Methods In Picking out A Disc Coupling

The following is often a sample application applied to illustrate the standard procedure for deciding on a Disc coupling. Any resemblance to any present company?¡¥s application is neither intentional nor meant to resemble that company?¡¥s real application.
Sample Application:
A company includes a compressor application making use of a 225 horsepower electric motor working at one,150 RPM to drive a 3 cylinder multi stage reciprocating air compressor. The electrical motor includes a 3-3/8 inch shaft having a 7/8 inch keyway plus the compressor includes a 92mm shaft that has a 25mm keyway. The shaft separation is roughly 7 inches amongst shaft ends with some means to modify the motor place. The shafts have a parallel misalignment/offset of roughly 1/32 of an inch.
Phase 1: The initial step is always to ascertain what coupling form would be to be selected for this application. Because the SU Sort coupling only supports
a single flex plane, it might only accommodate angular and axial misalignment, but not parallel misalignment. The following choice would be to look at an SX or DI Type coupling. The 6 bolt SX Form will accommodate the two parallel misalignment as well as defined shaft separation. The dimension might be established by the selection torque and also the shaft diameters.
Step two: Upcoming, determine the application torque and apply the services factor to calculate the choice torque.The formula used to calculate torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging inside 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 Service Issue = Variety Torque
12,331 in-lbs x 3.0 = 36,993 in-lbs
Phase 3: Make use of the SX coupling tables and note that the SX 202-6 is rated at forty,700 in-lbs, in excess of sufficient to take care of the selection torque calculated in step 2. The SX202-6, however, won’t support the 92mm shaft size. The following bigger dimension coupling, the SX228-6, will support the 92mm shaft size as well as the shaft separation dimension (BSE) is six.88 inches, incredibly close to the application?¡¥s desired seven inch separation. The SX228-6 is rated at 62,000 in-lbs which may possibly seem to be excessive, on the other hand, the coupling dimension is important to deal with the bore size.
Step 4: The SX228-6 coupling is rated for a maximum unbalanced speed of 3,400 RPM, a lot more than enough to support the application pace of 1,150 RPM.
Step 5: To find out if the coupling will manage the parallel misalignment, utilize the trig function 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 web page D-13, or five.50 inches.
The allowable parallel offset is 0.0174 x 5.50 = 0.096 inches. The maximum offset for the application is 1/32 inches (0.031), therefore this coupling can accommodate the parallel misalignment.
Note: It truly is generally proposed to try and set up the coupling at approximately 20% of your allowable misalignment. For this coupling the installer ought to try and attain much better than 0.020 parallel misalignment at the time of set up. This may make it possible for to the more misalignment that should come about as the outcome of gear settle and standard products wear.


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