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scatter Type (QMI)
- The light scatter device detector heads
are set – up by the manufacturer.
systems are self
calibrating against deviation.
- Maintenance consists of cleaning lenses and changing
- The CPU has a self
diagnostic facility which checks for errors.
- The device can be
tested by using aerosol which mimics an oil mist at alarm level (2%) LEL.
& slowdown are tested against a known concentration of mist
- The lenses
and mirrors should be cleaned periodically.
- In this
model the total mist concentration is measured with respect to clean air.
alternative models draws samples through both references and measuring
tubes which from C/C and atmosphere and compare the level of mist.
explosion in the event of OMD become inoperative:
- If the engine is not equipped with
bearing temperature monitors linked to slowdown/shutdown, then in the
event of the oil mist detector becoming inoperative, then subject to
classification society rules, the machinery space cannot operate under UMS
conditions and will have to be manned on a 24 hours watch keeping basis.
- Because one of the important safety
devices is now inoperative, extra vigilance will be required by the
engineers on duty.
- If bearing temperature probes are fitted,
then these must be closely monitored.
- The watch keeping engineer must use his
senses of smell, hearing, sight and touch to check for any unusual noise,
heat or smell which may indicate a potentially dangerous situation. In the
event of any doubt, them the engine must be stopped for further
- It will be even more important than ever
to ensure that the engine is not overloaded.
- The crankcase pressure should be closely
monitored; a rise in pressure on a trunk piston engine will indicate
excessive blow by from one or more units.
OMD should be investigated to establish the cause of failure, and necessary
spares ordered to rectify the problem as soon as possible.
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