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08 Feb, 2024 47 Views Author: Cherry Shen

Assessing Glow-Wire Flammability Index Using Glow-Wire Tester

The glow-wire tester is used to simulate the ignition of insulation materials or other combustible components inside equipment that may catch fire due to a hot wire or hot element. Under certain conditions, such as fault currents flowing through wires, component overloads, and poor contacts, certain components can reach a certain temperature that causes nearby parts to ignite. This can be tested through the glow wire flammability index test and the 850 degree hot wire test.

The glow-wire tester is suitable for testing the fire resistance of electrical and electronic products, components, plastic and non-metal insulation parts used in household appliances, such as switch casings, relay sockets, etc., under fault or overload conditions that may cause them to reach high temperatures or ignite nearby parts. The hot wire tester simulates the thermal stress caused by hot elements or resistors such as overload sources or ignition sources in a short period of time, and evaluates the fire hazard through simulation techniques.

The working principle of the glow-wire tester: a specified material of 4mm nickel-chromium wire (U-shaped hot wire head) is heated to the specified test temperature (300℃~1000℃) with a high current. The test sample is subjected to a 30s scorching test with a specified pressure (1.0N) applied. The ignition hazard of electrical and electronic equipment finished products is determined by whether the test sample and the padding material ignite or sustain combustion. After the test is completed, the scorching time, ignition time (Ti), flame extinction time (Te), and flammability index (GWFI) are recorded.

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The glow-wire tester is used to test the fire resistance properties of materials and finished products. The hot wire itself serves as the ignition source. The temperature of the hot wire is set and controlled by a temperature controller. During the test process, the temperature controller operates in manual mode to generate a specified voltage signal on the manipulated variable (hot wire), thereby avoiding feedback on the reference variable (thermocouple) on the temperature controller.

The temperature of the hot wire can be set from room temperature to 1000℃. The temperature of the hot wire is measured using a K-type sheathed thermocouple (Class 1) according to the IEC60584-2 standard. During the test process, the test sample is moved towards the hot wire at a constant speed of 11mm/s and then returned. The heating time of 30 seconds is controlled by a timer. The test sample holder is pulled towards the hot wire with aforce of 1N. The power supply is 230VAC±10% (50Hz). Other technical conditions can be provided if needed.

The glow wire flammability index test and the 850 degree hot wire test are two commonly used fire resistance testing methods for materials. They are widely used in fields such as construction, aviation, and chemical industry. The purpose of these tests is to evaluate the fire resistance performance of materials to ensure that they can effectively prevent the spread of fire and protect the safety of people and property in the event of a fire.

The glow wire flammability index test is a method for evaluating the combustibility of materials. During the test, the sample is exposed to a specific flame source, and its burning characteristics are observed to determine its flammability. The test result is usually expressed as a percentage, representing the percentage of the burning area of the material to the total area. A lower flammability index value indicates better fire resistance performance of the material.

The 850 degree hot wire test is a method for evaluating the thermal resistance of materials. In the test, a 1mm diameter metal wire is heated to 850 degrees Celsius and brought into contact with the test material. If the material can withstand the high temperature of the wire without significant damage ormelting, it can be considered to have good heat resistance.

These two testing methods play an important role in product design and material selection.

1. They help manufacturers and designers select suitable fire-resistant materials to ensure that products have sufficient fire resistance in the event of a fire. By evaluating the combustibility and heat resistance performance of materials, the risk of using easily combustible materials or materials that cannot withstand high temperatures can be reduced, thereby reducing the risk of fire occurrence and spread.

2. The glow wire flammability index test and the 850 degree hot wire test can also be used to evaluate the difference in fire resistance performance between different materials. By comparing the test results of different materials, it can be determined which material is more suitable for specific operating environments. For example, in the field of construction, materials with lower flammability index and higher heat resistance are required to provide higher safety. In high-risk fields such as aviation and chemical industry, the fire resistance performance requirements for materials are higher, making these testing methods particularly important.

3. The glow wire flammability index test and the 850 degree hot wire test can also be used for supervision and validation of product quality control. Manufacturers can use these testing methods to ensure that their products comply with relevant fire resistance standards and requirements.By conducting regular tests, performance issues with materials or products can be detected in a timely manner, and appropriate improvement measures can be taken to improve product safety and reliability.

4. The glow wire flammability index test and the 850 degree hot wire test are important methods for evaluating the fire resistance performance of materials. Their application and significance can be summarized as follows: assisting in the selection of suitable fire-resistant materials to reduce the risk of fire; evaluating the difference in fire resistance performance between different materials and selecting the most suitable material; used for product quality control to ensure compliance with fire resistance standards and requirements. These testing methods have broad applications in various fields and play an important role in ensuring the safety of people and property.

Note:

1. Users of this apparatus must have a stable power supply, as fluctuations in voltage can affect temperature changes.
2. The thermocouple is only used for calibration purposes and should be marked on the ammeter after calibration so that it can be used for subsequent tests. After the temperature has cooled to room temperature, the thermocouple should be carefully removed from the hot wire before starting the test (the thermocouple is a consumable item and is not covered by the product warranty).
3. The hot wire should not be operated at high temperatures for prolongedperiods to avoid shortening its service life. The current should be reduced and the power supply should be turned off promptly after each use.
4. After each test is completed, the combustion chamber should be cleaned while the power is off, and care should be taken not to impact the thermocouple and hot wire.
5. After the combustion occurs, the exhaust fan can be used to exhaust the waste gas, but the fan should not be turned on during the test to avoid affecting the test results.
6. If maintenance is required, especially when replacing the hot wire, be sure to tighten the loosened screws. Otherwise, poor contact may affect the current circuit and create a high-temperature interface. After replacing parts, all screws should be tightened.

The ZRS-3H Glow-wire Test Apparatus is according to IEC60695-2-1, IEC60695-2-10, IEC60695-2-11, IEC60695-2-12, IEC60695-2-13 (GB/T5169.10, GBT5169.11, GBT5169.12, GB/T5169.13) < Basic testing methods of Glow wire, basic testing methods of Glow wire device>, UL 746A, IEC829, DIN695 and VDE0471.

Assessing Glow-Wire Flammability Index Using Glow-Wire Tester

ZRS-3H Glow-wire Test Apparatus

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