Measures In Picking out A Disc Coupling

The following is often a sample application applied to illustrate the regular method for selecting 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:
An organization features a compressor application working with a 225 horsepower electric motor operating at one,150 RPM to drive a three cylinder multi stage reciprocating air compressor. The electrical motor features a 3-3/8 inch shaft which has a 7/8 inch keyway along with the compressor includes a 92mm shaft by using a 25mm keyway. The shaft separation is roughly seven inches in between shaft ends with some ability to change the motor area. The shafts possess a parallel misalignment/offset of approximately 1/32 of an inch.
Stage one: The first phase will be to decide what coupling sort is to be selected for this application. Since the SU Style coupling only supports
a single flex plane, it may possibly only accommodate angular and axial misalignment, but not parallel misalignment. The following alternative might be to seem at an SX or DI Form coupling. The six bolt SX Style will accommodate the two parallel misalignment and also the defined shaft separation. The size will probably be determined by the choice torque plus the shaft diameters.
Phase 2: Subsequent, calculate the application torque and apply the support element 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 while in the numbers from your application description:
Application Torque ( in-lbs ) =(HP x 63025)/RPM = (225 x 63025)/1150 = 12,331 in-lbs
Application Torque x Service Component = Assortment Torque
twelve,331 in-lbs x 3.0 = 36,993 in-lbs
Phase three: Utilize the SX coupling tables and note that the SX 202-6 is rated at forty,700 in-lbs, over ample to take care of the selection torque calculated in phase 2. The SX202-6, having said that, won’t support the 92mm shaft size. The subsequent bigger size coupling, the SX228-6, will help the 92mm shaft size as well as the shaft separation dimension (BSE) is 6.88 inches, very near to the application?¡¥s wanted 7 inch separation. The SX228-6 is rated at 62,000 in-lbs which could appear to be excessive, even so, the coupling dimension is important to take care of the bore size.
Step 4: The SX228-6 coupling is rated for any optimum unbalanced speed of three,400 RPM, more than adequate to assistance the application pace of one,150 RPM.
Phase 5: To find out in case the coupling will take care of the parallel misalignment, utilize the trig perform of tan 1?? = offset allowed for one inch = 0.0174
Multiply the 0.0174 x the distance between disc packs or ??S?¡¥ dimension in the table on webpage D-13, or five.50 inches.
The allowable parallel offset is 0.0174 x five.50 = 0.096 inches. The maximum offset for your application is 1/32 inches (0.031), consequently this coupling can accommodate the parallel misalignment.
Note: It’s often recommended to seek to install the coupling at approximately 20% of your allowable misalignment. For this coupling the installer should really attempt to attain far better than 0.020 parallel misalignment at the time of set up. This will likely make it possible for to the additional misalignment which will arise as the result of tools settle and basic equipment put on.