Application of aeration sprayer

Abstract: The principle and process parameters of aeration-type spraying are described. The characteristics of aeration-type spraying are introduced, and the precautions in the operation process are proposed.

Keywords: painting equipment, transformer

1 Introduction

Transformer coating generally adopts dip coating, shower coating, air spraying, high pressure airless spraying, etc.; for large components that are difficult to dip and spray, air spraying is usually used, and a few airless spraying is used, but air spraying coating utilization is low. At 50% or even only 30%, the compressed air consumption is large, and a large amount of paint mist is generated, which seriously pollutes the environment. The utilization rate of high-pressure airless spray coating is about 60%, the coating film is prone to sag, and the paint mist is also more. . The aerated spray has overcome both shortcomings and obvious advantages.

2, mixing gas spraying principle

The aerated spray coating is invented by combining the advantages of air spray and airless spray. The main points include: (1) The paint is pressurized to 4 to 5 Mpa by a special sprayer with a certain pressure ratio, and then sprayed through a nozzle. (2) The filtered and pressure-controlled compressed air is sent to the air cap and sprayed through specially designed holes. A part of the compressed air participates in the atomization process of the coating, that is, the expanded atomized coating is further atomized to make it finer and more evenly distributed, and another part of the compressed air forms a wind curtain around the fan-shaped paint mist of the coating, limiting The paint mist flows around and restrains it from being applied to the workpiece. In short, the atomization force of the aeration spray is derived from two aspects. One is from the liquid, and the paint is suddenly decompressed and expanded to be atomized after being pressed; the second is from the gas, that is, the flow of the compressed air, which causes the coating to further atomize. These two elements are combined and called twin atomization. This spraying method is called a gas mixing spraying method.

3, mixed gas spraying process parameters

The aeration sprayer is used for transformer coating, and the effect is good. After production verification, the process parameters are determined as follows:

Supply pressure: 0.4～0.6Mpa

Pump pressure: 0.3~0.4Mpa

Auxiliary gas pressure: 0.15 ~ 0.2Mpa

Painting amount: 1.2L/min

Spray width: 400mm

Spraying distance: 250 ~ 300mm

4, operating precautions

In order to improve the quality of the film and ensure the use effect, according to the production experience and experience, the following operational precautions are proposed:

a) The dust in the operating environment shall not affect the appearance of the coating film, and the temperature shall not be lower than 0 °C.

b) Filter before use, stir evenly, and the viscosity is controlled at 25~30S.

c) Spray the silver paint to remove the gun filter to prevent the gun from clogging.

d) When the pump is started and cleaned, the pump speed should not exceed 40 strokes/min, and the pump pressure should be 0.05~0.07Mpa.

e) The supply pressure should not exceed 0.6Mpa.

f) It is not advisable to use a gas-filled coating for workpieces such as tube radiators.

g) The thickness of one spray is 20~50un. The number of sprayed layers should be controlled as needed during construction.

h) To prevent sagging, control the viscosity and spray distance of the paint.

5, the application of aeration spray

Through a period of production applications, it has been proven that aerated spray has the following significant advantages:

a) Improve coating quality

The aerated spray method can obtain a high-quality decorative coating surface, and the key to obtaining such a surface is the atomization effect of the spray. The good atomization effect depends on two aspects of the spray mist flow, one is the fineness of each paint droplet after the spray is atomized, that is, the size of each droplet diameter; the second is the droplets of these paints. The uniform distribution of the composition of the paint mist over the entire width of the paint mist. The aeration spray method has achieved satisfactory results in both of these aspects due to the dual atomization principle.

Due to the good atomization effect of the aeration spray, the spray atomization droplets are fine and evenly distributed; the obtained coating film is uniform, flat and detailed than the air spray method, and can effectively overcome the coating defects such as sagging and "virtual smoke". Therefore, it has been widely used in various industrial sectors since the 1990s.

b) saving paint

It has been verified by production practice that the aerated spray saves 20-40% of the paint compared to the air spray, and saves 10-15% of the paint compared to the high pressure airless spray method. The reason is that the pressure of the paint used in the aerated spray is smaller than that of the high pressure and airless, and the pressure of the compressed air used is much smaller than that of the air spray (0.1 to 0.2 MPa). Under such working conditions, the initial velocity of the paint sprayed through the nozzle is much lower than that of the high-pressure airless spray, and the initial velocity of the compressed air is also greatly reduced, so that the outside of the mist flow has an annular air curtain constraint, restricting the paint mist from flowing to the periphery. Dissipate. These two factors determine that the aerated spray method greatly reduces the flying of the fugitive paint mist, which is more than 20 times lower than the air spray.

c) increase production efficiency

Because the aeration spray gun has a large amount of paint spray, it is 10 times that of the air spray gun; the paint spray flow width is up to 400mm, and the air spray range is only 70-100mm; the air spray spray can reach a film thickness of 20~50um, air spray gun Only 10 to 15 um can reduce the number of constructions; therefore, aeration spray has high production efficiency.

d) Improve the working environment

Due to the higher pressure of the aerated spray coating, the pressureless airless spray is much smaller, so that the initial velocity of the sprayed spray through the nozzle is much lower than that of the high pressure airless spray, and the spray mist of the spray paint hardly rebounds. At the same time, due to the effect of the air curtain, the paint mist is applied. Dissipation is limited; these two factors determine a significant reduction in paint fog during operation. After on-site inspection, the aerated sprayer produced paint mist more than 20 times lower than the air spray gun. The concentration of toluene and xylene is 5 times lower, which effectively improves the working environment.

e) has good processability
It has a wide viscosity adaptability and is suitable for a wide range of coatings, which can reduce the amount of thinner materials and is easy to operate, thus facilitating the promotion and application.
Although the aerated spray method has many advantages, it also has shortcomings, such as a one-time investment close to high pressure airless spray, and equipment and pipeline cleaning before going to work every day.

6, summary

The production practice proves that the mixed gas spraying machine has the advantages of good coating film quality, saving paint, high production efficiency, less paint mist and good processability, and is especially suitable for the coating of large components. It is a relatively advanced coating equipment. There are good prospects for the promotion of transformer coating.