Methods In Deciding on A Disc Coupling

The following is usually a sample application utilised to illustrate the typical system for deciding on a Disc coupling. Any resemblance to any present company?¡¥s application is neither intentional nor meant to resemble that company?¡¥s actual application.
Sample Application:
An organization includes a compressor application working with a 225 horsepower electrical motor operating at 1,150 RPM to drive a 3 cylinder multi stage reciprocating air compressor. The electrical motor features a 3-3/8 inch shaft that has a 7/8 inch keyway and the compressor has a 92mm shaft which has a 25mm keyway. The shaft separation is approximately seven inches amongst shaft ends with some capacity to alter the motor place. The shafts have a parallel misalignment/offset of approximately 1/32 of an inch.
Phase 1: The very first phase is always to establish what coupling sort should be to be chosen for this application. Since the SU Style coupling only supports
just one flex plane, it may only accommodate angular and axial misalignment, but not parallel misalignment. The subsequent decision will be to search at an SX or DI Style coupling. The six bolt SX Variety will accommodate both parallel misalignment and also the defined shaft separation. The dimension will be determined through the selection torque plus the shaft diameters.
Step two: Upcoming, determine the application torque and apply the services element to determine the variety 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 in the numbers from the application description:
Application Torque ( in-lbs ) =(HP x 63025)/RPM = (225 x 63025)/1150 = 12,331 in-lbs
Application Torque x Service Issue = Variety Torque
12,331 in-lbs x 3.0 = 36,993 in-lbs
Step three: Make use of the SX coupling tables and note the SX 202-6 is rated at 40,700 in-lbs, in excess of ample to deal with the variety torque calculated in step two. The SX202-6, on the other hand, is not going to help the 92mm shaft dimension. The following bigger dimension coupling, the SX228-6, will support the 92mm shaft dimension as well as the shaft separation dimension (BSE) is six.88 inches, incredibly near to the application?¡¥s wanted 7 inch separation. The SX228-6 is rated at 62,000 in-lbs which may well seem to be excessive, having said that, the coupling dimension is necessary to take care of the bore dimension.
Step 4: The SX228-6 coupling is rated for any greatest unbalanced pace of 3,400 RPM, in excess of sufficient to assistance the application velocity of 1,150 RPM.
Phase five: To find out if the coupling will take care of the parallel misalignment, utilize 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 through the table on web page D-13, or 5.50 inches.
The allowable parallel offset is 0.0174 x 5.50 = 0.096 inches. The utmost offset to the application is 1/32 inches (0.031), hence this coupling can accommodate the parallel misalignment.
Note: It really is often advisable to endeavor to set up the coupling at roughly 20% on the allowable misalignment. For this coupling the installer should really attempt to realize greater than 0.020 parallel misalignment in the time of set up. This will allow for the extra misalignment that should arise since the end result of products settle and basic equipment wear.