Ways In Choosing A Disc Coupling

The following is often a sample application utilized to illustrate the conventional procedure for choosing a Disc coupling. Any resemblance to any current company?¡¥s application is neither intentional nor meant to resemble that company?¡¥s actual application.
Sample Application:
An organization has a compressor application applying a 225 horsepower electrical motor operating at 1,150 RPM to drive a 3 cylinder multi stage reciprocating air compressor. The electric motor has a 3-3/8 inch shaft by using a 7/8 inch keyway plus the compressor features a 92mm shaft using a 25mm keyway. The shaft separation is roughly seven inches among shaft ends with some skill to adjust the motor place. The shafts possess a parallel misalignment/offset of roughly 1/32 of an inch.
Step 1: The primary stage is always to figure out what coupling variety is usually to be picked for this application. Since the SU Style coupling only supports
just one flex plane, it may possibly only accommodate angular and axial misalignment, but not parallel misalignment. The next option will be to seem at an SX or DI Style coupling. The 6 bolt SX Kind will accommodate both parallel misalignment plus the defined shaft separation. The size will likely be established by the selection torque as well as shaft diameters.
Stage two: Following, determine the application torque and apply the support 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 within the numbers from your application description:
Application Torque ( in-lbs ) =(HP x 63025)/RPM = (225 x 63025)/1150 = twelve,331 in-lbs
Application Torque x Support Element = Selection Torque
12,331 in-lbs x 3.0 = 36,993 in-lbs
Phase 3: Make use of the SX coupling tables and note the SX 202-6 is rated at 40,700 in-lbs, over ample to handle the choice torque calculated in phase 2. The SX202-6, nevertheless, is not going to support the 92mm shaft size. The following bigger dimension coupling, the SX228-6, will assistance the 92mm shaft size as well as shaft separation dimension (BSE) is 6.88 inches, incredibly near to the application?¡¥s sought after seven inch separation. The SX228-6 is rated at 62,000 in-lbs which might appear to be excessive, however, the coupling dimension is necessary to manage the bore dimension.
Step four: The SX228-6 coupling is rated for a highest unbalanced pace of 3,400 RPM, more than adequate to support the application speed of 1,150 RPM.
Step five: To find out should the coupling will take care of the parallel misalignment, use the trig function of tan 1?? = offset permitted for one inch = 0.0174
Multiply the 0.0174 x the distance in between disc packs or ??S?¡¥ dimension from your table on web page D-13, or five.50 inches.
The allowable parallel offset is 0.0174 x five.50 = 0.096 inches. The utmost offset for that application is 1/32 inches (0.031), consequently this coupling can accommodate the parallel misalignment.
Note: It truly is often recommended to endeavor to set up the coupling at roughly 20% with the allowable misalignment. For this coupling the installer should really try to achieve superior than 0.020 parallel misalignment at the time of set up. This can allow for the further misalignment that should happen since the outcome of products settle and common products dress in.