Electric cables are normally installed on the assumption of a safe working life

Electric cables are normally installed on the assumption of a safe working life of at least 20 years. Changes in the insulating material take place with the passing of time and these changes, which may eventually result in an electrical breakdown, are accelerated at higher temperatures. Thus, if the working life is fixed, the limiting factor is the temperature at which the cable is required to operate.

The number of electric wire contained in most common conductors is 3, 7, 19, 37, 61 or 91. Thus, 37/0·083 indicates that the conductor has 37 wires each having a diameter of 0·083 in.An area of rubber cable technology where much research and development work has been concentrated in recent years is that of the behaviour of cables in fires. Although they may overheat when subject to current overloads or mechanical damage, electric cables in themselves do not present a primary fire hazard.

As fire survival requirements on oil rigs and petrochemical plants become more severe, new control cable designs have been developed to meet fire tests at 1000°C for 3h with impact and water spray also applied, and also to have low smoke and low toxic properties.The type, amperage, voltage rating, and construction of the power cable must be compatible with the splice kit design.