Chapter 15 - Couplings

Abstract

Couplings connect pumps and/or gears to their drivers. There are different types of couplings—namely, rigid couplings, flexible couplings, lubricated couplings, and nonlubricated couplings. Rigid couplings are commonly used when connecting solid-shaft vertical motors to vertical pumps. Rigid couplings do not allow misalignment between the driven equipment and the driver. Another way to transmit torque from the driver to the pump involves using flexible couplings. These couplings also allow for some misalignment between the two shafts. Some flexible couplings use elastomers to achieve flexibility while others use various mechanical devices. The commonly used flexible couplings include pin and bushing, jaw, sleeve, gear, roller chain, diaphragm, disc, and universal joint. Pin-and-bushing couplings are one of the most widely used types of flexible couplings. This coupling uses elastomers with great pliancy to enable it to bounce back to its original form. Elastic bushings give the coupling its flexibility. The pump industry commonly uses the gear-type flexible coupling. Diaphragm-type couplings consist of a curved, flexible steel disc on each hub.