Procedure for application of protective enamel on internal surface of pipe and procedure for coating quality control

FIELD: machine building.

SUBSTANCE: procedure for application of protective enamel on internal surface of pipe consists in preliminary surface cleaning, in application of enamel and in drying. Also, initially pipe is heated and dried by blowing air of t=+40÷80°C through it. Further, internal surface of the pipe is cleaned by an abrasive-jet method for elimination of impurities and obtaining roughness as high, as RZ 40, where upon dust is removed by air blowing. There are applied not less, than two layers of enamel. Each wet layer of enamel has thickness, as high as 90÷180 mcm. Each enamel layer is dried at flow rate 2÷8 m/sec by blowing air of temperature +15÷25°C through pipe during not less, than 3 hours. Interval between application of layers should last no more, than 24 hours. Here is also disclosed the procedure for control over application of a protective cover on internal surface of the pipe. A sample in form of a cylinder of length equal to 0.5-1.5 diametre of a pipe is cut out from the pipe with protective enamel applied on it as a coating. The sample is subjected to compression in a radial direction till coating fractures. Quality of protective coating is determined by a value of deformation of the sample at the moment of detection of this coating fracture.

EFFECT: simplified process, raised efficiency, reduced power input and upgraded quality of coating.

2 cl

 

The invention relates to the field of engineering, and in particular to methods of applying protective coatings as anti-corrosion insulation on the inner surface of the pipe, and to methods of quality control of such coverage.

The closest technical solution to the proposed method is the method of applying the protective enamel on the inner surface of a pipe, comprising pre-cleaning the surface, enamel and drying (see patent RU No. 2179076, publ. 10.02.2002).

The disadvantage is its high complexity, high energy costs and low quality.

The technical objective of the proposed technical solution is to simplify the technology, increasing productivity, reducing energy consumption, improving the quality of the coating.

For the technical solution proposed application of protective enamel on the inner surface of the pipe to produce by pre-cleaning the surface, applying enamel and drying, and the first pipe is heated and dried by blowing air through it t=+40÷80°C, and then produce cleaning of the inner surface by abrasive blasting to remove impurities and obtain a roughness not less than RZ40, after that remove dust by blowing air, then put at least 2 x enamel layers, each layer performing a wet film thickness of 90÷180 μm and dried each enamel layer by blowing with a speed of 2÷8 m/s through a pipe of the air temperature t=+15÷25°C for at least 3 hours, the interval between coats shall be not more than 24 hours. A distinctive feature of the proposed method, known from the closest to the proposed solution is that the first pipe is heated and dried by blowing air through it t=+40÷80°C, and then produce cleaning of the inner surface by abrasive blasting to remove impurities and obtain a roughness not less than RZ40, after that remove dust by blowing with air, then put not less than 2 layers of enamel, each enamel layer is performed by wet film thickness of 90÷180 μm, and dried each layer by blowing with a speed of 2÷8 m/s through a pipe of the air temperature t=+15÷25°C for at least 3 hours, and the interval between coats shall be not more than 24 hours.

The closest technical solution to the proposed method of quality control of applying a protective coating on the inner surface of the pipe is the way, which consists in the deformation of the sample within certain limits and determine violations of the coating (see patent RU No. 2231044, publ. 20.06.2004).

The downside of it is the high complexity of the method and the low accuracy of the control.

The technical objective of the proposed technical solution is the simplification of the way, reducing the complexity and improving the accuracy of control PR is knosti adhesion of the protective coating with the pipe.

For the technical solution proposed quality control applying a protective coating on the inner surface of the pipe to produce by deformation of the sample and determine violations of the coating, and from a pipe coated with a coating in the form of protective enamel after polymerization cut the sample in the form of a cylinder with a length of 0.5-1.5 diameter of the tube, which is subjected to compression in the radial direction to the violation of the coverage and the quality of the protective coating is judged by the magnitude of the deformation of the sample at the moment of detection of violations of this coverage.

A distinctive feature of the method is that of a pipe coated with a coating in the form of protective enamel after polymerization cut the sample in the form of a cylinder with a length of 0.5-1.5 diameter of the tube, which is subjected to compression in the radial direction to the violation of the coverage and the quality of the protective coating is judged by the magnitude of the deformation of the sample at the moment of detection of violations of this coverage.

Method of applying protective enamel is the following. First, the pipe is heated and dried by blowing through her hot air t=+40÷80°C. Then produce cleaning of the inner surface by abrasive blasting to remove impurities and obtain a roughness not less than RZ40. After that, remove dust by blowing air h is the cut pipe. Then put not less than 2 layers of enamel, each enamel layer is performed by wet film thickness of 90÷180 μm, with head centrifugal atomization, while the moving speed of the head is determined by the formula:

where L is the pipe length (m)having a surface area for painting, equal to 1 m2;

T - time enameling (sec) 1 m2the pipe surface.

where t is the thickness of the coating layer (μm);

Q - rate of enamel through a nozzle (l/min);

Pn- the pressure at the outlet of the pump during operation of the spray head (MPa);

PW- the pressure when removing characteristics of the jet (MPa).

where DTr- diameter surface of the pipe (mm);

Du- bowl diameter spray head (mm).

Dry each layer of enamel by blowing with a speed of 2÷8 m/s through a pipe of the air temperature t=+15÷25°C for less than 3 hours, the interval between coats shall be not more than 24 hours. The proposed technology of preparation of the pipe before applying the coating and drying of the enamel layers provides reliable adhesion of the enamel to the surface of the pipe, as well as between layers. Enamel spray centrifugal cylinder, rotating at 1800-2500 the b/min provides a wide the spray with a droplet size of one micron. As calculated by the above formulas, the moving speed reaches the specified optimum value of the wet coating layer. Wide torch in combination with the high speed head rotation provides overlapping bands and more even coating layer.

The method of controlling the quality of the protective coating on the interior surface of the pipe is as follows. From a pipe coated with a coating in the form of protective enamel after polymerization cut the sample in the form of a cylinder with a length of 0.5-1.5 diameter of the tube, which is subjected to compression in the radial direction to the violation of the coverage and the quality of the protective coating is judged by the magnitude of the deformation of the sample at the moment of detection of violations of this coverage.

This method is most effective in assessing the quality of the coating of the pipe, with significant curvature, and allows testing on samples made of pipes coated.

Example. The proposed method of applying a protective enamel on the inner surface of the tube was used to cover the inner surface of the tubing with an inner diameter of 60 mm and a length of 12 m, two-component epoxy-novolak enamel ARGOV-EP. Warming up and drying tube was carried out by blowing air temperature of t=+50±5°C. Cleaning and getting the roughness of not less than Z40 was carried out using sandblasting equipment Airblast with a tip Circleblast (see Annex 1). On the inner surface of the pipe by using a head centrifugal atomizing type WIWA (see Appendix 2) were applied two coats of enamel thickness 140÷160 mm each layer. The moving speed of the head of 0.41 m/s. Drying is carried out by blowing air temperature of t=+18÷20°C with a speed of 3-4 m/s. After drying of the second layer and weekly excerpts from the pipe was cut from a sample length of 50 mm, which was subjected to compression in the radial direction on the test press. Violations of the coating was detected when reaching the deformation of the pipe of 7.5 mm Test tubes, covered with the proposed method, operating conditions showed on the reliability and durability of the coating and long-lasting resistance to an aggressive environment.

1. Method of applying protective enamel on the inner surface of a pipe, comprising pre-cleaning the surface, enamel and drying, characterized in that the first pipe is heated and dried by blowing through her air temperature t=+40÷80°C, and then produce cleaning of the inner surface by abrasive blasting to remove impurities and obtain a roughness not less than RZ40, after that remove dust by blowing air and then put not less than 2 layers of enamel, etc is what each layer performing a wet film thickness of 90÷180 μm, and dried each enamel layer by blowing with a speed of 2.8 m/s through a pipe of the air temperature t=+15÷25°C for at least 3 h, and the interval between coats shall be not more than 24 hours

2. The method of controlling the quality of the protective coating on the interior surface of the pipe, which consists in the deformation of the sample and determining violations of the coating, characterized in that the pipe is coated with a coating in the form of protective enamel after polymerization cut the sample in the form of a cylinder with a length of 0.5-1.5 diameter of the tube, which is subjected to compression in the radial direction to the violation of the coverage and the quality of the protective coating is judged by the magnitude of the deformation of the sample at the moment of detection of violations of this coverage.



 

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