QUESTION 10.7.3

Crankcase oil-mist and bearing-temperature protection

Oil, Chemical, LPG, LNGEngine Room, Engine Control Room

What is being checked

The inspector is checking whether the approved crankcase explosion warning arrangement is operational, correctly tested and maintained, and whether engineers understand the immediate response without opening a dangerous crankcase.

Ready onboard

0/6 complete

DETECTORSOil-mist detectors, bearing-temperature monitors or approved equivalent devices cover the required engine locations.FUNCTION TESTMaker-approved tests verify channels, sample flow, alarms, shutdown or slowdown outputs and remote indication.CLEANLINESSSampling pipes, lenses, filters, fans and drains are maintained to prevent false or missed alarms.SETTINGSAlarm and protective settings are controlled and unauthorised changes are prevented.RESPONSEStanding instructions require load reduction or stopping, bridge notification, cooling time and prohibition on premature crankcase opening.HISTORYFalse, intermittent and genuine alarms are investigated, recorded and trended.

Practice questions

Answer aloud, then open the preparation point.

1What is your first action on an oil-mist alarm?

Inform the bridge, reduce or stop the engine as required, maintain lubrication and cooling and follow the maker emergency procedure.

2When may the crankcase be opened?

Only after the maker-specified cooling period, atmosphere and fire precautions and authorisation. Premature opening can admit oxygen and trigger explosion.

3How is the detector tested?

Use the maker-approved method for the actual model and verify channel and output response, not an improvised smoke source.

4What can cause a false alarm?

Contamination, blocked drains or sample lines, condensation, poor airflow, electronics or incorrect maintenance, all of which still require investigation.

5What does a bearing-temperature trend add?

It can identify local friction or lubrication failure that may precede oil-mist formation and supports diagnosis.

Where an observation may arise

CHANNEL DEFECT

A detector channel or sample line is isolated, blocked or unreliable.

OUTPUT UNTESTED

The alarm is checked locally without proving slowdown, shutdown or remote indication as fitted.

SETTING CHANGE

Alarm thresholds are altered without maker or company authority.

UNSAFE RESPONSE

Crew intend to open the crankcase immediately after an alarm.

RECURRING ALARM

Repeated alarms are reset without root-cause investigation.

Master's practical note

Ask the duty engineer what they will not do. Avoiding premature crankcase opening is as important as knowing how to acknowledge the alarm.

Equipment boundary and references

Equipment boundary: Protective logic varies by engine design and may alarm, slow or stop. Follow the maker-approved response and testing method; do not introduce smoke or vapour that can damage the detector.

References

OCIMF SIRE 2.0 Question Library Part 2, Version 1.0, Question 10.7.3
SOLAS Chapter II-1 regulation 47
IACS UR M10
Engine and oil-mist detector manufacturer instructions

Last reviewed: 2026-09-10