Techniques In Deciding on A Disc Coupling

The following is usually a sample application employed to illustrate the standard method for selecting 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:
A company features a compressor application applying a 225 horsepower electric motor operating at 1,150 RPM to drive a 3 cylinder multi stage reciprocating air compressor. The electric motor includes a 3-3/8 inch shaft using a 7/8 inch keyway along with the compressor has a 92mm shaft having a 25mm keyway. The shaft separation is approximately seven inches amongst shaft ends with some capability to adjust the motor location. The shafts have a parallel misalignment/offset of roughly 1/32 of an inch.
Phase 1: The first stage is to identify what coupling kind is to be selected for this application. Since the SU Sort coupling only supports
a single flex plane, it might only accommodate angular and axial misalignment, but not parallel misalignment. The following option would be to appear at an SX or DI Kind coupling. The 6 bolt SX Kind will accommodate each parallel misalignment and also the defined shaft separation. The size are going to be established from the variety torque as well as shaft diameters.
Stage two: Subsequent, determine the application torque and apply the service element to calculate the selection torque.The formula used to calculate torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging within 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 Issue = Variety 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, in excess of adequate to take care of the choice torque calculated in stage two. The SX202-6, however, is not going to assistance the 92mm shaft size. The following bigger dimension coupling, the SX228-6, will support the 92mm shaft size and also the shaft separation dimension (BSE) is six.88 inches, extremely close to the application?¡¥s preferred 7 inch separation. The SX228-6 is rated at 62,000 in-lbs which could seem to be extreme, nonetheless, the coupling dimension is critical to manage the bore size.
Phase four: The SX228-6 coupling is rated to get a highest unbalanced velocity of three,400 RPM, over sufficient to help the application pace of one,150 RPM.
Step 5: To determine in the event the coupling will handle the parallel misalignment, use the trig perform of tan 1?? = offset permitted for 1 inch = 0.0174
Multiply the 0.0174 x the distance among disc packs or ??S?¡¥ dimension from your table on web 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), therefore this coupling can accommodate the parallel misalignment.
Note: It’s usually advisable to seek to install the coupling at roughly 20% in the allowable misalignment. For this coupling the installer ought to seek to achieve greater than 0.020 parallel misalignment with the time of installation. This will make it possible for to the more misalignment that could arise since the end result of gear settle and basic equipment put on.