Some of the important criteria to be kept in mind while selecting a pump coupling are
Power Rating
Having a coupling of the right power rating is necessary. If the power rating of the coupling is lower than the required rating, the coupling may fail during operation.
Operating speed
The operating speed of the coupling determines the centrifugal force it can withstand. Hence, the speed rating of the coupling should be suited to the operating speed.
Physical dimensions
The coupling will have to be fitted in a specific amount of space. The coupling should be checked with the other parameters such as the gap between the shafts, the location of the bolts in the shafts, etc.
Tolerance for misalignment
The coupling should be able to tolerate minor misalignments between the shafts.