1. Safe Operation of Storage Tanks: Decommissioning and Repair
Safety Talk Objectives
Upon completion of this safety talk, the worker will:
• Understand the complexity of tank preparations for hot work
• Understand the potential hazards associated with entry, hot work and recommissioning
• Understand the importance of written plans and procedures for such work
• Understand the importance of the work permit system for controlling each phase of work
Meeting preparation
Pre-planning. Supervisors are encouraged to review the BP Oil Key Safety Topic entitled, ‘Successful Group Meetings’ before delivering this or any safety talk.
Safety Talk 6

2. Decommissioning / Commissioning a storage tank stages including vapour freeing, cleaning and repair
Decommissioning / Commissioning (Slide 2)
Specific considerations for entry, hot work and recommissioning
Hazards
Hazards associated with decommissioning a storage tank were discussed in Safety Talk No.5.
The same potential hazards of fires, explosions and exposure to toxic substances can occur during entry, cleaning operations, hot work and recommissioning.
Consequences of such events will be serious as personnel are either in or around the tank during these tasks.
Plan and Written Procedure
Stage Decommissioning
Refer to Safety Talk No.5 for ‘decommissioning’.

3. Entry Permit (Slide 3)
Stage 5 Pumping Out
Although much sludge and scale can be removed without the need to enter the tank, inevitably entry will be necessary to remove the remaining material. A Risk Assessment needs to be done prior to Entry and interfaced with Work Permits in accordance with local procedures.
Gas tests and a visual inspection will be required to determine a safe working environment for cleaning operations.
Normal confined space entry precautions must be followed.
Dependent upon possible contaminants, personal protective equipment including air line breathing apparatus must be specified on the CONFINED SPACE ENTRY PERMIT. Other precautionary measures that must be considered are:
• Flameproof low voltage lighting
• Standby attendant
• Rescue plan
• Maximum ventilation using air movers, etc.
• Continuous atmospheric gas monitoring
Note: Presenters should consider replacing the overhead above with one of their local Confined Space Entry Permit, plus overheads of Risk Assessment forms and procedures used.

4. Standby attendant
A standby person must remain on duty outside the tank for the duration of the entry
The site procedure shall specify the training and duties of the attendant which should include the following:
– Maintain an accurate count of all persons in the tank
– Monitor activities inside and outside the permit space to determine if it is safe for entrants to remain in the tank
– Maintain effective and continuous contact with authorised entrants
– Order evacuation if conditions change or if any situation occurs that could endanger entrants
– Summon rescue services in an emergency
– Assist the rescue services as necessary without entering the tank
– Ensure permit conditions are followed
Standby attendent (Slide 4)
Standby attendents should be given proper training and provided with:
1. Full instructions on their duties
2. Appropriate PPE and breathing apparatus – so that they can look into the confined space
3. Strict instructions not to enter under any circumstances. Their role is to raise the alarm and wait for rescuers to arrive and then communicate vital information to the rescue team

5. Maximum ventilation Maximum ventilation (Slide 5)
Gas tests and internal inspection must be carried out to ensure there are no hidden hazards, eg.:
• Each air filled pontoon on an open top floating roof tank must be checked with an explosimeter
• Other accessories such as roof support legs, floating roof seals etc. must also be checked free of product and a hazardous atmosphere
An important safeguard during tank cleaning operations involving flammable residues is the provision of adequate ventilation. This should be sufficient to reduce the overall flammable vapour concentration, avoid vapour pockets, and minimise the vapour concentration above the sludge surfaces. The effective control of ignition sources is of equal importance. Specify in site safety plan / drawing.
Note: It is important to keep any pyrophoric scale wet until it can be removed to a safe location.

6. No hidden hazards ? No hidden hazards ? (Slide 6)
A rigorous check of all areas where hydrocarbon may remain must be carried out before relaxing Entry requirements in respect of breathing apparatus and allowing Hot Work.
Where there are holes under the floor, hydrocarbon will have accumulated and will migrate back into the tank. Special procedures exist, eg. API-2207, for repair of tank floors.
In certain areas snakes and poisonous insects may enter pontoons or other confined areas, particularly where the tank has been taken out of service with man-doors left open.

7. Guidance for tank entry conditions
OXYGEN FLAMMABLE TOXIC
Without Breathing 20.8% <1% LEL <10% OEL
Apparatus (BA)
With BA subject % 10% LEL to enter <STEL
to risk assessment 20% LEL exit
Unsafe <19.5% >20% LEL >STEL
or >23.5%
OEL (Occupational exposure limit – for 8 hours exposure)
STEL (Short term exposure limit – for 15 minutes exposure)
Guidance for tank entry conditions (Slide 7)
OXYGEN FLAMMABLE TOXIC
Without Breathing 20.8% <1% LEL <10% OEL Apparatus (BA)
With BA subject to % 10% LEL to enter < STEL risk assessment 20% LEL exit
Unsafe <19.5% or >20% LEL > STEL >23.5%
OEL (Occupational exposure limit – for 8 hours exposure)
STEL (Short term exposure limit – for 15 minutes exposure)

8. Site layout drawing Site layout drawing (Slide 8) Stage 6 Cleaning
Only use specialist tank cleaning contractors.
Due to the potential high risk, the contractor should be required to submit a written site safety plan describing exactly how the work will be done including:
• Confined space entry procedures and permit requirements
• Site layout drawing showing equipment placement
• Method of treating sludge and scale
• Disposal of hazardous wastes
Some contractors use centrifuges to separate oil / water and solids (some of which may be pyrophoric). Care needs to be taken to keep solids wet until removed to a safe place.

9. Tank cleaning protection
Appropriate PPE to be worn at various stages during cleaning
Respiratory protection
– air-line breathing apparatus
– air fed hoods
Body protection
– impervious clothing and footwear
– gloves
Eye / face protection
– goggles
– face visors
Tank cleaning protection (Slide 9)
Entry into a tank without the appropriate respiratory protection (for example breathing apparatus, air hoods, air supplied encapsulating suits) and suitable protective clothing should not be authorised until all deposits, scale and sludges likely to give off vapours harmful to health have been removed.

10. Potential hazards Potential hazards (Slide 10)
Examples of potential hazards which can remain after cleaning.

11. Hot work Hot work (Slide 11) Stage 7 Hot Work
After the tank has been cleaned, it must be inspected and gas tested again in preparation for repairs / hot work.
There are a number of potential hazards that must be addressed including:
• Possibility of flammable liquids / vapours in the ground beneath the tank floor and in double bottoms
• Cleanliness of all parts of the tank
• Organic lead if the tank had previously contained leaded gasoline
• Inorganic lead if the tank had been painted/primed with paint containing lead
• Contents of nearby storage tanks (fire risk)
• Nearby drains / sewers (fire risk)
• Toxic fumes from welding / cutting operations
Waxes and other deposits that will emit vapours must be removed. Remember that gas tests will not indicate the presence of these deposits.
Ensure there is no flammable or other material under the tank floor. If there is, other preparations will be required to ensure safe hot work. (Refer to API PSD 2207).
Leave all gas cylinders and welding machines outside the tank. Positively isolate the gas supply outside the tank at all breaks (lunch break, end of working day). Specify in site safety plan.
Maintain effective ventilation. Use local exhaust ventilation to remove welding fumes. Specify in site safety plan.
Ensure lighting is adequate with ground fault circuit interrupters. (Consult your local rules for guidance).
Continuously monitor for gas or vapours in the surrounding area if flammable liquids are handled in adjacent tanks.
Make sure contractors do not create flammable / toxic atmospheres during painting.

12. (Slide 12)
The written site safety plan should cover the details of the hot work and confined space entry permit procedures specifying all precautionary measures including first aid fire fighting equipment, requirements for a fire watcher, etc.
Note: Presenters should show overheads of local Risk Assessment Forms and Work Permits, as appropriate.

13. Recommissioning safety check
Inspection
The tank foundations have been inspected and confirmed in satisfactory condition
The dike / bund walls have been reinstated
The dike / bund drainage system is serviceable and clean
All necessary repairs to the tank have been carried out
All tank fittings and valves have been correctly reinstalled and are serviceable
Electrical
The tank shell is grounded
Any ground / earthing cables associated with the floating roof or internal floating cover are securely connected and intact
Any seal grounding / earthing shunts on a floating roof tank are correctly installed and intact
Any tank or associated piping cathodic protection system has been reinstated
The electrical fittings associated with any side entry mixers have been correctly installed
Recommissioning safety check (Slide 13)
Stage 8 Mechanical Integrity
Plant Inspectors must check the integrity of any repairs.
If there is to be either a full or partial water test of the tank it should remain isolated from the process pipework system until the successful completion of the Tank cleaning and repair operations often continue over a relatively long period and involve a wide range of individuals during the different phases of the work. It is therefore particularly important that appropriate checks are carried out to ensure that the tank may be recommissioned safely. Use the attached check list. (See overheads 14, 15, & 16).

14. Recommissioning safety check (cont’d)
Instruments
All tank level gauging equipment has been correctly reinstalled and reconnected and is functioning correctly
Any separate high and / or low level alarms have been correctly reinstalled and are functioning correctly
Any tank temperature measurement instrumentation has been correctly installed
Any instrumentation associated with the side entry mixers has been correctly replaced
Fire protection
Any foam lines and their associated fittings have been correctly installed
Any drencher or sprinkler system is correctly installed
Recommissioning safety check (cont’d) (Slide 14)

15. Recommissioning safety check (cont’d)
Mechanical
That all materials and debris arising from the tank cleaning operation and subsequent inspection and any repair work have been removed from inside the tank, from the roof tank, from any internal floating cover and from the vicinity of the tank, for appropriate disposal outside the dike / bund area
Any internal floating cover has been installed in accordance with the manufacturers requirements
Any side entry mixers have been correctly installed
Handrailings on stairways and around the tank roof of wind girder are intact and secure
Recommissioning safety check (cont’d) (Slide 15)

16. Recommissioning safety check (cont’d)
Mechanical (continued)
The roof ladder is correctly positioned and intact
The roof legs are in position and correctly set
The automatic vent legs are all in position and correctly set
The roof drain sumps are all clear of debris and all non-return / check valves operational
All pontoons are clean internally and all pontoon manway covers have been replaced
Any free vents, at the top of the shell or on the tank roof, have the correct ‘free area’ mesh / screen fitted and are clear and free from blockage
All roof manway covers and other roof fitting covers are closed
Primary and secondary seals are correctly installed
Recommissioning safety check (cont’d) (Slide 16)

17. Recommissioning safety check (cont’d)
Operational
The tank has been inspected internally and is acceptable for service
The tank has been inspected externally, including the roof and any internal floating cover, an is acceptable for service
All roof drains, water draw-off, suction and discharge valves are serviceable and properly indentified
All emergency roof drains, on single deck roofs, have been primed with water
The tank drain valves are closed
The roof drain valve is left open in accordance with local policy
Test fixed / semi-fixed fire protection systems
Recommissioning safety check (cont’d) (Slide 17)
Testing of fixed foam pourers on external floating roof tanks also gives the opportunity to test the roof drain system.

18. Recommissioning hazards
Deisolate tank – Cold Work Permit – check blinds against Blind List
When filling do not exceed inlet flow velocity of 3 ft / secs
– until inlet submerged by at least 2 ft (cone roof) if vapour space contains flammable gas / gas mixture or mist
– roof is floated (internal / external)
– where product contains free water
Do not jet mix if vapour space contains flammable gas / air mixture or mist
Do not dip / sample during initial fill operation
Recommissioning hazards (Slide 18)
Stage 9 Deisolation
After the water is dumped from the water test, prepare to deisolate the tank for recommissioning. This will be covered by a COLD WORK PERMIT. Check off blinds against those listed in Blinding list to ensure none are forgotten.
Stage 10 Recommissioning
Safety precautions should be available in your Operations manual and may include the following:
• Limit flow velocity at the tank inlet to less than 3 ft. / sec. if there is a possibility that a vapour space in a tank could contain a flammable / air mixture or mist, until the inlet is submerged by at least 2ft. (Refer to Safety Talk No. 1)
• In the case of internal / external floating roof tanks continue low flow rates (less than 3 ft. /sec.) until roof is refloated
• If the product contains free water, the flow rate (less than 3 ft. /sec.) should continue for the whole filling operation. (Refer to Safety Talk No. 1)
• Jet mixing should not be done if there is a possibility that the vapour space may contain flammable/air mixture. (Refer to Safety Talk No. 1)
• Do not manually dip or sample during the initial filling operation. Wait until the conditions have stabilised. (Refer to Safety Talk No. 1 & 3)

19. Flammable mixture during initial filling
Flammable mixture during initial filling (Slide 19)
Ensure that roof is lifted gently and to closely monitored during initial fill.

20. Flammable mixture will exist above internal floating roof during initial filling it will take time to disperse
Flammable mixture (Slide 20)
Space beneath the internal floating roof will vent into tank headspace. The tank should be filled to maximum dip to disperse vapours to atmosphere.