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Steps In Selecting A Disc Coupling

The following is usually a sample application utilized to illustrate the conventional system for choosing 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 applying a 225 horsepower electrical motor working at one,150 RPM to drive a three cylinder multi stage reciprocating air compressor. The electrical motor has a 3-3/8 inch shaft that has a 7/8 inch keyway as well as the compressor includes a 92mm shaft that has a 25mm keyway. The shaft separation is approximately seven inches in between shaft ends with some skill to modify the motor location. The shafts possess a parallel misalignment/offset of approximately 1/32 of an inch.
Step one: The primary step would be to identify what coupling style is usually to be chosen for this application. Because the SU Kind coupling only supports
just one flex plane, it may possibly only accommodate angular and axial misalignment, but not parallel misalignment. The following alternative will be to search at an SX or DI Type coupling. The six bolt SX Style will accommodate the two parallel misalignment and the defined shaft separation. The size will likely be established from the choice torque as well as the shaft diameters.
Stage two: Upcoming, calculate the application torque and apply the services element to determine the variety torque.The formula utilized to determine torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging during the numbers in the application description:
Application Torque ( in-lbs ) =(HP x 63025)/RPM = (225 x 63025)/1150 = twelve,331 in-lbs
Application Torque x Services Aspect = Assortment Torque
12,331 in-lbs x 3.0 = 36,993 in-lbs
Step 3: Utilize the SX coupling tables and note the SX 202-6 is rated at forty,700 in-lbs, over ample to manage the selection torque calculated in step 2. The SX202-6, however, won’t help the 92mm shaft dimension. The following more substantial size coupling, the SX228-6, will assistance the 92mm shaft dimension and the shaft separation dimension (BSE) is 6.88 inches, quite near to the application?¡¥s desired seven inch separation. The SX228-6 is rated at 62,000 in-lbs which may well seem to be extreme, even so, the coupling size is important to handle the bore dimension.
Phase 4: The SX228-6 coupling is rated for any maximum unbalanced speed of 3,400 RPM, greater than ample to support the application velocity of one,150 RPM.
Stage five: To determine when the coupling will manage the parallel misalignment, make use of the trig perform of tan 1?? = offset allowed for 1 inch = 0.0174
Multiply the 0.0174 x the distance amongst disc packs or ??S?¡¥ dimension from your table on page D-13, or five.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), consequently this coupling can accommodate the parallel misalignment.
Note: It really is often advised to try and set up the coupling at roughly 20% from the allowable misalignment. For this coupling the installer really should try to achieve far better than 0.020 parallel misalignment in the time of set up. This may make it possible for for the supplemental misalignment that may happen because the consequence of gear settle and common tools put on.


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