Techniques In Selecting A Disc Coupling

The following is a sample application utilized to illustrate the common course of action for picking 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 working at 1,150 RPM to drive a three cylinder multi stage reciprocating air compressor. The electrical motor includes a 3-3/8 inch shaft having a 7/8 inch keyway and the compressor has a 92mm shaft which has a 25mm keyway. The shaft separation is roughly seven inches amongst shaft ends with some capacity to adjust the motor spot. The shafts have a parallel misalignment/offset of roughly 1/32 of an inch.
Phase 1: The initial step is to identify what coupling style is always to be chosen for this application. Because the SU Kind coupling only supports
just one flex plane, it could only accommodate angular and axial misalignment, but not parallel misalignment. The subsequent choice could be to look at an SX or DI Type coupling. The six bolt SX Kind will accommodate both parallel misalignment along with the defined shaft separation. The size is going to be established from the assortment torque and the shaft diameters.
Step two: Following, determine the application torque and apply the service component to calculate the variety torque.The formula employed to calculate torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging during the numbers from the application description:
Application Torque ( in-lbs ) =(HP x 63025)/RPM = (225 x 63025)/1150 = twelve,331 in-lbs
Application Torque x Services Aspect = Choice Torque
12,331 in-lbs x 3.0 = 36,993 in-lbs
Step three: Use the SX coupling tables and note the SX 202-6 is rated at 40,700 in-lbs, in excess of sufficient to deal with the choice torque calculated in step two. The SX202-6, nevertheless, is not going to assistance the 92mm shaft size. The next greater size coupling, the SX228-6, will support the 92mm shaft dimension plus the shaft separation dimension (BSE) is 6.88 inches, really close to the application?¡¥s sought after 7 inch separation. The SX228-6 is rated at 62,000 in-lbs which may perhaps seem to be excessive, however, the coupling size is necessary to handle the bore dimension.
Stage 4: The SX228-6 coupling is rated for a highest unbalanced pace of three,400 RPM, over ample to help the application velocity of 1,150 RPM.
Step 5: To find out should the coupling will handle the parallel misalignment, use the trig function of tan 1?? = offset permitted for 1 inch = 0.0174
Multiply the 0.0174 x the distance among disc packs or ??S?¡¥ dimension through the table on page D-13, or 5.50 inches.
The allowable parallel offset is 0.0174 x five.50 = 0.096 inches. The maximum offset to the application is 1/32 inches (0.031), for that reason this coupling can accommodate the parallel misalignment.
Note: It truly is generally advised to attempt to install the coupling at roughly 20% from the allowable misalignment. For this coupling the installer ought to try and obtain superior than 0.020 parallel misalignment on the time of installation. This may allow for that added misalignment that may come about because the end result of products settle and general gear dress in.