Southwire Pulling Tension Calculator

Southwire Pulling Tension Formula:

\[ T_{out} = T_{in} \times e^{\mu \times \theta} \]

Output Tension (T_out):

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1. What is the Southwire Pulling Tension Formula?

The Southwire Pulling Tension Formula calculates the output tension when pulling cable or wire through conduit, accounting for friction and bend angles. It's essential for determining the required pulling force and ensuring safe installation practices.

2. How Does the Calculator Work?

The calculator uses the Southwire formula:

\[ T_{out} = T_{in} \times e^{\mu \times \theta} \]

Where:

\( T_{out} \) — Output tension (lb or N)
\( T_{in} \) — Input tension (lb or N)
\( \mu \) — Coefficient of friction (dimensionless)
\( \theta \) — Angle of bend in radians
\( e \) — Euler's number (approximately 2.71828)

Explanation: The formula accounts for the exponential increase in tension due to friction as the cable passes through bends in the conduit.

3. Importance of Pulling Tension Calculation

Details: Accurate tension calculation is crucial for preventing cable damage during installation, ensuring worker safety, and complying with electrical code requirements for maximum pulling tensions.

4. Using the Calculator

Tips: Enter input tension in lb or N, coefficient of friction (typically 0.15-0.5 for lubricated pulls), and bend angle in radians. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What are typical values for coefficient of friction?
A: For lubricated cable pulls, μ typically ranges from 0.15 to 0.5, depending on the cable type, conduit material, and lubricant used.

Q2: How do I convert degrees to radians?
A: Multiply degrees by π/180. For example, 90° = 90 × π/180 = π/2 radians ≈ 1.5708 radians.

Q3: What is the maximum safe pulling tension?
A: Maximum tension depends on cable type and size. Generally, it should not exceed 0.008 × n × CMA (circular mil area) for copper or 0.006 × n × CMA for aluminum.

Q4: When should I use this calculation?
A: Use for planning cable pulls through conduit with bends, especially in commercial and industrial electrical installations.

Q5: Are there limitations to this formula?
A: The formula assumes constant friction coefficient and doesn't account for weight of the cable or multiple consecutive bends with straight sections between them.