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Southwire Pull Equation:
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The Southwire Pull Equation calculates the output tension (T_out) in cable pulling operations based on input tension (T_in), coefficient of friction (μ), and angle of bend (θ). This equation is essential for determining the forces involved in cable installation to prevent damage to cables and conduits.
The calculator uses the Southwire Pull Equation:
Where:
Explanation: The equation calculates how tension increases exponentially as cable is pulled around bends, accounting for friction and bend angle.
Details: Accurate pull tension calculation is crucial for preventing cable damage, ensuring safe installation practices, and determining the maximum allowable pulling tension for different cable types and sizes.
Tips: Enter input tension in lb or N, coefficient of friction (typically 0.1-0.5 for most cable/conduit combinations), and bend angle in radians. All values must be valid positive numbers.
Q1: What are typical values for coefficient of friction?
A: For most cable/conduit combinations, μ ranges from 0.1 to 0.5. Lubricated pulls typically have lower coefficients (0.1-0.3) while dry pulls have higher coefficients (0.3-0.5).
Q2: How do I convert degrees to radians?
A: Multiply degrees by π/180. For example, 90° = 90 × π/180 = π/2 ≈ 1.5708 radians.
Q3: What is the maximum allowable pulling tension?
A: Maximum tension varies by cable type and size. Consult manufacturer specifications, but generally ranges from 0.008 to 1.0 lb per circular mil of conductor cross-section.
Q4: Does this equation account for multiple bends?
A: For multiple bends, calculate tension sequentially, using the output tension from one bend as the input tension for the next bend.
Q5: When should I use this calculation?
A: Use this calculation for any cable pulling operation involving bends to ensure you don't exceed maximum allowable tensions that could damage the cable.