|
|
|
|
|
|
|
|
|
|
The sustainable development of our country's economy, the country to vigorously develop the energy industry, long distance oil and gas pipeline is an important means of energy security, in the process of oil (gas) pipeline anticorrosion construction of steel tube surface treatment is one of the key factors determine the service life of the pipeline corrosion, it is a solid combination of anti-corrosion layer and steel tube can be provided. Verified by research institutions and the life of the coating depends on the quality of coating types, coating and environmental factors such as construction, steel tube surface treatment effects on coating life accounted for about 50%, therefore, should be in strict accordance with the specification on the coating on the surface of steel pipe requirements, continuously explore and summary, continuously improve steel pipe surface treatment.
1, clean
Using solvent, emulsion steel surface cleaning, to remove oil, grease, dirt, lubricants, and similar organic matter, but it cannot remove rust, scale, such as welding flux on the surface of the steel, so only as auxiliary means in the anti-corrosion production.
2, tools, cleaning
Main USES steel wire brush tool for steel surfaces such as grinding, can remove loose or cock scale, rust, slag, etc. Hand tools can achieve derusting Sa2 level, power tool cleaning can reach grade Sa3, if solid iron oxide adhered on the surface of the steel, tool cleaning effect is not ideal, anchor pattern depth of anticorrosion construction requirements. (
China sandblasting machine network
3, pickling
Commonly used chemical and electrolytic pickling process, two methods do use only pipeline anticorrosion chemical pickling, can remove scale, rust, old coating, sometimes can be used as sandblasting derusting after reprocessing. Chemical cleaning while can make the surface reaches a certain cleanness and roughness, but the anchor lines shallow, and easy to damage to the environment.
4, shot derusting spray (left)
Spray (cast) shot derusting spray is driven by high-power motor (cast) shoot high-speed rotating blades, make steel grit, steel shot, segment, minerals and other abrasive wire under the action of centrifugal force on steel pipe surface spray (cast) processing, not only can thoroughly remove rust, oxides and dirt, and steel pipe under the action of abrasive violent impact and friction, also can achieve the required uniform roughness.
After shot derusting spray (left), not only can enlarge the physical adsorption on the surface of the pipe, and can enhance anti-corrosion layer and mechanical adhesion on the surface of the pipe. Therefore, shot derusting spray (cast) is an ideal cleaning pipeline corrosion protection method. In general, shot peening (sand) cleaning is mainly used for the pipe inner surface treatment and shot (sand) is mainly used for pipe derusting outside surface treatment. Using spray (cast) shot derusting several problems should be paid attention to.
Descaling grade 4.1
Commonly used for steel tube, vinyl, epoxy phenolic anticorrosive coatings, such as the construction process, generally require steel tube surface is nearly white level (Sa2.5). Practice has proved that using the descaling grade removes almost all of the scale, rust and other debris and anchor pattern depth of 40 ~ 100 microns, and fully meet the requirements of anti-corrosion layer and steel adhesion, and shot derusting spray (cast) process can be used with low running cost and stable and reliable quality level to nearly white (Sa2.5) technical conditions.
4.2 spray (cast) shot abrasive
In order to achieve ideal cleaning effect, should according to the degree of hardness on the surface of the steel tube, the original corrosion, requirements of surface roughness, coating types to choose abrasive, for single layer, layer or three layer PE coating epoxy, using a mixture of steel shot and steel grit grinding are more likely to achieve ideal cleaning effect. Steel pill have the effect of the reinforcement steel surface, and it has steel grit etching on the surface of the steel. The mixture of steel shot and steel grit abrasive (usually the hardness of steel shot is 40 ~ 50
HRC, harder to 50 ~ 60 HRC can be used in all kinds of steel surface, even in the class C and D corrosion of steel surface, cleaning effect is very good also.
4.3 abrasive particle size and proportion
In order to obtain better uniform cleanliness and roughness distribution, ratio of abrasive particle size and design is quite important. Too much of the anticorrosive coating roughness in rush bum thin anchor lines; At the same time as the anchor lines too deep, in the process of anticorrosion coating is easy to form bubbles, serious impact on the performance of anticorrosive coating.
Roughness is too small will cause the loss of coating adhesion and impact resistance strength. For serious internal pitting, not only by the larger particles impact abrasive high strength, must also be polished away by small particles corrosion products to achieve clean effect, at the same time, reasonable proportioning design not only can slow the abrasive wear of pipeline and spray nozzle (blade), and the utilization of abrasive can be greatly improved. Usually, the particle size of steel shot 0.8 ~ 1.3
Mm, steel grit size is 0.4 ~ 1.0 mm, with 0.5 ~ 1.0 mm as main ingredients. Sand shot than the average of 5 ~ 8.
It should be noted that in practice, steel shot and steel grit in grinding ratio is very difficult to achieve the ideal, the reason is hard and brittle than steel grit steel shot and broken rate is high. To this end, sampling test should be continuously mixed abrasive in the operation, according to the particle size distribution, to adding new abrasive cleaning machine, and mixing in a new abrasive, the number of steel shot to account for the main.
4.4 rust removal rate
Of steel pipe derusting displacement speed depends on the type of abrasive and abrasive, abrasive per unit of time applied to steel tube, the total kinetic energy E and the kinetic energy of single abrasive particles E1.
Type: m - abrasive jet (left);
V - abrasive speed;
M1 - the quality of single abrasive particles.
M. Breakage related with the size of the abrasive, the broken rate size directly affect the cost of surface treatment and the cost of cleaning equipment. When the device is fixed, m is constant, y is constant, so E is a constant, but as a result of abrasive, m1 change, therefore, generally should choose the abrasive attrition rate is low, so clear to improve speed and long blade life.
4.5 cleaning and preheating
Before spray (cast) shoot processing, adopt the method of cleaning to remove oil on the surface of the steel tube and fouling, the heating furnace for preheating tube body a 60 to 40 ℃, the steel pipe surface dry state. In spray (cast) processing, due to steel tube surface oil free of dirt, can strengthen the effect of cleaning, drying of the surface of the steel tube also is helpful for steel shot, steel grit and the separation of rust and scale, make after cleaning of steel tube surface clean.
5 conclusion
Emphasis on the importance of surface treatment in the production, strictly control the descaling process parameters, in actual construction, the steel pipe anticorrosion layer of the peel strength value of more than standard requirements, to ensure the quality of the anticorrosive coating, on the basis of the same equipment, improve the technological level, reduce the production cost.
|
|
|
|
|
|
|
|
|
|
|
