Heavy-duty tension and sidewall pressure calculator. Features IEEE 1185 Weight Correction Factors ($W_c$) for triangular/cradled cables, jamming probability detection, and dynamic routing (Straight/Bend/Vertical) for complex industrial pulls.
When a cable is pulled through a bend, the tension increases exponentially due to the "Capstan Effect". Friction is amplified by the normal force against the conduit wall.
Where $\theta$ is the angle in radians, $\mu$ is the coefficient of friction, and $W_c$ is the Weight Correction Factor.
For multiple cables pulling in a single conduit, the weight is not evenly distributed. The **IEEE 1185** standard provides factors to account for the increased side-wall friction caused by "wedging" effects.
SWP is the radial force exerted by the cable on the conduit wall during a bend. Excessive SWP can crush the jacket and insulation. Typical limit is **1,000 lbs/ft** for power cables.
Recommended Practice for Cable Installation in Generating Stations and Industrial Facilities. Defines $W_c$ and SWP calculations.
Specification for Extruded Dielectric Shielded Power Cables Rated 5 through 46 kV. Sets the baseline for mechanical stress limits.
Insulated Cable Engineers Association guide for pulling tensions and side-wall pressure limits for power cables.
A: Sidewall Pressure (SWP) at the first or last bend is usually the limiting factor. Excessive SWP damage happens internally and isn't always visible.
A: If the ratio of Conduit ID to Cable OD is between 2.8 and 3.1, the cables can "wedge" or jam as they transition around a bend, potentially stopping the pull entirely.
A: Proper lubrication can reduce the coefficient of friction ($\mu$) from 0.5+ to 0.15-0.20, reducing total tension by 60% or more.
A: Generally, pull from the end closest to the sharpest/most bends. This minimizes the exponential tension build-up over the longest run.
A: Yes. In vertical rises, you fight gravitational weight directly ($W \cdot L$). In vertical drops, weight actually assists the pull, though back-tension is required for control.
A: Standard power cables (XLPE/EPR) usually have an SWP limit of 1,000 lbs/ft. Some ruggedized cables can handle more, while others (like instrumentation) are much lower.
A: It accounts for the actual contact points. In triangular pulls, cables are squeezed together, increasing the normal force relative to a single cable, thus increasing friction.
A: Total tension is cumulative. Each bend multiplies the incoming tension exponentially ($e^{\mu \theta}$). Avoid more than 360° of cumulative bends if possible.