Top Ten Factors for Selecting A Coupling

So you understand that a flexible coupling is a connection between two pieces of equipment used to transmit torque and compensate for misalignment... and would like to know what are the key criteria for narrowing down the near countless coupling options to just a few really great ones for further consideration? Perfect, we've got you covered.

Unless you are simply replacing an old coupling that worked well (and simply need to identify it to reorder it)... the 5 fundamental pieces of information that you need to size just about any coupling are:

• Horsepower of the motor
• RPM (at the point of the coupling)
• Shaft and keyway sizes
• Shaft separation or BSE (distance between shaft ends)
• Type of driven equipment (i.e. - pump mixer, conveyor, etc.)

In addition to these 5 fundamentals sizing factors, the following 5 fundamental application factors should also be reviewed and considered against the needs of the application:

• Operating temperature
• Chemical exposure
• Run cycle (continuous or start/stop)
• Amount of space available for the couplings
• Misalignment handling requirements (angular, parallel, & axial)

While these 10 baseline selection factors are far from exhaustive (many other system specific considerations such as fail-safe, maintenance-free, or backlash requirements may and should be considered), these 10 criteria will quickly narrow down your basket of options from dozens of coupling solutions to a select few for further review.

The following charts provide just a quick reference broadly summarizing four fundamental coupling types and their ability to accommodate angular, parallel, and axial misalignment, as well as torque, temperature, and chemical exposure. (For those looking for a bit more in-depth review, a much more complete coupling pre-selection guide... covering 12 coupling types and 12 selection criteria... can be found here.)

Additional Note on Misalignment: When evaluating coupling misalignment ratings, please note that ratings for each coupling type represent maximum allowable numbers. Couplings cannot and should not be aligned at the maximum allowable misalignment for more than one condition (i.e. - both angular and parallel misalignment occurring at the same time). Couplings misaligned beyond their allowable ratings will result in a dramatic drop in coupling life. Although coupling life cannot be specifically calculated, minimizing coupling misalignment greatly benefits coupling life.

For specific torque capacity (= Horse Power x 63025/RPM x Service Factor), temperature range, and chemical exposure resistance or capability, please consult the manufacturer product catalog for the specific coupling you are considering (and/or feel free to give us a call if you have further questions).

Lastly, in addition to these top 10 considerations, we highly recommend that you always procure couplings from a reputable coupling company that has a strong history of quality, a strong technical support arm, and an ability to rapidly troubleshoot and ship replacement product if and when something unexpected occurs in your power transmission system.