The following is actually a sample application employed to illustrate the typical process 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 features a compressor application working with a 225 horsepower electrical motor working at 1,150 RPM to drive a three cylinder multi stage reciprocating air compressor. The electric motor has a 3-3/8 inch shaft having a 7/8 inch keyway and the compressor has a 92mm shaft having a 25mm keyway. The shaft separation is approximately 7 inches between shaft ends with some capacity to adjust the motor place. The shafts have a parallel misalignment/offset of approximately 1/32 of an inch.
Step one: The primary stage is to establish what coupling sort is to be chosen for this application. Because the SU Kind coupling only supports
a single flex plane, it can only accommodate angular and axial misalignment, but not parallel misalignment. The next decision can be to seem at an SX or DI Variety coupling. The six bolt SX Sort will accommodate the two parallel misalignment and also the defined shaft separation. The dimension will probably be determined by the choice torque as well as the shaft diameters.
Phase two: Following, determine the application torque and apply the support factor to calculate the choice 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 during 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 
Services Component = Variety Torque
twelve,331 in-lbs x 3.0 = 36,993 in-lbs
Step 3: Make use of the SX coupling tables and note the SX 202-6 is rated at forty,700 in-lbs, over adequate to deal with the selection torque calculated in step two. The SX202-6, nonetheless, will not assistance the 92mm shaft dimension. The following bigger dimension coupling, the SX228-6, will assistance the 92mm shaft size plus the shaft separation dimension (BSE) is six.88 inches, really near to the application?¡¥s wanted 7 inch separation. The SX228-6 is rated at 62,000 in-lbs which may well appear to be extreme, even so, the coupling size is necessary to manage the bore size.
Step four: The SX228-6 coupling is rated for a highest unbalanced speed of 3,400 RPM, in excess of adequate to assistance the application pace of one,150 RPM.
Phase 5: To find out if the coupling will handle the parallel misalignment, use the trig function of tan 1?? = offset allowed for one inch = 0.0174
Multiply the 0.0174 x the distance between disc packs or ??S?¡¥ dimension from the table on page D-13, or five.50 inches.
The allowable parallel offset is 0.0174 x 5.50 = 0.096 inches. The utmost offset for your application is 1/32 inches (0.031), for that reason this coupling can accommodate the parallel misalignment.
Note: It is often suggested to try to set up the coupling at approximately 20% of your allowable misalignment. For this coupling the installer should really seek to obtain greater than 0.020 parallel misalignment on the time of installation. This may enable for that supplemental misalignment that should arise as the end result of gear settle and general tools dress in.
