Specialty Couplings - Lovejoy - #9

Steps In Selecting A Deltaflex Coupling

Step 1: Determine the proper service factor (SF) for the application. This may involve 2 steps:

A. Driven equipment service factor (SFa): Using the Application Service Factors Chart 1 (page SP-10) select the service factor which best corresponds to your application. If the application is not listed in Chart 1, use Chart 2.

B. When using Chart 1, add the following service factors (SFb) to the values in Chart 1 as required. Add 0.5 for above average torque load variations or start/stop conditions of not more than once per hour. Add 1.0 for reversing loads, start/ stop conditions more than once per hour, severe torque load variations or high inertia starting conditions.

The additional service factor is added to the Chart 1 service factors to obtain the total service factor.

SF = SFa + SFb

Step 2: Calculate the equivalent HP/100 RPM.

HP/100 RPM = HP* x 100 x SF RPM*

* HP and RPM of prime mover.

Step 3: Select the Deltaflex size.

Method 1: From the Deltaflex HP and Torque Ratings Chart 3 (page SP-11) select the smallest coupling which is rated equal to or higher than the calculated HP/100 RPM.

Method 2: For couplings driven by standard electric motors, you can multiply the HP of the motor by the service factor (SF) and then refer to the electric motor driven chart for selection.

Step 4: Determine the type of Deltaflex needed, e.g., Type 1, Type 2, etc.

Step 5: Check limiting conditions.

A. Check to be sure that the coupling's Peak Overload Torque Rating is sufficient to accommodate the maximum torque to be transmitted, such as the starting and stall torques of the motor, braking torques and cyclic peak torques, if any. If starting or braking cycles are frequent, the brake torque should be checked against the maximum continuous torque rating of the coupling.

T = Tp x SF

T = Maximum torque transmitted

Tp = Brake torque, starting torque or peak torque

SF = Service Factor (determined previously)

B. Check the maximum hub bore. If bore size is too large, the next larger size Deltaflex can be specified.

C. Check other dimensions such as the limits on shaft separation, hub spacings, space required for the coupling, etc.

D. Check maximum speed. If operating speed exceeds 60% of listed maximum speed, the coupling should be dynamically balanced.

Step 6. Ordering Information.

A. Quantity, size, style of couplings.

B. Bore and Keyway sizes.

C. Dynamic balancing specification, if required.

D. Additional non-standard data.

1) Custom mounting dimensions

2) Between shaft ends (BE) dimension for spacer and floating shaft types

3) Maximum operating speed for floating shaft couplings

Selection Examples

A centrifugal fan requires 20 HP, 1,150 RPM motor, direct coupled from the motor to the fan. The motor frame is 286T (1.875 inch shaft) and the fan shaft is 1.625 inches.

Step 3: In this case, the maximum bore for size #50 coupling is 1.875 inches; therefore, the selection size stands.

Step 4: Since this is a shaft-to-shaft application, you will be using the standard Deltaflex coupling Type 1. Determine if any other selection factors apply as described in steps 4 and 5 of the selection guide.

Floating Shaft Type Coupling Selection Example

Using the preceding data, assume that the shaft spacing from end of shaft to end of shaft is 36 inches. A floating shaft coupling is then required. The 36 inch is specified as BE (Between Ends) = 36 inches.

Refer to the Type 3 and 4 Chart (page SP-14) to find the overall length of the coupling; add dimension 2 x LTB to BE.

For a size #50 type 3, the overall length will be 36 inches + 2 x 1.69 = 39.38. Note that the length of the spacer tube assembly will be 36 inches - 2R = 36 - 1.62 = 34.38.

This is the amount of space, or dropout section, between the fixed portions of the coupling.

Step 1: Using the Application Service Factors Chart 1 (page SP-10), the driven equipment service factor for a centrifugal fan is 1.5 = SFa. The load is uniform and the driver is smooth, therefore SFb is 0.

The total service factor SF is 1.5 + 0 = 1.5 Step 2: HP/100 RPM = ^{20 x 100 x 1.5} = 2.6 HP/100 RPM

1,150

Using the Deltaflex HP and torque ratings Chart 3 (page SP-11), under the column of HP/100RPM, the smallest coupling you can select is #50 which is rated for 3.0 HP/100 RPM.

NOTE: You can also find the coupling size by multiplying

SF x 20:

SF x 20 = 1.5 x 20 = 30 HP

In Chart 3 (page SP-11) for motor drives the coupling to select is, again, #50 under 1,150 RPM motors. The size is rated at 34 HP @ 1,150 RPM.