The following can be a sample application made use of to illustrate the typical process for selecting a Disc coupling. Any resemblance to any current company?¡¥s application is neither intentional nor meant to resemble that company?¡¥s real application.
Sample Application:
A company has a compressor application using a 225 horsepower electric motor working at one,150 RPM to drive a three cylinder multi stage reciprocating air compressor. The electric motor has a 3-3/8 inch shaft that has a 7/8 inch keyway plus the compressor has a 92mm shaft having a 25mm keyway. The shaft separation is approximately 7 inches among shaft ends with some potential to modify the motor spot. The shafts have a parallel misalignment/offset of roughly 1/32 of an inch.
Step 1: The primary phase should be to establish what coupling form will be to be selected for this application. Since the SU Kind coupling only supports
a single flex plane, it might only accommodate angular and axial misalignment, but not parallel misalignment. The subsequent decision could be to look at an SX or DI Type coupling. The 6 bolt SX Style will accommodate both parallel misalignment as well as the defined shaft separation. The size are going to be determined through the variety torque and also the shaft diameters.
Stage two: Next, determine the application torque and apply the service issue to determine the choice torque.The formula made use of to calculate torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging in the numbers in the application description:
Application Torque ( in-lbs ) =(HP x 63025)/RPM = (225 x 63025)/1150 = 12,331 in-lbs
Application Torque x Services Aspect = Choice Torque
twelve,331 in-lbs x 3.0 = 36,993 in-lbs
Phase 3: Use the SX coupling tables and note that the SX 202-6 is rated at 40,700 in-lbs, a lot more than enough to handle the variety torque calculated in stage 2. The SX202-6, nonetheless, is not going to help the 92mm shaft dimension. The next larger size coupling, the SX228-6, will support the 92mm shaft size as well as shaft separation dimension (BSE) is 6.88 inches, extremely near to the application?¡¥s desired 7 inch separation. The SX228-6 is rated at 62,000 in-lbs which could seem to be excessive, however, the coupling dimension is necessary to manage the bore dimension.
Step 4: The SX228-6 coupling is rated to get a optimum unbalanced speed of 3,400 RPM, over sufficient to support the application speed of 1,150 RPM.
Stage five: To find out in the event the coupling will take care of 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 from the table on 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), thus this coupling can accommodate the parallel misalignment.
Note: It is actually generally proposed to attempt to install the coupling at approximately 20% with the allowable misalignment. For this coupling the installer should really make an effort to achieve greater than 0.020 parallel misalignment with the time of set up. This can allow for the supplemental misalignment that may take place because the outcome of tools settle and common equipment wear.