The next is really a sample application utilized to illustrate the regular method for deciding on a Disc coupling. Any resemblance to any existing 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 electrical motor operating at 1,150 RPM to drive a three cylinder multi stage reciprocating air compressor. The electric motor features a 3-3/8 inch shaft by using a 7/8 inch keyway as well as the compressor has a 92mm shaft which has a 25mm keyway. The shaft separation is approximately seven inches between shaft ends with some skill to change the motor location. The shafts have a parallel misalignment/offset of approximately 1/32 of an inch.
Phase 1: The 1st step should be to decide what coupling style is always to be chosen for this application. Since the SU Style coupling only supports
a single flex plane, it can only accommodate angular and axial misalignment, but not parallel misalignment. The subsequent option could be to look at an SX or DI Type coupling. The six bolt SX Form will accommodate both parallel misalignment as well as the defined shaft separation. The dimension will probably be established by the variety torque and the shaft diameters.
Step 2: Next, determine the application torque and apply the service factor to determine the choice torque.The formula utilised to determine torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging while in 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 Service Element = Variety Torque
twelve,331 in-lbs x 3.0 = 36,993 in-lbs
Phase 3: Utilize the SX coupling tables and note that the SX 202-6 is rated at 40,700 in-lbs, in excess of ample to take care of the choice torque calculated in step 2. The SX202-6, nevertheless, won’t support the 92mm shaft dimension. The next greater size coupling, the SX228-6, will help the 92mm shaft size and also the shaft separation dimension (BSE) is 6.88 inches, extremely near to the application?¡¥s desired seven inch separation. The SX228-6 is rated at 62,000 in-lbs which could seem to be excessive, even so, the coupling size is necessary to deal with the bore dimension.
Stage 4: The SX228-6 coupling is rated for a greatest unbalanced pace of three,400 RPM, more than sufficient to help the application speed of 1,150 RPM.
Step five: To determine when the coupling will handle the parallel misalignment, make use of the trig function of tan 1?? = offset permitted for 1 inch = 0.0174
Multiply the 0.0174 x the distance involving disc packs or ??S?¡¥ dimension through the table on webpage D-13, or 5.50 inches.
The allowable parallel offset is 0.0174 x 5.50 = 0.096 inches. The maximum offset for that application is 1/32 inches (0.031), hence this coupling can accommodate the parallel misalignment.
Note: It is usually recommended to endeavor to install the coupling at roughly 20% with the allowable misalignment. For this coupling the installer should try to realize far better than 0.020 parallel misalignment on the time of set up. This can let for your extra misalignment that can come about as the result of tools settle and basic tools put on.