Overcoming Cable Corrosion On Steel Wire Armoured & Braided Cables
Published 28 Jan 2019
uploaded by Chris Dodds - Thorne & Derrick Sales & Marketing Manager
Solutions To Cable Corrosion
3M Electrical Products provide an extensive range of cable repair solutions to prevent and overcome cable corrosion for the utilities, power, solar, construction, rail, mining, offshore, oil, gas and petrochemical industries – cable corrosion tapes and protection products are available to suit both direct burial (underground) and cables located onto containment in both indoor and outdoor installations.
Cable repair solutions are available for low and medium voltage cables suffering advanced cable damage caused by atmospheric steel corrosion – both onshore and offshore galvanised steel wire armoured and wire braided cables are especially vulnerable.
Formation of Rust
The overall chemical equation for the formation of rust is:
Iron + Water + Oxygen → Rust
Advanced Cable Corrosion & Degradation
The pictured low voltage cables evidently have serious damage caused by long-term cable corrosion effects. The cable sheathing has been aggressively damaged and stripped back down to the galvanised steel wire armours. Steel typically corrodes or rusts rapidly in moist or humid conditions and the rate of corrosion accelerates with exposure to salt water, for instance in the marine and offshore industry.
The cable sheath should provide both waterproof and corrosion protection to the steel wire armours and copper conductors – in this case there is an urgent demand to prevent further cable corrosion damage to both the accessible and inaccessible cables strapped and cable cleated to the cable tray.
The complexity of the cable repair is compounded two-fold : the area is a “no-heat” zone designated a hazardous area location Zone 2 according to the ATEX Directive therefore traditional heat shrink cable repair kits are precluded from consideration due to the presence of a potentially explosive atmosphere. Furthermore due to the brittleness of the cables, resultant from significant corrosion damage, it was not an option to man-handle and subject the cables to further physical movement and mechanical strain.
Chemical Corrosion of Cables In Industrial
& Hazardous Area Locations
Hydrocarbons in the onshore and offshore oil/gas exploration and production sector seriously impact upon the integrity and ability of cables and cable accessories to provide uninterrupted service – standard polyurethane cable repair and jointing products would overtime degrade to destruction in the presence of aggressive chemicals.
Consequently, 3M Electrical have developed a chemical resistant cable joint utilising their 1402FR resin for harsh and hazardous cable installation environments where hydrocarbon exposure is expected under normal conditions – the Scotchcast resin cable joints have been adopted as specification standard by international oil and gas companies including Exxon Mobil, Chevron, Total and Royal Dutch Shell.
Cable Corrosion – 3M Solution
2 solutions to suppress future cable corrosion using 3M Electrical cable repair products :
- Accessible Cables – 3M Scotchrap 50 Tape provides advanced corrosion protection to cables exhibiting excellent resistance to abrasion, moisture, corrosive salt water, soil acids, alkalis and salts.
3M Scotchrap tapes are UV resistant and also resist impact punctures and tears with a very high weather and corrosion proofing performance for use on underground cables.
3M Scotchfil Electrical Putty can also be used to build-up irregular surfaces to provide a smooth, waterproof taping surface around cables where there is localised pitting type corrosion.
Scotchfil putty provides a versatile corrosion resistance solution to general cable and electrical equipment applications, the Scotchfil putty can be wrapped, stretched or moulded to conform to both standard and irregular surfaces.
3M Scotchfil Electrical Putty when over wrapped with either Super 33+ or Super 88 Vinyl Electrical Tape. Scotchfil™ electrical putty can also be used to build up cable joints and fill out major irregularities and voids.
- Inaccessible Cables – where cable access is limited 3M 1603 Insulation Spray can be used to protect cables and surfaces (including galvanised steel cable tray) against weather, moisture, corrosion, oil, alkalies and acids. 3M 1603 sprays provide easy access to hard-to-reach spots. eabling versatile on-site cable repairs without specialist tooling or requirement to disconnect or isolate cable circuits. 3M insulating spray sealers to spray over insulation on wire and cable splices, as a general-purpose sealer, or for touch-up insulation on motor windings and frames. Precautionary and first aid information for this product may be found in its Material Safety Data Sheet and on the product container.
Another type of cable failure is evidenced by visual indication of burning or arcing on the surface of the semiconductive layer of medium voltage cables. If the burning or arcing becomes extensive, the MV cable can fail from the outside in (pictured below).
The MV cable failure cause was determined to be a damaged cable sheath or jacket, which created a flowpath for corrosive ground water to penetrate the cable and cause severe corrosion to the metallic shield.
Scotch 70 silicone rubber electrical tape is a high temperature arc-and track-resistant tape composed of self-fusing, inorganic silicone rubber and easy-tear and easy-strip liner – the Scotch 70 tape is used as an over-wrap for protection of high voltage terminations and cables against arcing and tracking.
Some Further Reading : Corrosion Types Encountered With Power Cables : Underground Cables and Anodic Corrosion (Stray DC Currents), Cathodic Corrosion, Galvanic Corrosion, Chemical Corrosion, AC Corrosion, Local Cell Corrosion. By Edvard Csanyi (Electrical Engineering Portal EEP).
Whatever the cable condition or type of installation, 3M can provide innovative cable corrosion protection solutions based on Scotch electrical tapes, Scotchcast resin, heat shrink, cold shrink or spray based technology.
LV Cable Joints (Low Voltage Cables)
Thorne & Derrick stock and distribute LV Joints in Cold Shrink, Heat Shrink or Resin Cast technologies – multicore and multi-pair cable joints are available for immediate backfill and energisation of Low Voltage power, control and instrumentation cables 600V/1000V 3.3kV.
Complete range of LV Cable Accessories ➡