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Focus for PSC: Oily water separator sampling point

The MEPC.107(49) requires a sampling point to be installed in a vertical section of the outlet pipe as close as possible to the 15 ppm bilge separator outlet. There have been several cases where ships have been detained for not complying with this requirement. This technical news summarizes this topic.

Relevant for ship owners and managers, shipyards, design offices, suppliers as well as flag states.

An oily water separator (OWS), bilge separator or oil filtering equipment is required by MARPOL Annex I, Regulation 14 to be installed on any ship above 400 GT. The unit shall be of a design approved by the administration and tested and installed according to guidelines in MEPC.107(49) as amended by MEPC.285(70)

In MEPC 107(49) Chapter 6.1.1, Installation Requirements, it states that “For future inspection purposes on board ship, a sampling point should be provided in a vertical section of the water effluent piping as close as is practicable to the 15ppm bilge separator outlet.”

The requirement to install the sampling point in a vertical section of the effluent pipe is, according to DNV’s understanding, to ensure that the sample is representative and homogenous. If the sampling point is installed in a horizontal section of the effluent pipe, there is a risk that the oil is floating at the top and will not be part of the sample.

Although it may be demonstrated that sampling from a horizontal section of the water effluent piping will also result in a representative sample, there is a risk that the PSC will nonetheless object to sampling in a horizontal section given the explicit requirement in MEPC.107(49) to have a sampling in a vertical section.

For many OWSs, the effluent pipe is short before the 3-way valve and only a small part is vertical, so for many installations the sampling point is in the bend of the vertical section and extracts the sample from the vertical section (see picture). DNV considers this solution acceptable and in compliance with the regulations.


DNV recommends that ship owners or operators review the insights provided in this newsletter and ensure that the OWS sampling point is in a vertical position.


• MARPOL Annex 1, MEPC.107(49)
MARPOL Annex 1 – Prevention of Pollution by Oil (Imo.org)
MEPC 107 49 (Imo.org)

Posted in DNV

Published at 29/06/2023

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