What are the types of cable fireproof materials? How do you choose fireproof materials for fire resi
The cable flame retardant fireproof material is composed of a series of materials such as flame retardant light-type closed box, light refractory partition, organic fireproof blocking material and fireproof coating. It is suitable for cable fire protection of various voltage levels, which can effectively realize the fireproof separation of cable passages and prevent cable fire and flame.
How to choose fireproof materials for fire resistant cables?
When we use a cross-linked polyethylene power cable that is short-circuited or burned near an open flame, it will cause flame retardation due to the flame, especially when the multiple cables are concentrated. Therefore, it is very important to take reasonable cable fire prevention measures to prevent the spread of cable fires.
Cable fireproof material
The so-called fire-resistant cable is a cable that can operate normally for a certain period of time under specified flame conditions, or a cable that can keep the line intact under combustion conditions. In the GB/T19666-2005 standard, it is stipulated: 0.6/1.0KV and below cable under rated voltage, fire temperature is 750+50°C, fire time is 90min+cooling time is 15min, 2A fuse is continuous or indicator light not bright. The selection of conductor materials, mica tapes, insulation materials, and auxiliary materials for fire-resistant cables is explained below.
1. Selection of conductor materials and conductive core structures
The melting point of aluminum conductor is 685 °C and the fire resistance temperature is 750+50 °C according to GB/T 19216. It is obvious that the aluminum conductor can not be used as fire-resistant cable; the melting point of copper is above 1000 °C, so it can be used as fire-resistant cable. Conductor.
A copper wire with a cross-section of 1.0 mm2 or less does not melt at high temperatures, but since the core is too thin, it is easily broken due to local overheating and slight external influence, and the normal energization function is lost. Therefore, 1.0 mm 2 or less is not recommended. The copper wire is made of fire resistant cable.
Large-section cable fan-shaped core conductors are not easy to be fire-resistant cables, and round core conductors are suitable for fire-resistant cables. Because the circular structure is smoother than the surface of the fan-shaped structure, the force of the mica tape is relatively uniform, and the mica tape is not damaged, and the circular structure saves the mica tape than the fan-shaped structure, and the cost is low.
2. The choice of mica tape
The refractory temperature of synthetic mica is higher than the refractory temperature of phlogopite. Since the grading requirements for fire-resistant cables have been eliminated in the national standards, in the actual production, fire-resistant mica tapes can be selected according to customer requirements. From the safety of fire-resistant cables and the stability of fire-resistant cables, it is recommended to use synthetic mica.
3. Selection of insulating materials
The common insulating materials for fire-resistant cables are mostly PVC and PE, XLPE, etc., but the effect of XLPE is better than that of PVC because the insulation of the cable does not exist at 750+50 °C, but different insulation. The residual materials after burning have different effects on the mica tape.
The composition of PVC is PVC resin and CaCO3 adheres to the outside of the mica tape according to its combustion mechanism. The mixture of combustion solid residue CaO Cacl2 is in a relatively stable state, adheres to the outside of the mica tape, and will burn during the combustion process. Internal stress is generated and the mica tape is squeezed to damage the mica tape and affect the fire resistance.
4. Selection of auxiliary materials
As an auxiliary material for fire-resistant cables, the tape and filling are not critical materials, but should be based on the principle of producing the least residue after combustion.