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www.siechem.com 52 Temperature Index as per IEC 60216/VDE 0304 part 21 The temperature index describes the long-term performance of insulating materials. The temperature index defines the ageing temperature (in °C), at which the insulating material still has an absolute elongation at break of 50 % after 20 000 hours. A 10 °C higher temperature index results in approximately doubling the life expectation of the insulating materials. In order to determine the long term temperature stability of an insulating material the different ageing times corresponding to different temperatures are measured and recorded in a so called Arrhenius- Diagram (ordinate-axis: log time, abscissa axis: the reciprocal absolute temperature). A straight line is drawn to connect the various recorded points. By prolonging the straight line until it intersects the 20 000 hour axis it is possible to determine the lifetime or the temperature index. 0 Temperature C Hours The European Electrical Committee categorized the fire performance of the cables into three classes, namely IEC60332-1, IEC60332-2 & IEC60332-3. IEC 60332-1 and IEC 60332-2 are used to assess the flame propagation characteristics of a single wire. IEC 60332-3 is used to assess the flame propagation chacteristics of bundled cables. Comparatively speaking, IEC 60332-3 for bundled cables is more demanding than IEC60332-1 for single wires. IEC 60332-1/ BS EN 60332-2-3-10 ; 2009 ( Flame Test on Single Vertical Insulated Wires/Cables ) This test details a method of test for the assessment of the flame propagation characteristics of a single wire or cable. In this test , a 60cm cable sample is fixed 0 vertically inside a metallic box and a 175 mm long flame is applied at 45 C from a gas burner placed at 450 mm from the top at the upper portion. The specimen is deemed to have passed this test, of after burning has ceased, the charred or affected position does not reach within 50mm of the lower edge of the top clamp which is equivalent to 425 mm above the point of flame application. The test method is not suitable for the testing of some small wires due to the melting of the conductors during the time of application of the flame. Wires & Cables Vertical Flame Test