The method of steel pipe pickling can be divided into groove pickling and cycle pickling, and cycle can be divided into online cycle pickling and external cycle pickling lines.
The tank pickling method is to remove the installed pipes or pipes, soak them in the chemical pickling tank in sections, transport them to the construction site after technical treatment, and restore the original installation state.
The acid pickling line has been circulated in place, and pipes have been installed to form the hose connection circuit. The circulating internal circulation is flushed with corrosion-resistant chemical cleaning solution. This method can not remove the installed pipeline, but the circuit must avoid the use of hydraulic cylinders, valves and other components. The outer ring of the pickling line is some short pipes or pipe fittings. The ring shall not be removed at the installation position, and the pickling recovered from the local ring shall be connected with the hose and accessories.
For example: pickling speed is fast and the effect is good; acid tank does not need large and special workshop; reduce the time of repeated disassembly and treatment of pipeline, shorten the cycle period, reduce the possibility of pipeline pollution due to rust again and again; the pipeline can adopt welding connection, reduce flange, parts, bolts and other joints; reduce the project cost. However, the cycle pickling process is more complex, and the pickling quality inspection is more difficult. Once there is an operation error, it will cause acid leakage accident, so the requirements of technical management are more strict. Pipeline loop pickling is suitable for a large number of centralized pipeline projects with high cleanliness requirements; for some large diameter, short and short pipeline projects, slotted pickling is more appropriate.
Pickling quality requirements
Pickling pipes are usually inorganic acids, such as sulfuric acid, hydrochloric acid and phosphoric acid. It not only ensures that the medium can remove the oxide, rust and scale on the wall, but also can not produce corrosion and rust again on the wall; there should be reasonable process and strict regulations in the pickling process to ensure that every part of the inner surface of the pipe is thoroughly and evenly pickled, and the residual acid, residual water and suspended solids on the inner wall are all discharged.
（1） Tank type dry hydrochloric acid pickling: pickling → pickling → neutralization and passivation are completed.
(2) Pickling of phosphoric acid tank: pickling preparation → pickling finished product.
(3) Type of hydrochloric acid pickling: composition circulation → leakage → degreasing → pickling → cleaning → pickling and passivation in the second time → drying → rust removal.