Flexible Coupling Guide: Types, functions, size, and selection of flexible couplings
17 Mar, 2020

Flexible couplings are used to move torque from one shaft to another in the case where the shafts are not aligned correctly. It is also used to make up for protective functions like vibration dampening when the torque is overloaded. With many more benefits to offer, the flexible coupling is often used in industrial power transmission.    

Functions of Flexible coupling

Three basic functions of a Flexible coupling are given below. 

 • Transmit Power – In order to transmit mechanical power from one machine to another, these couplings are a suitable option. Here, the mechanical power is present in the form of torque at some specific speed. However, a small amount of power gets lost by flexible couplings. 

• Compensate for Axial Displacement or End Movement–The flexible couplings are designed in such a way that it can make up for any axial movement of shaft ends. Even it can work for any connected equipment. 

• Accommodate Misalignment – There can be two types of misalignment and these are shaft alignment and coupling alignment. Both of these are accommodated with the help of flexible couplings. 

Types of Flexible Coupling 

The flexible coupling tries to get flexibility from compressing or stretching materials like rubber, thin metallic disc, or some grids. Depending on this, there are four types of flexible couplings

 • Flexible Plastic Drain Connectors –For any repair or modification work, this type is a suitable option. It can twist and turn in 180 degrees, and it will stay in position when used. 

• Jaw Couplings –In this, the flexible couplings move the torque through compression of an elastomeric spider insert. It is done by placing the couplings between two intermeshing jaws. It helps accommodate misalignment, used for torsion dampening, low torque problems including some general applications. It also helps transmit torque. 

• Flexible Rubber Coupling –This flexible coupling is suitable for plumbing work and repair and installation of the vent, drain and waste lines. One can get it in a straight cylinder that can bend to 90 degrees or 180 degrees forming a P shape as required.

• Flexible Ventilation Duct Coupling –To manage unusual twists and turns, it can be used in HVAC in case of ventilation, heating, and other exhaustive systems. 

 Therefore, for suitable continuity of any system, flexible couplings are of immense help that can be used for both repairing and installation work.

Sizing and selection of Flexible couplings

When looking for the right flexible coupling sizes, you have to consider some factors. The rich variety of flexible couplings is available in a wide range. The coupling service factors can compensate for torque variation and this also provides proper longevity of the coupling. To choose the right type of coupling, the following considerations shall help.

• Choose whether right prime mover types of the couplings like a diesel engine, electric motor and others. 

• Check both torsion and linear vibration in the couplings 

• The shaft size, keyway size, and the fitting between bore and shaft is important to be considered

• The variable torque can vary from cyclical to erratic loading one. It helps in suitable normal operation. 

Wrapping it up 

Never choose the couplings conservatively as you may end up choosing the wrong size. For properly selected couplings the system can break in case the system has been overloaded. Therefore, research before getting the right size and variety of the couplings.

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