Failure of Coupling

There are many types of couplings in use but all of them can be put into two classes, rigid or flexible. This chapter provides information on the four basic types of rigid couplings, namely the flanged rigid coupling, the ribbed rigid coupling, the sleeve rigid coupling, and the quill shaft rigid coupling. Historically, rotating equipment was first connected by means of rigid flanges. Flexible couplings join two pieces of rotating equipment while permitting some degree of misalignment or end movement or both. The three basic functions of a flexible coupling are to transmit power, accommodate misalignment, and compensate for end movement. The various types of general-purpose couplings, include gear, grid, compression donut, block jaw, urethane tire, corded tire, and disc. Special-purpose couplings are thoroughly covered in API 671. There are two categories “lubricated” and “nonlubricated.” Important points like safety factor, service factor, balancing requirement, and coupling fit need to be considered during selection process.