The following is really a sample application used to illustrate the normal procedure for selecting 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 has a compressor application applying a 225 horsepower electrical motor running at one,150 RPM to drive a 3 cylinder multi stage reciprocating air compressor. The electric motor includes a 3-3/8 inch shaft with a 7/8 inch keyway as well as compressor includes a 92mm shaft using a 25mm keyway. The shaft separation is roughly 7 inches between shaft ends with some capacity to modify the motor spot. The shafts have a parallel misalignment/offset of approximately 1/32 of an inch.
Phase one: The 1st step would be to ascertain what coupling form should be to be selected for this application. Since the SU Variety coupling only supports
just one flex plane, it could only accommodate angular and axial misalignment, but not parallel misalignment. The following preference might be to search at an SX or DI Kind coupling. The 6 bolt SX Sort will accommodate each parallel misalignment along with the defined shaft separation. The size will be determined through the selection torque and the shaft diameters.
Stage 2: Up coming, calculate the application torque and apply the support factor to determine the variety 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 in the application description:
Application Torque ( in-lbs ) =(HP x 63025)/RPM = (225 x 63025)/1150 = 12,331 in-lbs
Application Torque x Support Component = Choice Torque
twelve,331 in-lbs x 3.0 = 36,993 in-lbs
Step three: Utilize the SX coupling tables and note the SX 202-6 is rated at 40,700 in-lbs, more than sufficient to handle the choice torque calculated in phase 2. The SX202-6, even so, won’t help the 92mm shaft dimension. The next greater size coupling, the SX228-6, will help the 92mm shaft dimension and the shaft separation dimension (BSE) is 6.88 inches, quite close to the application?¡¥s 
sought after seven inch separation. The SX228-6 is rated at 62,000 in-lbs which could seem to be extreme, having said that, the coupling dimension is important to handle the bore size.
Step four: The SX228-6 coupling is rated for any greatest unbalanced velocity of three,400 RPM, greater than sufficient to assistance the application speed of 1,150 RPM.
Stage five: To find out if your coupling will manage the parallel misalignment, use the trig function of tan 1?? = offset allowed for one inch = 0.0174
Multiply the 0.0174 x the distance amongst disc packs or ??S?¡¥ dimension from your 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 that application is 1/32 inches (0.031), for that reason this coupling can accommodate the parallel misalignment.
Note: It is actually often advised to seek to install the coupling at roughly 20% with the allowable misalignment. For this coupling the installer ought to endeavor to attain greater than 0.020 parallel misalignment at the time of set up. This will likely let for the more misalignment which will come about as the result of equipment settle and common tools dress in.
