Crude oil washing safety check items for oil tankers

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Crude oil washing safety check items for oil tankers

Crude oil washing (C.O.W.) is a method of cargo tank washing wherein the oil itself is used as the solvent to speed the residue's removal on the tank's interior surfaces. Inerting is always required during this operation. The solvent action of crude oil makes the cleaning process far more effective than when water is used. However, such a technique of washing cargo tanks involves many hazards, and careful consideration will need to be made for safe planning and execution. Preceding operating utmost diligence in planning and execution needs to be made for a safe working environment. The following are the basic guidelines for quick reference. The Chief Officer, as qualified by the requirements as laid down by flag state administration of the ship and any port regulations that may be in force locally, supervise all C.O.W. operations.

The operation itself involves many hazards, and careful consideration will need to be made for safe planning and execution. We summarized here some basic checkpoints for safe crude oil washing. These procedures are only indicative, not exhaustive, and must always be guided by practices of good seamanship

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Check items before arrival :

Has Terminal/port permission been obtained?
Is the cargo intended to be used for carrying out Crude oil washing (C.O.W.), about I.M.O.'s guidelines on Crude Oil washing Systems and suitable and precautions exercised?
Will, the C.O.W. plan and discharge plan be drawn out above the basis of such history and performance under the ship's "Operation and Equipment Manual / C.O.W. manual" and other instructions?
"Has information exchange carried out well in advance with terminal regarding the vessel's discharge plan and/or Crude Oil Washing Plan carried out? Any particular terminal requirement of 'Dirty Crude' discharge at completion, etc"
Is oxygen analyzing equipment (portable and fixed type) tested, calibrated and working satisfactorily?
Have I.G. equipment and its alarm system been tested and working properly?
Have the tank cleaning heater and line been isolated by the line blinder from the Crude Oil Washing System?
Have main and stripper overboard discharge lines been isolated by line blinders?

"Is Blind Plate fitted on the sea chest? Has sea chest been tested for integrity? Has a short piece between sea chest blank and valve been proved efficiently drained?"
Have all seals of sea valves in the pump room been checked in position?
Have all branch lines' valves for portable tank cleaning machine been isolated by line blinders?
Have all valves of tank cleaning machines and drain lines to tank been closed?
Has the pressure test of the tank cleaning line been carried out? Is there no leakage? Date of Testing ( ........... ) // Tested pressure (.......kg/cm2)
Are pressure gauges (remote and local) for tank cleaning mainline in good working order?
Has the stripping system, monitoring equipment been checked?
Are pressure gauges of cargo, ballast pumps, and eductors in good working order?
"Are level gauges and high-level alarm systems in good working order? Is the Control (C.O.C.) side and Local (Float) side testing and verifying for Alarms (Audible and Visual) been carried out and verified?"
Have the ship's internal communication systems used for cargo operation been tested and kept ready (Battery Charged)?

Is cargo watch schedule posted with contact details, duties and responsibilities, including Record of Person Incharge of Oil Transfer?
Have discharging and crude oil washing procedures been planned as per guidance as laid out in the Ship's Crude Oil Washing Manual and the crew members properly instructed?
Is it confirmed there is no leakage from tank hatches (domes), vent-lines, and I.G. lines?

Have cargo tanks pressure been adjusted in proper range?
"Have results of checks and tests been informed to terminal/agent? Where terminal has a standard radio checklist, has this been completed and transmitted?"

Check items after arrival

Are all pre-arrival checking items and condition in good order?
Has safety check before start of discharging been carried out by discharging check list and Ship Shore Safety Checklist / Ship to Ship Transfer checklist as required?
Has the discharge / crude oil wash operation details been discussed with both ship and attending shore staff and is agreed plan readily available for easy reference?
Have conditions for suspending C.O.W been discussed with terminal? Are officers briefed on the actions to take in case of failure of I.G.S?
Have all valves of C.O.W. line been re-confirmed closed?
Do all cargo tanks have positive pressure?
Is oxygen content of each tank below 8% by volume?
Have I.G. delivery valves of discharging tanks been opened?
For heated crude, is temperature of CO Washing supplying oil suitably slightly higher than discharge temperature, but within the limits as per terminal's limitation?
Are the programmable C.O.W machines correctly set as per desired wash pattern? (Considering the nature of cargo and surrounding temperature)

Check items before crude oil washing operation

Are the caution marks posted in prescribed locations?
Is the Inert Gas System working properly, and is the content of inert gas being delivered below 5% by volume?
Is oxygen content of the tanks to be crude oil washed below 8% by volume and confirmed before washing operations commence?
Do the cleaning tanks have positive pressure? (more than 200mmAq)
Are I.G. system and cargo tanks and openings tightly closed for avoiding gas leakage to the atmosphere?
Has the terminal been notified of the start of C.O.W. and the possibility of discharge rate reduction?
Has the ship's crew been informed of the start of washing?
Has assignment of operation for each responsible person and person in charge been confirmed?
Is communication system between cargo and crude oil washing operations in good order?
"Has reasonable crew been posted to check leakage of cleaning lines? Has personnel been posted as per C.O.W. plan?"
Has the float gauge of tanks to be cleaned been raised? (if applicable)
Have precautions been exercised to gradually fill the C.O.W. line, taking care to avoid liquid hammer/air entrapment?
Has the stripping (educting)system for the planned tank(s) to be COWed been started before the washing commencing?
Have valves of tank cleaning line to the tank for cleaning been opened?
Is the water level of deck water seal tank proper?

Check items during crude oil washing operation

Are all C.O.W. lines, flanges, valves, expansion joints, etc are being monitored closely and confirmed in good order on deck, as well as in pump room ?
Are pumps in use checked for any potential source of leakage, during the gradual rise in pressure?
Are cleaning machines in good working order? (Proper movement verified by the visual movement of indicators on drive units, machine sound pattern and washing time cycle, as programmed)
Is the trim during bottom washing adequate as per crude oil washing operation and equipment manual?
Is the pressure in the tank wash line as specified in the manual?
Is Crude oil washing in progress in designated cargo tanks only?
Is oxygen content of delivered inert gas below 5% by volume, and is it being recorded?
Is cleaning tank pressure proper (more than 200mmAq)?
Is surrounding sea surface regularly monitored?
Is the level of collecting tank normal and being monitored?
For the heated cargoes, is the temperature being controlled? (if applicable)
Is the operation of stripping system during bottom washing in good order?

Check items after completion of crude oil washing operation

Are all interconnecting valves between discharging lines and tank cleaning lines closed?
Has residual oil in tank cleaning lines been well drained? (urgency to be considered for heated cargoes, as required)
Are all valves of tank cleaning machine and drain line to tank closed?
For heated crude, all part of crude oil line physically verified for complete draining by line tracing on deck?
Has remaining oil in tanks, pumps, and pipelines been well stripped after completion of discharging?

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