Fire-resistant cable is a cable with fire-resistant performance. With the continuous development of society and the continuous advancement of science and technology, people have a better understanding of fire-resistant cables. Today, TST CABLES will introduce fire-resistant cables in detail from the definition, classification, scope of use and testing precautions of fire-resistant cables. I hope to help friends who are interested in this aspect. If you still have questions after reading this article, you are welcome to communicate with us via email.
1. Definition of fire-resistant cable
Fire-resistant cable refers to a cable that can still maintain its cable function at high temperatures. It is used in places that require high security, such as high-rise buildings, chemical industry and other places. Compared with other cables, fire-resistant cables have higher safety and reliability, mainly because they have fire-resistant properties.
2. Classification of fire-resistant grades of fire-resistant cables
According to the fire-resistant performance of fire-resistant cables, they can be divided into four categories: A, B, C, and D, among which:
Class A fire-resistant cables can maintain good power and lighting conditions in 4 hours of high-temperature fire.
Class B fire-resistant cables can maintain good power and lighting conditions in 3 hours of high-temperature fire.
Class C fire-resistant cables can maintain good power and lighting conditions in a high-temperature fire for 1.5 hours.
Class D fire-resistant cables can maintain good power and lighting conditions in a high-temperature fire for 0.5 hours.
3. Scope of use of fire-resistant cables
Fire-resistant cables are widely used and are mainly used in places that require high safety, such as high-rise buildings, chemical industry and other places. Most of these places are closed environments, with frequent gatherings of people and traffic, so the electrical system is required to have high safety and reliability. Fire-resistant cables just solve this problem, so that good power and lighting conditions can still be maintained when a high-temperature fire occurs, ensuring people’s safety.
Testing of fire-resistant cables is a key step to ensure that they can maintain circuit integrity and electrical performance under fire conditions. These tests are carried out in accordance with international and national standards to verify the performance of fire-resistant cables under extreme temperatures. Testing of fire-resistant cables is a complex and rigorous process that requires professional testing agencies and equipment to ensure that the cables can provide reliable power support for critical systems when a fire occurs.
4. Fire-resistant cable test standards
The testing of fire-resistant cables usually follows a series of international and national standards, including but not limited to:
China National Standard GB/T 19216.21-2003: Involves the performance test of fire-resistant cables under fire conditions.
National Electrical Code NEC 505: Provides guidance on the installation and use of fire-resistant cables.
IEC 60331 series of standards: Covers a series of international test methods and requirements for fire-resistant cables.
5. Fire-resistant cable test items
The test items of fire-resistant cables mainly include the following aspects:
Fire resistance rating test: After the cable is subjected to a specified flame temperature (such as 750°C to 1000°C) for a certain period of time (such as 90 minutes), the circuit integrity should be maintained, that is, there should be no short circuit between the conductors of the cable, and there should be no leakage between the conductors to the ground.
Circuit integrity test: Under controlled fire conditions, the cable is tested to see whether it can maintain circuit continuity for a specified time. A special combustion test equipment, such as the equipment specified in IEC 60331, is usually used.
Refractory material alkaline resistance test: evaluate the stability of the cable’s refractory material in an alkaline environment.
Chemical analysis: determine the chemical composition of refractory materials such as carbon, silicon carbide, and nitride in the cable to ensure that it meets the standard requirements.
Sampling and analysis: sample the cable according to the method specified in the standard, and analyze the physical and chemical properties.
6. Fire-resistant cable testing process
The test process of fire-resistant cables usually includes the following steps:
Sample preparation: select representative cable samples to ensure that their length and structure meet the test requirements.
Pretreatment: may include steps such as cleaning, drying, and marking to ensure that the sample state is consistent.
Burning test: place the cable sample in a burning test device to simulate fire conditions and test its performance under high-temperature flames.
Circuit integrity monitoring: During the test, the resistance value of the cable is continuously monitored to determine whether its circuit remains intact.
Data recording and analysis: record various parameters during the test, such as temperature, time, circuit status, etc., and analyze them to determine whether the cable meets the fire resistance performance requirements.
7. Fire-resistant cable testing equipment
The equipment used for fire-resistant cable testing includes:
Flame test equipment: capable of generating and controlling flame temperature, usually requiring the flame temperature to reach at least 750°C.
Circuit monitoring equipment: used to monitor the circuit status of the cable during the test in real time, such as resistance change, current leakage, etc.
Above, we discussed the basic concepts, standards, items and processes of fire-resistant cable testing. Now, we will explore some specific test details and technical points in more depth to better understand the entire test process.
8. Technical points and precautions for fire-resistant cable testing
1. Temperature and time control
In the test of fire-resistant cables, accurate control of temperature and time is crucial. The test equipment must be able to accurately maintain the set temperature level and ensure that the test lasts for a specified time. For example, some tests may require the cable to remain functional for up to 3 hours in a flame of 800°C.
2. Cable fixing method
During the test, the way the cable is fixed will also affect the test results. Usually, the cable is fixed in a vertical or inclined position to simulate actual installation conditions. The selection and method of fixing points need to follow relevant standards to ensure consistency and comparability of test conditions.
3. Circuit testing
Circuit testing is to confirm the electrical performance of the cable under fire conditions by monitoring the voltage and current of the cable. This usually involves connecting the two ends of the cable to a circuit test device that can measure the resistance, voltage drop and current strength of the circuit.
4. Cooling and recovery period
In some tests, the cable will enter a cooling phase after experiencing high-temperature flames to evaluate its recovery ability after the fire. This phase may include a visual inspection of the cable and another circuit test to ensure that the cable can maintain circuit integrity after cooling.
5. Repeatability and reproducibility
Fire-resistant cable testing should have good repeatability and reproducibility, which means that the same test should produce similar results when performed at different times and places. This requires standardization of test methods and equipment, as well as training and experience of testers.
9. Fire-resistant cable laboratory and certification
Fire-resistant cable testing is usually conducted by independent third-party laboratories that have test equipment and qualifications that meet international standards. Once the cable has passed all necessary tests, it will receive the corresponding certification mark indicating that it meets the specific fire resistance level requirements.
10. Fire-resistant cable test report
After the test is completed, a detailed test report is generated, which contains the test conditions, test results, analysis and conclusions, and any non-compliance with the standards. This report is essential for evaluating the fire resistance performance of the cable and certifying its use.
Testing of fire-resistant cables is a comprehensive evaluation process that not only evaluates the material properties of the cable, but also verifies the design and manufacturing quality of the cable. Through rigorous testing, the reliability and safety of the cable in emergency situations such as fire are ensured, which is of great significance for protecting the safety of life and property and maintaining the operation of important facilities.
11. Latest progress in fire-resistant cables
With the development of technology, the testing standards for fire-resistant cables are also constantly updated, and new testing methods and technologies are being introduced. For example, some of the latest tests may take into account factors such as smoke emissions, toxicity, and heat release rate of cables in fires to more comprehensively evaluate the safety performance of cables. Fire-resistant cable testing is a field that is constantly updated and developing, and it is necessary to continue to pay attention to the latest industry standards and technology trends to ensure that cable products can meet the ever-increasing safety requirements. If you are interested in cable testing, cable engineering, cable materials, cable selection, cable market analysis, cable technology or have technical questions, you are welcome to follow TST CABLES official website. You can send emails to TST CABLES technical experts at any time (email: lixiangchao@testeck.com).
