The following is often a sample application employed to illustrate the common process for picking a Disc coupling. Any resemblance to any present company?¡¥s application is neither intentional nor meant to resemble that company?¡¥s real application.
Sample Application:
An organization includes a compressor application making use of a 225 horsepower electrical motor running at 1,150 RPM to drive a three cylinder multi stage reciprocating air compressor. The electric motor features a 3-3/8 inch shaft which has a 7/8 inch keyway and also the compressor has a 92mm shaft having a 25mm keyway. The shaft separation is approximately seven inches between shaft ends with some ability to change the motor location. The shafts have a parallel misalignment/offset of roughly 1/32 of an inch.
Step one: The first step should be to determine what coupling variety is usually to be picked for this application. Since the SU Variety coupling only supports
just one flex plane, it may possibly only accommodate angular and axial misalignment, but not parallel misalignment. The next choice might be to appear at an SX or DI Form coupling. The six bolt SX Kind will accommodate the two parallel misalignment as well as defined shaft separation. The size are going to be established by the selection torque plus the shaft diameters.
Step two: Up coming, calculate the application torque and apply the service element to calculate the choice torque.The formula used to calculate torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging from the numbers in the application description:
Application Torque ( in-lbs ) =(HP x 63025)/RPM = (225 x 63025)/1150 = twelve,331 in-lbs
Application Torque x Service Component = Choice Torque
twelve,331 in-lbs x 3.0 = 36,993 in-lbs
Step 3: Make use of the SX coupling tables and note that the SX 202-6 is rated at forty,700 in-lbs, in excess of enough to deal with the choice torque calculated in stage two. The SX202-6, having said that, won’t assistance the 92mm shaft size. The next greater dimension coupling, the SX228-6, will assistance the 92mm shaft size and the shaft separation dimension (BSE) is 6.88 inches, very close to the application?¡¥s sought after seven inch separation. The SX228-6 is rated at 62,000 in-lbs which may seem to be extreme, having said that, the coupling size is necessary to handle the bore dimension.
Stage four: The SX228-6 coupling is rated to get a highest unbalanced speed of three,400 RPM, greater than enough to help the application speed of 1,150 RPM.
Step 5: To find out should the coupling will deal with the parallel misalignment, make use of the trig perform of tan 1?? = offset allowed for one inch = 0.0174
Multiply the 0.0174 x the distance in between disc packs or ??S?¡¥ dimension through the table on page D-13, or 5.50 inches.
The allowable parallel offset is 0.0174 x 5.50 = 0.096 inches. The maximum offset for that application is 1/32 inches (0.031), consequently this coupling can accommodate the parallel misalignment.
Note: It’s generally advised to 
try and set up the coupling at approximately 20% of your allowable misalignment. For this coupling the installer ought to attempt to obtain greater than 0.020 parallel misalignment with the time of installation. This will likely enable for that further misalignment that may come about as the consequence of gear settle and common gear put on.
