¨ Maintenance & Checking accuracy of OMD
operation:
¥
Light
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 filters.
- 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.
¥
Graviner
type
- Alarms & 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.
- An alternative models draws samples through both references and measuring tubes which from C/C and atmosphere and compare the level of mist.
¨ Take to safeguard against the risk of C/C
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 investigation.
- 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.
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