2024-03-11
Application of Compressed Air in Spraying Operation
In the current spraying operation, compressed air is mainly used as the power source, not only in the whole process of mixing compressed air and spraying paint mixture directly, but also as a protective measure, compressed air is directly applied to artificial respiration system. This paper mainly introduces the latter, in the working environment of manual spraying, the air breathing mode of industrial compressed air after being filtered by the filtering device and supplied to the manual spraying worker wearing the gas mask.
Manual spraying operation will produce paint mist, organic solvent (toluene, xylene, etc.) gas, dust and other toxic substances spread to the working environment. If the operation is improper, inhaled into the body, a small amount will stimulate the upper respiratory tract and cause cough, headache, nausea, vomiting and other symptoms. A large amount of inhalation may damage the kidney, liver and blood system, and even cause death. Therefore, safety protection is particularly important. The state has clear standards for occupational environmental health HSE, and production is not allowed if it does not meet the standards.
1. Status quo
1.1 the current automobile spraying industry, only spray workers are distributed to wear gas masks. This air supply and breathing system does not have air humidification devices, and employees are prone to the following problems during long-term operation:
1) dry air leads to dry throat, swelling and other phenomena;
2) Because the air source is not good, the filter device is overloaded, and it is easy to produce peculiar smell for a long time, which affects the health and safety of employees.
2. Process flow
The fresh air taken from the outdoor air conditioner is sent to the multi-stage scroll booster compressor. The generated compressed air is stored and pressurized by the air storage tank, purified by the air purifier, humidified, heated and purified, and finally transported to the workshop through the sanitary stainless steel pipeline to supply the painter to breathe.
3. Equipment selection scheme
To achieve the purpose of stable and continuous gas source and comfortable breathing environment for 3.1 respiratory system transformation, the following aspects are required for equipment selection.
3.1.1 Gas quality
In order to ensure that the air is oil-free, the selected compressor must obtain the ISO8573-1:2010 compressor "zero content" certification. A slight positive pressure should be maintained in the breathing mask to isolate the gas from the working environment of manual spraying and to prevent external dust, paint mist and volatile solvent gases from entering. In this way, clean air is continuously fed and the exhaled CO2 and moisture are carried out, keeping the air in the hood fresh continuously. Compressed air produced by the compressor needs to reach the medical level, requiring that the treated air can be directly supplied to employees for breathing. The air quality indexes are as follows: oxygen content is 19.5~23.5; Compressed oil content ≤ 0.1mg/m3;CO content ≤ 11.4 mg/m3;CO2 content ≤ 1800mg/m3; No peculiar smell; Temperature is 18~25 ℃; Relative humidity ≥ 20%; Particulate matter meets Grade 2 standard in GB13277.1.
3.1.2 Gas Supply Flexibility
It is required that the selected equipment cannot be stopped in the case of production, and the gas supply can be stopped when the production is stopped. To ensure continuous gas supply, it is necessary to consider the standby or safety design for each component in the system, which is mainly reflected in the electrical control part, and at the same time, multiple compressor unit gaps can be considered.
3.1.3 Air humidification function
To ensure that the humidity in the breathing air, too dry is easy to make the throat dry, red and swollen, affecting the health of employees, so it is necessary to humidify the air in the respiratory system pipeline. But it should not be too wet, too wet to form water mist in the breathing mask, affecting the line of sight of employees.
Based on the above three requirements, the selected scheme is mainly composed of oil-free compressor, air purification equipment, humidification system and other ancillary facilities. All boxes, tanks and pipelines are made of high-quality stainless steel materials to avoid corrosion caused by long-term operation of the equipment.
Difficulties in Design and Manufacture of 3.2 Equipment
The difficulties in the design and manufacture of the equipment scheme are mainly the treatment of oil in the air and the humidification of the gas.
3.2.1 Selection of aerodynamic forces
The most difficult problem in compressed air is the oil in the air. There are usually two ways to solve the oil problem, one is to use an oil-free compressor system, and the other is to use an oil filter to remove oil.
The use of oil-injected compressor system, although the procurement cost is low, but the maintenance requirements are high. Often because the maintenance is not timely, the gas quality can not meet the requirements and affect the health of employees or damage to the terminal equipment, so the use of oil-free compressor gas supply, from the source to solve the problem of gas oil. The oil-free compressor unit is used as the gas source power center in the power part, and the compressor needs to obtain the "zero content" certification of the compressed oil to prevent the production of oil in the pipeline from the source.
3.2.2 Gas humidification
1) Humidification principle and process: humidify the gas in the compressed air pipeline and adjust it. Referring to the medical humidification device, the air pipeline from the compressor is divided into two branch pipes. One pipe is humidified through the pure water humidification tank, and the other pipe is bypassed. The two pipelines are merged at the outlet of the humidification tank. The air flow in each pipeline is controlled by the flow valve, and the air humidity in the pipeline is controlled by controlling the flow of dry and humidified air.
The liquid level gauge and alarm device are designed, and a drain valve is installed at the bottom of the humidification tank, which can regularly replace the residual water in the tank and clean the inside. Barreled pure water purification adopts the method of automatic replenishment of liquid level control, and realizes the functions of liquid level visualization, liquid level alarm, adjustable humidity and harmful gas detection by installing electronic detection equipment. According to the volume of the humidification equipment, every 3-4 stations with a set of principles, compressed air into the humidification equipment before the installation of pressure reducing valve, to ensure that the compressed air pressure into the humidification equipment adjustable. The humidifying equipment shall have a device to prevent water from flowing into the air line.
2) Main items in design
A. due to the high pressure of compressed air in the humidification tank, it is easy to produce gas boiling, so the device to prevent water from flowing into the air pipeline should be installed in the humidification tank equipment. Before the compressed air enters the humidifying equipment, a pressure reducing valve shall be installed to ensure that the pressure of the compressed air entering the humidifying equipment is adjustable, so as to inhibit the water in the heating tank from flowing out of the breathing mask.
B. Compressed air pipes shall be made of corrosion-resistant materials, and all pipes used in the humidification system shall be made of high-quality 304L stainless steel to prevent corrosion caused by long-term use.
Cleaning of 3.3 equipment before use
Overall equipment cleaning and air testing are required after installation and before use.
3.3.1 Equipment cleaning
After the whole equipment is installed, the compressed air pipeline shall be soaked with 75% medical alcohol to ensure that the pipeline is clean, disinfected and purged after cleaning, and a pressure resistance test (inert gas such as helium or nitrogen) shall be carried out under a pressure of 1.0MPa. The compressed air pipeline can only be used after passing the pressure resistance test.
3.3.2 Air detection
The air in the respiratory system needs to be tested by the professional department, and the respiratory system can be used normally after the test is qualified.
3. Overall maintenance and use of equipment
In the process of production and use, the humidification respiratory system needs regular maintenance and repair. In particular, the compressor unit must be maintained in accordance with regular maintenance requirements.
4.1 Humidification Tank Cleaning
The cleaning of the humidified tank is the key point here. The pure water in the humidified tank should be discharged from the drain valve during the interval period of shutdown, and the top cover should be opened for cleaning. Avoid long-term retention of pure water, breeding bacteria.
4.2 regular spot check of compressor unit
Equipment maintenance personnel shall make a spot inspection plan for components of compressor unit and filter unit, and carry out spot inspection, overhaul and replacement according to the plan.
Summary
In short, it is necessary to continuously improve working conditions, improve the working environment of spraying operations, meet the requirements of occupational health environment, and promote the development of enterprises. The respiratory system of spraying operation plays a role of safety protection for employees, and production shall not be affected due to substandard environmental requirements.
Spraying, Air, Equipment, Compressed Air, Piping, Compressors, Conducts, Gases, Requirements
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