Defying the Elements: Armoured Cables Designed to Last

When it comes to reliable SWA & AWA armoured cables, Tratos stands at the forefront, offering a comprehensive range of innovative solutions that cater to your diverse needs. Our cables are not just robust and hard-wearing; they are designed to exceed your expectations while complying with the latest industry standards.

Since the early days of cable making, people have sought different ways of providing mechanical protection to electric cables, particularly those to be buried or used in harsh environments, where they could be subject to mechanical abuse.

Tape or Wire?

Invariably these early armours consist of either two layers of metallic tapes applied with typically 50% registration for those armoured cables laid directly in the ground or laid in ducts buried in the ground, which needed mechanical protection to withstand a blow from a pick during excavation work. Alternatively, they consisted of a single layer of helically applied metallic wires in applications where the need for improved tensile strength is greater than impact resistance.

Given the dramatic decline in the use of picks and shovels during excavation work, the manufacture of tape armoured cables has also declined dramatically in the UK, most armoured cables are now manufactured with a single helical layer of round wire armour. The reason for this change is that the physical damage they need to withstand is usually tension, caused when an excavator digs the cable up, rather than impact damage from a pick or shovel. Tape armours are still popular in some overseas countries, however.

When used, the steel tape needs to be of the correct grade to afford the necessary mechanical protection without making the armoured cable itself too stiff, preventing bending during installation or, in the case of small cables, causing damage or distortion to the underlying components. Preferably the tapes should be galvanised on all four sides and not two, as would be the case for tapes slit down from a wider galvanized steel strip. Tratos ended the practice of applying varnished steel tapes years ago.

Similarly, the tensile strength of the round steel wire armour needs to be carefully considered, 34 hbar quality being acceptable for most applications, although 65 hbar quality can be used to good effect on armoured cables which will be subject to higher tensions, such as those installed in vertical suspended applications.  However, these higher tensile wires tend to be more “springy” than normal armour wires, and although the use of “wire killers” during application of the armour will certainly help, care needs to be taken when installing and terminating these cables if “corkscrewing” is to be avoided.

A.C. or D.C.

The most popular type of armour for power cables is now a single layer of Galvanised Steel Wire, known as SWA, which gives the correct balance of mechanical protection, tensile strength, and handle ability to ease installation. However, for single core armoured cables used in an alternating current system, where a magnetic armour can cause problems, Tratos can supply cables with a single layer of Aluminium Wire Armour (AWA) or other non-magnetic materials.

Special applications:

For more specialised applications, such as subsea cables, the armour can comprise a double layer of armour wires (DWA) which can be specially designed to be torque balanced to prevent the armoured cable twisting during installation or use. 

Where mining cables are to be installed vertically down mine shafts double wire armour, or even quadruple armour can be supplied for single point suspension applications.

Additional Types of Armour:

There are also additional types of armour used in the manufacture of cables intended for different applications and markets. Basket weave galvanised steel (GSWB) or phosphor bronze (PBWB) wire braids, for Ships and Offshore Installations as well as Pliable Wire Armour (PWA) cables for Tunnelling, Mines and Quarries applications, where cables are required armoured but also to be moved infrequently.


Some Standards and Regulations stipulate a minimum conductivity for the armour, for example 50% of the conductivity of a power core in the case of armoured cables for use in certain types of Mines and Quarries. Where this conductivity cannot be achieved by use of steel wire armour alone, Tratos can substitute a number of tinned, hard drawn copper wires for galvanised steel wires, to obtain the correct conductivity.

Tratos can also do this for certain types of MV cables where the armour also acts as a collective metallic screen.

Total Design:

Being a long-established manufacturer of armoured cables, not simply a stockist, Tratos have long experience of supplying cables across the globe, with various types of mechanical protection, including cables with metallic armour. 

When designing and manufacturing armoured cables Tratos Design Engineers do not consider the armour in isolation, years of experience have taught them that an armour can only be successful if it is designed to be an integral part of a carefully considered robust package of protection measures. 

Tratos can supply armoured cables for most applications and uses, from Control and Communication, Low voltage (LV) power through to Medium (MV) and High Voltage (HV) transmission systems, Tratos have a design to suit your particular needs.

Tratos have experts who can advise on the most appropriate type of armour to suit the intended application.

Popular insulations include thermoplastic PVC or Polyethylene for Control and Communication cables, Cross-linked Polyethylene (XLPE) or Hard Ethylene Propylene Rubber (HEPR) for power cables. Cross-linked Elastomeric Ethylene Propylene Rubber (EPR) is used for Ships and Offshore cables as well as Tunnelling, Mines and Quarry cables.

Popular sheaths include thermoplastic PVC, Medium (MDPE) or High (HDPE) Density Polyethylene, with thermoplastic Low Smoke, Zero Halogen LSZH sheaths available for armoured cables required to have improved performance in the event of a fire. Ships and Offshore cables as well as Tunnelling, Mines and Quarry cables are available with a range of Cross-linked sheaths, Polychloroprene, Chlorinated Polyethylene as well as cross-linked Low Smoke, Zero Halogen LSZH sheaths.

All Tratos armoured cables are designed from the outset to comply with the most up-to-date National and International standards as well as the applicable Regulations.

Tratos armoured cables will ensure that your electrical infrastructure remains secure and operational, under the difficult and trying operational conditions.


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