The problem of redundant oil-filled cables

Oil filled electricity cables have been put underground since about 1960 in the U.K. These cables can prove to be a logistical and environmental problem if left in the ground still full of insulation oil after decommissioning. The insulation oil may eventually leak from the cables and enter the surrounding land and water courses due to natural stress from ground movements, failure at the joint between two cables or third party damage (excavations, civil work etc).


Gilmerton Land Services (GLS) specialise in the safe and efficient removal of the insulation oil. The previous standard procedure has been to blow the lines with nitrogen but this only removes a small percentage of the oil, mainly from the oil duct and not from the actual insulation papers themselves, where the majority of oil is trapped. In treating redundant/de-commissioned cables, The GLS has designed a solution using compressed air and vacuum pumps to remove the oil form the cable systems.

GLS have worked with Scottish Power and National Grid on a number of projects to remove the oil and environmental liability from their Fluid Filled Cables.

The GLS System is designed to remove as much free flowing liquid as possible, using mechanical fittings that are connected directly onto the cable system, with engineered air lines and continuous pumping maintained during the process. The cable is purged in sections to maximise the recovery of oil for recycling and remove the environmental liability. The GLS air purging system allows for the cable to be recovered safely and efficiently and maximize the recycling targets of the project.

Why Use the GLS Air Purge Systems?

By removing the oil form the high voltage cables using the Air Purge Systems you are not introducing any other contaminants into the cable oil which will need to be separated off at great expensive.

Cost savings are archived following the environmental liability being removed and the cable being able to be recovered and a credit paid to the client. GLS have utilised the air purge system for over twenty years and successfully removed insulting oil from 132kv circuits at Kincardine and Ferrybridge power stations along with numerous other successful projects.

The oil removal system is simple and easy to set up with minimal resource required which in turn reduces the costs which enables the client to deliver a more cost efficient project. In most cases a credit can be issued for the cable and oil removal.

The Air Purge Systems is extremely safe. It has already been subjected to a number of safety and environmental tests over the years with ongoing internal and external audits completed successfully.

GLS understand that every project is different and that cable properties and specifications vary. GLS are able you use their 45 years of cable recovery and decommissioning to deliver the right solution to enable the environmental liability to be safely removed.

The Benefits of Air System Purging

  • Cost savings are achieved once the underground cable circuits have been Air purged as they no longer need to be alarmed and monitored.
  • During the purging process, oil lines are quickly emptied and the cable directly purged.
  • We can also work non-intrusively using existing oil line connections, sealing ends etc.
  • The Air Purging causes the least possible environmental impact during the working progress. It does not create additional waste streams as the cable oil is recovered uncontaminated for recycling, unlike expensive chemical methods which need to be separated off following the completion of the purging.
  • Our process involves portable equipment which avoids the need to set up permanent sites at the various work locations. This means we are able to work in locations that would normally be very problematic and cause major disruption to the traffic and the community.