Methods In Deciding on A Disc Coupling

The next is usually a sample application utilized to illustrate the common system for picking a Disc coupling. Any resemblance to any current company?¡¥s application is neither intentional nor meant to resemble that company?¡¥s real application.
Sample Application:
A company has a compressor application working with a 225 horsepower electric motor working at one,150 RPM to drive a 3 cylinder multi stage reciprocating air compressor. The electric motor features a 3-3/8 inch shaft that has a 7/8 inch keyway plus the compressor has a 92mm shaft which has a 25mm keyway. The shaft separation is roughly seven inches in between shaft ends with some capability to adjust the motor place. The shafts possess a parallel misalignment/offset of approximately 1/32 of an inch.
Stage 1: The very first phase is usually to figure out what coupling kind should be to be selected for this application. Since the SU Variety coupling only supports
a single flex plane, it may possibly only accommodate angular and axial misalignment, but not parallel misalignment. The next choice would be to look at an SX or DI Variety coupling. The six bolt SX Style will accommodate each parallel misalignment plus the defined shaft separation. The dimension will be determined by the assortment torque as well as the shaft diameters.
Phase two: Subsequent, determine the application torque and apply the service aspect to determine the selection torque.The formula utilized to calculate torque is as follows:
Application Torque ( in¡§Clb ) = ( HP x 63025 )/RPM
or Nm = ( KW x 9550)/RPM
Plugging during the numbers from the application description:
Application Torque ( in-lbs ) =(HP x 63025)/RPM = (225 x 63025)/1150 = twelve,331 in-lbs
Application Torque x Services Factor = Choice Torque
twelve,331 in-lbs x 3.0 = 36,993 in-lbs
Stage 3: Make use of the SX coupling tables and note the SX 202-6 is rated at 40,700 in-lbs, in excess of enough to handle the choice torque calculated in step 2. The SX202-6, however, won’t assistance the 92mm shaft size. The following more substantial size coupling, the SX228-6, will assistance the 92mm shaft size along with the shaft separation dimension (BSE) is 6.88 inches, pretty near to the application?¡¥s wanted 7 inch separation. The SX228-6 is rated at 62,000 in-lbs which might appear to be extreme, even so, the coupling size is necessary to handle the bore size.
Step four: The SX228-6 coupling is rated for a maximum unbalanced pace of 3,400 RPM, more than sufficient to support the application speed of 1,150 RPM.
Stage 5: To find out in case the coupling will deal with the parallel misalignment, use the trig function of tan 1?? = offset allowed for 1 inch = 0.0174
Multiply the 0.0174 x the distance among disc packs or ??S?¡¥ dimension from your table on page D-13, or 5.50 inches.
The allowable parallel offset is 0.0174 x five.50 = 0.096 inches. The utmost offset for your application is 1/32 inches (0.031), for that reason this coupling can accommodate the parallel misalignment.
Note: It is actually often encouraged to make an effort to set up the coupling at roughly 20% in the allowable misalignment. For this coupling the installer ought to attempt to achieve far better than 0.020 parallel misalignment in the time of set up. This may let for that more misalignment that should happen as the end result of tools settle and standard gear wear.