Take you to understand the A, B, C grades of flame-retardant cables

1. Classification and difference of flame-retardant cables
The ABC category of flame-retardant cables is classified according to the GB/T18380-2008 standard and is used to evaluate the ability of vertically installed bundles of wires and cables or optical cables to inhibit the vertical spread of flame under specified conditions.
1. Flame-retardant Class A means:Fire Retardant Cable is installed on the test steel ladder so that the non-metallic materials contained in the test in the total volume is 7L/m, and the fire supply time is 40 minutes. After the cable burning stops, dry the sample and measure The maximum carbonization range of the sample shall not be higher than 2.5m from the bottom of the torch
2. Flame-retardant Class B refers to: the cable is installed on the test steel ladder so that the non-metallic materials contained in the test in the total volume is 3.5L/m, and the fire time is 40 minutes. After the cable burning stops, dry the sample. The measured maximum carbonization range of the sample shall not be higher than 2.5m from the bottom of the torch

3. Flame-retardant category C refers to: the cable is installed on the test steel ladder so that the non-metallic materials contained in the test in the total volume is 1.5L/m, and the fire time is 20 minutes. After the cable burning stops, dry the sample. The measured maximum carbonization range of the sample shall not be higher than 2.5m from the bottom of the torch.
2. Which grade of flame-retardant cable is the highest?
It can be seen from the difference between the above three types of flame retardant ABC that the conditions of type A flame retardant are the most stringent, so the flame retardant rank order is A>B>C. A has the highest flame retardant level.
Three, flame-retardant cable application
Flame-retardant cables can be used in oil tank farms, important wooden structure public buildings, high-temperature places and other situations where fire resistance requirements are high and the installation and economic performance are acceptable. If self-contained oil-filled cables are laid in public corridors, passenger tunnels, bridges, etc. where fire protection is required, they can be laid in sand. Close to high voltage current,
For cable trenches of oil-containing equipment such as voltage transformers, the section trench cover should be sealed. When laying power cables in pipe bridges or exposed pipes, you need to choose fire-resistant ones. When laying through pipes in concrete, choose fire-retardant ones. Flame-retardant ones cannot replace fire-resistant ones, but fire-resistant ones can replace flame-retardant ones. When it comes to cost, it is better to choose cables with corresponding functions.

How to Improve Pass Rate of Fire-resistant Cable Fire Test

As fire-resistant cables are now more and more widely used, many manufacturers are producing them, but often the quality cannot be guaranteed. Therefore, under normal circumstances, when companies develop fire-retardant cable products, they first try to manufacture a section of the product, send it to the relevant national inspection agency, and then start mass production after obtaining the test report. A few cable manufacturers have established their own fire-resistant test inspections. As everyone knows, the fire resistance test is an inspection of the process results of the cables produced. The same process plan and the performance of the cables produced in different periods have certain differences. For companies that produce fire-resistant cables, it is like the fire-resistant test of the fire-resistant cable. With a pass rate of 99%, the fire-resistant cable has a 1% safety hazard, which is 100% dangerous for users. So how to improve the pass rate of fire-resistant cable fire-resistant experiments, from the raw materials, conductor selection, production process control and other aspects to explain1. There are three types of mica, synthetic mica, phlogopite, and muscovite. The quality performance of each is the best synthetic mica and the worst muscovite. For small-sized power cables, synthetic mica tape must be selected for wrapping, and mica tape cannot be layered. Use, long-term storage of mica tape is easy to absorb moisture, so the temperature and humidity of the surrounding environment must be considered when storing mica tape.

2. When selecting mica tape wrapping equipment, it should be used with good stability. The wrapping angle is best to wrap around 300-400. The mica tape is wrapped evenly and tightly. All guide wheels and rods that touch the equipment must be smooth. The wiring is neat, the tension is not too large, and the side plate and cylinder of the take-up tooling wheel are flat and smooth.

3. For the circular core with axial symmetry, the mica tape is wrapped tightly in all directions, so the conductor structure of the fire-resistant cable should adopt a circular compact conductor. The reasons are as follows:

①Some users propose that the conductor is a stranded flexible cable, which requires the company to communicate with users from the reliability of the cable to a round compact conductor. The soft structure of the bundle and the twisting can easily cause damage to the mica tape as a fire-resistant Cable conductors are not desirable, but some manufacturers think that users need what kind of fire-resistant cables, and manufacturers should meet user needs. I think users do not fully understand the details of cables after all. Cables are closely related to human life. Yes, cable manufacturers must clarify related technical issues to users.

②Sector-shaped conductors are not suitable, because the pressure of the mica tape of the fan-shaped conductor is unevenly distributed. As shown in the figure, it can be seen that the pressure at the three fan-shaped corners of the fan-shaped core around the mica tape is the largest Yes, because mica is a sheet-like silicate polymer, the molecular attraction between the layers is much weaker than the s1-0 covalent bond in the crystal. The layers are easy to slide and adhere to silicon, but the bonding strength is also Low, it is easy to fall off and split when external force is scraped and squeezed, especially when the fan-shaped structure is adopted, the wrapped wire core passes through the guide wheel, the wire splitting rod and the wire to the edge of the side plate of the tooling wheel, and the rear track When the process extrudes the insulation into the core, it is easy to be scratched and bumped, which leads to a decrease in electrical performance. In addition, from the perspective of cost, the section perimeter of the sector-shaped conductor structure is larger than the section perimeter of the circular conductor, which increases the precious material mica Belt, although the outer diameter of the circular structure cable has increased. The amount of polyvinyl chloride sheathing material has increased, but the product material is compared with the total cost, and the overall cost of the circular structure cable is still saved. Based on the above description, from the technical and economic analysis, it is best to use a circular structure for the conductor of the fire-resistant power cable.

Fire Resistant Cables Introduction

At present, the electrical system industry is accustomed to collectively refer to fire-retardant (Fire retardant), halogen-free and low-smoke (LS0H) or low-halogen and low-smoke (Lowsmokefume, LSF), fire resistant (Fire resistant) and other electrical appliances with certain fire resistance properties as fire-resistant cables.

1. Flame retardant cable
The characteristic of flame-retardant cables is to delay the spread of flame along the electricity so that the fire will not expand. Because of its low cost, it is a large number of cable varieties used in fire-proof electricity. Regardless of whether it is a single wire or a bunch of laying conditions, when the cable is burned, the flame can be controlled within a certain range, so it can avoid major disasters caused by the cable fire and prolonged combustion, thereby improving the fire protection of the electric line Level.

2.Halogen-free low-smoke flame-retardant cable (LSOH)
The characteristics of halogen-free low-smoke cables are that they not only have excellent flame retardant properties, but also that the materials that constitute low-smoke and halogen-free do not contain halogens. They have low corrosiveness and toxicity during combustion, and produce a very small amount of smoke, thereby reducing the impact on humans and instruments. In addition, the damage caused by the design is conducive to timely rescue in the event of a fire. Although the non-branch low-smoke flame-retardant cable has excellent flame-retardant, corrosion resistance and low smoke concentration, its mechanical and electrical properties are slightly worse than ordinary cables.

3. Low halogen and low smoke flame retardant cable (LSF)
Low-halogen, low-smoke and flame-retardant cables have a hydrogen chloride release and smoke density index between flame-retardant cables and halogen-free low-smoke flame-retardant cables. Low halogen (Lowhalogen) cable material will also contain halogen, but the content is lower.
The characteristic of this kind of cable is that it not only possesses flame retardant properties, but also emits less smoke and hydrogen chloride during combustion. This kind of low-halogen, low-smoke flame-retardant cable is generally made of polyvinyl chloride (PVC) as the base material, and then processed with high-efficiency flame retardants, HCL absorbents and smoke suppressants. Therefore, this flame-retardant material significantly improves the combustion performance of ordinary flame-retardant polyvinyl chloride materials.

4. Fire resistant cable (Fireresistant)
Fire-resistant and fire retardant cables can maintain normal operation for a certain period of time under the condition of flame burning, and can maintain the integrity of the circuit (Circuitintergrity). Fire-resistant and flame-retardant cables produce less acid gas and smoke when they burn, and their fire-resistant and flame-retardant properties are greatly improved. Especially when they are burned, accompanied by water spray and mechanical shock, the cable can still keep the line intact.