Tips on How to Choose the Best Coupling

  

The purpose of couplings is to connect two shafts together and transmit drive torque and angular velocity in mechanical and automotive applications. As the two connected components rotate, couplings also keep the system secure while allowing some level of misalignment expected from the operation.

In applications where motion control is required; disc, silt, curved jaw and other backlash-free couplings are utilised to deliver precise torque or transmission. For power transmission, like in pumps, grinding machines and material-handling machines, it is preferred to use chain, gear, grid-jaw and elastomer tire couplings to deliver greater average torque.

However, this is just one way to differentiate the many different types of couplings available. There are other critical factors to consider to effectively manage your operations, so in this article, the team at Industrial & Automotive Parts have provided you with our best tips to learn how to choose the ideal coupling.

How to Choose a Coupling For Your Application

gear-coupler

What is the Application?

The first thing to consider when you need to choose a new coupling is the features of the application. For example, is the coupling going on the end of a water pump that will be running two hours a day, or on a crusher that runs 18 hours a day under extreme conditions, with constant vibrations and load? The difference is critical to ensuring your coupling works exactly how it’s meant to.

Try to identify the features of your application, such as exposure to shock-loading, temperature conditions and shear features. Different types of couplings come with various attributes and levels of tolerance, too, so it's crucial to align your application with the right coupling for elements such as:

  • Torque
  • Shaft misalignment
  • Stiffness
  • RPM
  • Inertia
  • Space requirements
  • Shaft mounting

When inadequate couplings are used in applications, it can result in coupling failure, damage to expensive applications and equipment, and endanger people nearby.

The required torque and RPM

As couplings are responsible for transmitting torque, knowing the torque and RPM requirements of your application helps to identify the coupling that will meet that need. Once you know the input power and RPM of the drive, the size of the coupling needed will become clear. When matching your application with the coupling, make sure you relate it to the nominal torque rating, as maximum ratings display the peak torque that the system can handle.

Mounting of the Coupling

There are two main ways to mount a coupling onto a shaft. You can either mount it with a taper lock bush or directly onto the shaft bored and keyed. Traditional taper lock mounting is well suited to unidirectional applications with no alternative loads and minimal shock. If using a taper lock, however, loss of torque must also be considered.

For loads that reverse in direction and that endure shock, keyless locking devices are a suitable mounting method as they are backlash-free. If mounting directly onto the shaft, the amount of torque the coupling can handle will not be affected. Size restrictions must be taken into consideration to make sure the coupling does not interfere with other pieces of equipment.

Environment

When you need to choose a coupling from the different types available, the environment that it performs under needs to be considered. For example, in abrasive environments, gear couplings would be recommended as they are enclosed and there are seal kits available. If the requirements of the coupling state FRAS (fire-resistance and anti-static) requirements, such as in underground mining, then a tyre coupling with a FRAS rated element may be used.

In addition, it’s important to consider operating environment variables such as ambient temperature, chemical compatibility and the frequency of operation (how often it starts and stops) to learn which coupling is best suited.

Under some conditions, a safety factor may need to be applied to accommodate durability and added stresses exerted on the coupling during operation. Applications that have excessive stopping forces, such as the flywheel effect, need an additional level of tolerance added to the nominal torque, so a coupling with a larger rating is suitable.

Maintenance requirements

Future maintenance must be noted when you choose a coupling. Different types of couplings allow the customer to reduce downtime costs when replacing elements, motors, gearboxes and other components.

Some coupling elements can be replaced without dismantling or removing the drive, whereas others will need the drive to be removed or shifted for the element to be replaced. An advantage of being able to replace a coupling element in situ is not having to re-align the drive after reinstalling the element, so there’s less room for error and downtime costs.

Shaft alignment

The three different types of alignments to take into consideration are axial, radial and angular. Shaft misalignment occurs when the shafts joined by a coupling aren’t evenly aligned, and only flexible types of couplings can manage some of this movement and vibration, yet they each have a limit. Depending on the amount of misalignment expected in your application, you’ll have a better understanding of the type of coupling required.

Different types of couplings allow for greater misalignment than others, including sliding disc and universal/lateral couplings. These are suited to applications with expected misalignment; however, it means their backlash-free life will be reduced. Flexible types of couplings are the most preferred option for misaligned systems.

Torsional stiffness

Couplings must have an appropriate torsional stiffness capacity to be able to work in your application without causing resonance and failure. This is becoming an emerging issue in the industrial industry as more machines are used to rapidly stimulate cam profiles, which is how torsional vibration is introduced. 

Couplings pick up on the frequency of the entire system, so when the application consists of noise and vibration, the wrong coupling can fail as a result. If you can identify the resonance frequency and index of your application, you can determine a suitable coupling with an appropriate torsional stiffness.

Price

It’s tempting to use the initial price as a determining factor to choose a coupling, but a smaller initial cost can result in larger additional costs later. Although some couplings are cheaper than others, these can often be prone to damage and failure and come with more installation and maintenance needs, which can make them more expensive in the long run.

Spending more money upfront on a coupling that requires less downtime during maintenance, breakdowns and element replacement will save time and money in the future. However, if the application is not critical and the cost of service and downtime is minimal, then a generic, run-of-the-mill coupling may be a more cost-effective choice.

Learn More or Explore the Different Types of Couplings Available with Industrial & Automotive Parts

Browse through our extensive collection of different types of couplings available online with Industrial & Automotive Parts. Should you need any more information on how to choose the right coupling for your application, please contact us directly and we’ll be happy to provide a recommendation.


SIGN UP FOR UNBEATABLE OFFERS,
UPDATES AND MORE!