Exam Question

Oily bilge is drawn into the separator by the automatic self-priming pump. The pump is located on the outlet of the separate to prevent the formation of a mechanical emulsion. As the oily bilge water enters the separator, it flows upwards through the matrix plate pack, towards the top of the separator.
Some oil separates immediately due to the reduced flow velocity and the difference in specific gravity between oil and water. Oil droplets impinge on the surface of the matrix plate pack and begin the coalescing process. The oil droplets coalesce until they become large enough to detach from the corrugated plates and gravitate to the top of the separator. Smaller oil droplets that escape the matrix plate pack are removed by the polishing pack.
After the separated oil accumulates to a predetermined level, the oil sensor initiates the oil discharge and cleaning cycle by stopping the pump, closing the water discharge valve and opening the clean water inlet valve. This allows clean sea or fresh water to cleanse the matrix plate pack and flow upward in the reverse direction washing the polishing pack displacing the accumulated oil.
The outlet of the Oily Water Separator directed by 3-way valve either to overboard or to the storage tank. The valve is controlled by 15ppm monitor which allows overboard discharge if oil content below 15 ppm and stops discharge if oil content is exceeded.