Recent cases of detention due to oil pollution:

This vessel was detained by a PSCO for multiple fuel oil leakage points on the emergency generator.

This vessel was detained by the PSCO due to oil leakage signs at the stern tube in the engine room.

Before explaining the basis for detention due to oily water, we must clarify the concepts of the bilge water system, bilge tank and oily waste tank. The bilge water system is installed in compliance with SOLAS requirements, while the oily waste tank is mandated by MARPOL regulations.

The generation of bilge water is almost inevitable due to insufficient hatch cover tightness, leakage of pipelines and equipment, water seepage from shaft stuffing boxes, moisture condensation caused by temperature differences, plus water discharge during equipment maintenance.

Thus, SOLAS Chapter II-1 Regulation 35-1 explicitly requires all ships to be fitted with a dedicated bilge water system, which is normally designed for one-way flow. Given that the bilge water in the engine room contains oil, the system is usually equipped with a dedicated bilge pump to transfer bilge water from bilge wells to the bilge tank or discharge it directly overboard.

For instance, the figure below illustrates the bilge tank piping arrangement of a certain vessel.

Of course, the bilge water system is not only used for collecting and treating bilge water. In case of massive water ingress into the engine room, simply opening the emergency suction inlet will activate the system immediately for emergency drainage.

The oily waste tank is a requirement under Regulation 12 of Annex I to MARPOL. Per this regulation, oily waste tanks must not be connected to the bilge water system. In English notation, oily waste tanks are generally marked as Oil residue (sludge) tank. Waste oil collected from engine room oil tanks, lubricating oil tanks and auxiliary engine drip trays shall be discharged into the oily sludge tank. Oil-containing bilge tanks are generally marked as Oily bilge water holding tank, what’s in the bilge wells goes into this tank.

Just because of the different provisions stipulated in the conventions, detention for oily water is also mentioned twice in Annex 2 of PSC Circular A.1155(32).

It first appears as a detention item under the SOLAS Convention, which specifies that if a vessel is found to have the condition : Insufficient cleanliness of engine-room, excess amount of oily-water mixture in bilges, insulation of piping including exhaust pipes in engine-room contaminated by oil, and improper operation of bilge pumping arrangements, the vessel can be detained.

In fact, Regulation 11 of Chapter I and Regulation 4 of Chapter II-2 of the SOLAS Convention serve as the direct basis and legal support for the PSC Circular.

Regulation 11 of Chapter I of the SOLAS Convention addresses post-survey maintenance, requiring that all equipment functions be maintained following a vessel’s survey. Oil leakage clearly indicates a loss of functionality and poses potential hazards to onboard safety. Meanwhile, Regulation 4 of Chapter II-2 of the SOLAS Convention focuses on ignition risks, and its objective mandates that "measures shall be taken to control leakage of flammable liquids". Backed by these two regulations, the PSC Circular classifies the following as detention-worthy deficiencies: poor housekeeping in the engine room, oil slicks on bilge water, fuel oil pipeline leakage, oil contamination on insulation materials wrapping pipelines operating at temperatures above 220℃, and improper operation of bilge water by crew members.

It appears a second time as a detention item under the MARPOL Convention. Should oily bilge water and/or oil residue accumulate in machinery spaces, the vessel shall be deemed to have violated the provisions of Annex I to the MARPOL Convention and shall be detained accordingly.

Of course, the key point here is the excessive accumulation of oily waste or oil-containing bilge water.

In summary, when there is excessive oily water in the engine room, either SOLAS or MARPOL can be applied for detention, depending on the PSC’s priority – fire prevention or pollution prevention.

Due to the numerous detention cases mentioned above, some chief engineers or technical superintendents ask the engine room crew to roll up their sleeves and work harder, cleaning the engine room until it is as spotless as a mirror...

This is actually going a bit too far!

Reasonable leakage is permitted by the conventions. After all, the vessel’s installed bilge water system, oily water separator, bilge tank and oily waste tank are designed to collect and handle such substances. Simply pump excess bilge water from bilge wells into the bilge tank when detected, collect any leaked oil and discharge it into the oily waste tank, and record everything properly in the Oil Record Book – that’s all it takes.

--------------------------------Reprinted from PSCReady