- THERE ARE LARGE AMOUNT OF OIL DROPLETS WHICH ARE PRESENT EVERYWHERE IN THE CRANKCASE THE AVERAGE SIZE OF OIL DROPLET IS ABOUT 200 MICRONS WHICH IS NOT AN ISSUE AS REGARD TO CRANKCASE EXPLOSION.
- MAJOR REASON FOR CRANKCASE EXPLOSION IS BECAUSE OF OCCURRENCE OF HOTSPOT WHICH MAY BE DUE TO
- TOO MUCH CLEARANCE BETWEEN THE BEARING SO OIL FILM MAY BREAKDOWN.
- CRANKSHAFT IS NOT PROPERLY ALIGNED.
- STUFFING BOX NOT ABLE TO SEAL PROPERLY.
- IF PISTON CROWN CRACK THEN EXHAUST GAS MAY LEAK TO THE CRANKCASE.
- IN MAN B&W IF CHAIN IS TOO LOOSE OR TOO TIGHT THEN CHAIN MAY RUN HOT WHICH MAY ACT AS A HOT SPOT.
- IF MATCHING GEAR DOES NOT HAVE A PROPER BACKLASH THEN LUBRICATION IS NOT SO EFFECTIVE AND GENERATE A HOT SPOT.
- CIRCULATION OF LUBE OIL IS NOT PROPER.
- THE ABOVE GIVEN REASON CREATE A HOTSPOT. THIS HOTSPOT WHEN COMES IN CONTACT WITH LUBE OIL MAKES THE OIL TO VAPORISE WHICH FURTHER REDUCE THE DROPLET SIZE TO ABOUT 10 MICRONS. THE CONTINUATION OF THIS PROCESS CREATES A WHITE CLOUD JUST BELOW THE STUFFING BOX.
- THIS CLOUD WHEN AGAIN COMES IN CONTACT OF THE HOT SPOT RESULT IN PRIMARY CRANKCASE EXPLOSION.
- AFTER PRIMARY EXPLOSION OCCUR THE PRESSURE INSIDE THE CRANKCASE INCREASES ALL OF A SUDDEN THIS RESULT IN ACTIVATION OF RELIEF VALVE WHICH INTURN RELEASES ALL THE GASES TO ENGINE ROOM.
- IF WE ARE UNABLE TO CONTAIN FRESH AIR TO REACH THE CRANKCASE THIS WILL RESULT IN SECONDARY EXPLOSION WHICH WOULD A BIG DISASTER TO HANDLE.
HOW TO AVOID SECONDARY EXPLOSION
- ALL THE MAIN BEARING AND TRUST BEARING HAVE HIGH TEMPERATURE ALARMS THESE ALARMS WILL INDICATE US INCREASE IN TEMPERATURE INSIDE CRANK SHAFT.
- WE HAVE TO MEASURE WEAR DOWN OF MAIN BEARING IF UNEQUAL WEARDOWN TAKE PLACE IT MEANS OIL FLOW IS NOT SAME IN ALL THE BEARING.
- WE HAVE NON RETURN TYPE OF RELIEF VALVE WHICH RELIEF ALL PRESSURE GENERATED DURING THE PRIMARY EXPLOSION INSIDE THE CRANKCASE.
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