The Main Types of Shaft Couplings and their Applications

If you have an industrial facility where shafts of different pieces of equipment need to be connected, you will need to use couplings. These are mechanical devices for connecting rotating shafts, and absorbing some misalignments between them. They are mainly used for power transfer between two shafts, such as motors and compressors, pumps, and generators.  

To cater to different clients and equipment, there are many types of couplings that you can use. In this post, we will look at the main categories and further highlight their applications: 

Beam Couplings

Beam coupling, also referred to as helical coupling, is a flexible type of coupling used for torque transfer between shafts while providing for some parallel offset and angular misalignment. The coupling uses a single piece of material and operates flexibly by removing some sections on the spiral path, creating a curved flexible beam of a helical outlook. 

Since the beam coupling style uses a single material, it does not exhibit backlash, which is common in multi-piece couplings. Being a machined coupling, a beam coupling is also strong and more durable than most types of couplings you will find out there. 

Sleeve Couplings 

This is perhaps the simplest of the couplings you can get on the market. It is designed to transmit low to medium torque between two shafts via elastomeric inserts that feature male and female splines. The insert material is designed with neoprene or hytrel, and it can be a single or two-piece design. 

Sleeve couplings can help you to address moderate misalignment and damping torsional vibrations. They are preferred for low to medium and general-purpose applications. For example, if you have a standard pump and want to connect it to a motor, sleeve coupling might be a good find for the task. 

Flange Couplings 

This category of couplings is designed with two sets of cast iron flanges. The flanges are fitted on the ends of the driving and driven shafts and keyed firmly. Then, they are joined together using nuts and bolts. This type of coupling is recommended for handling heavy loads in industrial equipment. 

Disc Couplings 

Disc couplings are designed to transmit torque via flexible disc elements. The coupling operates using tension and compression of the corded segment on a bolt circle that is fixed between the driving and driven sides of the shaft. 

The coupling comes with two hubs, a centre member and two-disc packs. If the coupling had one hub, it would only handle axial and angular misalignments. But with the two-hub design, the coupling is now able to accommodate even the parallel misalignment of motors and compressors or other equipment. 

Diaphragm Couplings 

These couplings are designed with one or a single series of diaphragms of flexible membranes. The coupling transmits starting torque from the outside diameter of the plate to the inner part of the spool and then from the inside to the outside. Therefore, the outer diameter deflections in relation to the inner diameter help cater for the misalignments. For example, axial displacement tries to stretch the plates resulting in elongation of their profile.

These are the main couplings you will get on the market today. You might also want to check tire couplings, gear couplings, and grind couplings. Although these couplings are good in allowing your equipment to work with some shaft misalignments, it is important to also carefully analyze the causes of misalignments. This is because excessive misalignments can result in harmonics forces, excess stress on the rotating equipment and failure. You should also ensure that every piece of equipment is maintained in top condition all the time.