Repairing Damaged Cables, Cable Sheath & Jackets

Published 04 May 2018

Repairing Damaged Cables

A Solution To Repairing Damaged Cables | LV MV HV 11kV 33kV | Onshore & Offshore

Cable Repair

Earlier this year the UK government unveiled a total phase-out plan for coal-fired power plants. No big gasp there – cast your mind back to April 22nd 2017.

On that monumental date forever etched into the memories of energy analysts from Black Thunder to Kamuthi, Britain went 24 hours without turning on its coal-fired power stations for the first time in more than 130 years.

The share of power from the fossil fuel fell to zero for the first time since 1882 – the UK will be 100% coal-free by 2025.

King Coal has been unthroned and the new Clean & Green monarchs of UK Power have been coronated – bucket-wheel excavators please make way for the nacelle.

So welcome to the 21st Century – we are going greener faster with low carbon energy including wind and solar power generation overtaking both fossil-fuel and nuclear in the UK electricity source mix.

Despite this the engineering challenges facing Humankind of building, operating and maintaining LV HV power system infrastructures remain.

Without power distributed by electrical cables the wind turbine blades would stand as still as the motionless mine shuttle car.

Their common enemy is withdrawal of safe and reliable power distribution and this depends upon the integrity of electrical power and the monitoring and maintenance of cable condition and ensuring service is not disrupted by cable failure – the early warning system of potential looming power problems is the Cable Sheath or Jacket.

Cable Sheath

Image: Nexans

Repairing The Cable Sheath or Jacket

The cable sheath is the first line of moisture, mechanical, flame, fire, hydrocarbon and chemical defence for any cable – whether LV (low voltage), MV (medium voltage) or HV (high voltage), onshore or offshore, underground or overground.

Cable damage to the outer sheath is commonplace for aged or newly installed cables – whether unavoidable during normal service life or accidental strike by 3rd party.

Cable strikes are generally caused by non adherence to HSG47 while excavating underground cables with digging machines such as JCB, track machine or mini excavator.

Multi-disciplined contractors failing to observe the separation between underground utilities (electrical cables, gas or water pipes) often leads to cable strike. Moling devices set in the direction of underground electricity cables (often waveform or PILC main cables) not only leads to loss of electricity supply but also serious injuries.

Failure to maintain and observe accurate cable records during utility upgrades such as installing drainage apparatus further impacts upon cable damage. In conclusion, most utility LV cable strikes could be avoided if strict adherence to HSG47 is implemented.

Cable Damage - LV Cable Repair

LV Power Cable Strike Caused By Excavator – highlights dangers of using mini excavator in close proximity to a low voltage cable. Image : Scottish Power Energy Networks (SPEN).

Cable Repairs HSG47

Purchase HSE HSG47 Avoiding Danger From Underground Services

Cables are often damaged during the cable pulling process as cable sheathing is vulnerable to “snagging” damage from cable containment – where cables are being pulled into underground cable trenches the cable sheath can be damaged by surface abrasion from stones and rocks.

Cable Repair Solution

However damaged cable sheaths and jackets can be repaired and re-instated on site using heat shrink cable repair sleeves – watch the following video to learn the step-by-step process for reinstating insulation and protection to repair damaged cables and sheaths.

Video : HellermannTyton RMS – Cable Repairs Sleeve For Damaged Cable

Hellermann Tyton Cable Repair RMS : Features & Benefits

  • Fast, moisture proof and permanent repair of cable jackets and sheath LV MV HV
  • Only 6 sizes for a wide range of cable diameters from 15 mm up to 160 mm
  • Available in 4 standard lengths and also available in custom lengths of heat shrink
  • RMS kit is ready for use with instruction sheet, abrasive strip and cable cleaner
  • Weather resistant and halogen free cable repairs
  • TCP spots indicate the repair sleeve has been sufficiently heated

Heat Shrink Cable Repair - Hellermann Tyton

Hellermann Tyton RMS cable repair sleeves suit cable sheath outside diameters from 15-160mm. The wrap around sleeves are a fast, labour saving and permanent cable repair and water-tight sealing system – this includes repairing damage to the cable sheaths and jackets of LV MV HV cables.

The sleeve is simply wrapped around the cable and held in place using a rail and steel channel closure to provide a quick and inexpensive repair to in-stu damaged cables – cable repair sleeves are especially useful for repair of long and buried cables where it would be difficult or impossible to use a heat shrink tubing.

The wrap-around design (“lay-flat”) of the cable repair sleeve enables mid-span or mid-circuit repairs without resort to disconnecting the remote end of cable circuit at the cable termination point and cable gland location.

Heating by a gas torch will shrink the repair sleeve and melt the adhesive inner coating resulting in a moisture-proof, insulating and tight-fitting repair. The cable sheath repair will be permanent and waterproof.

Damage to the red cable sheaths of 11kV high voltage power cables can be made quick and fast – cable sheaths can be further degraded due to exposure to gases and emissions from diesel generator exhaust systems and this can be averted by heat shrink sleeve repair.

Cable Repair

Wrap heat shrink sleeve around the damaged cable.Install the steel closure channel over the raised profiles of the sleeve and centre the heat shrink sleeve over the damaged area before applying heat 

 ➡ Some Installation Tips When Repairing Damaged Cables

  • to ensure excellent sealing of the heat shrink onto the cable jacket use abrasive cloth strip to roughen the cable sheath jacket
  • wrap heat shrink sleeve around the cable and install the steel closure channel over the raised profiles of the heat shrink sleeve and centre the repair sleeve over the cable damage section
  • use yellow flame tip of a suitable heat shrink propane torch – start heating the metal channel area first for about half a minute
  • start heat shrinking the sleeve at the centre working the flame around all sides of the cable sleeve to apply uniform heat.
  • keep heating flame moving consistently to avoid scorching cable – after the centre part has shrunk work the torch to one end of the heat shrink sleeve then to the opposite end
  • when selecting cable repair sleeves choose the sleeve length so that the cable next to the damaged area is covered by at least 40mm of heat shrink sleeve length
Heat Shrink Cable Repair Sleeves For Damaged Cables

Heat Shrink Cable Repair Sleeves For Damaged Cables

Heat Shrink Cable Repair Sleeves - Hellermann Tyton RMS

Cable Repair Kit: Heat shrink wrap-around sleeve, steel closure, abrasive strip, cable cleaning sachet and instruction sheet

Offshore Cable Repairs

Cable repair kits are commonly used to repair offshore cables and prevent corrosion effects to steel wire braided or wire armoured cables which can rust rapidly in humid conditions and accelerate with exposure to salt water atmosphere, splash or immersion.

Flexible and trailing cables for ROV equipment and offshore pump systems can be spliced, jointed or repaired using 3M Scotchcast submersible cable joints which are flexible, flame retardant with seawater resistant resins compatible with EPR, neoprene, hypalon, PVC and nitrile cable sheaths.

There is direct causation between the type of cable maintenance approach and unplanned downtime.

Careful monitoring of cable condition carves down unplanned downtime whether onshore or offshore – the predictive maintenance approach is better than routine or preventative maintenance and this trumps the reactive PANIC as a result of “sit back and wait”.

Offshore cables are exposed to extreme and continuous operating environments – this includes temperature extremes, mechanical stress, gassy chemicals, hydrocarbons, drilling mud and seawater atmospheres. Not to mention the Weather…..

…..and what about potentially explosive atmospheres where “hot-working” is precluded. Heat shrink cable repairs cannot be safely effected in the presence of naked flames and flammable gases.

In this instance you can benefit from reading our earlier Blog about repairing and jointing cables in hazardous areas as defined by the ATEX Directive.

Down well hole extraction systems are vital to crude oil production.

The reliability of electrical down well pump systems is directly dependent on the performance of the electrical power supply and cable integrity through to the wellhead, power cable, cable joint, termination and related equipment such as the pump and motor.

Unplanned downtime of essential assets caused by offshore power outages in the oil and gas sector as the result of maintenance oversight requires rapid intervention and power restoration at the lowest possible cost.

Financial hits to the bottom line as a result of cable outage inflicted by failure to repair damaged cables include the repair cost (calculable) as well as those consequential and often hidden costs associated with lost or deferred productions (often incalculable).

Heat shrink cable repair sleeves provide a low-cost, simple to install and use solution to damaged cable problems.

If electrical power is the lifeblood of an offshore platform then the cable must be the main artery.

If neglected overtime damaged cables lead to cable failure.

Repair Damaged Cables Offshore 11kV

Here abrasion damage has been inflicted to the MV power cable sheath exposing the wire braid in an offshore transformer and is need of urgent cable repair or re-jointing.

Repair Or Replace Cable?

Answering the Cost Conundrum

Nose-diving global oil prices inevitably places downward pressure on operating margins and in turn operators dictate that maintenance work is conducted at the lowest possible cost.

The Big Conversation between North Sea operators, national regulators and industry experts in recent years has been consumed by a trend for declining production efficiency, lost revenues and questions over the long-term sustainability of oil and gas operations as costs continue to rise in one of the world’s most mature offshore regions.

Preventative maintenance would usually detect “wear and tear” on cable installations and depending on condition would be replaced, repaired or in worst cases scenarios jointed.

The hardening trend towards “cost-cutting” often delivers a patch-up repair in pocket areas of cable degradation and not scaled to complete circuits as part of a more holistic concept of cable care and repair.

Oil prices fell almost 50% between 2015 and 2014, averaging $52 per barrel in 2015 compared to $99 in 2014, according to the Energy Information Administration.

Offshore Cable Repairs

In 2015 US benchmark West Texas Intermediate (WTI) ended July on its biggest monthly fall since the 2008 financial crisis during July.

  • West Texas Intermediate (WTI), also known as Texas light sweet, is a grade of crude oil used as a benchmark in oil pricing.
How Much Does Downtime Cost

According to a recent report by GE Oil & Gas “The Impact of Digital on Unplanned Downtime” the major costs linked to unplanned downtime are shown below- the report informed “when looking at repair costs, the typical offshore oil and gas field worldwide most often incurs expenses resulting from unplanned downtime in the areas of repair costs (71%), followed by labour costs (40%) and transportation/logistics (37%). 

Repairing Offshore Cables

Offshore Cable Repair

Offshore high voltage cables (5kV ESP Cable) requiring outer sheath repair to damage caused by abrasion contact with adjacent pipe supports. The cables feed the platforms Electrical Submersible Pumps. Image : Statoil.



Cable Damage Cable Trench Cable Repair

Damaged green cable duct and Virgin Media cables from the street cabinet feeder pillars.


Should you require any assistance with the jointing, termination or repair of power LV-HV cables please do not hesitate to contact us to discuss your application.


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