Equipment Guide · Water Washing & Fixed Tank Cleaning Machines
A product tanker's tanks must be clean enough that the next cargo cannot tell what came before — and the tool for that is seawater, thrown by the same fixed programmable machines a crude ship uses for COW. Tap a step or press "Play" to follow the water from the sea suction through the heater to the machine, watch the charged mist build, and see where the washings go — then program a wash yourself in the simulator, and find out why nobody dips a steel tape into a freshly washed, non-inerted tank.
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Static relaxation is physics, not paperwork — the charge in the mist bleeds away on its own timetable and no checklist hurries it. A tank left still needs 5 hours after the last machine stops before anything conductive and unbonded goes in; run mechanical ventilation continuously and the mist disperses in about 1 hour. The earthed full-depth sounding pipe shields whatever runs inside it, so dips through the pipe are allowed at any time — during the wash included. The rule exists to kill the most tempting shortcut in tank cleaning: the quick check dip "just to see how much water is left in the bottom".
Choose the atmosphere, set the water temperature, program the arc and keep the stripping ahead of the machines. The clock is compressed (≈1 s per wash-minute, faster after the machines stop). When the wash ends the mist must relax before anything goes into the tank — or lower the steel tape early and see exactly why the 5-hour rule exists.
Marks — static safe below 20% charge (column) · slop tank 85% high / 98% full · lean ceiling 10% LFL · hot-wash limit in an undefined atmosphere 60°C
The machine climbs 3.6° a minute, so the arc is the clock; the water it throws must be stripped away as fast as it lands or the bottom pools; and everything stripped stacks up in the slop tank. The atmosphere decides what the charged mist can do: inerted — nothing; lean — nothing while the fans hold under 10% LFL; undefined — assume flammable and strip out every ignition source, including your own sounding tape.
Press Start to begin the wash — set the atmosphere, temperature, arc and stripping first, or lower the steel tape early and see exactly why the 5-hour rule exists.
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.