This page gives detailed information on the design and operation of flexible couplings for high-power machine drives.
It might be expected that when one machine is required to drive another, the two shafts should be coupled together rigidly and precisely. However, precise alignment is difficult to achieve. Also, the alignment can vary between the cold, static position the elements assume when the machine is aligned and the hotter, dynamic position when the machine is operating.
Some machines, such as large turbo-alternators, use rigidly coupled rotors. This is possible because both the turbine and alternator are fabricated and installed by the same manufacturer on a common base. Also, since these are large machines with plain bearings, the bearing clearances are proportionately large, allowing some flexibility for transient mis-alignments.
With the majority of coupled machines, however, each is generally supplied by a different manufacturer and installed at a site where the mounting conditions may vary. In these circumstances, it is sensible to use a flexible coupling between the two machines, so that they can move relative to each other. Such movement can occur as a result of temperature changes, pressure changes or any form of relative foundation movement.
The following articles come from a conference organised by Neale Consulting Engineers on flexible couplings. They include comprehensive detail on theory of operation, failure modes and design for several industry sectors.
Gear couplings cater for mis-alignment between theoretically concentric shafts by meas of mating internal and external gears.
Flexible Element Couplings
Flexible element couplings cope with mis-alignments by flexing one or more elastic torque-transmitting elements.
Disc couplings accommodate mis-alignment by the flexing of one or more a disc or diaphragm elements. Such couplings are relatively space efficient and require no lubrication.
These papers look at coupling selection by comparison of the various types of flexible coupling and also by looking at specific application areas.
Operation Experience With Flexible Couplings
This paper looks at operational experience with flexible couplings.