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Cargo ships guideline for oily water separator

All vessels are required to carry the above in order to comply with MARPOL regulations. It is essential that this item of machinery is operated and maintained correctly and strictly in accordance with international regulations and manufacturer’s instructions. It is to be noted that it is illegal to sail from a port without a functioning OWS and it is a requirement that sufficient spares for the unit are carried onboard. Guidance on MARPOL equipment is contained within the Critical equipment section.



The Chief Engineer is fully responsible for the maintenance and operation of the OWS and its operation must only be carried out by officers fully familiar with the equipment and under direct supervision of the Chief Engineer. When the equipment is not in use, the Chief Engineer is to ensure that a system is in place to lock-out the equipment to avoid unauthorised operation with keys being held by the C/E.

An operation manual for the OWS must be onboard. Crew members involved in the use of the equipment must be familiar with its contents. In addition, operating instructions and an operating diagram are to be posted on or next to the OWS unit. These are to be as clear and simple as possible.

Regular operational tests and checks of the OWS and associated equipment must be carried out in accordance with the PMS and also no later than 24 hours before arrival in port where possible. Minimum recommendations are that full inspection and cleaning of the OWS is to be carried out at least every two months with filters cleaned on a monthly basis. Such tests must be recorded in the engine log book and oil record book. The tank from which the OWS takes suction should be cleaned on a two monthly basis.

A spare set of OWS filter elements must be available onboard at all times and included in the Minimum Critical Spares List .

A sample is to be landed yearly for testing in a shore laboratory; the test standard is to be USEPA 1664. The Oil Content Monitor is to be calibrated annually.

Any defects discovered with the OWS and associated equipment must be rectified without delay. Where a defect cannot be repaired on board for want of spare parts or the need for specialist service, the management office must be notified and a remedial action plan agreed upon. If the vessel is about to enter port, knowing that the OWS is defective, the fact must be reported in the pre-arrival notices via agents according to local regulations. Defects remaining on the system must be reported to Class / Flag by the management office prior to leaving port limits.

All entries entered into the Oil Record Book (ORB) must be up-to-date, accurate, truthful and in full compliance with MARPOL requirements. An example of a typical ORB entry regarding OWS maintenance could be. “Opened and inspected OWS unit. Filters cleaned/renewed as required. Valves and piping on discharge side of OWS opened, inspected and cleaned. After maintenance, OWS and oil content meter checked for proper operation and found in order.”

An interlock should be fitted in order to prevent the improper use of flushing water diluting the oily water mixture running through the measuring cell. In other words, when flushing water is used to clean the measuring cell, the interlock stops any oily water mixture from being discharged overboard.

All pipe work associated with the OWS, the coil bilge system, emergency bilge suction line, bilge shore discharge connection, overboard connections for the GS system and boiler blow-down overboard connection must be correctly identified and labelled. A drawing showing the layout of the above should be available. On this drawing, all valves and flanges are identified and given a number. This drawing is to be attached to the Oil Record Book (ORB). See below Documents for a generic drawing for your reference. We would reiterate that only the flanges as marked 1 to 6 will require labelling.

ows piping layout
Fig:TYPICAL SINGLE HULL VLCCs OWS PIPING LAYOUT

All numbered flanges identified in the drawing should have had a small hole (about 5mm) drilled through in order to accommodate the fitting of a security seal. Each seal has a unique number and a form should be available to identify the flange number against the seal number. The date and time of fitting the seal should also be recorded as well as the date and time of the seal being broken including the reason for same. No seal should be broken without the joint permission of the Master and Chief Engineer.

Any flanges located at or near the OWS equipment and overboard discharge valves not and must be blanked off. These may exist as original or modified construction. Flanges should be removed from any flexible hoses maintained on board in order to avoid creating wrongful suspicion of an illegal by-pass of the OWS equipment.

The overboard discharge of the OWS should be coated internally with a suitable light colour epoxy coating. The reason for this is that uncoated pipes can react to corrosion and can result in what looks like a black oily residue adhering to the walls of the pipe. Some inspectors jump to the conclusion that this is oil. A light epoxy coating will prevent such corrosion and any discolouration caused by other sources will be readily apparent if the pipe is opened up for inspection.

The Bridge must be advised before the OWS is used to ensure that the operation is in compliance with MARPOL and so that they can keep a watch astern to ensure that no oily sheen is sighted on the water. If such a sheen is sighted, the operation must be stopped immediately. Where practicable, the oil water separator should only be used in daylight hours.



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