The next is actually a sample application utilized to illustrate the normal process for picking a Disc coupling. Any resemblance to any existing company?¡¥s application is neither intentional nor meant to resemble that company?¡¥s real application.
Sample Application:
An organization includes a compressor application employing a 225 horsepower electric 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 which has a 7/8 inch keyway plus the compressor features a 92mm shaft which has a 25mm keyway. The shaft separation is roughly seven inches involving shaft ends with some capacity to adjust the motor area. The shafts have a parallel misalignment/offset of roughly 1/32 of an inch.
Phase 1: The primary stage is always to identify what coupling form will be to be chosen for this application. Because the SU Style coupling only supports
a single flex plane, it could possibly only accommodate angular and axial misalignment, but not parallel misalignment. The next option could be to appear at an SX or DI Variety coupling. The six bolt SX Kind will accommodate both parallel misalignment as well as the defined shaft separation. The dimension is going to be determined from the variety torque and the shaft diameters.
Stage 2: Next, determine the application torque and apply the support component to determine the selection 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 Services Component = Assortment Torque
12,331 in-lbs x three.0 = 36,993 in-lbs
Step three: Make use of the SX coupling tables and note that the SX 202-6 is rated at forty,700 in-lbs, in excess of sufficient to take care of the assortment torque calculated in step 2. The SX202-6, on the other hand, will not help the 92mm shaft dimension. The next bigger size coupling, the SX228-6, will help the 92mm shaft dimension as well as shaft separation dimension (BSE) is six.88 inches, incredibly close to the application?¡¥s sought after seven inch separation. The SX228-6 is rated at 62,000 in-lbs which may perhaps seem to be excessive, even so, the coupling size is critical to deal with the bore size.
Stage four: The SX228-6 coupling is rated for a highest unbalanced speed of 3,400 RPM, in excess of ample to assistance the application pace of 1,150 RPM.
Stage five: To find out in the event the coupling will handle the parallel misalignment, use the trig function of tan 1?? = offset allowed for 1 inch = 0.0174
Multiply the 0.0174 x the distance involving disc packs or ??S?¡¥ dimension through the table on page D-13, or five.50 inches.
The allowable parallel offset is 0.0174 x five.50 = 0.096 inches. The utmost offset for the application is 1/32 inches (0.031), consequently this coupling can accommodate the parallel misalignment.
Note: It’s always advisable to seek to set up the coupling at roughly 20% of the allowable misalignment. For this coupling the installer ought to try and achieve much better than 0.020 parallel misalignment in the time of installation. This will permit for that more misalignment that can take place since the outcome of tools settle and common tools wear.
