Question

Sketch and discuss the precautions and protections that are provided to minimize the possibility of a diesel engine crank case explosion and the transmission of dangerous flame into the machinery space:

(a) By design and equipment

(b) By operating personnel

Answer 1

Part (a)

By design and equipment:

Bearing material should be chosen to minimize friction and heat generation. The material must have sufficient strength to handle the maximum expected load and should not readily deteriorate during service.
Shaft journal and bearing dimensions must be adequate to ensure that the permissible specific load is not exceeded.
Adequate lubricating oil should be delivered to the loaded areas to form a hydrodynamic oil film. All passages, grooves, bore reliefs, and tangential runouts in the bearings should be appropriately provided.
The lubricating oil pump, filter, cooler, and pipeline system should be properly designed and sized to deliver sufficient oil at the correct pressure and temperature to all bearings, the gear chain drive, and other moving parts.
Only high-quality oil, as recommended by the manufacturer, should be used.
Thermometers should be installed at strategic points in the lubricating oil supply and return lines to monitor temperatures.
Bearing temperature indicators and alarms should be installed.
Oil mist detectors should be installed, and alarms must be provided to warn of dangerous conditions.
Crankcase relief doors must be installed in compliance with classification society regulations to relieve excess pressure safely.

Part (b)

By operating personnel:

Maintain good housekeeping, and ensure pumps, filters, and coolers are in good condition. Oil samples should be sent for regular analysis, and remedial actions should be taken based on the analysis reports.
Use only high-quality lubricating oil as recommended by engine builders.
Maintain an adequate oil level in the drain tank.
Continue running the lubricating oil pump for at least 30 minutes after stopping the engine to ensure proper cooling and lubrication.
Run the lubricating oil purifiers continuously while the main engine is running, and even during standby.
Ensure lubricating oil temperatures do not exceed the recommended limits.
Conduct planned maintenance and regular inspections of the crankcase.
Investigate and address any signs of overheating, such as high lubricating oil temperatures or unusual warming of the crankcase door, immediately after slowing down or stopping the engine.
Ensure the oil mist detector, temperature monitoring, and alarm systems are functioning correctly.
Check bearing clearances and crankshaft deflection at scheduled intervals. Any abnormalities must be investigated and corrected promptly.
After renewing or working on a bearing, systematically run it in by starting the engine and performing the following checks:
- Inspect after 15 to 30 minutes of operation.
- Inspect after 1 hour of operation.
- At full load, check the bearing temperature by hand and compare it with other bearings to ensure the affected bearing's temperature is within safe limits.

✓ Verified Model Answer (Text Solution)

By design and equipment:

By operating personnel: