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Cable Socks – Technical Guide for Safe Cable Pulling Using Cable Socks

Published 21 Mar 2018

Cable Socks

Thorne & Derrick | Cable Laying & Pulling Equipment Distributors | LV MV HV

  • Uploaded By Chris Dodds – Thorne & Derrick Sales & Marketing Manager

Cable socks, sometimes called cable stockings or cable grips provide an efficient method of supporting cables for pulling and laying into open-trench or duct –  this includes LV Low Voltage, MV Medium Voltage or HV High Voltage cables.

The correctly sized cable sock can be used to pull in short lengths of cable by hand (e.g. fault repairs prior to jointing).

Cable socks are re-usable tools (subject to inspection before re-use) and are not confined to cable applications but basically can be used to support or pull any cylindrical object within their grip and load carrying capacity.

Standard cable socks are manufactured from high tensile galvanised and stainless steel wire rope or Kevlar.

A skilled, hand woven construction process, coupled with individual product inspection throughout manufacture ensures a high quality product for reliable and long lasting application.

UK DNO’s generally specify according to their Engineering Standards that all pilot and telephone, LV, 11kV, 20kV, 33kV, 66kV and 132kV cables shall normally be pulled in using a correctly sized cable socks which are securely fixed to the cable. More difficult pulls may require the use of a pulling eye attached directly to the cable conductors, which has been installed by the manufacturer – cable rollers shall always be used when pulling cables.

LV MV HV

Further information on the main ranges according to voltage application for underground power cable pulling or overhead line stringing can be found here:

Cable Socks

WL & FOS

The Working Load (WL) of a cable sock depends on the Factor of Safety (FOS) applied to the Minimum Breaking Load.

For example, where the operational risk is considered to be normal, it is recommended that a FOS of 5 be applied, for high risk operations a FOS of at least 10 should be considered.

The Approximate Breaking Load stated on any certification, the recommended Factors of Safety, and any implied or stated fitness for purpose, are all only applicable when the cable socks are new and unused.

There are many factors that the person using the cable sock must take into consideration when trying to calculate a safe working load as it is impossible to guarantee a suitable safety factor when there are many variables which change from cable pulling application to application.

In addition, before using any cable sock, the user must carry out a full assessment of its suitability for the proposed application, and the level of operational risk involved, including taking account of:

  • size of the cable sock, in relation to the size and shape of the gripped cable
  • stability of the cables when gripped
  • grip surface of the cable
  • anticipated path of movement, including possible obstructions
  • resistive force of the cables being pulled
  • minimum-breaking load (MBL) of the cable sock
  • condition of the cable sock
  • suitability and compatibility of any cable pulling attachments used
  • environment / operating conditions

When selecting the cable sock users must allow for a 20% variance in break loads and, if there is ‘twist’ in the cable, a suitable swivel link must be used.

When the correct cable sock is selected, cable installation through cable ducts, conduits and trenches is made considerably easier. The cable sock adds little to the overall diameter of the cable and ‘free passage’ is normally available through sheave blocks and pipes.

Cable socks can often be used on a ‘new for old’ cable replacement by applying two grips on a ‘back-to-back’ basis with a solid link or swivel in between grips, allowing the old cable to be used to pull through the new replacement.

Swivel links can be used to allow for reduced torque build-up induced by the cable pulling equipment and inherent lay in the cables themselves, whether LV, MV, HV or EHV. Lace up cable socks can be applied anywhere along the cable length, preventing overloading of the cable.

To prevent winched cable pulls exceeding the maximum tension force of the cables, a cable sock fitted with a swivel can be used to connect the bond to the cable and a dynamometer used to check that the maximum pulling tension for the cable is not exceeded.

When pulling cables by mechanical cable winch, the load-limiting device must be used to ensure that the pulling tension applied to the cable does not exceed the manufacturers specified maximum permissible tensions. The pulling of cables by direct and unmonitored mechanical means (e.g. hitched to a vehicle, Land rover winch) is not permitted.

Several UK DNO’s including Northern Powergrid, specify in their Policy for the Installation of Distribution Power Cables that cable pulling by winch shall only be carried out where there is a serviceable and accurate dynamometer calibrated in kgs.

Cable Socks – Typical Applications

  • Power cable pulling – LV MV HV
  • Overhead house service cables
  • Portable tool supply cables
  • Portable compressed air lines
  • Conduit risers
  • Moveable hydraulic hoses
  • Cable strain relief
  • Oil support cables
  • Marine applications
  • “Guy rope” adjusters
  • Fibre optic cable applications

Pulling Overhead Power Line Conductors Using Cable Socks

According to the Ericsson Universal Cable Handbook the most critical moment in the pulling out operation is when the cable end and cable sock passes through the line roller or suspension clamp. To make the pulling out easier the cable end should be “sectioned down” at the end before the cable sock is applied.

Between 150 – 200 mm/core is enough, see figure below.

Cable Socks

This will make the end smoother and more flexible when it passes the cable pulling devices.

If a cable sock of Kevlar is used this is more important as it is soft and does not form a natural cone the same as a galvanised steel cable sock. The cores can also be cut with a knife to avoid sharp edges which will simplify the pulling even more.

Type of Cable Socks

Single Eye Socks – available in single or double weave.

Double Eye Socks – standard support sock, with double eye. Available in single or double weave.

Lace Up Socks – cable sock for fitting at points along the length of a cable.

Open Ended Socks – socks designed to enable two cables, hoses or ropes to be connected for pulling or supporting purposes.

Single Eye Socks (Triple Weave) – high strength cable socks with heavy duty shoulders, for stringing or pulling-in non-insulated conductors on long, high voltage transmission lines, or other high load applications.

Cable Socks

Single Eye | Double Eye | Lace Up | 11kV 33kV Triplex Cable Socks

Note : Cable socks must not to be used as primary lifting devices.

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Cable Pulling & Cable Laying Equipment Suppliers & Distributors

Thorne & Derrick International distribute the most extensive range of Cable Pulling & Cable Laying Equipment to enable the installation of low, medium and high voltage power cables into underground trench or duct – products also supplied for fibre optic blowing, subsea trenching, offshore umbilical installations and pulling armoured cables onto cable tray.

Contact us for 3M Electrical, ABB, Alroc, AN Wallis, CATU Electrical, Cembre, Centriforce, CMP, CSD, Elastimold, Ellis Patents, Emtelle, Euromold, Filoform, Furse, Lucy Electric & Zodion, Nexans, Pfisterer, Polypipe, Prysmian, Roxtec, Sicame, WT Henley.

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