Several problems needing attention in the operatio

Several problems that should be paid attention to in the operation safety of electrical equipment in boiler room

abstract the problems that should be paid attention to in the design and operation management safety of electrical equipment and cable laying in industrial boiler room are put forward, and the essential safety requirements are put forward

key words boiler room electrical equipment for everyone to choose the judgment standard of quality in the experimental machine problems preparation design and operation management safety

questions on safe operation in electrical equipment of boiler room

SUN Shaojie

(Taiyuan area centralized heating company Heping District Shenyang 110003)

(Liao Ming Research Institute of safety science 110003)(for example)

Abstract Authors put forward some questions which ought to be noticed in the design and operation of electri-cal equipment and lay cable in the industry boiler room , give the safety requirement in essence .

keywords boiler room electrical equipment the safety of design and operation

in recent years, during the operation safety inspection of industrial boilers in use, we found that people pay enough attention to the hazards of fire and explosion of the main equipment boilers in the industrial boiler room and various pressure vessels (tanks) bearing high temperature and high pressure, from equipment (facilities) to operation management, Most of the fire and explosion-proof measures are specific and feasible, and the lack of a certain understanding of the safety requirements for the laying of electrical equipment and electrical lines in the boiler room leads to the lack of attention to the hidden dangers of electrical accidents. It is mainly reflected in the following aspects:

(1) the selection of motor, starting control equipment, lamps and conductor types is incompatible with the environment of different buildings and structures in the boiler room. For example, the electrical equipment of pulverized coal bunker and pulverizing system is not explosion-proof: the electrical equipment of water pump room and water treatment room does not have moisture-proof and corrosion-proof performance

(2) the wiring and laying of electrical lines are not reasonable. Some electric lines are set near or above steam and water heat exchangers, steam or hot water management, hot water distribution cylinders, and distribution cylinders; some are laid with open lines in places with high temperature, humidity, dust, and corrosion

(3) at the places and channels where boiler water level gauge, boiler pressure gauge, instrument panel and other main operations are installed, either the illumination value is insufficient or there is a lack of emergency lighting

(4) there is a lack of daily inspection and maintenance management on the downlead of the lightning rod of the chimney of the boiler room, the grounding protection line of the electrical system and the electrostatic grounding device of the liquid fuel pipe. The downlead (grounding wire) is either open circuit, or the grounding point is corroded and poorly contacted

the unsafe factors in the above electrical operation, except for a few cases of poor original design, are mostly caused by the construction and installation not in accordance with the design requirements, the neglect of management after construction, or the unauthorized change of the original design when the enterprise repairs and replaces the equipment

2 several problems that should be paid attention to to to ensure the safe operation of electrical equipment

2.1 principle of type selection of electrical equipment

the ignition temperature of coal-fired industrial boilers that deposit dust (5mm) on the high-temperature surface is generally 225~280 ℃, and the lower explosive limit concentration of coal dust is 34~75g/m3, which belongs to combustible substances. Among them, pulverized coal preparation room, coal crushing room and coal transportation corridor belong to class D fire hazard places. According to the division principle of fire hazard areas in GB code for design of electrical installations in explosive and fire hazard environments, they are zone 22. Correspondingly, the protection type of motors, electrical appliances and instruments is IP54, and the lighting fixtures are ip54x. The coal-fired boiler room belongs to a dusty environment. The ignition temperature of dust is greater than 270 ℃, the ignition temperature level is T11, and the protection grade of dust-proof shell should be IP5. The water pump room and underground condensate tank room belong to humid environment. The motors and electrical equipment selected in the buildings and structures in the above different environments are suitable for different environments. At present, urban central heating boiler rooms mostly use heat exchange stations, and new bonding materials have a long storage period to improve heating efficiency. The heat exchange room in the heat exchange station belongs to the environment of high temperature, high heat and high humidity. For the electrical equipment (motor, water pump, electrical switch, anti-corrosion performance; and the cable is strictly prohibited to be laid above or near the high temperature and high heat equipment), it is best to lay through the steel pipe buried wall (or along the wall), and the shell of the electrical equipment should adopt neutral protection

2.2 General requirements for distribution line laying

the surface temperature of boiler surface, flue surface, hot air duct, hot water tank and other heat carriers is 40~50 ℃ or above. In order to avoid overheating of line insulation and accelerating insulation damage, power lines should not be laid along the above surfaces. When it is necessary to lay along the surface of the heat carrier, thermal insulation measures shall be taken. The electrical lines in the boiler room, power distribution room and water treatment room should be wired with metal pipe cables, and the wire connections should not be exposed

2.3 configuration of lighting device

(1) voltage of lighting device power supply. The power supply voltage of the lighting device in the boiler room should use different voltage levels according to different places. When the distance from the underground condensate tank room, ash discharge place and the installation of hot water tank, boiler body, metal platform and other equipment and components is less than 2.5m from the ground and platform working surface, measures to prevent electric shock or adopt a voltage not exceeding 36V shall be taken; The voltage of portable light should not exceed 36V; When portable portable lamps are used in narrow places in these places or in pulverized coal preparation and boiler barrel, the installation requirements are higher, and the lighting voltage should not exceed 12V. The power switch of the water treatment room should be set outdoors, and the electrical socket should have waterproof performance

(2) setting of local lighting. The selection of the minimum illumination value of artificial lighting on the working face of each room and structure of the boiler room shall comply with the provisions of the current national standard "lighting design standard for industrial enterprises". The incandescent lamp illumination of the water level gauge and the on duty test table that need to be observed frequently on the boiler thermal control panel is 125ix, and the fluorescent lamp illumination standard is 390ix. General lighting is difficult to meet, so local lighting should be set in the above places. When the working lighting goes out due to failure, in order to ensure the continuous operation or shutdown of the boiler, it is necessary to pay close attention to the water level, pressure and operation of relevant valves, and start the emergency standby steam feed pump as required to maintain a certain water level in the boiler drum, and emergency lighting should be set; Emergency lighting should also be set in places and passages where boiler water level gauge, boiler pressure gauge, feed water pump and other main places are installed. The lighting lamp is arranged at a position where the air flow is not easy to impact in the event of an accident

2.4 grounding device

gas and liquid fuel pipelines should have electrostatic grounding devices. When their pipelines are made of metal materials, they can be lightning protected or when they are connected with the grounding protection line of the electrical system, they can not be equipped with another electrostatic grounding device. Brick or reinforced concrete chimneys should be equipped with lightning rods or lightning strips. Chimney ladders can be used as their downleads, but there must be reliable connections. The impulse grounding resistance of each downlead should not be greater than 30 Ω. If there is an underground oil tank, when the underground oil tank has a vent pipe leading out of the ground, the vent pipe should be treated as lightning protection. Anti static grounding measures shall be taken for the coal chute of the coal conveying system and the air duct in the dust removal device. The working zero line of the lighting network must be grounded at both ends, and the grounding resistance should not be greater than 4. The interval between the cut and the experiment should not exceed 24h Ω

2.5 safety measures to be taken for the electrical of belt conveyor line

the electrical interlocking of belt conveyor must meet the requirements of process and safety, and should be economical and reliable. According to article 3.2.9 of GB code for design of power distribution of general electrical equipment, the following requirements are put forward for the laying of distribution lines of belt conveyor lines:

(1) set up start-up warning signals along the line

(2) set the accident signal, equipment operation signal and allowable starting signal at the duty point

(3) the emergency power-off switch or self-locking button is set on the surface of the control box (screen, desk)

(4) according to the specific situation, set the emergency power-off switch or dust-proof closed switch next to the interlocking machinery. When dust tight switches or self-locking buttons are used, they should be set every 20~30m

(5) the belt conveyor line shall be able to release the interlock and realize the machine side control; Sound and light signals should be used for the connection between the control room or control point and the belt transportation line

2.6 safety protection of the distribution room

the doors and windows of the distribution room should be closed tightly; The holes, ventilation holes and underground cable trenches connected with the outdoor shall be provided with covers to prevent the entry of small animals such as rats and snakes, and the protection grade shall not be lower than IP3X grade in GB classification of degrees of protection of enclosures; The ventilation holes directly connected with the outdoor open air should also adopt the same measures to prevent rain and snow