What are some common coupling selection pitfalls?

Coupling Tips.com spoke with  Robert Watkins, VP of Sales for Ruland Manufacturing, to find out how to avoid the downtime, safety concerns, and financial risks of a poor coupling selection. Here are just a few of his best practices for making the right selection the first time.

Electrical isolation. Some applications require electrical isolation. Isolation many times is provided by the coupling. Is this a feature that you need? This needs to be taken into consideration in your coupling choice.

Fail safe design versus a fuse type coupling. This depends on your application. Certain types of couplings are fail-safe so that if something were to happen, with a spider coupling, for example, the spider will fail but you will lock up jaw to jaw on the hubs. Some are designed as a fuse-type coupling where they’ll break and you’ll disconnect. Deciding up front whether you need a fail-safe design or you’d prefer to have a fuse-type coupling is important.

Misalignment. The degree of misalignment that you need for your application is extremely important. These different types of couplings have different misalignment capabilities. If you need quite a bit of parallel misalignment for example, an oldham coupling might be a good place to look.

Environmental conditions. For example, temperature and outgassing. Certain types of couplings will outgas the spider couplings, the spider itself will outgas and again this is an important consideration to know whether or not you need a coupling that will out gas or not. This is part of the environmental condition questions that you need to ask.

Don’t select the coupling too late in the design process. This is really quite common. Here are a couple examples of couplings being selected too late in the design processing causing issues. First, if you know upfront that the coupling you require is going to be an element type coupling, a spider coupling with a spider or an oldham coupling with and oldham disc in the middle, you need to accommodate space between your shaft ends to allow a space for the spider or the oldham disc to sit. We run into applications all the time where the design is done, the shafts are very close together, and then an element type coupling is needed and the room isn’t there. You end up having to move things around to accommodate. It’s nice to have that information up front before you finalize your design.

Ruland
www.ruland.com