Electrostatic powder coating accident prevention
Posted by: FEIHONG Powders |on August 12, 2012
Compared to the electrostatic spraying and painting, painting or mechanical spray, can greatly improve the working environment of workers, so that the mist is no longer flying into the air to ensure workers’ health. But for various reasons such as national standards and norms operating in the electrostatic powder coating operation fails due to operator, leading to the frequent occurrence of fire, explosion and serious accident in the electrostatic spraying operations. Therefore, electrostatic powder coating accident prevention must draw the attention of relevant personnel.
Electrostatic powder coating operation cause of the accident
1. combustible material powder
Electrostatic powder coating operations, the most serious accident is caused by the combustion and explosion of the powder coating, occurs because there are three kinds: First, the powder coating combustible material, with the possibility of combustion and explosion; normal spraying, the spraying device electrodes with improper spacing of the workpiece (or other objects), it is possible to discharge ignition phenomenon occurs, if the constant current source control failure, the ignition energy is likely to exceed the minimum ignition energy of suspended powder blasting; three dusting compartment within the powder and air mixture, the recycling air flow is not sufficient to reduce the concentration of the powder and air mixture to the allowable concentration, can easily reach the LEL, when the electrostatic ignition energy than the powder minimum ignition energy, it may lead to explosion.
2 electrical fault
Electrostatic powder coating electrical fault accident, many of which the spray room, spray gun equipment, electric heaters, drying tunnel, and other equipment are high failure rate. High pressure spraying equipment electrostatic cause electric shock, often caused by electrical short circuit fault; heating element in the electric furnace aging, static electricity, electrical grounding confusion, mistake of answering or poor grounding will result in the wounding of the apparatus charged; mobile device power cable insulation wear leakage cause the accident.
3 machinery accident
Electrostatic powder coating machinery accident hazards can not be ignored, especially in the pre-treatment process in the wet degreasing, rust removal, phosphating, washing and other spray equipment or equipment slot Baptist, the Shotblast in the dry pre-treatment process, spray sand equipment preheating furnace, dusting cabin, curing oven, and cooling devices are all likely to cause accidents. Workpiece or catenary, the hook parts falling parts are likely to cause serious equipment damage, or even a blasting accident.
From the process analysis, electrostatic powder coating accident factors include a number of aspects, such as the rationality of the process, the process parameters, device convergence is appropriate; chain design for power system control device is reasonable or not; set a reasonable safety warning signs or not, blasting preventive measures how effective; security alarm system, fire system equipment is appropriate, especially information sensing speed and processing mode conditions. Analysis from the perspective of operations management, should consider the degree of perfection of labor protection measures; safe operating procedures, the standard implementation of standards; job by job, including technical training, including safety education; to check the validity of security technology; equipment maintenance, maintenance cycle and quality; safety emergency equipment, including the state of preparedness of the emergency repair equipment, supplies a number of factors.
Countermeasures for Accident Prevention
The overall layout of a paint shop
Coating operating areas shall be arranged on the windward side of the plant year-round minimum frequency of wind direction, and before the plant area, a crowded place, cleanliness requirements aside adequate safety distance between the high of the plant, in principle, should be set according to an independent plant, at the same time need to set by the relevant provisions of GB50016-2006 “architectural design code for fire protection fire exits to ensure the smooth flow of import and export of more than two. Bit of painting operatives and entrance security door in the large plant emergency evacuation distance is generally not more than 25m. When the painting space for painting painting process using closed and closed to maintain negative pressure, while setting the concentration of combustible gas alarm system or automatic suppression burst systems (including qualified venting devices), and the paint section in fire district accounted for the paint shop area of less than 20%, fire hazard classification of the plant according to the production of D, E production plant to determine the fire protection requirements.
2 operators safety management
The operator must be familiar with the equipment system, including emergency relief facilities, fire facilities, and alarm devices, and skilled operators. Workers to accept the pre-service training to understand the safety of equipment performance, and consciously abide by the safe operating procedures. The operator must be familiar to comply with the knowledge of individual labor protection requirements to take the vacuum dust cleaning measures. Regular inspection and maintenance of the equipment, ensure that equipment running in good condition. Full-time security staff must be on the production site inspections and periodic testing.
3 coating equipment safety
Coating equipment should be designed to meet the country’s general safety requirements and Safety code for painting, professional safety requirements. Coating equipment equipment should have the following technical data: manual (including safety instructions); complete product nameplate (name, model, the main parameters of the manufacturer’s name and address, the manufacturing time).
Spraying equipment and other mobile electrical equipment should be equipped with dust cover, power cable to the bracket support care; relaxation laid to prevent wear of the insulation layer and plug port loose. Lighting equipment and switches used in the powder coating operation area must meet the requirements of explosion-proof dust. , Check the power source for the powder system and fan, electrical interlock system must be regularly tested. Equipment conductor in the coating operation area, including the transmission chain, dusting tank, duct, recovery, etc., must be firmly grounded to prevent electrostatic spray gun near ground to produce the arc discharge charge accumulated in the insulated conductors.
Strict routine inspection of the pre-treatment equipment systems, pumps, valves, sub-set pressure relief valve on the steam pipeline, closing valves, and whether pressure monitor heaters, heat exchangers and steam pipelines. The curing oven must be set to the air circulation duct or exhaust pipe, to prevent long-term operation to produce the accumulation of irritating volatile atmosphere or flammable gases. Oil, gas, dry type, and curing equipment, regular maintenance pipe, pumps, valves, is strictly prohibited leakage exist. Processing section in the former coating involved spray shot blasting, grinding power tools and high-pressure water cleaning methods such as mechanical pre-treatment, degreasing, pickling, and table tune, phosphating, passivation, cleaning and other chemical pre-treatment, as well as organic solvents In addition to processing, the workpiece old paint processes. Coating pre-treatment section in the process equipment shall meet the requirements. In addition to the extra large workpiece, no matter what kind of paint spraying process should be in the room spray (powder). (Powder) paint room ventilation should be organized airflow, the ventilation rate must also meet the requirements of explosion-proof safety and industrial hygiene. A variety of painting equipment and access to spray paint (powder) room spray equipment, assistive devices should comply with the conditions of security technology used in the dangerous area of the explosive gas atmospheres.
Specifically set up for painting plant or designated to produce the combustion space, should be classified as mild danger zone, but must ban all fire, to prevent the entry of foreign fire. The painting project should be designed to meet the fire resistance rating and plant explosion-proof safe evacuation requirements. Building structure, components and materials should be based on the fire, explosion-proof requirements selection; escape doors minimum width of not less than 0.8m, and the evacuation should be open; evacuation walkways clear width of not less than 1.4m; evacuation facilities should be equipped with emergency lighting and safe evacuation signs. Painting workplace should be the correct partition layout process route, starting from conducive to the safety, health, fire protection, energy saving, environmental protection and other design elements to take the necessary partition, isolation facilities, and pay attention to fire spacing and fire division. Central air conditioning layout pipeline of painting workplace in the fire danger zone damper should be set.
Selection of the excellent performance of the gun. Safety of low pressure into the gun and circuit feedback techniques should be set to the constant current source output control. When the gun electrodes close to the ground workpiece, the high-voltage generator can be reduced output voltage, short circuit and ground can be automatically cut-off, turn off the power. Choose reasonable parameters, as far as possible the low pressure, low-voltage electrostatic spraying, voltage output 30 to 70kV is appropriate.
Dusting cabin ventilation rate must be based on the opening section to debug, to ensure that the the dusting cabin openings Yat powder phenomenon occurred. Meanwhile, the total recovery amount of wind in the spraying process to ensure that the concentration of the spray powder in its lower explosive limit. Recycling compartment connected with the dusting, cleaning devices should have a rapid pressure relief openings for outdoor space, to prevent the explosion accident occurred. Dusting cabin high wind speed at the entrance of the vacuum pipe should be installed to the grid gate or magnetic separation device to prevent metal or hard objects into the pipe and friction, collisions generate sparks. Dusting the cabin should be set clear powder institutions, best continuous Qing powder, and keep the cabin deposited powder. Used to suck powder recycling wind pipe, horizontal pipe, elbow, etc. The wind speed must be large enough (≥ 15m / s), to ensure that no powder accumulation tube, to prevent dust blasting, spraying space caused by the greater destructive secondary explosion. Dusting tank, flame detectors and the linkage of fire extinguishing equipment, set the dusting cabin with recovery between the vent pipe on the blocking valve.
Regular maintenance correction linked with to prevent the failure of the hook loose, skew caused by the transmission chain hook to hang the accident; but also to prevent the hanging swing frame, shedding caused by the collision sparks and electrostatic loop electrode and the distance is not enough critical discharge or short circuit discharge occurs phenomenon.
4 Electrical Safety
The electrical safety of the painting – the venue, must comply with the requirements of the overall explosion-proof, electrical, electronics, lighting, lines, switches, connectors and other explosion-proof safety requirements is strictly prohibited random access temporary wire. In addition, most of the electrostatic coating of an accident should be grounded not been grounded, and the formation of insulating state. Conductive objects within the painting to be a clear distinction between the high voltage potential or ground potential, should be imposed outside of the high voltage or parts, must indeed be grounded.
Way by grounding Safety Measures: The operator must wear conductive shoes; full sweeping soles; coating between conductive objects must indeed be grounded; washed with solvent tank for fixed and, indeed, be grounded; the use of electrostatic hand-held spray gun operator to the bare spray gun; hanger hanging to be painted should be fully clean, remain to be painted as the ground potential; coating between the ground need to keep the conductive state. Charged coating machine or coating trough, full ventilation after the implementation of the ground, and the residual charge is removed. Use and operation of the main points: the end of the coating, the high voltage must be turned off to confirm the high voltage in the wash before. In the use of conductive paint, and paint supply system from the ground shall be insulated, the implementation of the coatings supply in the paint trough, the first implementation of the coatings slot grounded. If you use solvents to wash the part of the insulating material, applying high voltage confirm the solvent drying; regular cleaning of the coating machine coating dust pollution; shall not be used the stranded solvent vapor coating machine, in order to prevent pollution; really tighten loose or off the high voltage cable or paint hose; in order to prevent the discharge is located in the high-voltage equipment interlock device. Coating machine systems and ancillary equipment, security control points: the set of the necessary interlock device; requires the sequential action of its operation other than the order can not require; set up the conveyor entrance doors to the gas exhaust, fire service installations with the coater appropriate interlocks; set up a security fence to prevent the operator to enter the device; longer hanger to reduce the contact point of the conveyor with hangers; using automatic wash systems; set the automatic fire extinguishing device.
In addition, the tall plant should lightning directly stroke prevention facilities, precision electrical equipment, control system should prevent lightning facilities. Fire, explosion hazardous area is forbidden to set the electromagnetic radiation equipment, facilities, tools, and prone to electrostatic discharge objects. Explosion danger, anti-static grounding and lightning protection and grounding separate difficulties, the grounding resistance should be lightning protection and grounding resistance value selected.