Short Answer: The Key Property of a Chemically Resistant Cable
The key property of a cable for petroleum products, oils and aggressive media is the material of the outer sheath, resistant to a specific chemical influence. There is no universal “chemically resistant” cable: resistance to mineral oils, petrol, diesel fuel, acids and alkalis is provided by different polymer compositions. For petroleum products and oils, sheaths made of oil- and petrol-resistant thermoplastic elastomers, polyurethane or specialised rubber compounds are used.
The designation “M” in the cable marking indicates resistance to the effects of hydrocarbons, oils and petrol. Cables in the “M” design are permitted for use at facilities of the oil, gas and petrochemical industries. For chemically aggressive media, including acids and alkalis, a separate check of the sheath resistance according to the manufacturer’s documentation is required. Ordinary PVC compound without special additives is not designed for prolonged contact with petroleum products.
What Influences the Cable Must Withstand
For oil and gas and chemical facilities, not only direct chemical influences are dangerous. The cable is exposed to a complex of factors, each of which affects the choice of design.
| Condition | Risk to the cable | What is required of the cable |
| Mineral oils, greases | Swelling and destruction of the sheath made of ordinary PVC | Oil-resistant sheath (thermoplastic elastomer, polyurethane, rubber) |
| Petrol, diesel fuel | Dissolution and cracking of the sheath | Petrol-resistant sheath, resistance to hydrocarbons |
| Acids and alkalis | Corrosion of the sheath, loss of mechanical properties | Chemically resistant sheath (polyurethane, halogen-free compositions) |
| Low operating temperature | Embrittlement of the sheath and insulation | Cold-resistant design KhL or EKhL |
| Explosion hazard zone | Spark formation, damage to insulation | Cables complying with GOST IEC 60079-14 |
| Rodents | Damage to the sheath | Armour of steel tapes or wires |
The resistance of cables in the “M” design to the effects of hydrocarbons, oils and petrol is confirmed by tests. For laying in soils containing substances that have a destructive effect on cable sheaths, the PUE RK requires the use of cables with lead sheaths and reinforced protective coverings, or cables with aluminium sheaths and particularly reinforced protective coverings in a continuous moisture-resistant plastic hose.
Which Design Provides Protection
The chemical resistance of a cable is determined by the sheath and insulation materials. Structural elements such as armour and screens protect against mechanical influences but do not affect resistance to aggressive media.
Sheath. For chemically resistant cables, oil- and petrol-resistant thermoplastic elastomers, polyurethane, specialised rubber compounds based on isoprene or butadiene rubber, as well as halogen-free polymer compositions are used. A sheath made of oil- and petrol-resistant, cold-resistant, wear-resistant thermoplastic elastomer provides resistance to lubricating oils and diesel fuel. A polyurethane sheath combines chemical resistance with mechanical strength and frost resistance.
Insulation. For chemically resistant cables, insulation made of ethylene propylene rubber (EPR), cross-linked polyethylene (XLPE) or organosilicon ceramising rubber is used. These materials retain dielectric properties in contact with aggressive media and at negative temperatures.
Armour. Steel tapes or galvanised wires protect the cable from mechanical damage and rodents. For installation in the ground without a pipe, armour is mandatory. Armoured cables in the “HF-KhL” design are permitted for use at facilities of the oil, gas, petrochemical and chemical industries.
Filling. Internal filling made of a polymer composition of reduced fire hazard prevents the spread of moisture and aggressive media along the cable when the sheath is damaged.
If the cable must not propagate combustion or must maintain operability during a fire, the indices ng, LS, HF or FR are added to the chemically resistant design. Combinations of these properties are analysed in the materials: table of differences between LS, HF, LSLTx, FRLS and FRHF and fire-resistant and non-flame propagating cable. The properties of smoke formation and toxicity of combustion products are checked separately: smoke, halogens and toxicity of a cable.
How to Choose a Suitable Cable
The selection algorithm is built from the operating conditions to the specific design.
- Determine the type of aggressive medium. Mineral oils, petrol, diesel fuel, acids, alkalis or a combination thereof. The sheath material depends on this. For hydrocarbons, the “M” design is required; for acids and alkalis — a separate check of the sheath resistance according to the manufacturer’s documentation.
- Determine the operating temperature range. For the northern regions of Kazakhstan, winter temperatures reach minus 40–45 °C. Cables in the KhL design are operated at minus 60 °C, EKhL — at minus 70 °C and below. The temperature range of a specific type is checked against the technical specifications.
- Determine the minimum installation temperature. For cables in the KhL design, installation is permitted at minus 30 °C, for EKhL — at minus 40 °C. At a lower temperature, pre-heating is required. KG-KhL cables permit installation at minus 40 °C.
- Check the UV resistance of the sheath. For open sites, the sheath must be light-stabilised. Resistance to UV and atmospheric precipitation is analysed in the material cable for open air.
- Take mechanical loads into account. For installation in trenches and on open sites, armoured cables are used. For fixed installation in trays and pipes, an unarmoured one is sufficient if the route is protected.
- Check the fire characteristics. If the cable is laid in buildings or at facilities with fire safety requirements, the indices ng, LS or FR are added.
- Check explosion protection. For explosion hazard zones, cables must comply with GOST IEC 60079-14. Compliance is confirmed by a certificate.
The designation “M” or “HF-KhL” indicates resistance to aggressive media, but does not remove the need to check the specific characteristics of the cable according to the manufacturer’s documentation. Temperature ranges and chemical resistance may differ for different types and designs. For a cold climate, the KhL or EKhL design is additionally checked: cable for frost: KhL and EKhL designs.
Where It Is Applied
Oil and gas facilities. At the fields of Kazakhstan, cables operate on open sites at temperatures down to minus 40 °C and below, under the influence of mineral oils, petrol and other petroleum products. Cables in the “M” or “HF-KhL” design with an oil- and petrol-resistant sheath, armoured to protect against mechanical damage, are used. SKAB-S 660Bsng(A)-HF-KhL cables are permitted for use at facilities of the oil, gas, petrochemical and chemical industries.
Chemical enterprises. In shops with acidic and alkaline media, cables with a polyurethane or halogen-free sheath resistant to a specific chemical influence are used. For explosion hazard zones, compliance with GOST IEC 60079-14 is additionally required.
Industrial facilities with unheated premises. Fuel and lubricant warehouses, hangars, pumping stations require cables that retain flexibility at negative temperatures and are resistant to petroleum product vapours. For such conditions, the KhL design with an oil- and petrol-resistant sheath is suitable.
Mobile mechanisms and drilling rigs. KG-KhL cables are used to power mobile equipment at construction sites, in quarries and on drilling rigs. They are resistant to lubricating oils and diesel fuel, and retain flexibility at minus 60 °C.
Outdoor routes on open sites. For installation on trestles, in trays and along building walls outdoors, cables with a sheath resistant to UV and frost, combined with chemical resistance, are used. The choice between copper and aluminium conductors affects the permissible current and voltage drop.
Typical Mistakes
Using a cable with an ordinary PVC sheath for contact with petroleum products. Ordinary PVC compound without special additives swells and breaks down upon prolonged contact with mineral oils and diesel fuel. For such conditions, a sheath made of oil- and petrol-resistant thermoplastic elastomer or polyurethane is required.
Assuming that resistance to oils and resistance to acids are the same thing. A material resistant to hydrocarbons may break down under the action of acids or alkalis. For each aggressive medium, the resistance of the specific sheath material is checked according to the manufacturer’s documentation.
Ignoring the minimum installation temperature. A cable resistant to chemical influence and operating at minus 60 °C may permit installation only at minus 30 °C. Installation at a lower temperature without heating leads to cracking of the sheath.
Using an unarmoured cable for installation in the ground on chemically aggressive soils. Without armour and a protective hose, the sheath is mechanically damaged and destroyed by aggressive substances in the soil. The PUE RK requires cables with reinforced protective coverings for such conditions.
Choosing a cable only by the designation without checking the documentation. Different manufacturers use different materials and indicate different resistance ranges for the same design. The specific values are checked against the technical specifications and the cable passport.
FAQ
Which cable should be chosen for contact with diesel fuel?
For contact with diesel fuel, cables with an oil- and petrol-resistant sheath made of thermoplastic elastomer or polyurethane are used. KG-KhL cables are resistant to lubricating oils and diesel fuel. Cables in the “M” design are resistant to hydrocarbons, oils and petrol. The specific type is chosen according to the manufacturer’s documentation, taking into account the operating and installation temperature.
What does the “M” design in the cable marking mean?
The “M” design indicates the resistance of the cable to the effects of hydrocarbons, oils and petrol. Such cables are permitted for use at facilities of the oil, gas and petrochemical industries. The resistance is confirmed by tests according to the methods specified in the standards and technical specifications.
Can a cable with a PVC sheath be used in a chemically aggressive environment?
Ordinary PVC compound without special additives is not designed for prolonged contact with petroleum products and aggressive media. For such conditions, specialised PVC compositions, thermoplastic elastomers, polyurethane or halogen-free polymers are used. The resistance of the specific material is checked according to the manufacturer’s documentation.
At what temperature can a chemically resistant cable be installed?
The minimum installation temperature depends on the design. For cables in the KhL design, installation is permitted at minus 30 °C, for EKhL — at minus 40 °C. KG-KhL cables permit installation at minus 40 °C. At a lower temperature, pre-heating is required. The operating temperature is usually wider: KhL cables are operated at minus 60 °C, EKhL — at minus 70 °C and below.
Is an armoured cable needed for installation in the ground at an oil depot?
For installation in the ground on the territory of an oil depot, armoured cables with a protective hose are used. The armour of steel tapes protects against mechanical damage, and the protective hose made of a polymer composition — against the aggressive influence of the soil and petroleum products. The PUE RK requires the use of cables with reinforced protective coverings for soils containing substances that have a destructive effect on cable sheaths.
Sources
- Electrical Installation Code of the Republic of Kazakhstan 2015, as amended by the order of the Minister of Energy of the Republic of Kazakhstan dated 31.10.2022 No. 340 — clauses 505–513 — in force — IPS “Adilet”, adilet.zan.kz — requirements for laying cables in soils with aggressive substances, in rooms with a chemically active environment.
- GOST 31996-2012 “Power cables with plastic insulation for rated voltages of 0.66; 1 and 3 kV” — in force — official text on meganorm.ru — requirements for the design of power cables, climatic designs, resistance to external influencing factors.
- GOST IEC 60079-14-2013 “Explosive atmospheres. Part 14. Electrical installations design, selection and erection” — in force — official text — requirements for cables for explosion hazard zones.
- GOST 31565-2012 “Cable products. Fire safety requirements” — in force — official text on meganorm.ru — classification of cables by fire hazard, fire hazard classes.
- Technical specifications TU 16.K99-061-2013 for SKAB cables — in force — technical documentation of the Spetskabel plant — resistance to aggressive media, oils, petrol, temperature ranges.
- Technical specifications TU 3544-005-40914170-2013 for KG-KhL cables — in force — manufacturer’s technical documentation — oil- and petrol-resistant sheath, resistance to lubricating oils and diesel fuel, temperature ranges.
- Technical specifications TU 3530-004-85082376-2016 for NED-Plaguit cables — in force — manufacturer’s technical documentation — “M”, “UV”, “Vz-” designs, resistance to hydrocarbons, oils and petrol.
