Fire hazard and prevention of the hottest motor in

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Fire hazard and prevention of motor in production and operation

I. fire hazard and corresponding preventive measures in the production process of motor

the process of motor production is very complex, including shell production, coil winding and embedding, coil impregnation treatment, etc. Among them, the coil impregnation process has the greatest fire risk, which mainly includes three processes: pre drying, paint dipping and drying

1. Fire hazard

(1) a large amount of static electricity will be generated during the filtration, dumping and mixing of the impregnation solution. If it is not released in time and accumulates into high-voltage static electricity, it will cause danger

(2) when the electric heating method is used for pre drying, if the temperature rise is out of control, it may cause a fire

(3) a large number of flammable and combustible gases will be produced during the process of thermal impregnation and pre drying. When the concentration reaches a certain level, it is very easy to burn and explode in case of open fire or arc. When vacuum pressure impregnation method is adopted, because inert gas is not used for protection, high-pressure mixed gas may explode once it reaches its explosion limit in repeated recycling

(4) the drying operation is too rapid, the coil droplets after impregnation can be dried before they are dry, and the residual liquid dripping when drying with electric heating wire may cause a fire

2. Prevention

(1) it is best to use steam heating or vacuum heating in the pre drying process, and control the temperature and time of pre drying according to the heat-resistant grade of insulating materials, pre drying equipment and coil structure, so as to prevent fire hazards caused by too high pre drying temperature and too long pre drying time

(2) when the hot dip method is used for paint dipping operation, the hot dip workshop should be a building with grade I and II fire resistance rating, the room should be well ventilated, and the fan impeller should be made of non-ferrous metal. All open flames and operations with sparks expected to occur by 2025 are strictly prohibited in the workshop. All electrical equipment should meet explosion-proof requirements and be well grounded. When cleaning the mandrel with toluene, the action should be light to prevent splashing. It is not allowed to wipe the mandrel with a volume of synthetic fiber after a certain amount. Large rotors should be hoisted by crane, and the crane should run slowly and steadily. The paint and thinner in the paint tank should not be too full, and the paint dirt dripping on the floor should be removed timely and regularly. The paint cylinder shall be covered and placed, and the workpiece shall be covered immediately after being taken out. The soaked workpiece should be placed in a ventilated place to dry before drying

(3) when using vacuum pressure method for paint dipping operation, in addition to the fire prevention requirements of hot dipping method, attention should also be paid to: select inert gas for pressurization; The paint solution used for impregnation should be tested and filtered frequently to eliminate impurities; When pouring the paint liquid, it should be filtered with metal, the pouring amount should be small, and the mixing should be slow to avoid static electricity

(4) when drying, the drying room should maintain good ventilation conditions. If mechanical ventilation is adopted, the axial-flow blower shall adopt explosion-proof device, and the hot air sent into the drying room shall not be recycled. The drying room shall be equipped with a spring door without a bolt. It is better to use steam for data processing, steam heating, hot air drying or vacuum drying, and avoid using electric heating wire drying to reduce the fire risk. When electric heating wire must be used for heating, the electric heating wire should be completely separated from the workpiece, and the temperature should be measured every other hour to prevent the soaking liquid from dripping on the electric heating wire and causing combustion. The drying temperature should be stable from low to high, so that the solvent can evaporate slowly and will not form an explosive mixture. The maximum temperature during drying shall not exceed the heat-resistant allowable temperature of the insulating material

(5) during the maintenance of the drying room, the relevant approval procedures should be handled before the hot work, and it can be carried out only with the consent. The hot work maintenance room should be well ventilated, and all hot work equipment pipelines close to the tank immersion equipment room should be removed. The immersion tank must be vacuumed, and the paint tank must be removed from the hot work inspection site

(6) unit operations with similar production properties, such as pre drying, paint dipping, drying, etc., should be concentrated in the same fire-proof building to facilitate production and management

(7) paint materials, thinners, etc. required for on-site impregnation should be received as soon as they are used according to the dosage, and their storage time should generally not exceed one day. After use, it should be sealed and stored in metal containers

II. Fire hazards during motor operation and corresponding preventive measures

1 Fire hazard

(1) the selection of motor power is too small, resulting in the phenomenon of "small horse pulling the cart", which can cause the motor to burn out. Wrong selection of motor form not according to the environmental conditions of the place will also cause fire hazard. In addition, if the starting method is incorrect during use, there is a risk of instant fire

(2) the load of the motor has a certain limit. If the load exceeds the rated power of the motor, or the voltage is too low for a long time, and the motor operates in single-phase (or phase loss operation), the motor will overheat. Vibration, sparks, abnormal sound, poor synchronization and other phenomena, sometimes even burn the motor and ignite the surrounding combustibles

(3) the motor runs overloaded for a long time or starts repeatedly in a short time. In addition, poor heat dissipation will accelerate the aging of the insulation layer and reduce the insulation strength. Others, such as careless manufacturing and repair, artificial damage to the insulation layer, overvoltage or lightning strike, will cause insulation damage, short circuit and fire

(4) poor contact between coil contacts and motor grounding contacts will cause local temperature rise, damage insulation, spark, arc and even short circuit, which will ignite combustibles and cause fire. At the same time, when the motor with poor grounding leaks electricity, the human body or other conductors contact the live casing, which is very easy to cause electric shock injury accidents

(5) the motor is a high-speed rotating equipment. If the lubrication is poor or the structure is inaccurate, such as the deflection of the rotating shaft, in the high-speed rotation, severe mechanical friction can wear the bearings and generate huge heat, which further aggravates the rotating resistance. At least, the motor will work abnormally, or the rotating shaft of the motor will be stuck, which will burn the motor and cause a fire

(6) the quality of the iron core silicon steel sheet of the motor is unqualified, the iron loss consumption is too large, and the motor may have an overload accident

(7) open motor causes fire due to inhaling fiber, dust, blocking ventilation duct and poor heat dissipation

2. Prevention

(1) when purchasing a motor, it is necessary to refer to its rated power, working mode, insulation temperature rise, explosion-proof grade and other parameters, and carry out reasonable selection in combination with its set environmental conditions and actual work needs, so as to achieve both safety and economy

(2) the motor should be installed on a solid base, and there should be a space or passage of not less than 1 meter around. No sundries should be stacked nearby, and the room should be kept clean. The wires used must comply with the safety regulations. The section connecting the motor shall be protected by metal hose or plastic sleeve, and must be firmly tied and fixed

(3) there are two starting methods for squirrel cage motors: full voltage starting and step-down starting. Generally, full voltage starting is preferred. However, when the motor power is greater than 20% of the transformer capacity or the motor power is more than 14 kW, star delta (Y - △) conversion starting can be adopted. Reactance step-down starting and autotransformer starting. When starting a wound rotor motor, a rheostat is often connected to the loop of its rotor winding, and the starting current is adjusted by changing the resistance value from large to small loop. Commonly used rheostats include starting rheostat and frequency sensitive rheostat

(4) during the operation of the motor, faults may occur due to its own or external reasons, so reliable and effective protection devices should be set according to the motor performance and actual work needs. In order to prevent short circuit, various types of fuses can be used as short circuit protection; In order to prevent overload, thermal relay can be used as overload protection; In order to prevent accidents caused by motor leakage, good grounding protection can be adopted, and the grounding must be firm and reliable. Other safety protection facilities include under voltage protection, temperature protection, etc

(5) whether the motor is normal during operation can also be observed from the characteristics of current, temperature and temperature rise, sound difference and so on. Therefore, when analyzing and judging the operating condition of the motor, the staff should carry out necessary monitoring and maintenance. It includes monitoring the current, voltage and temperature rise of the motor, especially the parts prone to heating and fire. In case of blue smoke, burning smell, abnormal sound and other phenomena, as well as belt slip, axial movement and impact, stator and rotor friction, sudden drop of speed and other faults, it should be shut down immediately, find out the causes and repair in time

(6) the motor should be repaired and maintained frequently. When the power is cut off, the sub switch and main switch of the motor should be disconnected to prevent danger when no one is present when the power is restored; Unplug the power plug of the motor to ensure safety after work or when no one works

III. conclusion:

this paper briefly expounds the fire hazard and preventive measures of the motor in production and operation, which has a certain warning effect on the production and maintenance of the motor

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