The following can be a sample application applied to illustrate the typical system for choosing a Disc coupling. Any resemblance to any existing company?¡¥s application is neither intentional nor meant to resemble that company?¡¥s real application.
Sample Application:
An organization features a compressor application employing a 225 horsepower electrical motor running at one,150 RPM to drive a 3 cylinder multi stage reciprocating air compressor. The electric motor features a 3-3/8 inch shaft using a 
7/8 inch keyway along with the compressor has a 92mm shaft using a 25mm keyway. The shaft separation is roughly seven inches in between shaft ends with some capability to alter the motor place. The shafts have a parallel misalignment/offset of roughly 1/32 of an inch.
Phase 1: The 1st phase is usually to decide what coupling form is usually to be chosen for this application. Because the SU Style coupling only supports
just one flex plane, it might only accommodate angular and axial misalignment, but not parallel misalignment. The next option can be to seem at an SX or DI Kind coupling. The six bolt SX Type will accommodate the two parallel misalignment and also the defined shaft separation. The dimension might be established from the choice torque plus the shaft diameters.
Stage 2: Following, determine the application torque and apply the service factor to calculate the variety torque.The formula utilised to calculate torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging in the numbers from the application description:
Application Torque ( in-lbs ) =(HP x 63025)/RPM = (225 x 63025)/1150 = twelve,331 in-lbs
Application Torque x Service Component = Selection Torque
twelve,331 in-lbs x three.0 = 36,993 in-lbs
Step 3: Use the SX coupling tables and note the SX 202-6 is rated at forty,700 in-lbs, a lot more than adequate to take care of the variety torque calculated in stage two. The SX202-6, however, won’t assistance the 92mm shaft dimension. The subsequent more substantial dimension coupling, the SX228-6, will support the 92mm shaft dimension and also the shaft separation dimension (BSE) is six.88 inches, pretty near to the application?¡¥s desired seven inch separation. The SX228-6 is rated at 62,000 in-lbs which may well appear to be excessive, on the other hand, the coupling dimension is critical to deal with the bore dimension.
Step four: The SX228-6 coupling is rated for any optimum unbalanced velocity of 3,400 RPM, over enough to help the application velocity of one,150 RPM.
Step five: To determine if your coupling will deal with the parallel misalignment, make use of the trig function of tan 1?? = offset permitted for one inch = 0.0174
Multiply the 0.0174 x the distance concerning disc packs or ??S?¡¥ dimension in the table on web page D-13, or five.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), as a result this coupling can accommodate the parallel misalignment.
Note: It is actually usually advisable to make an effort to install the coupling at approximately 20% of the allowable misalignment. For this coupling the installer should try to achieve improved than 0.020 parallel misalignment on the time of set up. This may let to the supplemental misalignment that will occur since the outcome of tools settle and basic gear dress in.
