January 26, 2021

The following is usually a sample application used to illustrate the conventional process for deciding on 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 includes a compressor application employing a 225 horsepower electrical motor working at 1,150 RPM to drive a 3 cylinder multi stage reciprocating air compressor. The electric motor includes a 3-3/8 inch shaft by using a 7/8 inch keyway and also the compressor has a 92mm shaft which has a 25mm keyway. The shaft separation is roughly 7 inches concerning shaft ends with some capability to modify the motor location. The shafts have a parallel misalignment/offset of approximately 1/32 of an inch.
Stage 1: The initial phase is to ascertain what coupling type will be to be picked for this application. Since the SU Type coupling only supports
a single flex plane, it may possibly only accommodate angular and axial misalignment, but not parallel misalignment. The next option can be to look at an SX or DI Variety coupling. The six bolt SX Variety will accommodate the two parallel misalignment as well as defined shaft separation. The size is going to be established through the assortment torque as well as shaft diameters.
Stage two: Next, calculate the application torque and apply the support issue to determine the selection torque.The formula utilized to calculate torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging within 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 Support Factor = Variety Torque
twelve,331 in-lbs x three.0 = 36,993 in-lbs
Step 3: Make use of the SX coupling tables and note that the SX 202-6 is rated at forty,700 in-lbs, in excess of ample to manage the selection torque calculated in step two. The SX202-6, however, will not assistance the 92mm shaft dimension. The next bigger size coupling, the SX228-6, will help the 92mm shaft size plus the shaft separation dimension (BSE) is six.88 inches, really near to the application?¡¥s preferred 7 inch separation. The SX228-6 is rated at 62,000 in-lbs which may appear to be excessive, nonetheless, the coupling size is critical to manage the bore dimension.
Stage four: The SX228-6 coupling is rated for any highest unbalanced velocity of 3,400 RPM, over ample to assistance the application velocity of 1,150 RPM.
Step five: To find out in the event the coupling will take care of the parallel misalignment, utilize the trig function of tan 1?? = offset permitted for 1 inch = 0.0174
Multiply the 0.0174 x the distance amongst disc packs or ??S?¡¥ dimension from your table on web page D-13, or five.50 inches.
The allowable parallel offset is 0.0174 x 5.50 = 0.096 inches. The maximum offset for your application is 1/32 inches (0.031), therefore this coupling can accommodate the parallel misalignment.
Note: It’s usually advisable to try and set up the coupling at approximately 20% of your allowable misalignment. For this coupling the installer ought to try to reach far better than 0.020 parallel misalignment on the time of set up. This may enable for that more misalignment that can arise as the result of tools settle and standard equipment put on.