Vibrations in Turbo Machinery

Special Considerations for Electric Motors Driving Reciprocating Compressors

Paper No. 109

By Troy Feese and William (BJ) Schnitzler – GMRC Louisville, KY, October 2021.

In the natural gas transmission, refining, and chemical industries, motors are commonly used to drive reciprocating compressors. However, the excitation produced by reciprocating compressor can be much greater than from centrifugal equipment. Therefore, motors driving reciprocating compressors need to have a more robust design to be reliable.

This paper presents several case studies on the following topics:
• How Motor Mounting Can Affect Vibration
• Axial Vibration of Couplings
• Natural Frequencies of Motor Bearing End Bell Support
• Motor Cooling Fan Failures
• Torsional Failure of VFD Motor Shaft
• Excessive Motor Current Pulsation
• Motor Electromagnetic Effects when using Torsionally Soft Couplings

Some problems with motor driven reciprocating compressor systems may not be predicted in the design stage and could appear after commissioning the unit. Also, personnel normally dealing with electrical equipment driving centrifugal pumps or fans may not be familiar with the vibration characteristics of reciprocating compressors.

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