power cables

These tests are generally carried out as specified in ASTM-D-2863 Standard.

Temperature Index is the temperature at which the vertically held sample ceases to burn off on its own within 3 minutes at an Oxygen concentration of 21% i.e. atmospheric air.

Oxygen and Temperature Index Tests
Oxygen index is the measurement of oxygen content at which the vertically held sample when ignited ceases to burn off its own within 3 minutes. This is a relative measure of combustion resistance of materials in the context of atmospheric oxygen.

This is carried out as specified in IEC-754-1 standard.

A sample of cable compound is subjected to controlled rate of heat for a certain period and the decomposed gases are collected in alkaline solutions. Such alkaline medium is then analysed to estimate the HCL evolved.

HCL Gas Emission Test
All PVC Compounds when decomposed due to fire emit gaseous fumes, which are basically corrosive in nature. This is entirely due to the ingredients used in the formulations. These fumes, if containing higher amounts of corrosive gas i.e. Hydrochloric Acid Gas, may damage various instruments and equipments in the vicinity of fire. More and more stress is being given these days to control this content in reasonable limits.

The extent of damage to the cable under these tests gives an indication of the behaviour of these cables in actual fire conditions and gives a measure of fire-resistance in actual conditions.

The flame medium is generally LPG in the first three tests methods and Ethnol in the third method.

There are certain tests, which are carried out on the completed cable manufactured with such compounds, in which the cable samples are subjected to flames in different conditions. The method and duration of such flames vary to a large extent. The most prevalent tests methods under fire conditions are specified as under:

Flammability Tests
All other tests mentioned are generally carried out on the materials to ascertain basically the components, which have certain bearings on the fire resistance characteristics of the cables. These results contribute to select a proper formulation for a particular application.

The test is generally carried out as specified in ASTM-D-2843 standard.

Smoke Generation Test
Optical method is most practiced to measure the amount of smoke generated while burning the sample. A fixed dimension sample of material is put to flame of specified intensity for 4 minutes and the percentage obscuration on an optical path is measured a 15 seconds interval. A graphical plot of such measurements evaluates the average smoke density. This area integration method is only the quantitative indication of smoke generation by the PVC compound.

FRLS Tests
Following special tests are most commonly carried out at present on Rallison - PVC FRLS cables.