Equipment Guide · Crude Oil Washing
Crude Oil Washing (COW) cleans a cargo tank with the cargo itself. Instead of hosing sludge out with water and making slops, high-pressure jets of the crude re-dissolve the clingage off the structure so it drains away with the outturn. Tap a step or press "Play" to follow a wash program — see how much of the tank you wash and how often, how the crude is piped from the pump to each machine, and how a stage is programmed in degrees and timed to the minute.
Loading…
A 17-tank VLCC on a ballast voyage crude-oil-washes about 25% of its cargo tanks for sludge control. A quarter of 17 is 4.25 — and because you cannot wash a fraction of a tank, you always round UP to 5. Washing only 4 is a common slip that leaves you short of the requirement. The next ballast voyage takes the next batch, and so on, so all seventeen come around inside about four voyages ≈ four months — exactly the MARPOL ceiling no tank may exceed. Any tank about to load departure ballast is pulled forward and washed first, whatever the rota says.
Set the inert gas, jet pressure and stripping — then the wash arc in degrees. Watch the stage time compute itself from the machine's pitch and speed, and see why one arc can never clean the whole tank.
A wash cleans a zone only when three things are true at once — the atmosphere is inert (O₂ < 8%), the jet is hard (≥ 8 bar) and the well is stripped dry — and only for the zone the programmed arc actually reaches. The far bottom corner sits at 40° off straight-down, so an arc kept within 0–40° is a proper bottom wash; to clean the upper structure the arc must rise above 120° — which is why a whole tank needs both a bottom and a top stage. The nozzle turns a full 360° each pass, so each stage paints its zone in overlapping rings.
Press Start to run the wash — then switch the inert gas off, drop the pressure, or turn stripping off to see the wash fail.
Working principle — explained in our own plain words with our own schematic from general marine knowledge (not copied from any OEM manual). Conceptual; varies by ship/model. Reviewed and verified by a Master Mariner.