Testing is a very critical aspect of Wire & Cable manufacturing. They are a very wide array of safety standards to comply with which can be very confusing. For example, flame resistance and fire propagation tests are often confused with one another on
the basis of their very similar designations. However, the test methods
employed are quite different:
IEC 60332-1-2: Test for vertical flame propagation for a single insulated wire or cable
This flame resistance test is passed by most cables constructed of flame-retardant materials, e.g. PVC and chloroprene rubber, or materials with special flame-retardant additives such as PUR. In the test, a single core or cable with a length of approx. 60 cm is mounted vertically using two clamps, after which a pre-defined flame is applied to the bottom end for a period of 60 seconds (or 120 seconds in the case of cable diameters > 25 mm). The test is deemed passed if, after the flame has been removed, the burning cable extinguishes itself and the fire damage is at least 50 mm from the upper mounting clamp. It is irrelevant how long the cable burns before extinguishing itself.
IEC 60332-3: Test for vertical flame spread of vertically-mounted bunched wires or cables
This fire propagation test is also known as the "bundle fire test" and is generally only passed by specially developed cables and wires with highly flame-retardant insulation and sheath material. In most cases, the flame resistance of the plastics used is greatly enhanced by the addition of aluminium or magnesium hydroxide. Multiple cables are bundled or layered in lengths of approx. 3.5 m and vertically affixed to a ladder-like metal structure, after which a flame is applied to the lower end of the cables using a propane burner. The cable volume and time of flame application is defined by the test method, since IEC 60332-3 comprises four different bundle fire tests:
• IEC 60332-3-22 Category A: 7 liters of combustible material per meter / flame application: 40 minutes
• IEC 60332-3-23 Category B: 3.5 liters of combustible material per meter / flame application: 40 minutes
• IEC 60332-3-24 Category C: 1.5 liters of combustible material per meter / flame application: 20 minutes / cable diameter > 12.0 mm
• IEC 60332-3-25 Category D: 0.5 liters of combustible material per meter / flame application: 20 minutes / cable diameter< 12.0 mm
IEC 60332-2-22 Category A is often used for maritime
applications on oil rigs and ships, for example. The test is deemed passed if,
after the burner has been switched off, the burning cables extinguish
themselves and the fire damage does not cover more than 2.5 m measured from the
bottom cable end. It is impossible to say which of the four test categories
poses the most difficult challenge, since there are a range of different
factors to consider.
IEC 60331: Functional integrity and fire resistance of electric cables
Unlike IEC 60332-1-2 and IEC 60332-3, this test does not assess the flame propagation but instead checks the electrical functioning of the cable in the event of a fire. In the test, a flame is applied across the entire horizontal length of a single, 120 cm cable for a period of 90 minutes. The test is deemed passed, if the cable continues to conduct electricity without shorting throughout the 90 minute flame application and for a subsequent 15 minute cooling period. This test is generally only passed by cables and wires with special, flame-retardant glass or mica wrapping enclosing the individual cores as well as the entire cable bundle.
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Flameproof cable can save faulty equipment from explosion. They are best in industrial and hazardous area. BICC
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