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افتراضي control cables



Control Cables


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 permits 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.
General Construction of PVC Cables

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.
Core Identification & Colour Scheme
Cores are identified by colour scheme of PVC insulation.
The following colour scheme is adopted.
One core
Red, Black, Yellow or Blue
Two Core
Red and Black
Three Core
Red, Yellow and Blue
Four Core
Red, Yellow, Blue and Black (reduced neutral core is also Black)
Five core
Red, Yellow, Blue, Black and Light Grey
For cables having more than 5 cores
Two adjacent cores (counting and directional) in each layer are coloured Blue & Yellow respectively and the remaining cores are Light Grey.


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 Galvanized Round Steel Wires; above this size, the armour can be Galvanized Flat Steel Strips or Galvanized 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 Aluminum Wires/Stripes or any other non-magnetic material.

Armouring of PVC Mining Cables consists of Galvanized 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 mechanical control cables, over the inner sheath (for single core cables over the insulation), a tough outer sheath of PVC are applied by extrusion. This is normally Black in colour. This provides a tough but smooth outer covering to PVC Cables. The trademark "HMT" along with the year/code of manufactured 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 electrical control cables
Type Designation
The following code is used for designating the type of cable.
Constituents
Code
Aluminum 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




Testing of PVC Cables

Testing is a vital part of cable manufacturing and all raw materials and finished cables are thoroughly tested to ensure quality control. HMT has a well equipped testing laboratory for carrying out electrical, mechanical and chemical tests which are required as per relevant specifications. The various tests as provided in the Indian Standards are carried out on HMT Cables. These are classified in three different groups:
  • Routine Tests
  • Type Tests
  • Acceptance Test
Routine Tests

The following tests constitute Routine Tests, which are carried out on each and every length of cable before it leaves the factory:



Conductor Resistance Test


This test ensures that conductor resistance is with the specified limits, thereby ensuring that the continuity of conductor is maintained throughout the cable length and that the conductor has the required cross section area. The DC resistance is measured at room temperature and is then corrected to standard reference temperature at 20°C.



High Voltage Tests


This test ensures that the insulation will safely withstand the rated voltage within permissible normal operation.



Type Tests


These tests are carried out on samples taken from each production lot. They are carried out to prove conformity as regards the general qualities and design to the specification of particular type of cable. These tests are enumerated in the relevant Indian Standards.

Acceptance Tests


The customers can request the various acceptance tests as provided in the relevant Indian Standard to be carried out before accepting the cables.





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cables, control

control cables


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