Referring to the illustration, suppose while in the oil separation processing mode, the oil content detector display screen shows 17.9 ppm and the oily-water separator is discharging back to the bilge water holding tank for recirculation. What is most likely the cause? Illustration GS-0175
• 15 ppm discharge standard for oily water separators under MARPOL and 46 CFR (overboard vs recirculation) • Function of the oil content meter (OCD) and automatic three‑way valve in the diagram (line to overboard vs line back to bilge holding tank) • How excessive oil concentration in the feed tank affects what the OCD reads even after treatment
• Compare the OCD reading of 17.9 ppm to the legal discharge limit. Should the system be sending water overboard or back to the bilge tank at this moment? • Look at the flow path shown by the illustration when the unit is in "processing/recirculation" mode. What condition in the incoming bilge water would cause the OCD to keep the discharge going back to the holding tank instead of overboard? • Which options describe problems that mainly affect quantity/flow (how much you can pump) versus problems that affect quality of the separated water (how clean it is)?
• Verify what ppm level triggers discharge to overboard vs back to the bilge tank in an automatic OWS system. • Identify on the illustration where the OCD sample point is and whether it measures water after the separator media. • For each choice, decide: would this most directly cause the OCD to show a value above 15 ppm even though the separator is operating correctly?
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