Lubricating Cable Pulls - LV & HV

By Chris Dodds on 19th March, 2014

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Cable Pulling with Lubricant

Cable runs and cable pulling has been practiced for many decades but today the installations are more numerous, cables being put underground are heavier and the runs are often longer and more complex as the installations often have to follow the route of the roads in order to be installed where the way leaves exist.

Installation using modern cables also requires a trouble free installation with minimum stress on the cable. In no instance can the cable being pulled in be subjected to stresses in excess of its design stress or cable damage and premature ageing may result.

The heaviest cable stresses are experienced when a cable installation run is halted during installation and has to be restarted from a standing start. If a low voltage or high voltage cable pull requires restarting, when a substantial distance has already been pulled in, the full weight of the cable already installed has to be moved from a stationery position incurring maximum and often excess load stress on the cable, as the total weight of the cable can far exceed the acceptable design stress permissible.

Pictured: Lubricating Cable Pulls - LV & HV 

It is essential that once commenced a cable pull is completed without stopping in order that continuing momentum of the cable being installed can contribute to reduce stress keeping the cable always below its allowable design stress limit. Cable pull planning is essential in such installations and planning engineers work and plan installation runs to minimise cable friction during the pull.

Cable lubricants are used in order to ensure that minimum cable friction is experienced. Traditional cable lubricants have varied from oils to waxes, bentonite slurries and even washing up liquids have found favour in many countries. Each of these alternatives has value properties but also attendant potential flaws.

Today’s state of the art technology incorporates water-based polymer gels to replace the traditional product types. Water-based polymer gels such as the Techlube cable lubricant range from Socomore (formally PT Technologies Europe) have been designed specifically for underground ducted cable installations and incorporate properties specific to the needs of different installations and conditions.

Socomore cable pulling lubricants are all biodegradable and non toxic. This results in risk free installations when residues and spillages occur as they can be hosed to drain without fear of significant resultant pollution or risks of exposure to personnel in the field, using water.

Techlube products are tested for cable jacket compatibility. In many instances where specific lubricants are not specified by the Networks Authorities detergents such as washing up liquid are used to reduce friction. Many such products contain electrolytic salts which are used for viscosity enhancement or detergent properties.

These salts can have a detrimental effect on certain cable jackets resulting in cable jacket stress cracking. Electrolyte residues left on the cable after installation can result in earth tracking discharges, loss of cable efficiency, localised heating and premature cable failure under load.

All cable lubricants used by network authorities should be tested for Bellcore stress cracking or equivalent specifications standards of compatibility before being permitted for use by a contractor working on the network.

• Further reading :

Cable Laying & Pulling - Installing LV-HV Cable In Duct (Part 1 of 2) 

Cable Laying & Pulling - Installing LV-HV Cable In Trench (Part 2 of 2) 

 

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Category:  Cable Laying & Cable Pulling

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