KG or KGTP: what is the difference between flexible cables?

Introduction: Two Modifications of Flexible Power Cable

KG and KGTP cables belong to the same group of flexible power conductors with stranded copper conductors and rubber insulation. Both are intended for connecting mobile mechanisms, welding machines, construction tools and other equipment where the cable is constantly bent and subjected to mechanical loads. The difference between them lies in the composition of the rubber sheath and the design, which determine the temperature range, resistance to aggressive media and permissible laying conditions.

KG is a general-purpose flexible cable manufactured according to GOST 24334-80. KGTP is a flexible tropical-design cable with a sheath made of oil- and petrol-resistant rubber that does not propagate combustion. The letter “T” indicates tropical design, the letter “P” — increased sheath resistance. More details about KGTP are given in the material KGTP Cable, and a comparison with other flexible wires is given in the article KGTP or PVS cable.

Comparative Table of KG and KGTP

Design and Materials: What Is the Difference

The basis of both cables is a current-carrying conductor made of copper wires of the fifth flexibility class, twisted into a common core. The insulation of each conductor is made of rubber. The main difference is the formulation of the outer sheath. In the KG cable, it is made of general-purpose rubber, which resists abrasion and moisture well, but softens and loses strength upon contact with oils, petrol or diesel fuel. In KGTP, the sheath is made of oil- and petrol-resistant rubber, which retains its properties even during prolonged immersion in technical fluids.

An additional difference is the tropical design of KGTP. The sheath of such a cable contains additives that prevent mould and fungus damage in a humid hot environment, and also does not support combustion when laid singly. The sheath colour of both types is usually black, which masks dirt. The marking is applied to the surface and contains the type, number of conductors, cross-section and year of manufacture. Decoding: KG — flexible cable; KGTP — flexible cable, tropical, with increased sheath resistance. The range of copper versions is available in the section copper.

Technical Characteristics According to GOST

Both cables are manufactured according to GOST 24334-80, which sets a nominal voltage of 660/1000 V AC with a frequency of up to 400 Hz. The number of conductors is from 1 to 5, cross-section from 0.75 to 240 mm². The continuous permissible heating temperature of the conductors is 75 °C for rubber insulation. In the event of a short circuit, short-term heating up to 200 °C is allowed for no more than 5 seconds. The bending radius for multi-conductor cables is not less than 8 outer diameters, for single-conductor — not less than 10 diameters.

In terms of mechanical properties, KGTP surpasses KG: the sheath made of oil- and petrol-resistant rubber withstands more abrasion cycles and does not crack under the influence of petroleum products for longer. Tests for non-propagation of combustion are carried out according to GOST IEC 60332-1 for a single cable. KG in the basic version does not pass such tests, therefore in places with increased fire requirements, either KGTP or special non-flammable modifications of KG with the index “ng” are used. Current loads are determined by the PUE and are the same for the same cross-sections: for 1.5 mm² — 23 A, for 2.5 mm² — 30 A, for 4 mm² — 41 A, for 6 mm² — 50 A, for 10 mm² — 70 A when laid in air.

Areas of Application and Operating Conditions

KG cable is a universal flexible power conductor for construction sites, agricultural work, connecting mobile machines, welding stations, pumps. It works well in a dry and moderately humid environment, but should not be laid near hot pipelines, in oil pits or in areas where contact with solvents is possible. If the sheath is mechanically damaged, the cable quickly absorbs moisture, which leads to insulation breakdown.

KGTP is created for more severe conditions: oil refining enterprises, chemical productions, car repair shops, ships and port facilities. Its sheath does not break down from contact with diesel fuel, industrial oil, cutting fluids. The tropical design protects against fungus in conditions of high humidity and temperature. At facilities where fire is possible, KGTP is preferable due to the non-propagation of combustion of the sheath, which reduces the risk of fire spreading along the cable route.

When to Choose KG Cable

• Construction sites with moderate humidity and no contact with fuels and lubricants.
• Connection of welding machines in workshops with good ventilation.
• Agricultural machinery, irrigation installations, temporary lighting lines.
• Internal mobile connections in dry heated workshops.
• Budget projects where there are no aggressive media and increased fire requirements.

When to Choose KGTP Cable

• Oil and gas facilities, car repair shops, garages, where the cable contacts petrol, oil, diesel.
• Chemical productions with aggressive vapours and liquids.
• Ships, port cranes, berthing facilities — conditions of high humidity and salt fog.
• Tropical climate with high temperature and humidity, danger of mould.
• Fire-hazardous zones, where non-propagation of combustion of the sheath is important.

Typical Mistakes in Selection

• Using KG in a car repair shop where oil constantly spills on the floor. The sheath swells, cracks, and the cable fails within a few months.
• Ordering KGTP for an ordinary household extension cord. The overpayment for oil and petrol resistance is not justified, and the cable rigidity is slightly higher.
• Laying KG in places with fire safety requirements without checking the certificate for non-propagation of combustion.
• Ignoring the marking: ordinary KG with a similar sheath is sold under the guise of KGTP. It is necessary to require a passport indicating GOST and tests.
• Working with KG at –40 °C without taking into account that all rubber cables retain flexibility, but the sheath becomes more brittle to impacts.
• Using KG in a tropical climate without protection from UV and mould. The general-purpose sheath quickly breaks down.

Frequently Asked Questions

What is the difference between KG and KGTP?

KGTP differs from KG in the sheath material: it is oil- and petrol-resistant, tropical-design and non-flammable. KG is a basic cable with a general-purpose rubber sheath.

Can KGTP be replaced with KG cable?

Replacement is possible only in conditions where there are no oils, fuel, aggressive media and high fire safety requirements. Otherwise, the service life will be sharply reduced.

How is the KGTP marking deciphered?

K — cable, G — flexible, T — tropical design, P — increased sheath resistance. Sometimes the letter “KhL” is added for cold-resistant design.

Which cable to choose for welding: KG or KGTP?

For welding stations in a clean room, KG is sufficient. If welding is carried out outdoors near machinery, KGTP is preferable due to resistance to oils and fuel.

Are both cables produced with a cross-section of 2.5 mm²?

Yes, both KG and KGTP are produced with a cross-section of 2.5 mm², as well as with other cross-sections from 0.75 to 240 mm². The choice depends on the load.

Is KGTP suitable for laying in the ground?

No, flexible cables are not intended for fixed laying in the ground. Armoured cables are used for this. KG and KGTP are used only for mobile connection.

Conclusion

KG and KGTP are two models close in design but different in environmental resistance. KG is a reliable flexible cable for most construction and domestic tasks where there are no aggressive liquids and strict fire requirements. KGTP is a reinforced version with an oil- and petrol-resistant non-flammable sheath, created for oil and gas, chemistry, fleet and tropics. The choice between them is based on an analysis of the working environment, not on the difference in price, since replacing one with the other in unsuitable conditions leads to rapid wear and accidents.