Steps In Selecting A Disc Coupling

The next is a sample application utilised to illustrate the typical course of action for selecting 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:
An organization has a compressor application using a 225 horsepower electric motor running at one,150 RPM to drive a 3 cylinder multi stage reciprocating air compressor. The electric motor has a 3-3/8 inch shaft having a 7/8 inch keyway plus the compressor features a 92mm shaft having a 25mm keyway. The shaft separation is roughly seven inches concerning shaft ends with some capacity to alter the motor place. The shafts possess a parallel misalignment/offset of approximately 1/32 of an inch.
Phase one: The 1st stage will be to identify what coupling kind will be to be picked for this application. Since the SU Form coupling only supports
just one flex plane, it could possibly only accommodate angular and axial misalignment, but not parallel misalignment. The next alternative could be to appear at an SX or DI Style coupling. The six bolt SX Type will accommodate the two parallel misalignment plus the defined shaft separation. The size will probably be established through the variety torque along with the shaft diameters.
Step 2: Up coming, calculate the application torque and apply the services factor to determine the assortment torque.The formula used to determine torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging during 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 Service Element = Selection Torque
12,331 in-lbs x 3.0 = 36,993 in-lbs
Stage three: Utilize the SX coupling tables and note the SX 202-6 is rated at 40,700 in-lbs, over adequate to handle the variety torque calculated in step two. The SX202-6, nevertheless, will not assistance the 92mm shaft dimension. The following larger size coupling, the SX228-6, will support the 92mm shaft size and also the shaft separation dimension (BSE) is six.88 inches, incredibly near to the application?¡¥s wanted 7 inch separation. The SX228-6 is rated at 62,000 in-lbs which may well seem to be excessive, nevertheless, the coupling size is critical to handle the bore dimension.
Stage 4: The SX228-6 coupling is rated for a optimum unbalanced speed of 3,400 RPM, greater than adequate to support the application speed of one,150 RPM.
Phase 5: To find out should the coupling will handle the parallel misalignment, utilize the trig function of tan 1?? = offset permitted for one inch = 0.0174
Multiply the 0.0174 x the distance among 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 maximum offset for that application is 1/32 inches (0.031), consequently this coupling can accommodate the parallel misalignment.
Note: It can be generally encouraged to seek to set up the coupling at roughly 20% with the allowable misalignment. For this coupling the installer really should seek to achieve improved than 0.020 parallel misalignment on the time of set up. This will let for that supplemental misalignment that may happen because the outcome of gear settle and basic equipment wear.