A coupling is used to connect two rotating shafts, transfer torque and accommodate misalignment, and is a very important part of your pump. If you’re having issues with your coupling, we’re here to help. Couplings are one of the many important components in your pump system. If you’re burning through them, there is usually a larger issue at hand. Nobody likes an unreliable pump, so let’s go over a few things you should check if you’re experiencing shaft coupling failures.
First off, you should know the warning signs to look for if you think you have a coupling failure. You might notice excessive noise or vibration coming from the pump. Or you could be finding premature mechanical seal wear or bearing failure. Increased power consumption is also a sign of a problematic pump. If you’re experiencing any of these issues, you could be having shaft coupling problems.
The most common cause of coupling failure is due to a misaligned pump and motor shaft. Misalignment accounts for approximately 70-80% of failures. Flexible couplings can accept some degree of misalignment. Like any coupling, these have their limits. Sometimes a flexible coupling will fail because the degree of misalignment was underestimated. Please verify these limits with the manufacturer’s specifications. If your shafts are misaligned past the manufacturer’s specifications, it should first be rectified with a laser alignment before installing a coupling.
Every coupling has a torque limit. Torsional failures account for approximately 10-15% of coupling failures. If you miscalculate the torque required in your application, you could damage your equipment. Too much torque, especially at low speeds, can wreak havoc on the coupling. The maximum instantaneous torque and the steady state torque need to be considered when selecting your coupling.
Unfortunately, the shaft coupling isn’t always prioritized like it should be when assembling a pump. It is often overlooked and underappreciated. The wrong type of coupling can be selected, or it could simply be chosen too late in the application design process.
If you select couplings early on in the process, each aspect and requirement can be considered. This will ensure that the coupling is properly size and suitable for the application requirements. If the process changes in the future, you must revisit the coupling specifications.
While rare, a unique environment condition could cause problems with your coupling. Non-compatible chemical exposure can negatively affect the life of your coupling. Thermal expansion and excessively warm or cold ambient temperatures can also affect the reliability of your coupling. These instances aren’t as common, but can happen.
Safety should always be the number one concern when specifying any piece of equipment. A coupling should be no exception. When the coupling fails, what happens to the components? Do you want a positive drive on your equipment, or do you need your equipment to disengage when your coupling fails? What happens to the components at failure? These are questions that should be considered when selecting a coupling.
Also, be sure to proactively maintain your equipment, and monitor your couplings. If they require lubrication or flushing, stay on top of the equipment maintenance schedule. Selecting the right coupling will improve your application’s efficiency and increase its uptime and reliability.
For more information on coupling failures, read our "3 Causes of Coupling Failures" blog post. Otherwise, you can contact us if you’re in Wisconsin or Upper Michigan and have any questions about couplings. One of our experienced engineers can talk with you about your specific process.