Cyclic pickling of seamless carbon steel pipes

Posted by zora li on December 5th, 2022

Pipeline pickling method and general requirements

The pickling of seamless carbon steel pipes will use chemical action to remove oxides on the surface of the container, remove rust and oil stains, so as to obtain a bright metal surface and ensure the purity of the pipe wall. The anti-rust treatment after pickling also makes the bottom of the pipe The wall metal is protected to prevent further corrosion, and pipe pickling is a key link in the pipeline construction process. There are many methods of pickling pipes. The current pickling methods include tank pickling and cyclic pickling, and cyclic pickling can be divided into online pickling and offline pickling. The cyclic pickling method is to connect the pipelines with hoses or flexible joints to form a loop, and use an acid pump to pump acid into the pipelines for cyclic pickling. The installed pipeline cannot be dismantled, as long as the hydraulic components are disconnected and connected with a hose, this is the so-called pipeline cycle pickling. If some short pipe fittings or pipes that are not suitable for the installation position to form a loop are removed, some hoses or joints are connected into a loop for cyclic pickling, which is called off-line cyclic pickling.

The general requirements for pipeline cycle pickling are as follows:

(1) There must be a correct formula, that is, the pickling formula solution should be able to fully remove the oxides on the pipe wall through chemical action, and should not cause excessive corrosion and re-rusting of the pipe wall.

(2) There should be a reasonable pickling circuit to ensure that all parts of the pipe wall are pickled thoroughly and evenly.

(3) There must be a reasonable process flow and strict operating procedures, and a special working team should be equipped to deal with the problems in the pickling process in time to ensure the smooth progress of the pickling work.

(4) After pickling and neutralization, the water should be thoroughly cleaned and rinsed with hydraulic oil in time to ensure that the pipeline is evenly oiled and the suspended matter generated in the pipeline during pickling should be washed away.

Circulating pickling facilities and construction requirements

Circular pickling facilities and personnel requirements: Each set of pickling equipment should be equipped with 8-12 pickling workers to form pickling circuit construction operators to ensure the normal and continuous pickling of the system and timely reset of the pipeline after pickling. And the oil circulation flushing should be started in time.

Selection of pickling site: The circulating pickling site is generally located on the top of the underground oil depot or near the oil station of the pickling pipeline system to be pickled, and generally should meet the following conditions:

(1) It does not affect on-site construction, and it is not easy to damage electrical, mechanical and other precision components in case of acid leakage.

(2) Ensure that the pipeline connection is simple, and the cycle pickling hose is as short as possible.

(3) Close to the water source, power source, and gas source, and it is convenient to discharge all kinds of sewage.

External conditions require:

(1) Water requirements for pickling

The water consumption during pickling is large, and the water quality requirements are high, and tap water or industrial water is usually used. Pickling water consumption varies with the circuit of the pickling system. In general, it should be ensured that:
Pressure P = 0.5 MPa
Flow rate 100-200 m3/h

(2) Requirements for compressed air

Compressed air is usually used for cleaning and drying cycle pickling pipelines, which requires dry compressed air, large flow rate and sufficient pressure. If there is no centralized delivery of compressed air, each pickling device should be equipped with an air compressor and an air bag, so that the sundries and accumulated water in the hydraulic pipeline can be cleaned in time after pickling.