Polysacchar paint spraying equipment and process

0 Introduction
is a new solvent-free, pollution-free coating developed in order to meet the needs of environmental protection in the past 10 years. It is characterized by: the construction process is simple, not affected by the construction environment, can be below - 20 degrees C and above 40 degrees C construction, not affected by moisture and temperature, coating curing time can be in the range of 10 s to 30 min as needed arbitrary adjustment; No solvent volatile in construction, is a complete green paint; Because of the characteristics of rapid curing, construction can be carried out on any surface, vertical surface and a variety of complex components, sprayed after the surface is smooth and beautiful; With water resistance, acid and alkali resistance, radiation resistance, oxidation resistance, anti-microorganisms and other excellent physical and chemical properties. Another feature of it is that in a variety of substrates (including steel, iron, aluminum, cement, wood, etc.), have a very strong adhesion, within a few s can form a strong co-price binding force with the substrate, it is difficult to remove
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from the substrate. Once the coating is formed, 30 min is ready for use and has strong technical properties, such as high heat, water and corrosion insulation. This technology has been rapidly popularized and applied in the anti-corrosion repair of pipeline networks worldwide. Research on this technology has also been carried out in the country.
1 components of the spray equipment and operation and maintenance
1. 1 Components of spraying equipment
Because the A, B (R) two components of polysaccharise coating react very quickly, the general static mixed spraying technology can not be applied to construction, so it is necessary to use two components of high temperature high pressure airless spray equipment. Specialized spraying equipment must include: a smooth material handling system, accurate material metering system, uniform material mixing system, good material atomization system and convenient material cleaning system. This spraying equipment must have heating insulation, pressurized, impact mixing and other functions, because of the strong dependence of polysaccharin coating on spraying equipment and the complexity of the spraying equipment itself, so the spraying equipment and process to carry out special research, inspection and research is to ensure that the pipeline anti-corrosion overhaul with polysaccharin coating research is an important condition. Through the investigation of the spraying tool, the H20/35Pro type automatic spraying equipment was selected. The performance, function and operation and maintenance of each part are studied. Spraying equipment is mainly composed of spray host, pump pump, spray gun, spray gun cleaning tank, spray auxiliary equipment, etc.
1. 1. 1 Spray host
20 /35Pro host with a pair of piston metering pumps, can eliminate uneven load at work, can extend the life of the seal, the overall pump base can ensure the stability of pressure during pump cycle, thus providing a very stable spray type and pouring applications when reliable re-consequest. At the same time, the H20/35Pro host's hose heating and automatic temperature control system heating capacity, fast warm-up, by the near-gun submerged in the raw material flow of the temperature sensor to automatically control the temperature, can accurately control the temperature. Table 1 shows the system technical parameters for the H20/35Pro host. In Table 1, 1psi is 6. 89 kPa.
technical parameters of the 1 H20/35Pro host
the metering pump equipped with positive displacement and double-acting piston pumps. Available in a specific scale range of 1:4 to 4:1. UHMW seals and hardened chrome piston rods and cylinder walls guarantee optimum reliability of the pump system. Overpressurized safety switches are available on each pump. In addition, GUSMER's unique metering pump response device automatically positions the isocyanate pump shaft fully in the cylinder to prevent humidity contamination and extend the life of the pump seals.
1. 1. 2 Pump pump
H20 /35Pro type host is equipped with 2:1 pneumatic pump, pressure ratio of 2.25:1, output continuous operation of 21 L /min, and intermittent operation of 42 L /min. The pump can be used in 200 L industrial drums as well as in the transport of a variety of small packaged materials. There are strict requirements for the length and weight of the lines between the pump and the host, otherwise it will lead to insufficient feeding.
1. 1. 3 Spray gun
also selected GX - D71 gun. The GX-D71 gun implements high temperature, high pressure, and colliding shocks for a uniform mix of A and R (B) materials. Hybrid indoor collision mixing is achieved by precisely machined hybrid modules with long service life, available in a variety of different models, providing the most suitable mixing and pattern engineering when used in conjunction with mode control blocks. At the exit of the gun, there is a different form of pattern control disc (Pattern Control Disc, or PCD). By changing the PCD model, round, fan spray and pouring and different output quantities can be achieved, providing more efficient mixing and pattern engineering. The stem on the gun, in collaboration with the front and rear seals and air caps, completes the mechanical self-cleaning process when shooting/off the gun, cleaning all mixed ingredients that are cleaned from the mixing chamber after each injection, reducing expensive, environmentally harmful solvent cleaning procedures. Longer stop guns (e.g. troubleshooting, overnight stays, etc.) only need to be thoroughly cleaned with special gun cans and organic solvents, without removing the body of the gun.
1. 1. 4 Gun cleaning tank
the internal structure of the gun is very fine and A, R material is very easy to cure, so the ordinary cleaning method can no longer be thoroughly cleaned the gun, must be specially equipped with high-pressure spray gun cleaning tank cleaning. The GX-D71 gun is a mechanical self-cleaning spray gun that is an organic combination of an impact-type, aerosol-free spray gun mixing chamber and a stem. As can be seen from the characteristics of the GX-D71 spray gun above: This design does not require a conventional spray gun to clean the head with organic solvents or high-pressure air when the spray is suspended, greatly reducing the maintenance and maintenance workload. However, for longer periods of time (e.g. weekends, overnight stays, etc.), the canister must be cleaned with a special spray gun and thoroughly cleaned with a small amount of organic solvent, but the body of the gun must not be removed. In the actual use of GX - D71 gun continuous construction, only need to dismantle the gun once a week cleaning is sufficient, removal, installation is relatively simple.
1. 1. 5 Spray assistive devices
and spray equipment mainly include air compressors and oil and water separators. The air compressor is the necessary equipment for the whole spray system to provide power for pump pumps, spray guns, and proportion pumps for pneumatic hosts. The most common air compressors on the market are piston and screw 2. Although the piston air compressor is noisy, it is small in mass and small in volume. The piston air compressor was finally selected. Oil and water separators are mainly used to remove moisture, oil and tiny impurities from the air. Compressed air that is not dried and purified can cause serious damage to various components in the pneumatic mechanism; What's more, the oil, moisture and impurities contained in the compressed air can cause defects such as shrink holes and bubbles in the coating, which can damage the appearance quality and intrinsic quality of the coating.
1. 2 Operation and maintenance of spraying equipment
1. 2. 1 Spraying equipment connection
In the spray site, spray equipment including H20 /35Pro host, GX-D71 spray gun, feed pump, feeding tube, A components, R components, heating hose and many other components, must be reasonably connected to ensure the smooth completion of spraying operations. Figure 1 is a diagram of the equipment connection at the spray site. Air comes out of the air compressor and must pass through the air dryer. 2 pick-up pumps are inserted into industrial barrels with A and R components respectively, and the material enters the main unit from the pick-up pump with the feeding tube, and the volume ratio is controlled by the precision metering pump in the host with a volume ratio of 1:1, while receiving heating and pressurized by the host. Subsequently, the material flows out of the host, through the insulation hose, to the spray gun, after pulling the trigger, from their respective directions through the filter in the mixing chamber high-pressure impact mixing, and then high-speed spray, at the nozzle to receive compressed air to form a uniform fan-shaped or round material surface, sprayed to the steel pipe solidified into shape.
1. 2. 2 Field operation of spraying equipment
Spraying equipment structure is complex, complex connection, a wide range of operating steps, and errors in any one step of the entire spraying process may lead to the direct scrapping of the equipment, so the entire spraying process equipment operating steps must be standardized to determine. After repeated spray test groping, the field operation steps of the spraying equipment are determined, and the operation is carried out in strict accordance with the set operating procedures to ensure the normal conduct of the spraying test.
1. 2. 3 Maintenance of spraying equipment
In the long-term non-working state of the equipment, in order to prevent A, R barrels and pumps from contact with moist air crystallization, curing, quality, the need to remove the A, R pump from the 200 L barrel, and inserted into the protective case equipped with cleaning agents, while the A, R material barrels filled with nitrogen storage. Close the main machine, but do not turn off the air compressor and A material, R feed ball valve. When the feed pump is working normally, after the construction (experiment) of the top of the DOP lotion, the raw materials in the tube are continued to be recycled with DOP, and the residual liquid is sealed in the infusion tube after cleaning. When circulating cleaning, wash the lotion 20 kg, pressure 3 to 5 MPa cleaning 30 min, in 3 times. Cover the machine protective mesh and store the secure warehouse.
2 The determination of the spraying process
polypropyl coatings using high temperature, high pressure, hedging impact mixing process, so whether the spray process is fully reacted to, whether the performance is good depends to a large extent on the correct determination of the spraying process. The determination of the spraying process consists mainly of the determination of two key parameters: the spray temperature and the spray pressure.
2. 1 Determination of spray temperature
in the spraying process of polysaccharus coating, the increase of temperature is very beneficial to improve the spraying effect. At the same time, the reaction temperature constant temperature sensitivity of polysacchargium coating is low, so the increase in temperature will not cause a sharp acceleration of the reaction speed, but will be due to the material viscosity of the obvious decline, so that A, R material mixing and mobility can be improved, from the surface seems to heat up but make the reaction more flat. The actual temperature is controlled at 70 to 75 degrees Celsius. The hose is heated to ensure that the temperature of A and R materials does not decrease with the extension of transmission distance during the transmission of the material, thus increasing the viscosity of the system, resulting in poor mixing effect. Therefore, the heating temperature of the hose should be basically the same or slightly higher than the temperature in the main heater, and is generally set at 75 degrees C. In addition, the temperature of the hose rises more slowly than the temperature of the main heater, so the hose is generally opened for easy operation.
2. 2 Determination of spray pressure
polypyre coating is mixed with high pressure impact, so increasing pressure has obvious benefits for the performance of the entire system. After the pressure is increased, the atomization effect is better, and the rough and orange peel of the coating surface disappears obviously. However, the disadvantage is that after the pressure increases, the anti-splash phenomenon of spraying increases, and the protection of non-spraying areas and construction personnel needs to be further strengthened, thus bringing greater safety hazards to the whole construction process. Experiments have resulted in a spray pressure of between 2,000 and 3,500 psi for polycep coatings.
2. 3 Adjustment of spray pressure difference
For polysaccharated coatings, the ideal mixing effect is: A, R material density is consistent, heating temperature is consistent, spray pressure is consistent, so as to ensure the equivalent reaction of polysaccharated coatings. However, in fact, because the density of A, R material, viscosity and other physical properties are often different, so it is difficult to achieve the ideal mix. Reflected in the operation is spraying, A, R material spray pressure difference is difficult to adjust to 0. Special attention should be paid to the pressure difference between the A and R parts when spraying, and when the pressure difference is ≤500 psi, the uniform mixing of 2 materials can be guaranteed. When the pressure difference is greater than 500 psi, the material must be re-adjusted to ensure that the material is mixed evenly and that it is not cured in the spray gun. Therefore, in the actual spraying process, according to different polysaccharies coating formulation, the pressure difference of A and R materials for field adjustment is an important step in the preparation of high-performance polysaccharies coatings. In preparation for spraying, the first test spray 2 polyplate plate, in the process of test spraying, observe the A, R material out of the pressure meter, calculate the pressure difference between the two. If the pressure difference between the two is greater than 500 psi, the spray should be stopped immediately and the pressure should be adjusted.
to adjust the pressure is to adjust the heating temperature of A and R materials. Generally increase the heating temperature of the A material, reduce the heating temperature of the R material, and then re-spray the work, re-observing the pressure difference, until the pressure between the two is within 500 psi, preferably within 200 psi. It is important to note that neither the increase nor the decrease in temperature should exceed the temperature range of 70 to 75 degrees Celsius.
3 Conclusion
Through the study of typical equipment in existing polysaccharidis spraying equipment, we have studied in detail the performance and function of the various important components of polysaccharidis coating coating equipment, and developed a set of methods for equipment connection, operation, maintenance and maintenance. The spray temperature, spray pressure and other parameters in the spraying process are determined by experiment.