Methods In Deciding on A Disc Coupling

The following can be a sample application utilised to illustrate the common method for picking out a Disc coupling. Any resemblance to any current company?¡¥s application is neither intentional nor meant to resemble that company?¡¥s actual application.
Sample Application:
An organization includes a compressor application employing a 225 horsepower electrical motor working at one,150 RPM to drive a 3 cylinder multi stage reciprocating air compressor. The electric motor includes a 3-3/8 inch shaft by using a 7/8 inch keyway as well as the compressor has a 92mm shaft that has a 25mm keyway. The shaft separation is roughly 7 inches amongst shaft ends with some capability to alter the motor place. The shafts have a parallel misalignment/offset of approximately 1/32 of an inch.
Phase one: The initial phase will be to figure out what coupling form is to be selected for this application. Since the SU Sort 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 search at an SX or DI Sort coupling. The 6 bolt SX Kind will accommodate the two parallel misalignment and the defined shaft separation. The size will likely be determined through the assortment torque as well as shaft diameters.
Phase two: Following, determine the application torque and apply the support aspect to determine the variety torque.The formula made use of to determine torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging during the numbers through the application description:
Application Torque ( in-lbs ) =(HP x 63025)/RPM = (225 x 63025)/1150 = 12,331 in-lbs
Application Torque x Services Element = Selection Torque
twelve,331 in-lbs x three.0 = 36,993 in-lbs
Step three: Utilize the SX coupling tables and note that the SX 202-6 is rated at 40,700 in-lbs, a lot more than ample to manage the choice torque calculated in phase 2. The SX202-6, nonetheless, is not going to assistance the 92mm shaft dimension. The following greater size coupling, the SX228-6, will help the 92mm shaft dimension plus the shaft separation dimension (BSE) is 6.88 inches, very near to the application?¡¥s sought after 7 inch separation. The SX228-6 is rated at 62,000 in-lbs which might seem to be excessive, on the other hand, the coupling size is critical to handle the bore size.
Phase four: The SX228-6 coupling is rated to get a optimum unbalanced speed of 3,400 RPM, over adequate to assistance the application speed of 1,150 RPM.
Step 5: To determine if your coupling will take care of the parallel misalignment, use the trig perform of tan 1?? = offset permitted 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 5.50 inches.
The allowable parallel offset is 0.0174 x five.50 = 0.096 inches. The utmost offset to the application is 1/32 inches (0.031), as a result this coupling can accommodate the parallel misalignment.
Note: It is always advisable to try to install the coupling at roughly 20% in the allowable misalignment. For this coupling the installer should attempt to realize superior than 0.020 parallel misalignment in the time of installation. This can permit to the extra misalignment that could occur because the result of gear settle and general tools wear.