Cable Installation: Bending Radius, Pulling and Storage

How should cable drums be stored and handled?

Store drums upright on firm ground, chock them so they cannot roll, and protect both cable ends from moisture and dirt. Uncontrolled rolling can damage drum flanges and the cable on the drum, and prolonged standing water around the drum can damage the cable ends and the drum itself.

• Roll and lift drums only by approved methods.
• Confirm drum dimensions and unloading equipment before delivery, so the drum can be moved safely on site.
• Keep the cable ends sealed during storage, not only during the pull.
• Avoid prolonged standing water around the drums.

How do you prepare the pulling route?

Inspect the whole route before the pull starts. Check conduits, rollers, bends and tray edges for obstructions, rough surfaces and damage. Long or complex routes need the pulling tension and sidewall pressure calculated in advance, not estimated on site. Use suitable pulling eyes, stockings and lubricant for the cable construction. For how drum packing and shipping affect the cable on arrival, see the drum packing and shipping guide.

What is the minimum bending radius, and does temperature change it?

The minimum bending radius is not one value that applies to all cables. It depends on the conductor construction and insulation, and on whether the cable is armoured or screened. Take the figure from the manufacturer's datasheet for the exact cable you ordered, and do not borrow a value from a different cable type.

Temperature matters because cold cable is less flexible. Follow the minimum installation temperature stated in the manufacturer's data. If the cable has been stored in cold conditions, confirm that it has reached that temperature before it is bent or pulled.

Armoured and screened cables need extra care at each bend. Excessive curvature can damage the armour wires or the screen layers, so the bending limit for the construction must be respected at every point on the route.

Which installation risks should you check, and where do the limits come from?

Pulling tension and sidewall pressure are the two forces most likely to deform the cable at a bend. Many installers check only the long straight section of a route. The final bend near switchgear often controls pulling tension, sidewall pressure and the minimum radius, so model the complete route and the terminal approach before the pull begins.

Limits differ by cable construction and project. Use the values in the manufacturer's installation data and the approved method statement, not general figures.

How should the cable be pulled safely?

Position all rollers before the pull begins, so the cable runs freely over each one. Monitor the pulling force where the method statement or the cable data requires it, and stop to investigate if the force approaches the stated limit. Keep the pull steady rather than jerking the cable through bends.

• Position rollers before the pull starts.
• Use pulling eyes, stockings and lubricant suited to the cable.
• Monitor pulling force where required by the method statement.
• Check sidewall pressure at the bends, especially the final one.

What should be checked after installation?

After the pull, inspect the sheath for scrapes, cuts and other damage, and verify phasing and identification of every core. Complete the electrical tests specified for the project, and seal all entries as described in the gland guidance. For how glands are chosen to suit the installation, see the cable gland selection guide.

Record the installed drum numbers and route data. These records help maintenance staff later, because they show which drum was used, how the cable was routed and what tests were completed.

Frequently asked questions