Techniques In Selecting A Disc Coupling

The next is often a sample application applied to illustrate the normal process 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 employing a 225 horsepower electrical motor running at one,150 RPM to drive a 3 cylinder multi stage reciprocating air compressor. The electric motor includes a 3-3/8 inch shaft by using a 7/8 inch keyway and also the compressor includes a 92mm shaft with a 25mm keyway. The shaft separation is approximately seven inches among shaft ends with some means to adjust the motor location. The shafts have a parallel misalignment/offset of roughly 1/32 of an inch.
Phase 1: The primary stage is always to ascertain what coupling type would be to be picked for this application. Since the SU Form coupling only supports
a single flex plane, it can only accommodate angular and axial misalignment, but not parallel misalignment. The following decision could be to search at an SX or DI Form coupling. The six bolt SX Form will accommodate both parallel misalignment as well as the defined shaft separation. The size will likely be established through the selection torque and also the shaft diameters.
Phase 2: Next, calculate the application torque and apply the services element to calculate the assortment torque.The formula used to determine torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging from the numbers in the application description:
Application Torque ( in-lbs ) =(HP x 63025)/RPM = (225 x 63025)/1150 = 12,331 in-lbs
Application Torque x Support Aspect = Choice Torque
twelve,331 in-lbs x three.0 = 36,993 in-lbs
Step three: Use the SX coupling tables and note that the SX 202-6 is rated at forty,700 in-lbs, a lot more than ample to manage the assortment torque calculated in stage two. The SX202-6, nevertheless, is not going to support the 92mm shaft dimension. The following greater size coupling, the SX228-6, will help the 92mm shaft dimension plus the shaft separation dimension (BSE) is six.88 inches, incredibly close to the application?¡¥s preferred seven inch separation. The SX228-6 is rated at 62,000 in-lbs which may well appear to be extreme, nonetheless, the coupling size is important to take care of the bore dimension.
Phase 4: The SX228-6 coupling is rated for a maximum unbalanced pace of three,400 RPM, over adequate to assistance the application speed of 1,150 RPM.
Stage five: To determine in the event the coupling will manage the parallel misalignment, make use of the trig perform of tan 1?? = offset allowed for one inch = 0.0174
Multiply the 0.0174 x the distance among disc packs or ??S?¡¥ dimension from the table on page D-13, or five.50 inches.
The allowable parallel offset is 0.0174 x 5.50 = 0.096 inches. The utmost offset to the application is 1/32 inches (0.031), as a result this coupling can accommodate the parallel misalignment.
Note: It can be normally advisable to try and install the coupling at roughly 20% of your allowable misalignment. For this coupling the installer should attempt to realize much better than 0.020 parallel misalignment with the time of installation. This can make it possible for to the added misalignment that can arise since the result of products settle and general equipment wear.


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