Why crankshaft fail

Crankshaft is the intermediate part of a marine engine, which transfers the power of a firing cylinder from the reciprocating piston to the rotating propeller or alternator in case of a generator.

The working of other components of the engine depends upon the correct rotation of the crankshaft such as camshaft for fuel timing, firing order of units etc. Failure of a single part of the crankshaft can stall the engine as well as the ship. As a marine engineer working on a ship, one should know various reasons which can lead to failure of this important component.

Fatigue Failure: Majority of steel crankshaft failure occurs because of fatigue failure, which may originate at the change of cross-section such as at the lip of oil hole bored in the crankpin. Failure due to Vibration : If the engine is running with heavy vibration especially torsional vibration, it may lead to crack in the crankpin and journal.

Insufficient lubrication : If the lubrication of bearing in the crankshaft is starved, it may lead to wipe out of the bearing and failure of the crankshaft. Over Pressurised Cylinder: It may happen that there is hydraulic lock water leakage inside the liner and due to extreme pressure the crankshaft may slip or even bent if safety valve of that unit is not working.

Crankshaft of a marine engine is a massive component when fully put together in the engine. Initially the complete crankshaft is aligned in a straight line connection drawn from the centre of the crankshaft makes a straight line before setting it on the top of main bearings. But with time due to various factors, the straight line may deviate and misalign. You are commenting using your WordPress. You are commenting using your Google account.

You are commenting using your Twitter account. You are commenting using your Facebook account. Notify me of new comments via email. Notify me of new posts via email. Skip to content. There can be more reasons for the failure of the crankshaft but the main reasons are mentioned below: Fatigue Failure: Fatigue failure is one of the major reasons for the crankshaft failure in the steel crankshafts.

Share this: Twitter Facebook. Like this: Like Loading The prescribed bearing clearance was not adhered to. Causes: worn or warped crankcase, oversized or undersized bearing journals or errors in geometry such as conical or spherical bearing journals. Lubricating oil deficiency on commissioning as the oil system was not filled with oil and compressed beforehand.

Following bearing damage, swarf was left in the engine-oil circuit. The oil cooler, engine oil and oil filter were not replaced. The bore diameters of the crankshaft bearings in the crankcase were not checked or repaired following preexisting damage. Correct oil specification, do not use contaminatedor old oil.

Avoid contaminating the engine oil with coolant or fuel. Prevent faults in the oil circuit that could lead to oil-pressureproblems e. Prevent high engine-oil temperatures as these may cause the lubricating film to rupture.

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