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Safety measures for fireproof cable wiring

Industry news
2021/08/05 17:09

Safety measures for fireproof cable wiring
  【一】Fire prevention measures for indoor and outdoor wiring
  1. Reasonable design
  When wiring indoors and outdoors, it is necessary to choose the correct route, try to take short cuts, go straight, avoid twists and turns, and reduce crossovers. At the same time, when selecting the line conductor, the type of conductor should be selected correctly according to the specific environmental characteristics. Generally, factors such as moisture resistance, moisture resistance, heat resistance, and corrosion resistance should be considered to prevent fire accidents.
  2, strict construction
When installing indoor and outdoor circuits, the burying of fixings and the connection and laying of wires must be strictly constructed in accordance with regulations to ensure quality and prevent problems before they occur. In particular, when the wires pass through walls, they must pass through wall bushings. Otherwise, It is prone to wear and tear, resulting in leakage, short circuit and fire.
  3, the wiring must meet the requirements
In actual production and life, electrical equipment is in different environments, and the types of wires and cables required to be used are also different, and the installation and laying methods should also be adapted to them. Only in this way can the safe operation of the wires in various environments and prevent fires happened. In order to ensure the safe operation of indoor and outdoor circuits, when wiring, attention should be paid to keeping a certain distance between the wires, between the fixed points of the wires, and between the wires and the pipes and the ground to prevent short circuits from causing fires.
  4, the wire connection should be firm
   The connection between wires or the connection of wires and electrical equipment is the main part that causes excessive contact resistance and local overheating and fire. Therefore, the wire connection must be firm to prevent loosening, oxidation, etc. of the contact surface. The insulation strength of the insulating material wrapped around the joint should be the same as that of the original wire.
   5. Regular inspection
   In order to ensure the normal operation of indoor and outdoor circuits, frequent inspections are required. In the work of checking the lines, it is necessary to arrange the use time of electrical equipment correctly and reasonably according to whether the line can withstand the current total power consumption. Check whether the joints of the line are loose and sparking, and re-reinforce or replace the old and aging wires. At the same time, the temporarily connected line must be removed in time to avoid fire accidents.
  【二】Fire protection measures for cable wiring
  1, standard construction
   When laying cables, the construction personnel must ensure the construction quality and standardize the construction. During construction, it is necessary to prevent mechanical damage caused by excessive traction, excessive bending, improper filling, and insufficient embedding depth. The middle joint and terminal head of the cable are collectively called the cable head. The cable head is a key part that affects the insulation performance of the cable and is the easiest source of ignition. Therefore, the withstand voltage and insulation resistance of the cable head should be measured before it is put into operation to ensure the construction quality and ensure the good connection of the joints.
  2, plugging cable holes
Cables must pass through the holes in floors, walls, cable trenches, roads and cable shafts, and seal them with non-combustible materials to isolate them to prevent the spread of cable fires; at the bifurcations of cable trenches and roads and the cable leading to the building For the exiting population, fire partition walls or fire doors should be installed. Non-combustible materials should also be used to seal the pores through which cables pass through fire partition walls; if the cables pass through floors, walls and other places, if metal pipes are used, the gaps between the metal pipe openings should be tightly filled with asbestos or asbestos mud.
   3. Use cable fireproof materials
  Common cable fireproof materials are fireproof coatings. Non-combustible trough boxes, fire-resistant partitions, fire-resistant blocking materials, fire-resistant nets, etc. Through the use of fireproof materials, it has a better effect on preventing heat transfer, preventing direct flame damage, reducing the scope of the fire, and preventing the spread of fire.
  4. Strengthen testing and maintenance
   It is necessary to conduct frequent inspection and maintenance of cables, strengthen line inspections, withstand voltage and load measurement, and eliminate faults and temperature rise in time to ensure the safe operation of cables and prevent accidents during operation.
   [3] Fire protection requirements for temporary power lines
  Temporary power lines are mainly used for surprise projects and short-lived power. Temporary use of electricity due to the simple wiring, improper installation, lax pipeline, and the selection of the wire cross-section is too small, causing the wire to overheat or pulling the wire randomly, causing the wire to touch the wire or the poor contact to ignite and cause a fire.
   Temporary power lines should strengthen fire prevention measures:
   Temporary power lines shall be approved by relevant departments before installation and laying. And appoint special personnel to be responsible for safety precautions, and remove them in time after use. According to the characteristics of the specific environment, correctly select the wire type and wire cross section, and wire it reasonably. Temporary overhead power lines shall not hinder the passage of personnel or threaten personal safety, and shall not hang wires on trees to avoid wear and tear of the wires and endanger personal safety. The power supply of temporary power lines must have good safety protection devices. When power consumption is stopped, the power supply of the temporary circuit should be cut off. When the outdoor temporary line encounters heavy storms, the power supply should be cut off temporarily and the work should be stopped.
  【四】Grounding and zeroing
   Grounding and zeroing are important safety technical measures to prevent electrical lines from being struck by lightning, overvoltage, or accidental electrification of electrical equipment shells.
  Grounding is to make a good electrical connection between a certain part of electrical equipment and the earth through a grounding device. When a certain contact of electrical equipment or insulation breakdown causes the equipment housing to become live, the ground current will simultaneously form a loop along the protective grounding device.
   Because the human body resistance is large, and the grounding resistance of the protective grounding system is small, the larger fault current flows through the ground to the earth, and only a small amount of current flows through the human body, thus ensuring personal safety. If there is no grounding device, all the fault current flows from the human body to the ground, causing a personal electric shock accident. Zero connection is to connect the non-charged metal part of the electrical equipment with the neutral line of the power grid. When the insulation of a certain phase of the equipment is damaged and grounded or touches the case, it forms a phase-zero closed loop with the neutral line. At this time, the short-circuit current is very large, which immediately causes the protection device to act, and the faulty equipment is disconnected from the power supply. To take protective zero connection, in addition to working grounding, the zero line must be grounded again at regular intervals. Grounding again is an indispensable safety measure in the protection zero connection system. Its function is to reduce the voltage of the neutral line to ground when a ground short circuit occurs in the power system or the equipment touches the case. When the zero line is broken, the degree of failure can be reduced.
  【五】Short circuit protection
   When an electrical circuit is short-circuited, the thermal effect, magnetic effect, force effect and voltage drop of the short-circuit current will have serious consequences on conductors, electrical equipment, electrical energy users, and the entire power system. Therefore, short-circuit protection should be performed on the electrical circuit to prevent accidents. In the short-circuit protection measures, fuse protection and automatic air switch protection are mainly used.
   Fuse is a protection device for short circuit or overload of power system and electrical equipment. It is generally installed at the power supply end of the protected network or equipment. When an overcurrent fault occurs, the melt melts, isolating the network from the equipment. In order to cut off the power supply line according to the expected current and the scheduled time, a melt with an appropriate rated current must be selected, and it is strictly forbidden to replace it with steel wire. Only in this way can the short circuit and overload protection of electrical circuits or electrical equipment be effectively protected.
   The automatic air switch is used for making and breaking the circuit under normal conditions and reconnecting the circuit after a fault. It has the functions of overcurrent protection, overload protection and undervoltage protection. In order to ensure that the automatic air switch can operate reliably when the distribution lines and electrical equipment are overloaded or short-circuited, and protect the wires, cables and equipment from burning out or causing fires due to overheating. Therefore, it is necessary to correctly select the appropriate switch type to make it truly protective.
  【六】The cause of transformer fire and fire prevention measures
The main causes of transformer fire are: transformer overload operation, causing temperature rise, resulting in poor insulation, poor stacking of transformer cores or aging of insulation between chips, resulting in increased iron loss and transformer overheating; transformer coils are mechanically damaged or damp , Causing inter-layer or inter-turn short circuits, resulting in high heat; oil leakage and oil leakage in transformer tanks and bushings, forming surface dirt, and burning in open flames; poor contact in transformer wiring and tap switches, causing local overheating, etc.
The main measures to prevent transformer fires are: before installation, check the transformer insulation, ensure that all parts are well insulated, and ensure that the transformer's rated voltage is consistent with the power supply voltage; when installing, pay attention to firm wiring and reliable grounding; pay attention to the transformer current and voltage during operation It is necessary to strengthen the inspection of various parts of the transformer, and deal with abnormal phenomena such as breakage and oil leakage in time; control the oil temperature below 85℃, and perform regular sampling tests on the oil to find deterioration or acid content. If it exceeds the specified value, it must be replaced in time. While taking fire protection measures for transformers, corresponding fire protection measures should also be taken for the transformer room.

1. The oil-immersed power transformer room should adopt a first-class fire-resistant building, and the door should be a non-combustible or difficult-to-combust body.
   2. Oil-immersed transformers should generally be installed in the transformer room, and there should be oil storage facilities.
   3. There should be good natural ventilation in the transformer room, and the indoor temperature should not exceed 45°C. If the room temperature is too high, mechanical ventilation can be used.
   4. There should be a certain distance between the transformer shell and the wall, and meet the relevant requirements.
  5. No other items are allowed to be stacked in the transformer room, and it should be kept clean, and the floor should be free of oil and water.
  【7】Causes of fire in switchboards and fire prevention measures
  The switchboard is an intermediate link between the power supply and distribution of electrical equipment. According to the different equipment controlled by it, it can be divided into lighting switchboards and power switchboards. The main reasons for the fire in the switchboard are: the wiring of the switchboard is not in firm contact with the electrical appliances, meters, etc., resulting in excessive contact resistance; the selection of switches, fuses, and meters does not match the actual capacity of the switchboard; long-term overload operation; The fuse selection does not meet the requirements; the switch of the switchboard generates sparks and arcs when the switch is closed or the fuse is blown.
The main measures to prevent fire in the switchboard are: the metal frame of the switchboard, the iron plate surface and the gold chip shell of the panel equipment should be well grounded, and the grounding resistance should not be greater than 4 ohms; the wiring of the switchboard should use insulated wires, and should prevent wrong or missed connections. And poor contact; all kinds of switches and circuit breakers installed on the switchboard should not be live with the blades and movable parts when the power is off; when the switchboard is installed in a place with combustible dust and combustible fibers, it should be sealed with iron sheets Power distribution box; explosion-proof power distribution panels should be used in places where there is a risk of explosion; power distribution panels should be kept clean, and no combustible materials such as clothes, gloves, and silk waste should be stacked nearby. While strengthening the fire prevention of switchboards, strict fire prevention measures must be taken for the high and low voltage distribution rooms.
  1. The high-voltage power distribution room should be a building with Class I or II fire resistance. The fire resistance rating of the low-voltage power distribution room shall not be lower than Class III. The windows of the power distribution room should have measures to prevent rain, snow, water, and small animals from entering. When the high and low power distribution devices are in the same room, the distance between them should not be less than 1m.
2. Each oil-filled electrical equipment, such as circuit breakers, voltage transformers, etc., should be installed in the compartment with partitions on both sides, or in the explosion-proof compartment. When the total oil volume exceeds 1 kg, it should be installed in a separate Inside the explosion-proof room. Or adopt a complete set of high and low voltage power distribution devices. The total oil volume is more than 60 kg, such as oil-immersed voltage transformer, there should be oil storage facilities or oil blocking facilities.
  3. Holes left by connecting busbars, cables, ventilation pipes, etc., passing through walls, floors, and the ground, should be blocked by refractory materials to prevent fire expansion after oil-filled equipment catches fire.
   4. A certain number of fire extinguishing equipment should be equipped in the power distribution room.
  【8】Causes of motor fire and fire prevention measures
The main causes of motor fires are: improper use or insufficient maintenance, resulting in short circuit or grounding between phases and turns of the motor, and overload operation during phase failure; poor contact of the contact points of the connecting coils and excessive iron loss; excessively high or excessive power supply voltage Low, wrong wiring method; power frequency is too low; bearing wear, rotor scan boring, open welding between coil turns, short circuit open loop, open circuit operation, etc.
The main measures to prevent motor fires are: correctly select the motor model and capacity according to the use requirements of the motor. Generally, the capacity of the motor should be about 10% greater than the power of the machine; install it correctly according to the model and purpose of the motor, so that the motor and the starting device are compatible with each other. Keep combustible materials at a distance of more than 1m and be installed on a non-combustible base; the section of the power cord for the motor close to the motor must be protected by a metal hose or plastic sleeve. The connection between the other end and the motor inlet box should be well fixed. Both the motor and the power cord pipe should be grounded, and the grounding wire should be firmly fixed on the motor bolt.
  According to the model and capacity of the motor, select the appropriate protection device. Strengthen the inspection and maintenance of the motor, clean it in time to keep it clean, and add lubricating oil in time; no combustible or combustible materials are allowed to be stacked around the motor, and no objects are allowed to be stacked near the starting part, so as not to affect the operation. The passage from the motor and the linked machinery to the switch should be kept unblocked. Strictly control the operating temperature of the motor, and the temperature rise during operation should generally not exceed 55"E; Strict operating procedures, find unsafe factors, remove them in time, and cut off the power supply in time after the motor is used.
  【九】Fire hazard and fire prevention measures of lighting equipment
   1. Fire hazard of lighting equipment
   Lighting equipment is a kind of electrical equipment that converts electrical energy into light energy. Commonly used mainly include incandescent lamps, fluorescent lamps, tungsten halogen lamps, high-pressure mercury lamps, stage spotlights, etc. The fire hazards are:
  The high temperature and high-temperature heat radiation on the surface of the lamp can easily burn the adjacent combustibles; the bulb is broken, and the hot filament can ignite the combustibles. The power supply voltage exceeds the voltage marked on the bulb, uneven heating of the glass shell of the high-power bulb, water droplets splashing on the bulb, etc., can cause the bulb to burst. The temperature of the filament is relatively high, after a certain distance of air cooling [the distance between the bulb and the landing place], there is still a relatively high temperature and a certain amount of energy, which can cause the burning of combustible substances; the contact part of the lamp holder generates heat or sparks due to poor contact, and When the lamp cap and the glass shell are loose, twisting the lamp cap may cause a short circuit, etc., which may also cause a fire accident; overheating of the ballast can cause combustible materials to catch fire. When the ballast is working normally, the ballast itself consumes power and has a certain temperature. If the heat dissipation condition is not good or the matching with the lamp is unreasonable, and other accessories fail, the internal temperature rises and destroys the insulation strength of the coil. The formation of a short circuit between turns will generate a high temperature, which will cause the surrounding combustible materials to be burnt. Combustible dust and combustible fibers accumulate on the bulb, which will be burned and ignited.
  2, fire prevention measures for lighting equipment
   According to the fire hazard of the place where the lamp is used and the environment, choose different types of lighting fixtures. For example, waterproof lamps should be used outdoors, and explosion-proof lamps must be used in places with explosion hazards, and should meet the requirements of on-site explosion protection. The distance between incandescent lamps, high-pressure mercury lamps and combustibles; the distance between tungsten halogen lamps and combustibles should not be less than 50cm. The wires used near the tungsten halogen lamp tube should be insulated with glass wire, asbestos, porcelain tube, etc. heat-resistant wire, instead of: directly use insulated wires with ductile properties to prevent the high temperature of the lamp tube from destroying the insulation layer and causing short circuits. It is strictly forbidden to cover the lamps with paper, cloth or other combustible materials. No combustible materials are allowed to be stacked directly below the bulbs. The bulbs in the warehouse should be installed above the aisle. Natural lighting should generally be used in the combustible materials warehouse. If lighting is really needed, light bulbs below 60W can be used. It is best to use lamps with glass shields, but halogen lamps, fluorescent lamps and those above 60W are not allowed. When installing incandescent lamp ballasts, attention should be paid to ventilation and heat dissipation. The brigadier ballast is directly fixed in the combustible ceiling, counter, exhibition kitchen window; the voltage and capacity of the ballast and the lamp tube must be the same and match.
  【十】The fire hazard of electric heating equipment and its fire prevention measures
  Electric heating equipment has a wide range of uses, with various types and different types. There are electric heating equipment everywhere from industrial enterprises to households. Industrial electric furnaces, electric ovens, electric irons, electric soldering irons, etc. are all electric heating equipment. The working temperature of electric heating equipment is generally very high, especially large electric furnaces used by industrial enterprises. If the equipment is defective, damaged or used improperly, there will be a greater risk of fire. Some electric heating appliances with lower power are often overlooked by people, so that the equipment is not maintained, careless in operation and use, and not strictly managed, and it is easy to cause fires.
   1. Fire hazard of electric heating equipment
  The heating temperature of the electric heating equipment is too high or the time is too long. Some electric heating equipment is not equipped with temperature control and alarm devices, or these devices are damaged or malfunctioning, etc.; the temperature and time are not controlled according to the process requirements; the operators do not strictly monitor the heating time and temperature according to the regulations.
Electric heating equipment malfunctions, damages, heat source leakage, or improper installation of electric heating equipment or overload of power wires, damage to heat insulation and refractory materials, causing high-temperature heating bodies and hydrothermal fluids to leak to electric heating elements; use in flammable and explosive hazardous locations Open-type electric heating appliances; incorrect and unreasonable selection of power supply wire specifications and models for electric heating devices, no necessary heat insulation measures or short-circuiting of electric heating elements, etc., which may damage the wire insulation, cause insulation burning and short-circuit fire.
  Improper use or lax management. Electric irons, electric soldering irons and other portable electric heating appliances do not have a unified management system. They are randomly placed on combustibles, or the power supply is not cut off after work is over or after a power outage, causing the electric heating appliances to bake combustibles for a long time and cause fires; use in violation of regulations Electric furnaces cause circuit overload; electric furnaces are placed and used casually to ignite the surrounding combustible materials; if they are not operated in accordance with process requirements and operating procedures, explosion accidents occur; electric heating appliances are used incorrectly. If the power cord of the electric heating appliance is not equipped with a plug, it is directly plugged into the socket or connected to people regardless of its power level, which is easy to cause a short circuit or poor contact; the lighting circuit is overloaded and a fire occurs.
  2. Fire prevention measures for electric heating equipment
  Industrial large-scale electric heating equipment should be installed in first or second-grade fire-resistant buildings, and small electric heating catering should be installed separately in non-combustible materials, and ventilation, heat dissipation, exhaust and explosion-proof pressure relief measures should be taken.
  The power of electric heating equipment is relatively large. In order to prevent line overload, it is best to use a separate power supply line. The wiring should be made of fire-resistant and heat-resistant insulating materials, and protective devices such as fuses should be installed.
  Industrial electric heating equipment should be managed by a dedicated person, formulate safe operating procedures, and strictly abide by them.
   Various industrial electric heating equipment shall be equipped with temperature and time control and alarm devices. And should strictly control the running time and temperature.
  Small electric heating equipment and electric heating appliances such as electric ovens, electric irons, electric soldering irons, etc., should pay attention to fire safety in the use and management. When electric heating equipment is energized, do not leave easily. Adults should be in the habit of cutting off the power supply. Units that use more electric heating appliances should have a special person responsible for cutting off the main power supply after get off work.
  According to the nature of the electric heating equipment, it is equipped with necessary fire extinguishing equipment so that it can be extinguished in time at the initial stage of the fire.
  【11】Fire hazard and fire prevention measures of electric welding equipment
   1. Fire hazards of electric welding equipment and electric welding
   There are many types of electric welding, and arc welding is currently the most widely used. Arc welding uses the electrode as one electrode of the circuit, and the weldment is the other electrode. It uses the principle of contact resistance to generate high temperature and forms an arc between the two electrodes to melt the metal for welding, usually called electric welding.
  The main equipment used in welding is electric welding machine. Electric welding machines are divided into two types: DC welding machines and AC welding machines. DC welding machines are composed of electric motors and dedicated DC generators. AC welding machines are composed of step-down transformers and current regulators. During electric welding, the arc temperature can reach 3000 ℃-6000 ℃, and a large number of sparks are ejected, which can easily cause combustible materials to catch fire. Due to electric welding, the temperature of the weldment is also very high, so there is a great risk of fire.
  2, electric welding equipment and fire prevention measures for electric welding
  The welding equipment should be kept in good condition. The insulation of the welding machine and the power cord should be reliable, and the welding wire should be made of red copper core wire, and should have enough cross-section to ensure that the insulation will not be damaged due to overload during use. When the wire is broken, it should be replaced or dealt with in time;
   Use bolts or nuts to connect electric welding wires with electric welders and welding tongs. They should be tightened and flammable, flammable and explosive materials should be avoided.
   During arc welding operations, electrical equipment is often contacted, so welders should understand and master the structure and principles of electrical equipment related to this project, and be proficient in their basic operation, maintenance and safe electricity knowledge.
   Various rules and regulations for safe electricity use should be formulated, safe operation regulations and shift system should be strictly implemented, and a post responsibility system should be established.
   Arc welding should be carried out in a special building. It is strictly forbidden to use the metal components, pipes, rails or other metal objects of the factory building as wires.

Safety measures for fireproof cable wiring