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# Model Selection of Disc Couplings Select couplings on the basis of the following steps.

1.1 The basic information of the selection.
Driving machine’s name, drive machine’s quantity, input power, working speed, working machine’s name, the type of loading, working environment, working nature, frequent start, positive & negative going motion, input and output shaft diameter and its length.

Please refer to attached table 1 for basic information.

1.2 Calculation of selection
The main parameter of coupling is the nominal torque Tn, each torque should accord with the following relationship when selecting it:
T＜Tc≤Tn≤［T］＜［Tmax］＜Tmax
In the formula:
T ─ Theory of torque, N·m;
Tc — Computed torque, N·m;
Tn — Nominal torque, N·m;
[T] — Allowable torque, N·m;
[Tmax] — Allowable maximum torque, N·m;
Tmax — Maximum torque, N·m;

1.2.1 Theory torque calculation of Couplings
T=9550Pw/n
In the formula: Pw — driving power, Kw;
n — working speed, r/min.

1.2.2 Computed torque calculation of Couplings
Calculation formula: Tc=T·Kw·K·Kz
In the formula:
Kw — Coefficient of engine (see table 1)
K — Coefficient of working condition (see table 1)
Kz — Start coefficient (see table 1)

Table 1

1.2.3 When the following situation occurs, it is proper to calculate and select by the following methods:
② Brake (brake wheel or brake disc is part of coupling)
③ High frequency axial channeling shift

Repetitive peak loads exist with high motor power, impact load, frequent start-up or braking or intermittent operation. In these cases, rated toques of couplings are equal to or bigger than model toques on base of calculation.

Selection torque (N·m) = system peak torque
or selection torque (N·m) = system peak power (Kw)×9550/rotate speed (rpm)
Selection torque (N·m) = 1.5×system peak torque
or selection torque (N·m) = 1.5×system peak power (Kw)×9550/rotate speed (rpm)
During the expectation life of coupling, use the following formula if the system peak loading is appeared less than 1000 times:
Selection torque (N·m) = 0.5×system peak torque
or selection torque(N·m) = 0.5×system peak power (Kw)×9550/rotate speed (rpm)
For reverse situation, select the step b.

Brake
If the brake torque exceeds the motor torque, it is needed to calculate the braking power according to the following formula:
Selection torque (N·m) = brake torque × Coefficient of working condition

High frequency axial channeling shift
If the frequency of axial channeling shift exceeds more than 5 times per hour, so the coefficient of working condition should be increased by 0.25.
Selection torque (N·m) = power (Kw)×9550×(Coefficient of working condition +0.25) /rotate speed (rpm)

1.3 Primary selection of coupling model specifications
1.4 Selection validation
1.5 Determination of the coupling model specifications
1.6 Product mark

Examples of selection

2.1 General information
Motor rated power: 2500KW
Output speed: 995rpm
Input and output end distance: 1168mm
Coupling type: disc coupling
Surrounding environment: there is dust, etc
Nature of work: continuation
Tc=23994*1*2.5*1=59985（N·m）

2.2 Calculation of selection
According to the general information, the disc coupling should be chose for this project.
Selection & calculation
Theory toque calculation
T = 9550Pw/n = 9550*2500/995 = 23994 (N·m)
Computed torque calculation
Calculation formula: Tc = T·Kw·K·Kz
In this formula: choose 1 for Kw
choose 2.5 for K
choose 1 for Kz
Tc = 23994*1*2.5*1 = 59985 (N·m)

2.3 Primary selection of coupling model specifications
DT22 Disc coupling with joint pipe
Nominal torque: 64000 Nm
Meet the torque requirements
Primary selection of disc coupling with joint pipe DT22

2.4 Verification
① Hole diameter
Meet the requirements
② Rotary space(compared with on-site conditions)
There is no restriction to the max diameter of the on-site coupling.
This shall be regarded as it meets the requirements
③Allowable speed
The actual output speed of coupling is relatively lower 995rpm
Meet the requirements of allowable speed

2.5 Selected coupling model specifications
Choose the coupling model specifications with joint pipe DT22 220*L/190*L L1=1168

2.6 Marking sample
DT22 Disc coupling with joint pipe
DT22 220*L/190*L C=1168 with joint pipe    