Knowledge of cable laying fire prevention
First, choose flame retardant wire and cable
Fire-proof mechanism of flame-retardant wire and cable: Under the heat of combustion reaction, the flame retardant located in the condensed phase thermally decomposes and absorbs heat, which slows down the temperature rise in the condensed phase and delays the thermal decomposition speed of the material. At the same time, it releases the chain reaction free radical blocker, which interrupts the flame and branches of the chain reaction, slows down the gas phase reaction speed and prevents the temperature rise in the condensed phase, thus achieving the fire-proof effect. Classification and selection of flame-retardant wires and cables: Flame-retardant cables mainly include ordinary flame-retardant wires and cables, halogen-free low-smoke flame-retardant cables, low-halogen low-smoke flame-retardant cables and fire-retardant cables. These products have different manufacturing technologies, performance characteristics and application ranges.
Second, scientific design and installation
Blocking: Fire-proof plugging is to plug the gap where the cable crosses with fire-proof plugging material to prevent the cable from catching fire. The joints between cable trench and electrical panel, box and cabinet, the holes in partition wall and floor slab, etc., shall be sealed with flame retardant. The cable fire door should be closed for a long time, the gap between the cable fire board and the cable ditch cover plate should be closed, and the densely laid place of the cable should be sealed with soft plugging material;
Partition: Fire partition wall can divide the long cable tunnel and cable channel into small sections, and reduce the fire interval. Fire partition wall, aluminum silicate fiber felt, fire blocking material, fire retardant coating, etc. can be used. The fire-proof partition wall is made of slag wool, which is used with fire doors in tunnels;
Coating: Coating fire-retardant coating can prevent the cable from burning after it catches fire. The fire-retardant tape is easy to construct, not easy to fall off, strong in adaptability and cheap in price. In the part from the cable entering the cabinet to the terminal head, all cables shall be coated with secondary fire retardant coating or fire retardant tape in the area of 2 ~ 3m on both sides of the fire partition wall.
Third, set up fire prevention facilities
Setting up fire alarm system: according to the actual situation, choose appropriate alarm probe and alarm system suitable for the characteristics of cable layer. At present, linear (or cable-type) temperature detector is widely used in cable trench and pipeline well;
High-pressure water spray fire extinguishing: High-pressure water spray fire extinguishing should be adopted in cable corridors and areas with dense cables. In order to make water spray fire extinguishing work in time and effectively, a highly sensitive monitoring and control system should be equipped;
Strengthen the ventilation of the cable layer (well): make use of natural ventilation conditions, and set up vents near the outer wall of the cable layer as much as possible. At the same time, a mechanical smoke exhaust system with uninterrupted power supply should be established, so that the smoke exhaust fan can be turned on through automatic alarm linkage at the early stage of fire.
Fourth, standardize daily management
Keep in good running condition: prevent cable short circuit and open circuit arc fire caused by cable internal insulation defects, aging, moisture and damage, and find cables with poor insulation in time and quit running; Maintain a good operating environment: it is strictly forbidden for waste gas and waste water of thermal system to flow into cable trench and cable tunnel;
Strengthen the monitoring and management of cable head: cable head is affected by many factors, which is the weak link of cable insulation. The terminal head and intermediate joint of power cable placed in cable trench, cable tunnel, cable box and cable interlayer must be registered, and supervision should be strengthened to avoid hot fire of running cable head.