Crankcase Explosion Page 8 Flashcards
What is the name of the equipment used to warn of conditions that could lead to a crankcase explosion in a diesel engine?
Oily Mist Detector
What is the function of the spring loaded self-closing valve in a crankcase explosion?
It stops entry of atmospheric air into the cylinder and allows excess pressure to escape during an explosion.
What prevents flame from escaping in the valve assembly during a crankcase explosion?
Oil wetted gauze
What should the Engineer Officer of the Watch do first when an alarm is activated on the oil mist detector?
Inform the bridge and request the engine to be slowed down, and inform the Chief Engineer and Master.
What action should be taken if the engine cannot be stopped after an alarm on the oil mist detector?
Evacuate the engine-room, shut and secure all doors, open skylights, and set up boundary cooling.
What should be started after an alarm condition is activated on the oil mist detector?
Start Emergency Generator.
What should be done once the engine is stopped after an alarm on the oil mist detector?
Stop auxiliary blowers.
What should be shut off after stopping the engine in response to an oil mist detector alarm?
Shut off fuel supply.
What should be stopped in the engine room after an alarm condition is activated?
Stop all engine room fans.
What must be maintained during an alarm condition on the oil mist detector?
Maintain lubrication and cooling.
What should be engaged and started after stopping the engine in response to an oil mist detector alarm?
Engage turning gear and start.
Oily Mist detector
b) Sketch and describe the device used to relieve any excess pressure that might develop as a result of a crankcase explosion in a
diesel engine (14)
Spring loaded self-closing valve stops entry of atmospheric air into cylinder.
A Strong Spring Seals the valve during normal conditions however, in the event of an excess of pressure caused by an explosion then overcomes the spring force for a brief period to allow the pressure to escape before re-closing.
Oil wetted gauze prevents flame escaping
- Enumerate the important actions to be taken by the Engineer Officer of the Watch in the event of an alarm
condition activated on the oil mist detector (16)
(i)Inform the bridge and request the engine to be slowed down, they should inform Chief Engineer and Master
(ii)If the engine cannot be stopped, evacuate the engine-room shut and secure all doors, open skylights, set up boundary cooling
ensure to keep clear from all doors
(iii)Start Emergency Generator
(iv)Once engine is stopped, Stop auxiliary blowers
(v)Shut off fuel supply
(vi) Stop all engine room fans
(vii)Maintain lubrication
(viii)Maintain cooling
(viiii)Engage turning gear and start
What are four possible sources of ignition in the crankcase of a large marine diesel engine?
- Overheated bearing (Hot spots)
- Piston blow by (Trunk only)
- Piston skirt seizure
- Scavenge fire overheating diaphragm plate
- Piston rod binding on stuffing box
What are two methods to detect a potentially dangerous situation within the crankcase?
- Oil mist detector
- Bearing temperature monitor
- Plash oil monitor
What are two indications of a possible dangerous situation within the crankcase?
- Incongruous noise from crankcase
- Irregular running of main engine
- Smell of oily mist bottom deck of engine room
