Cable Pulling – Preparing Cable For Pulling When Installing Into Ducts


Cable Pulling – Preparing Cable For Pulling When Installing Into Ducts

By Jack Nottidge, Thorne & Derrick

Thorne & Derrick are the UK’s leading distributor of Cable Pulling Equipment.

T&D service utilities, power, construction, rail, mining, street lighting, subsea, offshore, oil, gas and petrochemical industries.

Cable Pulling Equipment enables the installation of low and high voltage power, fibre optic, telecoms, subsea cables and umbilicals into cable duct or cable trench.

In this first of 2 guest blogs about cable pulling, T&D look at the preparation for cable pulling when installing cables into ducts. In the second blog T&D will discuss the typical equipment layout for pulling cables into open trench (underground).

Preparing For Cable Pulling Into Ducts

Cables installed into underground cable ducts are typically used on projects where the cable duct is buried deep into the ground, sometimes up to 1200mm. This is to provide adequate protection for the duct and therefore the cables which are often high voltage and potentially hazardous if inadequately protected or incorrectly pulled into the duct.

Due to the nature of the cables that are often installed in these applications, there are a number of checks that must be carried out prior to beginning the cable pull:

·         The duct lines must be checked for any obstructions and anything that is found must be removed. This is often done with the use of duct brushes or ‘foam pigs’ which are pulled through the cable duct.

·         It is essential to ensure that the cable duct is of adequate size to accommodate the cable to be pulled. This is done by pulling through a 3 metre length of cable through the duct which is subsequently checked for damage prior to the full cable being installed.

·         If, during these checks, the 3 metre length of cable has any damage greater than half the depth of the outer sheath the duct route must be repaired before the full length cable is pulled through. This protects the integrity of the final cable. 

The Equipment Used For Cable Pulling Into Ducts

Various equipment must be used when installing cables into underground cable duct.  Cables can vary in size and voltage however the same process and equipment is used.

When installing cables, there is typically up to 9 different pieces of cable pulling equipment used :

1         Cable Winch– The cable winch is used for physically pulling the cable through the duct, reducing the need for manpower and increasing productivity. Electrically powered, the cable winch is much safer and reliable than manually pulling cables through the duct.

2         Rope Guide Roller– The rope guide roller is exactly as the name suggests – a roller to guide the draw ropes or cabling ropes that are coming out of the jointboxes or manhole. This is to reduce the damage and strain put on the ropes therefore pro-longing the lifespan of the equipment used.  The rope guide roller is made from an aluminium roller mounted onto a frame that has been plated with zinc.

3         Bellmouth – The bellmouth is used as a means of providing additional protection to the cable when it is being pulled through the duct. The rollers on the bellmouth ensure that the cable can be pulled in any required direction without any damage being caused.  The bellmouth is located at the exit of the cable duct through which the cable is being pulled.

4         Cable Drum Trailer Or Cable Jacks– The cable drum trailers and cable jacks are used as a means of storing and transporting cable drums. Cable drums are large wooden wheels which are used to hold cable. Cable drum trailers make the transportation of extremely heavy cable drums easier, safer and more reliable.

Often equipped with braking and road lighting, the cable drum trailers are attached to the back of an appropriate vehicle to assist in the transportation of cables. Cable jacks (hydraulic or screw type) are used as a means of supporting, stabilising and lifting the cable drums.

Cable drums are located at the edge of the manhole cover or opening when installing cable into underground ducts for the cable to be easily rolled off.

5         Swivel Link– The swivel link is a zinc plated, solid steel link that is attached to the winch rope. This link can, as the name suggests, swivel a full 360° allowing the rope to be pulled through without any twists occurring.

6         Conduit Rod–The conduit rod is fed through the manhole cover opening and is used to install draw or winch ropes. The conduit rod is manually fed through the underground duct and is extremely easy to handle. The conduit rod comes with a range of cable pulling accessories available such as flexible guide tips, end connectors and rod repair kits.

7         Cable Socks– Cable socks can also be called cable stockings or cable grips. These are used to support the pulling of cables through a duct. Attached to the end of a cable prior to pulling, the cable stocking is an efficient method of support when pulling the cable.

8         Manhole Roller– The manhole roller is specifically designed to be placed at the entrance of the manhole to assist in the guiding of the cable. Not only does the roller make the cable installation easier, it also protects the cable from being scraped on the edge of the manhole. The manhole roller is constructed of a steel frame and aluminium rollers.

9         Cable Lubricant–Cable lubricant is applied to the outside of the cables when being pulled through the duct. The lubricant assists in the pulling process by removing friction between the cable and the cable rollers. This not only speeds up the process but also prevents snagging and therefore damage to the cable.

Thorne & Derrick UK are distributors of LV-HV Cable, Installation, Cable Jointing & Electrical Equipment – we service UK and global businesses involved in cable installations, cable jointing, earthing, substation and electrical construction at LV, 11kV, 33kV and EHV. T&D service utilities, power, construction, rail, mining, offshore, oil, gas and petrochemical industries.T&D distribute Electrical Safety Equipment protecting workers on underground cables, overhead powerlines, switchgear and substations at LV, MV and HV. 

Part 2 – Pulling Cable in an Open Trench

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