Why use Rigid Couplings? - Industrial Now News

This article will take a closer look at rigid couplings in particular, noting the differences between them and flexible couplings, and explaining why using a rigid coupling is a better choice in certain situations.

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What Are Rigid Couplings?

Rigid couplings are designed to connect two shafts together as you would expect, but their rigidness ensures that there is no relative motion occurring between the two shafts. You should use rigid couplings when your application requires precise alignment of the two shafts, especially when there will not be any significant radial or axial misalignment.

A rigid coupling consists of two flanges which are mounted on each shaft. Their installation and operation require exact alignment between the two shafts. Should the application produce significant misalignment, then a rigid coupling would suffer a high amount of stress which will likely lead to early coupling failure, with significant misalignment causing considerable wear on the bearings and seals. Thus, you should use flexible couplings in such instances where there will be a lot of misalignment, as they are specially designed to transmit torque while allowing for various levels of axial, radial and angular misalignment.

As a rigid couplings supplier, Yorkshire's YB Components know that a good quality rigid coupling will not allow any axial or radial motion between both the driving and driven shafts. For this reason, rigid couplings are commonly used in vertical pump applications.

Using Rigid Couplings to Correct Misalignment

Although it sounds somewhat contradictory to the above section, rigid couplings can sometimes be used to correct shaft alignment in misaligned systems. To achieve this, the mounts of the driving and driven shafts should be relaxed to ensure free movement while the rigid couplings work to align the two shafts. This will also result in greater wear on the rigid couplings, but can bring a misaligned system into line in the process.

Once aligned, the shaft mounts should be fixed fast once again and the shafts should now be aligned.

Choosing a Rigid Coupling

There are not as many rigid coupling designs as there are flexible coupling designs as the purpose of a rigid coupling is pretty straightforward. There are also hybrid couplings which are notionally rigid but do contain a certain amount of flexibility. The manufacturer of your application should advise as to which type of coupling to use, although you can always check with your local rigid couplings supplier in Yorkshire.

Source: YBComponents

There are two primary types of pump couplings: rigid couplings and flexible couplings. Both can have their advantages and disadvantages. Which type of coupling to use will depend on the pump equipment and application.

Rigid vs. Flexible Coupling

It's pretty simple to understand the main difference between a rigid and flexible coupling. One provides a rigid connection with no flexibility. This ensures the two shafts are firmly connected with precision alignment. Ultimately, a rigid coupling can provide smoother transmission of torque throughout the pump system. It requires accurate alignment with little-to-no tolerance for misalignment.

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Flexible coupling provides some flexibility to compensate for shafts which are slightly misaligned. The connection has more tolerance. However, torque power is generally decreased with flexible pump couplings compared to rigid. 

Advantages and Disadvantages of Rigid Couplings

Rigid couplings can be more difficult to install and maintain because they require such precision alignment. They should be inspected regularly for wear, lubrication and any slight misalignments that can start to occur over time. When utilized properly, a rigid coupling can significantly reduce backlash at zero or near-zero levels. They are simple in design and much more affordable. Operators requiring higher torque ratings may prefer rigid couplings for certain applications. Here are some of the advantages of rigid couplings:

' Improved torque transmission

' Lower cost

' Optimized shaft alignment

' Simplicity

' Increased torsional stiffness

' Reduced backlash

Rigid Coupling Applications

Rigid couplings are best suited for high-torque pumping applications, push-pull use cases and shaft support applications. Examples include semiconductor manufacturing, product packaging and machining tools. Rigid couplings can be used on horizontal and vertical pumps, but they are most commonly utilized for vertical pump applications that require higher torque.

Types of Rigid Couplings

There are multiple types of rigid couplings:

Flanged'Flanged couplings are utilized when there is clear access to both shafts. The coupling is composed of two halves, which are bolted together to form the rigid connection.

Split'Split couplings (also known as clamp couplings) are used when access is limited on one side. The coupling is essentially a sleeve that has a horizontal split along the shaft. It is clamped and bolted together for the rigid connection. Split couplings are used primarily on vertical pumps.

Compression'Compression couplings are designed with three pieces. There will be a compressible core and two coupling halves applying force to the core once connected. This allows for rigid coupling when the use of keys and keyways is not an option as required for both split and flanged couplings.

To learn more about rigid coupling and to find the right pump coupling solution for your specific pump system, contact DXP Pacific today.