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What are the hidden dangers of coating production lines?
In order to save costs, many people randomly chose a supplier for construction when choosing a coating production line. Without systematic evaluation and comprehensive consideration, they rushed into construction. As everyone knows, various problems occurred during the production line operation. It has even become a serious security problem. For this reason, I have compiled the hidden safety hazards that may occur in the coating production line for you, and help you to provide references in the design, construction, operation and maintenance process.
1. Blasting caused by poor ventilation of the drying furnace
The ventilation facility of the paint drying furnace is the main method to reduce the concentration of combustible gas in the furnace. The size of the exhaust gas volume must be confirmed through strict calculations. If the ventilation volume is too large, it is difficult to keep the furnace temperature balanced; if the ventilation volume is too small, the combustible gas in the furnace cannot be discharged in time, and the more the accumulation, the more likely it is to occur. However, most paint drying furnaces in China are planned and made by barrel manufacturers. Most of them do not set scientific exhaustion and set the exhaust air volume at will. Some exhaust air volume is too small, the foundation can not meet the requirements; some exhaust air volume is too large, open and stop during the production process, so it is very easy to cause accidents. According to the survey, many manufacturers of drying furnace planners do not know how to calculate the exhaust air volume and how to calculate the power of the drying furnace. They just make it at will based on other people's ready-made stoves, and then adjust them at will. Therefore, the hidden dangers have greatly increased.
2.Too much paint on the hanger caused the incineration of the drying furnace
At present, most steel barrel production lines are painted by electrostatic spraying or high-pressure airless spraying. The conveying system is mostly suspended and the bottom chain is used. No matter what method is adopted, the conveyor chain, especially the hanger, always sticks to paint during spray painting. The conveyor chain repeatedly passes through the paint spraying room, and the paint on the hanger becomes thicker and thicker, and sometimes the accumulated paint has more than doubled the original hanging concrete volume.
Repeated heating of the hanger in the drying furnace makes the lacquer hard and brittle. Due to the activities of the hanger, the accumulated paint is often broken and dropped from the hanger. When the steel barrel enters the drying furnace, the falling paint blocks often fall on the electric heating elements to cause high-temperature incineration. The incinerated paint blocks will soon cause the incineration of the surrounding accumulated paint and increase the temperature in the furnace. The smoke happened. At this moment, if the concentration of flammable gas in the furnace is very high, severe explosion may occur.
Therefore, the hanger of the steel barrel drying furnace should be replaced frequently and arranged at any time. In general, two sets of hangers can be prepared for replacement and replacement. The paint remover can be dipped in paint to remove paint. If there is no condition, you can also place the hanger in a safe place to burn off the paint. Do not place the hanger too centrally during incineration to avoid deformation of the hanger due to too high temperature.
3.Incineration of drying furnaces or spray booths caused by open flames
The spraying room produced by the coating of steel drums is adjacent to the drying furnace. When the concentration of the solvent evaporated in the air reaches a certain amount, when the air temperature is close to the flash point of a certain solvent, if there is an open flame, it can cause incineration. May also cause blasting. The open flames in the paint application area come from smoking matches, lighting a lighter, welding torches, metal objects hitting each other, starting electrical switches, and sparks from static electricity. Open flames or sparks can occur from different heat sources (such as gas, fuel oil, far-infrared or infrared), light curing, electric beams, high-frequency and other drying furnaces, such as electric ignition or over-temperature and equipment failure. Incidents of incineration and blasting in the drying furnace or spraying room caused by open flames are common in China.
Regarding the electrical equipment in the coating operation area of steel drums, explosion-proof methods should be adopted, which can effectively prevent electric sparks from being exposed. At present, moreelectrostatic spraying methods are used, and the operation is slightly careless. For example, if there is no constant field circuit in the circuit composition of the high-voltage striker, it is very simple to cause electrostatic ignition. Take powder spraying, although the flash point is much higher than the solvent, generally above 430 ~ 500 ° C, but the flash temperature of electrostatic ignition can be as high as about 700 ° C, which is enough to cause powder burning and blasting (at concentration). Therefore, in order to effectively avoid open flames, the operator is first required to comply with safe operating procedures and coating processes, otherwise fire incidents cannot be avoided.
4. Blasting caused by poor coating process on the surface and inside of the steel drum
A factory produces a batch of inner-coated barrels for food, and the inner wall of the barrel is made of steel inner coatings for food. This coating requires high pressure airless process construction, drying temperature is 150 ℃, drying time is 15 minutes. Because it is necessary to carry out the internal coating before the installation of steel barrel parts, the barrel body and the lid must be sprayed and dried separately. Domestic domestic barrel body internal coating and drying are generally selected by horizontal production lines. The factory does not have the production conditions, but it is unwilling to lose this business. Therefore, there are "capable people" who have called to choose the existing vertical exterior coating and drying furnace. The method is: firstly spray the barrels inside, then leave them to dry naturally outdoors, and then install them. The barrels that have been installed can enter the exterior coating production line for coating, and enter the drying furnace for surface and interior coatings. drying. The factory chose this method, but when the steel barrel entered the middle of the furnace, the steel barrel in the furnace exploded. Not only the steel barrel burst, but also the furnace burst, causing heavy losses.
So what caused the steel drum to burst? It turned out that the steel drum did not enter the coating film to dry after coating, but was dried in a dry state. Because the drying conditions were not reached, the appearance of the inner coating seemed basically dull, but the internal solvent did not completely evaporate. In this way, when the steel drum is installed, a closed space is formed in the drum. When entering the drying furnace, the temperature gradually increased, and the solvent in the inner coating guess began to evaporate. But because the evaporated solvent accumulates in the barrel and cannot be emitted in time, the concentration is getting higher and the pressure is getting higher and higher. When the pressure in the barrel exceeds the pressure limit of the steel barrel (due to the wrong pressure capacity of the steel barrel, the pressure bearing capacity is very low), the steel barrel bursts, and a lot of flammable gas inside the barrel is released after the explosion. The electric heating element can ignite after being ignited; in another case, the concentration of flammable gas in the barrel reached the blasting limit, so blasting occurred.
Therefore, the coating and production of steel barrels must be carried out in accordance with the correct coating construction process, and must not be speculative. Before the inner coating is completely dry, it must not be installed. This is for your own safety considerations and the other is for the user's consideration. Because there is no boring inner coating, it generally has a certain degree of toxicity. This is not allowed for barrels.
5.Blasting caused by failure of spraying room recovery equipment
Under normal circumstances, many solvents evaporate in the air in the operating area produced by the coating, and there are solvent-containing or non-solvent-containing coating dust, which forms a mixed gas with the air. This combustible mixed gas reaches a certain concentration in the air. When it is fired, it can be incinerated and blasted. The blasting flash point at this certain blasting concentration is the blasting limit, also known as the lower blasting limit. The highest blasting flash point is called the upper blasting limit. If the evaporated combustible gas is too little in the mixed gas, the air absorbs the heat released from the blasting point, so that the blasting heat in the blasting area is no longer dispersed, and only mixed combustible gas can be incinerated at this moment. If the flammable gas is mixed into the air, the concentration of the mixed gas is too high, and the oxygen in the air is reduced a lot. If the oxygen is not satisfied, it will not burst. Therefore, the concentration of the flammable gas in the air is too low or too high. None will explode, but there may be incineration.
In general, in the steel barrel spraying room, in order to reduce the deterioration of the paint and the concentration of paint mist in the spraying room, the method of paint recovery is often used. Regarding the powder coating process carried out by some manufacturers, this method is more useful. It not only saves a lot of paint, but also reduces the dust in the operating environment, which reduces the incidence of accidents and reduces environmental pollution.
The above is the relevant content of "What are the hidden dangers of the coating production line?" The information is provided by Guangdong Chuangzhi, a 25-year-old coating production line manufacturer. For more information about the coating production line, please follow us for updates !