Measures In Deciding on A Disc Coupling

The next is really a sample application made use of to illustrate the normal process for selecting a Disc coupling. Any resemblance to any present company?¡¥s application is neither intentional nor meant to resemble that company?¡¥s actual application.
Sample Application:
A company includes a compressor application using a 225 horsepower electric motor running at 1,150 RPM to drive a 3 cylinder multi stage reciprocating air compressor. The electric motor has a 3-3/8 inch shaft using a 7/8 inch keyway plus the compressor includes a 92mm shaft by using a 25mm keyway. The shaft separation is approximately seven inches involving shaft ends with some capability to adjust the motor spot. The shafts possess a parallel misalignment/offset of roughly 1/32 of an inch.
Step one: The first stage is usually to establish what coupling form will be to be selected for this application. Because the SU Variety coupling only supports
just one flex plane, it may possibly only accommodate angular and axial misalignment, but not parallel misalignment. The subsequent selection can be to look at an SX or DI Sort coupling. The six bolt SX Form will accommodate each parallel misalignment and the defined shaft separation. The size will probably be determined by the selection torque as well as shaft diameters.
Step two: Upcoming, determine the application torque and apply the service aspect to calculate the selection 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 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 Service Element = Selection Torque
12,331 in-lbs x 3.0 = 36,993 in-lbs
Stage 3: Use the SX coupling tables and note that the SX 202-6 is rated at forty,700 in-lbs, greater than ample to manage the choice torque calculated in phase 2. The SX202-6, having said that, will not assistance the 92mm shaft size. The next larger dimension coupling, the SX228-6, will assistance the 92mm shaft dimension and also the shaft separation dimension (BSE) is six.88 inches, quite near to the application?¡¥s sought after 7 inch separation. The SX228-6 is rated at 62,000 in-lbs which could appear to be extreme, on the other hand, the coupling size is necessary to manage the bore dimension.
Stage four: The SX228-6 coupling is rated for any greatest unbalanced velocity of 3,400 RPM, over adequate to assistance the application pace of 1,150 RPM.
Step 5: To find out when the coupling will handle the parallel misalignment, make use of the trig perform of tan 1?? = offset permitted for 1 inch = 0.0174
Multiply the 0.0174 x the distance concerning 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 maximum offset for that application is 1/32 inches (0.031), as a result this coupling can accommodate the parallel misalignment.
Note: It truly is generally encouraged to make an effort to set up the coupling at roughly 20% of the allowable misalignment. For this coupling the installer need to endeavor to achieve greater than 0.020 parallel misalignment with the time of set up. This will permit for that further misalignment that may take place since the end result of products settle and basic products dress in.


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