T&M GWFI vs. GWIT: Understanding Glow Wire Testing
This article explores the differences between GWFI (Glow Wire Flammability Index) and GWIT (Glow Wire Ignition Temperature) in the context of glow wire testing. These tests are crucial for ensuring the safety of appliances and other products by evaluating the flammability of their materials.
Introduction to Glow Wire Testing
Safety is a paramount concern, especially with the potential for misuse, short circuits, or overcurrent issues in appliances. To address these concerns, stringent fire protection standards have been developed to assess and rate the flammability of materials used in these products. Glow wire testing is a key component of these safety standards.
What is Glow Wire Testing?
Glow wire testing is a method used to evaluate the fire resistance of materials. These methods are broadly categorized into:
- Direct Flame Method: A flame is applied directly to a sample (either horizontally or vertically mounted) under controlled conditions.
- Indirect Flame Method: A non-flaming heat source is applied to the sample. Glow wire testing falls under this category.
IEC 60335-1 specifies the requirements for glow wire testing in home appliances, while IEC 60695-2 outlines the specific testing methodology.
Glow wire testing involves heating an element, known as the “glow wire,” to a predetermined temperature. This test is performed on both finished products and test plates made from the raw materials used in these products. The outcome of the test is a simple PASS or FAIL at a specific temperature.
A “PASS” requires that the sample does not ignite or, if it does, self-extinguishes within 30 seconds of the heated element being removed. Furthermore, the sample should not ignite any tissue paper placed below if drips occur during the test.
GWFI: Glow Wire Flammability Index
GWFI and GWIT are properties associated with the raw materials used in manufacturing. They are determined by performing glow wire tests on test plates of raw materials at a specified thickness, as outlined in IEC publications.
Definition of GWFI
The Glow Wire Flammability Index (GWFI) is the highest temperature at which a material does not ignite or self-extinguishes within 30 seconds after the heated element is removed.
- This definition is found in IEC 60695-2-12.
In simpler terms, GWFI represents the maximum temperature a material can withstand during glow wire testing without sustaining a flame.
GWIT: Glow Wire Ignition Temperature
Definition of GWIT
The Glow Wire Ignition Temperature (GWIT) is the lowest temperature at which a material ignites and burns for longer than 5 seconds while the heated element is in contact with the test plate.
- This definition is found in IEC 60695-2-13.
Essentially, GWIT indicates the point at which a material will catch fire and continue burning under the influence of the glow wire.
Key Differences Summarized
| Feature | GWFI (Glow Wire Flammability Index) | GWIT (Glow Wire Ignition Temperature) |
|---|---|---|
| Definition | Highest temperature at which material does not ignite or self-extinguishes within 30 seconds after removal of the heat source. | Lowest temperature at which the material ignites and burns for longer than 5 seconds while the heated element is in contact with the test plate. |
| Focus | Measures the material’s resistance to ignition and self-extinguishing ability. | Measures the material’s propensity to ignite and continue burning under test conditions. |
| Temperature | Highest temperature that the material can withstand without sustaining a flame. | Lowest temperature that causes the material to sustain a flame. |
In conclusion, GWFI and GWIT are both vital parameters derived from glow wire testing. GWFI highlights a material’s ability to resist ignition, while GWIT indicates the point at which a material becomes susceptible to sustained burning. Understanding these differences is key in selecting the appropriate materials for safe and reliable products.
