Methods In Choosing A Disc Coupling

The following can be a sample application applied to illustrate the common system 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:
An organization includes a compressor application utilizing a 225 horsepower electric motor working at one,150 RPM to drive a three cylinder multi stage reciprocating air compressor. The electrical motor includes a 3-3/8 inch shaft with a 7/8 inch keyway as well as compressor features a 92mm shaft using a 25mm keyway. The shaft separation is roughly 7 inches among shaft ends with some ability to modify the motor place. The shafts possess a parallel misalignment/offset of roughly 1/32 of an inch.
Step one: The very first stage would be to ascertain what coupling kind should be to be picked for this application. Since the SU Kind coupling only supports
just one flex plane, it may only accommodate angular and axial misalignment, but not parallel misalignment. The next decision can be to appear at an SX or DI Sort coupling. The 6 bolt SX Kind will accommodate the two parallel misalignment as well as defined shaft separation. The size is going to be determined from the selection torque as well as the shaft diameters.
Phase 2: Subsequent, calculate the application torque and apply the services element to calculate the variety torque.The formula made use of to calculate torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging during the numbers from the application description:
Application Torque ( in-lbs ) =(HP x 63025)/RPM = (225 x 63025)/1150 = 12,331 in-lbs
Application Torque x Services Component = Assortment Torque
12,331 in-lbs x three.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, greater than sufficient to handle the assortment torque calculated in phase two. The SX202-6, even so, is not going to assistance the 92mm shaft size. The following larger dimension coupling, the SX228-6, will support the 92mm shaft dimension plus the shaft separation dimension (BSE) is six.88 inches, quite close to the application?¡¥s wanted 7 inch separation. The SX228-6 is rated at 62,000 in-lbs which may perhaps appear to be extreme, having said that, the coupling dimension is critical to take care of the bore size.
Phase four: The SX228-6 coupling is rated to get a maximum unbalanced velocity of 3,400 RPM, over adequate to assistance the application velocity of 1,150 RPM.
Stage five: To find out if your coupling will manage the parallel misalignment, utilize the trig perform of tan 1?? = offset allowed for one inch = 0.0174
Multiply the 0.0174 x the distance in between disc packs or ??S?¡¥ dimension in 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 for the application is 1/32 inches (0.031), consequently this coupling can accommodate the parallel misalignment.
Note: It really is constantly advisable to try to install the coupling at approximately 20% of the allowable misalignment. For this coupling the installer need to make an effort to attain superior than 0.020 parallel misalignment with the time of installation. This will likely allow for that added misalignment that could happen because the end result of products settle and standard equipment dress in.