The True Price Of A Bad Separation

Tests by water treatment specialists at RWO indicate how shipowners waste money when they are
persuaded to use non-OEM filters in their oily water separator systems.

The International Convention for the Prevention of Pollution from Ships (MARPOL) sets specific
demands for the water treatment equipment fitted on board ships of 400 gross tonnage and above,
including oily water separators (OWS).

The International Maritime Organization instrument limits effluent levels of water discharged into the
marine environment limits to 15 parts per million, with specific classification notations applying a tighter
5 ppm limit. To demonstrate their compliance, OWS systems must be tested and installed in line with
the IMO’s Marine Environment Protection Committee resolution MEPC 107(49).

For several original equipment manufacturers (OEM), the OWS operation comprises two stages: the
coalescence stage and the filter stage, which relies on active carbon filter cartridges.

In common with other areas of marine equipment, filter cartridges for OWS are available from OEM and
non-OEM suppliers. The non-OEM parts are frequently cheaper and as a result, many operators with
challenging maintenance/OPEX budgets choose the non-OEM option in the belief they are ensuring
compliance with a similar-quality product for a lower cost.

However, while seeming to be equivalent, non-OEM parts will not have been subject to rigorous type
approval performance testing. By choosing non-OEM filters, an operator is not only invalidating the
guarantee but also the certification of the OWS, leading to a significant compliance issue. Non-
compliance caused by using non-OEM spares may result, in certain circumstances, in hefty fines by
administrations in the event of a pollution incident.

Beyond superficial similarities such as shape and colour, a close physical comparison of OEM and non-
OEM filter cartridges can reveal key differences between the two. For example, OEM cartridges are
heavier and more robust, with their smaller pores creating a smoother surface structure which offers
superior oil capture.

Beyond the visual clues, tests show that OEM filters contain more active carbon, which ensures better
performance and durability.

Test comparison

RWO conducted a performance test to compare its own cartridges with those offered by two non-OEM
traders. The tests were carried out under IMO type approval testing regime, with the effluent water
analysed by an independent water laboratory to ensure impartiality.

With filter cartridge 1, the OWS reached the 15-ppm effluent limit within 10 minutes of operation. A
vessel operator might need to exchange the filter set more than 15 times to meet RWO filter
performance. Filter cartridge 2, meanwhile, initially appeared to perform adequately, but here too
effluent levels reached the 15-ppm limit before the type approval requirement. In this case, the owner
would need to exchange the filter set at least twice to meet RWO filter performance. For full
comparative test results, see here.

Even if non-OEM spares cost the operator half the price of those supplied by the OEM, RWO’s test data
indicates that the life-cycle cost of using non-OEM spares may end up being higher due to more
frequent replacement – depending on bilge water composition.

There are reports that several unauthorized distributors provide non-OEM spares that they claim are
original but, where RWO cartridge filters are concerned, the real thing will always be recognizable by the
RWO stamp on it as well as its performance.

Those requiring replacements can be assured that genuine RWO cartridge filters are available
worldwide. Furthermore, as well as ensuring that regulatory compliance is upheld, their
efficiency protects the business interests of the user by minimising running costs, labour hours
and downtime throughout the OWS lifecycle.

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