About the Cable
PVC rapidly replaced rubber for wiring cables shortly after 1945 and for Power cables insulation in late 1950s in Europe. In India, the PVC power & Control Cables came into operation in early 1960s. The use of PVC provided cables of excellent quality which were clean and much easier to handle. Further, simplified terminators and jointing techniques make these cables eminently suitable among other applications for Industrial and Mining installation.
The main advantages of PVC Cables can thus be summarized as under:
- The insulation resistance and breakdown strength are practically unaffected by moisture. These cables are thus suitable for laying even under water.
- Cables can be overloaded for short periods without any appreciable effect on cable life.
- The cables can be laid vertically and on steep slopes as there is no impregnating compound involved.
- The cables are flame retardant since PVC ignites with great difficulty and is self extinguishing.
- These cables are immune to chemicals normally encountered in practice.
- Due to their lightweight, PVC Cables are easy to install and handle. Small bending rapider permit the termination of these cables in limited space.
- Low tension PVC Cables do not normally require sealing ends, when terminated indoor. The terminations can therefore be effected quickly and economically.
- PVC Cables have tough but smooth outer covering and are thus abrasion proof.
- PVC cables are not affected by vibration.
- PVC Cables have high short circuit capacity since they can withstand a high transient temperature without any deformation of insulation or displacement of conductor.
- PVC Cables have a long service life.
Application
These cables are used for outdoor and indoor installations in damp and wet locations, connecting signalling and control units in industry. They are laid in air, in ducts, in trenches or direct in ground.
General Construction
Conductor
The conductor shall be composed of plain copper or aluminum wires complying with IS: 8130-1984. Mining Cables to be used in gassy mines shall be of copper conductor only.
Insulation
The conductors are insulated with suitably compounded PVC, which is applied to the conductor by extrusion process.
Inner Sheath
For all cables having two or more cores, a common covering (inner sheath) is provided over the laid up cores either by extrusion or by wrapping of plastic or proofed tapes. Single core cables do not require inner sheath.
Armouring
Depending upon the application, the cables can be armoured. The armouring can be Round Steel Wire or Steel Strips. In case of cables where diameter over the inner sheath does not exceed 13 mm, the armour consists of Galvanished Round Steel Wires; above this size, the armour can be Galvanished Flat Steel Strips or Galvanished Round Steel Wires as per customers' requirement. In case of single core cables intended for use of an A.C. Systems, the armouring shall be of Aluminium Wires/Stripes or any other non-magnetic material.
Armouring of PVC Mining Cables consist of Galvanised Round Steel Wires/Strips, but wherever necessary, a few Tinned Copper Wires/Strips are also included to meet the resistance requirements of armouring for Mining Cables.
Outer Sheath
Over the armouring, or in case of unarmoured cables, over the inner sheath (for single core cables over the insulation), a tough outer sheath of PVC is applied by extrusion. This is normally Black in colour. This provides a tough but smooth outer covering to PVC Cables. The trademark "Arrow" are embossed on the outer sheath. Wherever desired the customer name can also be embossed on the cable. The embossing script repeats at desired length of cable.
Type Designation
The following code is used for designating the type of cable:
Constituents Code
Aluminium Conductor A
PVC insulation Y
Steel round wire armour W
Steel strip armour F
Steel double round wire armour WW
Steel double strip armour FF
PVC outer sheath Y