The next is a sample application applied to illustrate the normal procedure for choosing a Disc coupling. Any resemblance to any existing company?¡¥s application is neither intentional nor meant to resemble that company?¡¥s actual application.
Sample Application:
A company has a compressor application making use of a 225 horsepower electrical motor running at 1,150 RPM to drive a 3 cylinder multi stage reciprocating air compressor. The electric motor features a 3-3/8 inch shaft having a 7/8 inch keyway plus the compressor has a 92mm shaft which has a 25mm keyway. The shaft separation is approximately 7 inches in between shaft ends with some potential to modify the motor place. The shafts possess a parallel misalignment/offset of approximately 1/32 of an inch.
Stage 1: The first step will be to identify what coupling type is usually to be picked for this application. Because the SU Type coupling only supports
a single flex plane, it might only accommodate angular and axial misalignment, but not parallel misalignment. The following selection could be to search 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 dimension will be determined from the assortment torque as well as shaft diameters.
Step two: Next, determine the application torque and apply the service 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 from the numbers from your application description:
Application Torque ( in-lbs ) =(HP x 63025)/RPM = (225 x 63025)/1150 = twelve,331 in-lbs
Application Torque x Services Issue = Choice 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 forty,700 in-lbs, a lot more than adequate to handle the variety torque calculated in step two. The SX202-6, on the other hand, won’t help the 92mm shaft dimension. The following more substantial size coupling, the SX228-6, will help the 92mm shaft dimension as well as the shaft separation dimension (BSE) is 6.88 inches, incredibly close to the application?¡¥s preferred seven inch separation. The SX228-6 is rated at 62,000 in-lbs which might appear to be excessive, nonetheless, the coupling dimension is important to manage the bore dimension.
Phase four: The SX228-6 coupling is rated for a highest unbalanced speed of 3,400 RPM, greater than sufficient to assistance the application velocity of 1,150 RPM.
Step 5: To find out in case the coupling will handle the parallel misalignment, make use of the trig perform of tan 1?? = offset allowed for 1 inch = 0.0174
Multiply the 0.0174 x the distance among disc packs or ??S?¡¥ dimension from the table on webpage 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), thus this coupling can accommodate the parallel misalignment.
Note: It truly is generally suggested to try and set up the coupling at approximately 20% of your allowable misalignment. For this coupling the installer should seek to attain greater than 0.020 parallel misalignment in the time of installation. This will likely make it possible for for your more misalignment that should occur because the consequence of equipment settle and standard tools wear.