NM Couplings for Compressors

A compressor drive can look simple on a layout drawing and still be demanding at the coupling. Starting behavior, cyclic torque and the driven machine’s characteristics can matter more than steady-state motor power. That makes compressor RFQs a poor place to size from bore diameter alone.

Separate the rating check from the duty review.

First, use the NM table to find models that cover the required nominal torque, running speed and shaft diameters. Then describe the compressor duty: starts per hour, loaded or unloaded start, reversing if any, and whether the drive sees pronounced torque pulsation or process upset. The NM ratings do not define one universal peak-torque multiplier, so unusual transient duty should be included in the quotation review.

Keep alignment and support conditions visible.

Flexible does not mean indifferent to alignment. Confirm the driver and compressor shafts are within the model’s radial and angular values after the machine is at its operating condition. Soft feet, base distortion or piping strain can change alignment after initial assembly.