Technical requirements for corrosion protection of seamless steel pipes

First, anti-corrosion of seamless steel pipe

Seamless steel pipe corrosion according to the requirements of the drawings, the use of epoxy coal tar lacquer outsourcing glass fiber cloth, painted topcoat anti-corrosion.

The construction process of the outer wall: pipeline rust removal → coating primer → first time paint → second time paint → glass fiber cloth → topcoat;
The inner wall construction process flow: pipeline rust removal → priming → first pass paint → second pass paint → third pass paint

Corrosion requirements:
1, Pipeline rust removal the surface of the pipe should be cleaned of grease, ash, rust, and oxide scale before being primed. The use of sand blasting rust quality standards Sa2.5.
2. The surface of the pipe shall be rusted and then primed. The time interval shall not exceed 8 hours. When the primer is applied, the base surface shall be dry. The primer brushing is uniform and full, and there should be no clotting or foaming phenomenon. No brushing is allowed in the range of 150-250mm at both ends of the tube.
3. After the primer is dry on the surface, it is painted with a brush top and covered with a glass cloth. The time interval between the primer and the first time the paint is applied shall not exceed 24 hours.
4, Epoxy coal asphalt coating using two components, room temperature curing type coating; glass silk cloth using dry, dewaxing, no saggers, edge sealing, in alkali, the latitude and longitude density of 10 * 12 / cm ~ 12 * 12 / Cm glass cloth. Immediately after the top coat is applied, the glass cloth is bandaged. The width of the edge of the glass cloth is 30 to 40 mm, and the overlap length of the joint is not less than 100 mm. The lap joints of the layers are staggered with each other. Glass fiber cloth oil penetration rate of 95% or more, no more than 50mm * 50mm blank, leaving a 150 ~ 250mm ladder-shaped pipe end.
5, The construction of the pipeline interface should be carried out after welding pressure test qualified, the new and old anti-corrosion pressure edge not less than 50mm, the length of the joint lap should not be less than 100mm, the joint should be firmly bonded, tight.
6, The outer wall of steel pipe coating mechanism: a bottom two surfaces and one cloth, the total thickness of the dry film 400μm.
7, Steel pipe inner wall coating mechanism: a bottom three, the total thickness of the dry film 300μm.

Second, anti-corrosion testing of seamless steel pipe
1, Coating inspection and acceptance:
a. During surface coating and after construction, the coated workpieces should be protected to prevent flying dust and other debris.
b. After coating, inspection should be consistent with the coating color, bright color, no wrinkles, blisters, sagging, leaking and other defects.
c. Coating film thickness measurement, using a contact film thickness meter to determine the thickness of the film, paint film thickness meter generally determine the thickness of 3 points, take the average.

2, Quality inspection
a. The quality inspection is carried out according to the design regulations using a sampling test.
b. Visually examine by root. Cover layer surface should be uniform, flat, no air bubbles, wrinkles, bulges and uneven embossing cover defects
c. The thickness of the paint film is measured with a magnetic thickness gauge, and measured at a distance of 1.5 meters at both ends of the single steel tube and in the middle circumference. The thickness of the paint film should satisfy two 85%: that is, 85% of the measuring point thickness reaches the design requirement. , The thickness of the measuring point can not be reached, the minimum value should not be less than 85% of the design thickness;
d. Check the pinhole with a pinhole tester. If a pinhole is found, grind it with a sandpaper grinder.
e. Insufficient paint film thickness or pinholes, re-inspection after re-fixation and re-repair until unqualified;
f. Adhesion inspection, use a hard knife on the coating to draw a cut angle of 60 to conduct spot checks, should be painted through the coating directly to the substrate, paste the scratched part with tape, tear off the tape after the observation of the scratch, coating The layer should not peel off. It may also be checked on a sample plate painted under the same conditions.

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