Techniques In Choosing A Disc Coupling

The following is actually a sample application applied to illustrate the normal process for choosing 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:
A company features a compressor application making use of a 225 horsepower electric motor working at one,150 RPM to drive a 3 cylinder multi stage reciprocating air compressor. The electrical motor includes a 3-3/8 inch shaft by using a 7/8 inch keyway plus the compressor has a 92mm shaft that has a 25mm keyway. The shaft separation is approximately seven inches concerning shaft ends with some means to change the motor place. The shafts possess a parallel misalignment/offset of roughly 1/32 of an inch.
Step 1: The 1st step is to identify what coupling type would be to be picked for this application. Because the SU Form coupling only supports
a single flex plane, it may possibly only accommodate angular and axial misalignment, but not parallel misalignment. The following alternative might be to search at an SX or DI Style coupling. The six bolt SX Form will accommodate both parallel misalignment and the defined shaft separation. The dimension are going to be determined by the variety torque as well as shaft diameters.
Stage two: Up coming, determine the application torque and apply the support factor to calculate the variety torque.The formula applied to determine torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging from the numbers in the application description:
Application Torque ( in-lbs ) =(HP x 63025)/RPM = (225 x 63025)/1150 = twelve,331 in-lbs
Application Torque x Service Aspect = Assortment Torque
twelve,331 in-lbs x 3.0 = 36,993 in-lbs
Step 3: Use the SX coupling tables and note that the SX 202-6 is rated at 40,700 in-lbs, more than ample to handle the variety torque calculated in phase two. The SX202-6, however, will not support the 92mm shaft size. The following more substantial dimension coupling, the SX228-6, will assistance the 92mm shaft size and the shaft separation dimension (BSE) is six.88 inches, very close to the application?¡¥s preferred seven inch separation. The SX228-6 is rated at 62,000 in-lbs which may seem to be excessive, on the other hand, the coupling size is important to manage the bore size.
Phase 4: The SX228-6 coupling is rated for any maximum unbalanced pace of 3,400 RPM, greater than enough to assistance the application pace of one,150 RPM.
Step five: To find out in case 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 involving disc packs or ??S?¡¥ dimension from the table on page D-13, or five.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), thus this coupling can accommodate the parallel misalignment.
Note: It is actually generally advised to try and set up the coupling at approximately 20% on the allowable misalignment. For this coupling the installer should attempt to accomplish improved than 0.020 parallel misalignment at the time of installation. This may enable to the further misalignment that should happen as the consequence of gear settle and common products put on.


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