Marine Installation Manual
2021-08
4-85
4 Ancillary Systems
4.8 Leakage collection system and washing devices
X72DF
4.8
Leakage collection system and washing devices
The latest version of the
Marine Installation Drawing Set
relevant for the
leakage collection and washing system (DG 9724) is provided on the WinGD
webpage under the following link:
4.8.1
Sludge oil trap solutions
General description of the sludge oil trap
General description
A sludge oil trap is used to collect cylinder oil residue, product of combustion,
and leaky system oil from the gland box. When the main engine is running, oil
residue in the piston underside is collected from the cylinder lubrication as it is
being scraped down from the cylinder liners. This oil is removed through the
drains of each piston underside unit area and collected into the designated sludge
oil trap. The sludge oil trap is connected with the scavenge air receiver, therefore
the sludge oil trap is classified as a pressure tank, and in principle it requires ap
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proval and certification by the classification society. On the main engine side, the
maximum scavenge air pressure in the scavenge air receiver is approximately
3.5-4.0 bar (g). Therefore, the tank pressure must be designed and produced ac
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cordingly.
Installation requirements
It is recommended to install the sludge oil trap as close as possible to the main
engine. The drain pipe must have a minimum slope of 15° as the sludge tends to
stick which could cause a blocking of the drain pipe. It is advised to install heat
tracing and insulation around the drain pipe to keep the sludge in a liquid state.
A heating coil must also be installed in the sludge oil trap. The heating system in
the sludge oil trap must be designed to keep the sludge at approximately 50 to
60°C. The sludge oil trap design must follow the fire extinguishing requirements
in case of a fire in the scavenge air receiver. For these reasons, a manual shut-off
valve must be installed between the piston underside drain and the sludge oil
trap.
In view of the current issues with the sludge oil trap design and based on the feed
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back from shipyards and shipowners, WinGD has provided an overview of the
advantages and disadvantages of different solutions. A summary of these dif
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ferent systems and design options for shipyards and design institutes is provided
below.
