Techniques In Selecting A Disc Coupling

The next is often a sample application utilised to illustrate the regular process for selecting 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:
An organization includes a compressor application applying a 225 horsepower electrical motor running at one,150 RPM to drive a three cylinder multi stage reciprocating air compressor. The electric motor has a 3-3/8 inch shaft with a 7/8 inch keyway along with the compressor has a 92mm shaft by using a 25mm keyway. The shaft separation is roughly 7 inches between shaft ends with some capacity to modify the motor location. The shafts have a parallel misalignment/offset of approximately 1/32 of an inch.
Step 1: The 1st phase would be to establish what coupling style is to be picked for this application. Since the SU Style coupling only supports
just one flex plane, it may only accommodate angular and axial misalignment, but not parallel misalignment. The next option would be to appear at an SX or DI Sort coupling. The six bolt SX Kind will accommodate the two parallel misalignment plus the defined shaft separation. The dimension are going to be determined by the variety torque plus the shaft diameters.
Phase 2: Upcoming, determine the application torque and apply the support aspect to determine the assortment torque.The formula made use of to determine torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging within 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 Services Element = Selection Torque
12,331 in-lbs x 3.0 = 36,993 in-lbs
Phase 3: Use the SX coupling tables and note that the SX 202-6 is rated at 40,700 in-lbs, over sufficient to take care of the selection torque calculated in phase two. The SX202-6, nevertheless, won’t help the 92mm shaft size. The following greater dimension coupling, the SX228-6, will support the 92mm shaft dimension and also the shaft separation dimension (BSE) is 6.88 inches, quite near to the application?¡¥s sought after 7 inch separation. The SX228-6 is rated at 62,000 in-lbs which may seem to be excessive, nevertheless, the coupling dimension is necessary to deal with the bore size.
Phase four: The SX228-6 coupling is rated for a highest unbalanced velocity of three,400 RPM, a lot more than ample to support the application pace of 1,150 RPM.
Phase five: To determine when the coupling will take care of the parallel misalignment, utilize the trig perform of tan 1?? = offset permitted for 1 inch = 0.0174
Multiply the 0.0174 x the distance in between disc packs or ??S?¡¥ dimension through the table on web page D-13, or five.50 inches.
The allowable parallel offset is 0.0174 x five.50 = 0.096 inches. The utmost offset for that application is 1/32 inches (0.031), consequently this coupling can accommodate the parallel misalignment.
Note: It really is constantly recommended to make an effort to install the coupling at approximately 20% with the allowable misalignment. For this coupling the installer really should try and achieve far better than 0.020 parallel misalignment in the time of set up. This can let for the added misalignment that could come about since the end result of products settle and common gear dress in.


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