Methods In Picking A Disc Coupling

The following is actually a sample application employed to illustrate the conventional approach for picking out 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 applying a 225 horsepower electrical motor running at 1,150 RPM to drive a 3 cylinder multi stage reciprocating air compressor. The electrical motor features a 3-3/8 inch shaft having a 7/8 inch keyway and also the compressor features a 92mm shaft that has a 25mm keyway. The shaft separation is roughly 7 inches in between shaft ends with some capacity to change the motor spot. The shafts have a parallel misalignment/offset of roughly 1/32 of an inch.
Step 1: The initial stage is always to determine what coupling kind would be to be selected for this application. Since the SU Form coupling only supports
just one flex plane, it can only accommodate angular and axial misalignment, but not parallel misalignment. The following preference might be to look at an SX or DI Kind coupling. The 6 bolt SX Type will accommodate each parallel misalignment as well as defined shaft separation. The dimension will likely be determined by the variety torque and the shaft diameters.
Step 2: Subsequent, calculate the application torque and apply the service issue to determine the choice torque.The formula employed to determine torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging within the numbers from your 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
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, over adequate to manage the assortment torque calculated in step 2. The SX202-6, even so, won’t help the 92mm shaft size. The next greater dimension coupling, the SX228-6, will support the 92mm shaft size plus the shaft separation dimension (BSE) is six.88 inches, incredibly close to the application?¡¥s preferred 7 inch separation. The SX228-6 is rated at 62,000 in-lbs which might seem to be excessive, nevertheless, the coupling size is critical to handle the bore size.
Stage 4: The SX228-6 coupling is rated for a maximum unbalanced pace of 3,400 RPM, in excess of ample to assistance the application speed of one,150 RPM.
Stage 5: To determine if your coupling will deal with the parallel misalignment, make use of the trig function of tan 1?? = offset allowed for one inch = 0.0174
Multiply the 0.0174 x the distance involving disc packs or ??S?¡¥ dimension from the table on web page D-13, or five.50 inches.
The allowable parallel offset is 0.0174 x five.50 = 0.096 inches. The maximum offset for your application is 1/32 inches (0.031), for that reason this coupling can accommodate the parallel misalignment.
Note: It really is usually suggested to try and install the coupling at approximately 20% on the allowable misalignment. For this coupling the installer really should seek to reach better than 0.020 parallel misalignment in the time of installation. This will likely make it possible for for the added misalignment that will arise as the end result of products settle and general gear wear.


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