What is Glow Wire Testing?

Glow wire testing is an electrical safety test designed to evaluate the flame resistant properties of plastic materials used in electrical devices. IEC60695-2-11 describes the glow-wire test conducted on end products (the GWEPT, or glow-wire end product test). Its purpose is to ensure the end product does not ignite or spread flames should an ignition source (such as an overheated part) come into contact with the plastic material. This may occur in normal use, under reasonable abnormal use, malfunction or failure of the product. The glow wire simulates an over-heated part which then comes into contact with plastic materials.

In this part of the standard, the specimen to be tested is the end product, preferably the entire product if this is possible. The glow wire is either applied to the area most likely to come into contact with an ignition source, or the area of the product where the plastic material is the thinnest. The glow-wire is heated to the required temperature, which is given in the individual product standards, and then applied to the specimen for 30 seconds. It is then removed, and the specimen is observed for a further 30 seconds.

The Standard

The glow wire test is covered by the International Electrotechnical Commission (IEC) standard IEC 60695-2 Fire Hazard Testing, with four parts covering four different aspects of the glow-wire test. These are:

IEC 60695-2-10: Glow-wire apparatus and common test procedure

IEC 60695-2-11: Glow-wire flammability test method for end products (GWEPT)

IEC 60695-2-12: Glow-wire flammability index (GWFI) test method for materials

IEC 60695-2-13: Glow-wire ignition temperature (GWIT) test method for materials

The British and European equivalent of the glow wire standard is BS EN 60695-2

Apparatus

The apparatus includes:

The glow wire, Circuit to heat the wire, System to measure the temperature of the wire, Piece of tissue paper to catch any falling debris, Draught-free test chamber, Timing device, Clamped or mounted specimen, Ruler to measure flame height

Test Procedure

The test is conducted by first heating the glow-wire to the required temperature. Either the specimen is then brought into contact with the tip, or the tip is moved into contact with the specimen. Observations and results are then recorded in accordance with the relevant glow-wire standard.

Observations

Whether ignition occurs

If ignition occurs, how long this took to happen

The time it takes for the flames to extinguish

If the sample is completely consumed by the flames

Whether the tissue underneath the sample was ignited by falling debris

The specimen passes the test if either a) it does not ignite or b) the flames extinguish within 30 seconds of the removal of the glow wire and the tissue underneath does not ignite.