Pulling Tensions
Given the amount of tension on cables going into a section of conduit (T1), the following equations determine the amount of tension on cables coming out of the conduit section (T2).
In subsequent sections of conduit, T, of a preceding section of conduit is T1 of the next section of conduit.
- T2 = Outgoing tension (lb)
- T1 = Incoming tension (lb)
- L = Length of conduit section (ft)
- K = Effective coefficient of friction (dimensionless)
- W = Total weight of cables (lb/ft)
- T = Offset angle (degrees)
- e = Base of natural logs (2.718)
- a = Bend angle (radians) (see table below)
|
Degrees |
Radians* |
|---|---|
|
11.25° |
.196 |
|
22.50° |
.393 |
|
30° |
.524 |
|
45° |
.785 |
|
60° |
1.047 |
|
90° |
1.571 |
* 1 radian = 57.30°
|
A. For straight horizontal pulls: 
|
T2 = T1 + LWK |
|
B. For straight upward pulls: 
|
T2 = T1 + LW (sin T + K cos T) |
|
C. For straight downward pulls: 
|
T2 = T1 - LW (sin T - K cos T) |
|
D. For horizontal, upward, or downward pulls around bends: 
|
T2 = T1 eKa |