Pickling treatment process of hydraulic system pipeline

The pickling of the hydraulic system pipeline is to remove the oxide and oil stains on the inner surface of the metal pipe through chemical action, so that the metal surface is smooth, and the hydraulic system is guaranteed to work reliably. Pipeline pickling must be done scientifically, normally, and reasonably in order to enable the hydraulic system to operate normally and give full play to its effectiveness. Pipeline pickling includes tank pickling and circulating pickling.

1. Pipeline pickling method

At present, both the tank pickling method and the pipe circulating pickling method are used in the construction.

(1) Trough pickling method. Remove the installed pipeline, put it into the pickling tank after disassembly, and then install it again after the treatment is qualified. This method is suitable for short pipes with large diameters, straight pipes, easy to disassemble and small pipeline construction, such as piping in hydraulic devices such as pump stations, valve stations, and hydraulic systems with small on-site piping, all of which can use grooves. Type pickling method.

(2) Circulating pickling method in the tube. The hydraulic components are disconnected or removed in the installed hydraulic pipeline, and connected with hoses, pipes, and flushing covers to form a flushing circuit. The acid pump is used to pump the acid liquid into the loop for cyclic pickling. The pickling method is a relatively advanced construction technology in recent years. It has fast pickling speed, good effect, simple procedure and convenient operation, reduces the pollution to the human body and the environment, reduces labor intensity, and shortens the pipeline installation period. It solves the problem of difficult pickling of long pipelines and complex pipelines, and avoids the problem of secondary pollution during assembly when tank pickling is prone to. It has been widely used in the construction of large hydraulic system pipelines.

2. Pipeline pickling process

Unreasonable pipeline pickling formula and technology will cause the oxides on the inner wall of the pipe to be unable to be completely removed, the pipe wall is over-corroded, the inner wall of the pipe is corroded again, and the remaining chemical reaction deposits in the pipe occur. For ease of use, a set of pipeline pickling processes with better pickling effects selected in practice are introduced as follows.

a. Trough pickling process and formula

(1) Degreasing. The formula of degreasing liquid is: (NaOH) =9%~ 10%; (Na3P04)=3%; (NaHC03)
=1.3%; (Na2S03)=2%; the rest is water. The operating process requirements are: liquid temperature 70~80°C, soaking for 4h.
(2) Water flushing. Rinse clean water with a pressure of 0.8MPa.
(3) Pickling. The acid lotion formula is: HC1 is 13%~14%; (CH2)6N4 is 1%; the rest is water.
The operating process requirements are: normal temperature soaking for 1.5 ~ 2h.
(4) Water flushing. Rinse clean water with a pressure of 0.8MPa.
(5) Secondary pickling. The acid lotion formula is the same as above. The operating process requirements are: soaking at room temperature for 5 minutes.
(6) Neutralization. The neutralization solution formula is: NH40H diluted to a pH value of 10~11 solution. Operation process
The requirement is: soak at room temperature for 2 minutes.
(7) Passivation. The passivation solution formula is: NaN02 is 8%~10%; NH40H is 2%; the rest is water. operate
The process requirements are: soaking at room temperature for 5 minutes.
(8) Water flushing. Rinse it with purified water with a pressure of 0.8MPa.
(9) Quick drying. Dry with steam, superheated steam or hot air.
(10) Seal the mouth of the tube. Use plastic pipe plugs or multiple layers of plastic cloth to bind firmly.

If the pipe treated in the above method is clean and the pipe wall is bright, it can be kept for about 2 months without rust; if it is stored well, the time can be extended.
 

b. Circulating pickling process and formula

(1) Leak test. Use compressed air with a pressure of 1 MPa to fill the leak test.
(2) Degreasing. The formula of the degreasing solution is the same as that of the degreasing solution in the trough pickling process. The operating process requirements are: liquid temperature 40~50°C, continuous circulation 3h.
(3) Gas cap. Use compressed air with a pressure of 0.8 MPa to eject the degreasing liquid.
(4) Water flushing. Wash out the remaining liquid with clean water with a pressure of 0.8MPa.
(5) Pickling. The formula of the pickling solution is: HCl is 9%~11%; (CH2) 6N4 is 1%; the rest is water. The operating process requirements are: 50min intermittent circulation at room temperature.
(6) Neutralization. The neutralization solution formula is: NH40H diluted to a pH value of 9~10 solution. The operating process requirements are: continuous circulation at room temperature for 25 minutes.
(7) Passivation. The passivation solution formula is: (NaN02)=10%~14%; the rest is water. The operating process requirements are: 30min intermittent circulation at room temperature.
(8) Water flushing. With a pressure of 0. 8MPa, a temperature of 60°C purified water for continuous flushing 10min.
(9) Dry. Blow dry with superheated steam.

(10) Oiling. Fill the hydraulic oil with a hydraulic pump.

Eastern Steel Manufacturing Co.,Ltd is a leading manufacturer and distributor of carbon seamless steel pipe(seamless line pipe/seamless boiler tube/seamless galvanized pipe/hydraulic steel tube), welded steel pipe, OCTG products and fittings. We supply first-step processing, semi-finished parts and finished parts to help our clients meet fabrication requirements beyond their capacity or to improve operations by moving forward the pre-production processing.

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