Renovation plan of the painting line of the hottes

Water based paint pretreatment steel plate coating line transformation scheme

water based paint pretreatment steel plate coating line transformation scheme

December 25th, 2020

with the rapid development of engineering machinery, utility boilers, offshore engineering, hydropower, petrochemical, military equipment and other industries, the demand for steel plates from derived demand equipment or products is increasing. Steel plate is the main production material in port machinery manufacturing. The pretreatment quality of steel plate before production directly determines the service life of products. In the early stage of modern industrial development, almost all traditional coatings used in steel plate pretreatment are solvent-based coatings with organic solvents as the dispersion medium. The volatile organic compounds in solvent based coatings are harmful to human body, polluting the environment, flammable and explosive. Water based paint uses water as the main solvent or dispersion medium. Water based paint can reduce air pollution and is conducive to the healthy life of human beings and the sustainable development of the environment. In order to actively respond to the strict requirements of environmental protection and emission reduction of heavy industry manufacturing enterprises, protect the environment and improve the working conditions of coating personnel, it is imperative to apply water-based paint to construction machinery. Water based paint gradually replaces the pretreatment of traditional solvent based paint, and the coating line came into being in the pretreatment of heavy industrial steel plate. This paper describes a set of examples of transforming the traditional pretreatment steel plate coating line into a water-based paint pretreatment steel plate coating line, which is of great significance in reasonably doing a good job in sewage source management and environmental protection

1. Reconstruction of water-based paint pretreatment steel plate coating assembly line

according to the investigation and analysis, if the end treatment is adopted, the later maintenance and treatment cost is high, and the one-time equipment investment of a new assembly line is about 4million yuan, and the annual maintenance cost is more than 1million yuan. Therefore, the development and transformation of traditional assembly lines has become the most economical and feasible emission reduction plan. In view of the shortcomings of the equipment on the traditional pretreatment steel plate coating assembly line, it is proposed that people will also improve the endurance and sports performance of the car, and carry out local upgrading on the basis of the original equipment. The original station, operation system, control system and heating system remain unchanged, and only the spraying equipment is required to be upgraded to a water-based special spraying system, At the same time, increase the exhaust system to ensure the ventilation volume and the air supply pressure of the air supply system when the coating is dry

2. Assembly line workflow

the water-based paint pretreatment steel plate coating assembly line can realize closed-loop control principles such as equal rate loading, equal rate deformation, equal rate displacement, and equal rate strain: through the assembly line operation of transportation, painting, and waste gas treatment equipment, the uniform and qualified spraying of steel plate primer can be realized. This assembly line mainly includes six parts: paint drying room, water-based paint delivery pipe, waste gas treatment system, as well as the steel plate delivery system, paint mixing room and paint spraying room on the original assembly line (see Figure 1). The water-based paint that meets the requirements of steel plate primer proportioning is sent to the paint booth by high-pressure airless spraying pump, and the steel plate that has been on the conveyor and the surface has been derusted and ash removed is subject to primer coating pretreatment

3. Construction steps of assembly line reconstruction

install paint mixing room equipment (equipped with pneumatic agitators and mixing barrels) → connect paint mixing room and paint spraying room → install paint drying room equipment (add several temperature sensing probes) → install a set of electrical control cabinet (controlled by PLC) → install waste gas treatment system (washing tower and electric flocculation device, connected with water pipes) → assembly line commissioning

4. Key points of assembly line transformation

through research and development, design, transformation and other aspects, water-based paint has been successfully used in the traditional pretreatment coating assembly line. In the pretreatment process of steel plate primer in heavy industry manufacturing industry, it not only greatly reduces VOCs emissions, improves the workshop working environment, but also reduces the investment cost of enterprises in end treatment equipment, Help enterprises achieve compliance and legal environmental protection production to the greatest extent of economy. The transformation of the assembly line mainly carries out technological innovation and tackling key problems in five aspects: (1) change the nozzle selection for painting on the traditional assembly line from 38z55 to 19z40. The new nozzle has rust prevention performance, which can not only improve the spraying quality on the surface of steel plate, but also successfully replace the 38z55 nozzle on the traditional assembly line. (2) A set of automatic spray paint equipment for spraying water-based paint is formed by combining the spray paint trolley, high-pressure paint delivery pipe, high-pressure airless spray gun and the new nozzle, and equipped with an induction device. (3) In order to solve the problem of equipment corrosion when using water-based paint in the paint mixing room of the traditional assembly line, one set of high-pressure airless spraying pump (compression ratio of 42:1), one set of agitator and one set of mixing barrel (80L) equipment are added, and the original paint mixing room is reformed to realize the mixing ratio of water-based paint and water of 15:3, so as to ensure the spraying quality. (4) In order to solve the problem of uneven heating temperature in the paint drying room, add blowing nozzle groups above and below the plate chain conveyor, transform the original paint drying room, and evenly transmit the hot air of the electric heater in the circulating air duct to the surface of the steel plate, so that the water-based paint can be cured quickly on the surface of the steel plate, and the aging can be increased by 50% (≤ 5min), and the quality requirements of the paint film thickness can also be met. (5) In order to solve the problem of up to standard emission of end-of-line waste gas (the emission limit of paint mist particles is 20mg/m3), a set of waste gas treatment system is added to receive the waste gas generated in the drying room and paint spraying room to the dry paint mist filter, and then enter the washing tower for spraying and filtration before reaching the standard emission, so as to reduce the harm to the health of construction personnel, enhance the internationalization of the base and participate in global competition

for the sake of sustainable development, solvent based coatings are about to withdraw from the stage of history, and water-based coatings will probably replace solvent based coatings in an all-round way. The water-based paint coating transformation of the traditional pretreatment steel plate coating line has the advantages of less transformation content, low cost, low transformation difficulty, and obvious effect after the transformation, which is in line with the development concept of green production, process reform, quality improvement and efficiency increase. It can avoid VOCs emission, resource waste, potential safety hazards, working environment pollution and non renewable and other shortcomings caused by the use of solvent based coatings, and guarantee sustainable development in action