Cable Pulling Calculator

Section by section along the route, starting from the back tension at the reel. A straight adds the friction of the cable's weight, T = L × W × K' × g. A bend multiplies the tension entering it by e^(K'θ), so bends late in the pull, where the tension is already high, add the most. Slopes add or remove the weight component along the slope (IEEE Std 1185-2019 Equations 5 to 12).

The force per metre the cable presses against the inside of a bend, roughly the tension divided by the bend radius. Too much crushes the insulation. Each bend is checked against the cable's allowable sidewall pressure, the calculator starts at 7300 N/m, a common figure for power cables, but use the manufacturer's rating.

With more than one cable in the conduit the cables wedge against each other and the wall, which raises friction. The weight correction factor Wc multiplies the coefficient of friction: for three cables, cradled or triangular depending on the conduit-to-cable diameter ratio (IEEE 1185 Equations 16 and 17), for four a diamond (Equation 18), and 1.4 for more.

Usually from the end nearest the bends, so the bends see the tension while it is still low. The calculator works the route both ways; switch the pull direction to compare the maximum tension and sidewall pressure.

It depends on the cable jacket, the conduit and the lubricant; well-lubricated pulls are commonly worked at 0.2 to 0.5. Use the lubricant manufacturer's figure for your cable and conduit where you have it; the calculator starts at 0.3.