Coupling alignment for higher horsepower drive applications

Edited by Mike Santora

*Below is an excerpt from a Design World webinar presentation by Andy Lechner of R+W America. Here, Lechner covers some best practices for handling coupling installation in precision motion control applications.

There are a few different alignment considerations with the higher horsepower drive applications we find in pumps, compressors, agitators, industrial mixers, and so on. The first two of which tend to run at a little higher speed and can often be found in critical or hazardous applications. In many industries, it was once thought to be acceptable to not give a whole lot of thought to alignment. Tools tended to be not as practical to use as they are now; straight edges, for example, were common to be used to align a traditional coupling in a power transmission application, but some widespread studies have been conducted over the past few decades, especially in the petrochemical and processing industries, where improved shaft alignment has shown marked improvements in plant efficiency and drastic reductions in vibration alarms in refineries, for example. Even if a coupling is holding up or tolerating shaft misalignment, that doesn’t mean that you are doing the best service to your plant or machine to not line things up a little bit better.

Modern laser shaft alignment systems make things an awful lot easier. There would be no room for this kind of device in some smaller motion control applications. But in larger industrial applications it’s often beneficial and more common to be found that there are larger shafts and larger distances between shafts that will allow for alignment tools like this. In the past, dial indicator setups would be used. A little bit more of a painstaking process to get things lined up precisely than we have now, and there are alignment service companies all throughout the world that can assist end-users with this process. In fact, the American Petroleum Institute has some very specific standards for distances between shaft ends and coupling spacer lengths, just to ensure not only the ability to have access for alignment tools but for better service in general.

All in all, really just about any rotating system is going to perform better and more reliably if it’s well-aligned. Yes, couplings are there to take up what remains, but really aren’t a substitute for due-consideration to a well-assembled machine.

R+W America
www.rw-america.com