Marine Installation Manual
2022-03
4-93
4 Ancillary Systems
4.9 Leakage collection system and washing devices
X62DF-S2.0
Solution 3: An automatically bottom-drained sludge oil trap
Solution 3 description
For the automatic bottom-drain solution, there is no continuous drain to the
sludge oil tank. The advantage of this solution is that it provides fully automatic
operation of the bottom drain without manual crew operation. Also, this solu
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tion keeps the scavenge air loss to a minimum, while at the same time it ensures
that the sludge oil tank is not at all pressurised during normal operation, as well
as during drainage.
The basic design principle is the same as that of the manually drained sludge oil
trap (i.e. Solution 2). The piston underside drain is collected in the sludge oil
trap. The flow is ensured by venting some air at the top of the sludge oil trap and
through an orifice (5 to 10 mm inner diameter) to the atmosphere. In addition, a
sight glass is installed in the venting pipe to check the air flow. An external
heating device at the bottom of the sludge oil trap must be installed to ensure that
the sludge emulsion can be properly drained through the automatic bottom
drain, which is designed as an automatic valve.
Automatic drainage
There is a high-level switch and a low-level switch to control the automatic
bottom-drain valve. This valve automatically opens and closes the bottom drain.
If the automatic bottom drain is connected to the sludge oil tank, which is inte
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grated in the double bottom structure, then the draining of the sludge will be
pushed by scavenge air pressure and gravity. The low-level switch will ensure
quick closure of the automatic bottom-drain valve as soon as the sludge oil trap
becomes empty. Otherwise, the sludge oil tank would become pressurised by the
scavenge air. The advantage of the automatic drain solution, compared to the
manual solution, is that the risk of blowing scavenge air to the sludge oil tank is
eliminated.
Manual sludge removal
For manual sludge removal, partially unscrew and lift the cover to first drain the
liquid to a tray, and then fully open the cover and manually remove the sludge.
A design proposal for the automatically bottom-drained sludge oil trap is pro
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