Couplings

A coupling

 is a device used to connect two shafts together at their ends for the purpose of transmitting power. Couplings do not normally allow disconnection of shafts during operation, however there are tourqe limiting  couplings which can slip or disconnect when some torque limit is exceeded The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end movement or both. By careful selection, installation and maintenance of couplings, substantial savings can be made in reduced maintenance costs and downtime.

Shaft couplings are used in machinery for several purposes:-

1) - To transmit power between two shafts.

2) - To reduce the transmission of shock loads from one shaft to another.

3)- To provide for the connection of shafts of units that are  manufactured separately such as a motor and generator and to provide for disconnection for repairs or alternations

 4)-To introduce protection against overloads

 main types of coupling 

rigid coupling and flexible coupling.

rigid coupling :

Rigid couplings are mainly used to connect shafts In perfect alignment. The smallest degree of misalignment will cause considerable stress on the coupling

torsional rigid coupling

  Flexible coupling :

Flexible couplings are designed to transmit tourqe  while permitting some radial, axial, and angular misalignment. Flexible couplings can accommodate (damping) angular misalignment up to a few degrees and 

some parallel misalignment

Grid coupling

chain coupling :

Helical coupling: