Additional Work Completed

 

Root-Cause Analysis of Repeated failure of Motor Rotor Bars

 

An electric motor driving a six-throw reciprocating compressor had been experiencing repeated failure on the rotor bar when the compressor is fully loaded. Modal analysis conducted on the motor rotor showed that a torsional frequency was occurring very close to 6X of the operating speed of the motor. A coupled dynamic analysis was conducted using the torsional accelerations calculated in torsional vibration analysis to predict the dynamic stresses. It was concluded that high cyclical stresses in the rotor bars was causing the failure. The design of the rotor bars was changed to eliminate interference of the natural frequency with operating speed, resolving the problem.

 

Benchmarking FE Analysis Model

 

 

Properties of rubber mounts under the engine driven generator play vey important role in predicting natural frequencies and stresses in the skid / base frame. Finite element analysis was conducted on the system and the predicted natural frequencies and accelerations were correlated to the measured values in test lab. The correlated models can be used further in different packages and new product development.

Restraining Lateral Movement of Pressure Vessels


Pressure vessels in a reciprocating compressor package were vibrating in their lateral direction at different frequencies. After simulating the field scenario using FEA, IDC designed cross bracing between the vessels so that these vessels would be restrained from lateral movement.

Diagnosis of Coupling Failure on Motor Driven Compressor

 

A motor driven compressor had been experiencing periodic failures of the shim packs in its metal coupling. Strain gages and wireless telemetry were used to measure dynamic torque levels in the coupling and determine that there was a torsional resonance occurring very close to the system operating speed of 600 rpm. A torsional model of the driveline was correlated to match the test results and was then used to determine the appropriate size of internal compressor de-tuner that should be added to move the system away from resonance at operating speed.

 

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