Background

High vibration levels were experienced on a large diesel-generator rated for 30 megawatts at 103 revolutions per minute. The diesel engine was manually stopped and an explosion was heard with subsequent smoke filling the engine space and control room. An inspection of the engine after shutdown revealed that the crankshaft assembly had fractured.

Services Provided

Rimkus Consulting Group was retained to inspect and document the failure of the engine components, assist in determining the cause and origin of the crankshaft failure, review planned teardown and reassembly work, including removal of the failed crankshaft, review planned crankshaft repairs, including the overall schedule and assist with expediting repairs and shipping, review various repair versus replacement options of engine / generator / auxiliary system components and review the costs of the project including loss of use. Based on our analysis, we concluded the following:

• A metallurgical anomaly that may have contributed to the crankshaft failure was found; namely, calcium particles at the fracture origin. These particles suggest that a calcium-rich inclusion may have been present. Examination of the other side of the fracture surface confirmed this.
• The fracture markings were consistent with fatigue failure.
• No slag inclusion or weld repair metal was found at the fracture origin.
• The steel chemistry in the vicinity of the fracture origin met the crankshaft manufacturer specifications.
• The preliminary stress analysis of the failed web showed stresses to be below the failure point without a material defect.