Operation steps for pickling and passivation of stainless steel welded pipes

Date:2024-01-26View:403Tags:stainless steel welded pipes, stainless steel welded pipes Inspection
he operation steps of pickling and passivating stainless steel pipe welded pipes are divided into the following 8 points:
1. Preparation
2. Chemical degreasing

1) Chemical degreasing adopts immersion method in the tank. The degreasing tank is made of steel plate and the inner wall is paved with PVC or polyethylene.

2) Use 12~15% nitric acid (by volume) for chemical degreasing treatment at a temperature of 40°C~60°C and a time of 2~4 hours.

3) When immersing pipe fittings in the tank, attention should be paid to their placement to avoid air remaining in the pipe.

4) During the soaking process, the pipe fittings should be moved up and down, back and forth, or turned over to continuously replace the solution in the inner cavity to improve the effect. If necessary, remove the pipe fittings, rinse them with water and then soak them.

5) Chemically remove oil until the surface of the pipe fittings is completely wetted with water.

3. Rinse with hot water

1) Take out the degreased pipe fittings from the degreasing tank, soak them in a hot water tank at about 40°C to 60°C and rinse them for 5 to 20 minutes.

2) The hot water tank is made of steel plate, and the inner wall is paved with PVC or polyethylene.

3) The chloride ion content in the water is less than 25ppm.

4. Rinse with water

1) Rinse pipe fittings that have been rinsed with water using pressurized water (pressure P≥0.1Mpa).

2) The chloride ion content in the water is less than 25ppm.
5. Passivation

1) Passivation adopts the soaking method in the pool, and the passivation liquid formula and soaking time are selected according to the table in 2.3.

2) Made of passivated channel steel plate, and the inner wall is covered with acid-proof plastic.

3) When soaking in the tank, pay attention to the placement position to avoid air retention in the tube.

4) During the soaking process, the pipe fittings should be moved up and down, forward and backward, or the pipe fittings should be turned over to continuously replace the solution in the inner cavity to improve the effect. If necessary, remove the pipe fittings, rinse them with water and then soak them.

6. Dry

Passivated pipes must be blown dry with clean compressed air or nitrogen as soon as possible, and sufficient time (at least 2 hours) must be allowed to passivate naturally in the air.

7.Inspection

After the pipe fittings are passivated, they should be self-inspected and mutually inspected, and then submitted to the quality inspector for acceptance as required.

8.Protect

1) If the outer surface of pipe fittings needs to be painted, it should be painted in accordance with the painting requirements.

2) After passing the inspection, the pipe fittings shall be sealed with plastic plugs, wrapped and protected with three-proof cloth, and marked.

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