the tank to remain in the flammable range for a long period of time. Natural ventilation also is a source for flammable vapors outside the tank.

Mechanical ventilation

Mechanical ventilation is the preferred method for vapor-freeing a tank. It reduces the period during which the atmosphere inside the tank is flammable.

Equipment classification

Mechanical ventilation equipment must be approved for the electrical classification of the area and be bonded to the tank to reduce risk of static discharge. Tank farms are Class I, Division II, Group D.

Procedure for mechanical ventilation

Follow these following recommended steps for freeing a tank of flammable vapors through mechanical ventilation:

Step Action

1 Install an eductor at the venting egress point. For the top opening of a cone-roof tanks, fit the eductor with a hose in order to draw vapors off the bottom of the tank. Start it at a low rate to avoid creating a vacuum inside the tank.

2 Use ducting to discharge vapors at least 50 feet from ignition sources and in a direction away from workers.

3 Open a second manway before increasing eductor flow rate. 4 For a floating-roof tank, configure air movers to both induce flow

(force air in) and exhaust air from tank. 5 For an internal floating-roof tank, it is recommended to locate an

additional air mover at top of tank. It must be fitted with a hose that extends to the floating roof, to draw vapors off of the floating roof. Make-up air enters through eave vents.

6 Turn off ventilation equipment for 15 minutes before gas-testing the space.


PRACTICE 534




8.4 – Vapor and Gas Freeing Tanks, Continued

Vapor discharge

Vapors should be discharged through a top man-way when possible. This reduces the risk of having a flammable atmosphere outside the tank at ground level.

Controlling degassing emissions

Terminals subject to controlling emissions during tank degassing can choose one of the following methods of control:

Displace liquid using liquids with a vapor pressure specified by local, state, or Federal rules. Diesel fuel will meet this requirement in most cases.

Vent to a control device that meets the efficiency specified by local, state, or Federal rules. Typically, the control efficiency must be at least 90 percent.

Degassing should begin while ambient temperatures are falling. Increasing temperature will cause more vapors to be generated, increasing the time it takes to gas free the tank.

Consult TESH Specialists

TESH Specialists should be consulted when determining the application of this requirement and selecting the appropriate method for tank degassing.

8.5 – Handling Hazardous Waste

Instructions Marketing Operating Procedures for each terminal contain instructions on

handling hazardous waste. Refer to these procedures when handling wastes generated during tank cleaning.

Waste categories

Wastes typically generated during tank cleaning and repair generally fall into the following categories:

Substance Classification Waste Code

Gasoline tank bottoms Hazardous D018 Benzene D001 Ignitable

Diesel and jet tank bottoms Sometimes Hazardous D001 Ignitable Aviation gas or leaded gasoline tank bottoms

Hazardous D001 Ignitable D008 Lead D018 Benzene

Grit blast from lead-based paint Hazardous D008 Lead


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8.6 – Using Agents

Types of agents Occasionally, an agent may be used to flush or clean a tank. Using agents to

clean tanks increases the amount of waste to be handled. Agents include water, steam, cleaning agents, and oxidizing agents. Water is the most common agent used to clean tanks.

Water Using water facilitates product recovery. Product floating on the water can be

skimmed off into tankage while the tank is being emptied. The water can be collected in product/water separators for waste minimization.

Steam Steam ventilation is advantageous if available. However, steam can generate static charges. The following precautions must be taken against static charges:

The nozzle through which the steam discharges must be electrically bonded to the tank and to tank appurtenances that may be electrically insulated from the tank shell, such as floating roofs.

The tank must also be grounded.

Steam will only be effective if the tank’s internal temperature can be raised to 170F.

Cleaning agents Use of organic solvents and soaps can facilitate tank cleaning but must be

carefully controlled. Spraying solvents and diesel fuel is prohibited. Nozzles through which these substances are introduced

must be bonded to the tank. Local or state rules may prohibit use of certain solvents

that have a high VOC content. The use of solvents can change the flammability range inside a tank. Consult with your TESH Specialist for guidance on the use of these materials.

Oxidizing agents

The use of oxidizing agents for controlling pyrophoric deposits and hydrogen sulfide is prohibited. Crude oil, asphalt, and sour stock tank cleaning is not addressed in this Safe Work Practice. Pyrophoric deposits and sour stocks are best controlled through use of water fogs.

PRACTICE 534




SECTION 9 – TANK MAINTENANCE

Introduction Tank maintenance can proceed once the proper work permits are obtained and

the conditions on the permits are met. Refer to the appropriate Safe Work Practice Standard for guidance on obtaining permits and satisfying permit conditions. Tank maintenance includes door sheet removal and reinstallation, tank repairs, and dismantling.

9.1 – Door sheet Removal and Reinstallation

Door sheets Depending on the type of repairs required, it may be appropriate to cut the

door sheet in the tank large enough to move equipment and materials in and out easily. The guidelines and procedures that follow are for tanks that will be repaired and put back into service.

Door sheet cutting methods

Use one of the following three methods to cut the doorsheet:

Method Description

Hot cutting Requires tank to be vapor free. Cut on surfaces that have been cleaned to bare metal 9 inches on each side of cut.

Cold-air chisel cutting

Can be used on tank that has not been cleaned. Use a pneumatic hammer equipped with cutting chisel to cold-cut doorsheet from outside. Chisel point must be kept sufficiently cool to prevent sparks from igniting flammable vapor inside tank.

Hydrocutting Can be used on tank that has not been cleaned. Ultra high-pressure water (35,000+ psi) mixed with fine abrasive cuts opening from outside.

Supporting doorsheet

Door sheets must be properly supported prior to being completely cut free from the tank.

Procedure for supporting doorsheet

Follow the steps identified below to properly support a door sheet:



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9.1 – Door sheet Removal and Reinstallation, Continued

Procedure for supporting doorsheet

Step Action 1 Attach an adequately sized clip to doorsheet. 2 Support door sheet with crane or hoist. 3 Brace tank shell to prevent shell from going out-of-round.

Vertical or curved horizontal angle or channel bracing must be tack welded to shell. Areas to be welded must be cleaned to bare metal 9 inches around welds.

4 Support door sheet to maintain proper curvature and shape.

Cutting procedure

Follow these steps when cutting a door sheet:

Step Action

1 Whenever possible, do not cut a door sheet within 20 feet of a previous doorsheet.

2 Make door sheet edge cuts no closer than 6 inches from any parallel weld seam, other than the bottom of a 10-inch riveted seam.

3 Cut all door sheet edges square and level. Do not freehand unless tank will be dismantled.

4 Avoid cutting seals on floating roofs or pans. 5 If … Then … Tank bottom will not

be replaced. Make bottom horizontal cut a

minimum of 4 inches above existing bottom.

Cut all 4 corners with a radius equal to 5 to 10 times plate thickness, but not less than 4 inches.

Tank bottom will be replaced.

Make bottom horizontal cut at same distance above existing bottom as top edges of slots for new bottom.

Cut bottom corners square. Cut the two upper corners with a

radius equal to 5 to 10 times plate thickness, but not less than 4 inches.


PRACTICE 534




9.1 – Door sheet Removal and Reinstallation, Continued

Reinstalling door sheet

Procedures for tank work include reinstallation of the door sheet. Such procedures must include the following:

Welding protocol Pre- and post-weld heat-treating Welding sequence and direction

Door sheet testing

Once the door sheet is reinstalled, it must be tested to ensure tank integrity.

Testing procedure

Follow these steps to test a reinstalled doorsheet:

Step Action

1 Test all butt welds on the door sheet using radiography. Butt weld acceptance must be based on the standards in ASME Code Section VIII. With approval of Engineering, butt welds may be inspected by ultrasonic methods in lieu of radiography.

2 Test all fillet welds using a dye penetrant on the welded area. Operations, Engineering, or a Company Representative must witness and approve the test.

3 Grind out any weld defects and repair weld. All repaired areas must be re-inspected.

4 Hydro-test reinstalled door sheet to the safe fill height for at least 24 hours. API 653 and the approval of the Operations Manager govern exceptions to hydro-testing. There are acceptable alternatives to Hydro-testing. Consult with the Standards Engineer to determine these alternatives. Typically, no hydro-test is required unless the tank bottom has been replaced.



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9.2 – General Tank Repairs

Permits and precautions

Tank repairs can proceed after the appropriate permits are obtained and authorized.

Precautions Experience has shown that tanks can become hazardous during the course of

repair work. The following precautions must be followed: Make a careful inspection and ensure proper drainage

by drilling all void spaces free of weep holes. Individually inspect and test pontoons on floating roofs

to ensure that these spaces are free of flammable vapors.

Remove foam log tank seals that have become saturated.

Suspend work during lightning storms.

PRACTICE 534




9.3 – Tank-bottom Repairs

Tank-bottom repair hazards

Flammable liquids can accumulate under tank bottoms. Before beginning extensive tank-bottom work, the space under the tank must be tested and made safe for work.

Safety procedures

Follow these safety procedures prior to performing tank-bottom repairs:

Step Action

1 Make appropriately sized holes in tank bottom by cold-cutting or drilling. Use coolant on cutting edges of tools to prevent sparking.

2 Make enough holes to facilitate thorough inspection of ground beneath tank.

3 Test area beneath tank for flammable vapors.

Minor tank-bottom repairs

Minor repairs (welding corrosion pits, patching, or other localized jobs) can be done by tapping the inspection holes, connecting tubing, and using inert gas to purge the space under the tank. Controls must be used to prevent over-pressuring the bottom of a tank. CAUTION: Inert gases can displace oxygen in the tank. Continuous air monitoring is required while using inerting agents. Oxygen content must remain between 19.5 and 23 percent in the tank.

Major repairs Flammable liquids must be displaced before major repairs can be made on

tank bottoms. To displace the liquids, follow these steps:

Step Action 1 Construct an earthen dike around tank higher than highest floor

plate in tank. 2 Drill and tap holes for ½ -inch tubing at highest point on tank

bottom. 3 Flood space under tank with water to displace liquid.


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9.4 – Dismantling Tanks

Demolition company

Select the demolition company for dismantling the tank using the process prescribed in the CHESM Process.

Cleaning Tanks to be dismantled must be completely cleaned before the work begins.

Dismantling preparation procedure

In addition to the Terms and Conditions of the Contract, the following steps must be taken before work begins:

Step Action

1 Contractor must provide written demolition procedures. 2 Operations must approve the procedures. 3 An on-site contractor foreman must ensure that the procedure is

followed and that the job is done safely. 4 All electrical and utility connections must be disconnected and

isolated. 5 Barricades must be erected and site access-controlled. 6 Specific areas must be designated for storing scrap. Scrap must be

removed expeditiously.

Tanks with leaded gasoline

Steel from tanks having been in leaded gasoline or aviation gasoline service must not be recycled in a manner that will lead to the steel’s use in edible or potable service.

PRACTICE 534




SECTION 10 – RETURNING THE TANK TO SERVICE

Introduction When maintenance work is completed and all procedural requirements

fulfilled, a tank may be returned to service.

Procedure for returning tanks to service

Before a tank is returned to service, the following procedure must be fulfilled:

Step Action

1 The Engineer, Operations, and the Maintenance Contractor must make an inspection to ensure that:

The work is completed. The tank is clean. All tools have been removed. All requirements for returning a tank to

service, as outlined in API 653, have been met and documented.

2 Maintenance and Operations must review the work before “head up” or closing of the equipment.

3 All blind tags, locks, and tags must be removed.

10.1 – Initial Fill

Initial-fill hazards

During an initial fill, the vapor space of the tank will pass through the flammable range.



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10.1 – Initial Fill, Continued

Initial-fill safety procedure

In order to comply with Process No. 10.10.2.8.5, Initial Filling of Tank or Refloating a Roof, and to minimize risk of fire, explosion, and injury during initial fill, the following steps must be taken:

Step Action

1 Minimize number of people in area around tank. 2 Control ignition sources around tank. Vapors will escape through

vents. 3 Do not fill tanks during electrical storms. 4 To reduce the formation of static charge and the risk of ignition,

the tank should be filled at an initial rate such that the product velocity in the incoming fill piping (not the diffuser) does not exceed 3 ft/ sec.

5 The 3 ft / sec fill rate shall not be exceeded until the roof is floated (no longer resting on legs).

6 Visually inspect all flanges, fittings, and man-ways to ensure that tank and piping are leak free.

7 Entry onto a floating roof to pin legs must be done in accordance with Confined Space Entry SWP. It is strongly recommended that entry onto the roof not be performed until the tank level has been brought to the highest level at which it will operate.

PRACTICE 534




Appendix A

Standard Procedures and Drawings – Floating Roof Temporary Support Details

Chevron Products Company 534:39 Environmental, Safety, and Health Work Practices SWP – 5 13 Ver2 Revision 0 May 2010


534:40 Environmental, Safety, and Health work Practices May 2010

swp534v2 cleaning repairing & dismantling tanks

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