Crude oil washing operation onboard oil tankers involve many hazards and careful consideration will need to be made for safe planning and execution. Crude oil washing (COW) is a method of cargo tank washing wherein the oil itself is used as the solvent to speed the removal of the residues on the interior surfaces of the tank. Inerting is always required during crude oil washing. We summarized here some basic check points for safe crude oil washing. These procedures are only indicative, not exhaustive in nature and one must always be guided by practices of good seamanship.
Check items before arrival :
Has Terminal/port permission been obtained?
Is the cargo intended to be used for carrying out Crude oil washing (COW), in reference with IMO’s guidelines on Crude Oil washing Systems and suitable and precautions exercised?
Is the COW plan and discharge plan drawn out above basis of such past history and performance, in accordance with the ship’s “Operation and Equipment Manual / COW manual” and other instructions?
“Has information exchange carried out well in advance with terminal regarding 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 short piece between sea chest blank and valve been proved efficiently drained?”
Have all seals of sea valves in 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 pressure test of 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 main line 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 (COC) 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?
Have you confirmed there is no leakage from tank hatches (domes), vent-lines and I.G. lines?
“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 has been confirmed before washing operations commences ?
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 start of C.O.W. and the possibility of discharge rate reduction?
Has the ship’s crew been informed of 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 prior to 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 being checked for any potential source of leakage, during the gradual rise in pressure?
Are cleaning machines in good working order? (Proper movement verified by 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 pipe lines been well stripped after completion of discharging?
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