The next is a sample application applied to illustrate the normal procedure for choosing a Disc coupling. Any resemblance to any existing company?¡¥s application is neither intentional nor meant to resemble that company?¡¥s actual application.
Sample Application:
A company includes a compressor application using a 225 horsepower electrical motor running at one,150 RPM to drive a three cylinder multi stage reciprocating air compressor. The electric motor features a 3-3/8 inch shaft having a 7/8 inch keyway plus the compressor has a 92mm shaft that has a 25mm keyway. The shaft separation is approximately 7 inches in between shaft ends with some potential to modify the motor location. The shafts possess a parallel misalignment/offset of approximately 1/32 of an inch.
Stage 1: The first phase is always to ascertain what coupling type is always to be picked for this application. Since the SU Type coupling only supports
a single flex plane, it might only accommodate angular and axial misalignment, but not parallel misalignment. The following selection could be to search at an SX or DI Variety coupling. The six bolt SX Sort will accommodate the two parallel misalignment as well as defined shaft separation. The dimension will be determined from the assortment torque as well as shaft diameters.
Step 2: Next, determine the application torque and apply the service element to determine the selection torque.The formula used to determine torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging inside 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 Services Issue = Choice Torque
12,331 in-lbs x 3.0 = 36,993 in-lbs
Step 3: Use the SX coupling tables and note the SX 202-6 is rated at forty,700 in-lbs, a lot more than adequate to take care of the choice torque calculated in step two. The SX202-6, nonetheless, won’t help the 92mm shaft size. The following more substantial size coupling, the SX228-6, will assistance the 92mm shaft dimension as well as the shaft separation dimension (BSE) is 6.88 inches, incredibly close to the application?¡¥s desired seven inch separation. The SX228-6 is rated at 62,000 in-lbs which might appear to be excessive, nonetheless, the coupling dimension is critical to manage the bore dimension.
Phase four: The SX228-6 coupling is rated for a highest unbalanced speed of 3,400 RPM, in excess of enough to assistance the application velocity of 1,150 RPM.
Phase 5: To find out in the event the coupling will handle the parallel misalignment, use the trig perform of tan 1?? = offset allowed for 1 inch = 0.0174
Multiply the 0.0174 x the distance among disc packs or ??S?¡¥ dimension from the table on webpage D-13, or five.50 inches.
The allowable parallel offset is 0.0174 x five.50 = 0.096 inches. The utmost offset for the application is 1/32 inches (0.031), as a result this coupling can accommodate the parallel misalignment.
Note: It truly is generally suggested to try and set up the coupling at 
approximately 20% of your allowable misalignment. For this coupling the installer should really endeavor to attain greater than 0.020 parallel misalignment in the time of installation. This will likely make it possible for for the more misalignment that should occur as the consequence of equipment settle and common tools wear.
