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Oily Water Separator

Oily Water Separator (15 ppm)

The 15 ppm oily water separator is the standard bilge-cleaning unit fitted to meet the global MARPOL discharge limit; its defining feature is not the separator alone but the certified 15 ppm bilge alarm and automatic stopping device wired into it.

9models
Parker Hannifin
Knowledge

What to check on an Oily Water Separator (15 ppm).

9 models from Parker Hannifin in Oily Water Separator (15 ppm). Below: the full model list.

What sets the 15 ppm type apart

Every ship generating oily bilge water needs some means of cleaning it before overboard discharge, but the term "15 ppm separator" refers specifically to a unit type-approved against the IMO discharge standard of 15 parts per million oil content, tested and certified under MEPC.107(49) (or the earlier MEPC.60(33) for older units still in service). What distinguishes this type is the combination of a mechanical treatment stage with a certified 15 ppm bilge alarm and automatic stopping device: the separator alone only removes oil, the complete system also monitors the outlet continuously and shuts discharge to the bilge holding tank the moment the reading rises toward the limit. A separator without a certified monitor and shutdown fitted is not a compliant 15 ppm unit, whatever its treatment performance on paper.

15 ppm oily water separator, process flow
Flow diagram of a 15 ppm oily water separator: bilge water enters the coalescing stages, passes the 15 ppm bilge alarm, and the three-way solenoid valve either discharges clean water overboard or recirculates it to the bilge, while separated oil residue drains to the sludge tank.

Legend

  1. sludge tank
  2. oil residue
  3. separator unit
  4. stage 1 - gravity
  5. overboard discharge (under 15 ppm)
  6. bilge water inlet
  7. stage 2 - coalescer
  8. 15 ppm bilge alarm
  9. 3-way solenoid valve
  10. recirculate to bilge (over 15 ppm)

Main components

Gravity / coalescing separation stage

Bilge water enters a first chamber where free oil rises by gravity, then passes through a coalescing stage of plates or a filter/coalescer pack that merges small oil droplets into larger ones that can also rise out.

Fine filter or second-stage polisher

Many designs add a second treatment stage, often a replaceable cartridge filter, membrane or coalescer, to bring the outlet reliably below 15 ppm even with emulsified oil that gravity alone cannot separate.

Read the full guide

15 ppm bilge alarm and monitor

An oil content meter, sampling the treated water continuously, wired to sound an alarm and automatically stop overboard discharge (diverting flow back to the bilge holding tank) if the reading approaches 15 ppm. This unit carries its own separate type approval certificate.

Sludge and waste oil handling

Separated oil drains to a sludge tank; the separator's own performance depends on this tank not being allowed to back up into the unit.

Selection and sizing

ParameterTypical basis
Rated capacitysized to the vessel's expected bilge water generation rate, commonly 0.5 - 10 m3/h
Inlet oil content design basisup to several thousand ppm depending on approval class
Outlet requirement15 ppm continuous, monitored
Materialsbronze, stainless or coated steel wetted parts for seawater/bilge service life

Undersizing against actual bilge generation is a common yard mistake; a unit rated for the design flow rarely copes once engine room leakage exceeds the original estimate.

Regulations and class

Governed by MARPOL Annex I, Regulation 14, which requires ships to discharge oily mixtures only through equipment meeting the 15 ppm standard, with special area restrictions (Antarctic area: no discharge at all) layered on top. The equipment and its alarm/monitor both need individual type approval certificates referencing the applicable MEPC resolution, and both are checked at survey together with the associated Oil Record Book entries and IOPP Certificate. Class surveyors check the automatic stopping function actually operates, not just that the alarm sounds.

Typical faults

  • Coalescer fouling - sludge and detergent residue block the coalescing media, and treated output quality drops even though the pump still runs normally.
  • Monitor calibration drift - an uncalibrated oil content meter reads falsely low, allowing out-of-spec water overboard undetected until the next survey catches it.
  • Emulsified oil bypass - detergents or cleaning chemicals in the bilge break oil into an emulsion that gravity separation cannot remove, overloading the polishing stage.
  • Sludge tank back-pressure - a full sludge tank prevents separated oil from draining away, and it re-mixes into the treated stream.

What to look for in a supplier

  • Type approval certificate for the complete system, separator and monitor together, matching the resolution actually in force for the ship's flag and build date.
  • Spare parts and calibration service availability for the specific oil content monitor model, since these need periodic recalibration to stay certified.
  • Documented performance at realistic inlet oil concentrations, not only the clean-water test condition.

A 15 ppm unit that passes its annual survey with clean test water can still fail in service the moment someone runs degreaser through the bilges - emulsified oil is the real test of a separator, not the paperwork test.

Models

Models in this type.

The best-documented model of each manufacturer first, then the next — 9 of 9 models in Oily Water Separator (15 ppm). Every row links to full specifications, documents and service notes.

Showing only Parker Hannifin. Show all manufacturers
All manufacturersAlfa Laval 117Victor Marine 79Facet 65RWO/Veolia 65GEA 35Jowa 31Kangrim 31MAHLE NFV 31Wärtsilä 22Mahle Industriefiltration 20Taiko Kikai 13Wartsila AQUARIUS 13Miura 9Parker Hannifin Marine 9SKF 9GEA Westfalia 8Mitsubishi Kakoki (MKK) 8Hi Fuji 5Sea Recovery 4Yokogawa 4
Parker Hannifin MarinePH-OWS-05 Parker Hannifin MarinePH-OWS-10 Parker Hannifin MarinePH-OWS-100 Parker Hannifin MarinePH-OWS-15 Parker Hannifin MarinePH-OWS-150 Parker Hannifin MarinePH-OWS-20 Parker Hannifin MarinePH-OWS-30 Parker Hannifin MarinePH-OWS-50 Parker Hannifin MarinePH-OWS-80
9 models Separator spare parts
By manufacturer

Manufacturers.

All 89 manufacturers with models of Oily Water Separator (15 ppm). Names with a manufacturer page open it; the others open a search across the full library.

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Related types

Also in Oily Water Separator.

The other equipment types in this category.

15 ppm Bilge Alarm (Oil Content Meter)15 ppm OWSOily Water Separator
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