Pickling of Carbon Seamless Steel Pipe by Citric Acid Cycle

The installation of hydraulic transmission equipment is to use the pipeline to the hydraulic equipment and valve components, according to the drawings required to link up and be fixed position. Therefore, the installation of hydraulic system equipment, in addition to pumping station equipment, a lot of work is the installation of the pipeline, in the pipeline installation process the most important work is the pipeline of online cycle pickling rust, especially carbon steel pipe, because the corrosion ratio stainless steel pipe is serious, and a little water on the return to rust, carbon steel pipe rust process than a lot of complex stainless steel pipe, but the material price is much cheaper than stainless steel pipe, so 90% of the hydraulic system is used in more than carbon seamless steel pipe, so the corrosion of carbon steel pipe is the whole hydraulic system piping construction process is very important part of the advantages and disadvantages of pickling effect is a measure of the quality of the main pipe signs, it will directly related to the hydraulic system cleanliness , And ultimately affect the system can function properly. There are many types of pickling process and recipes in the industry. There are various advantages and disadvantages in the industry. The recipe and technology used in this unit for a long time have been integrated. Here, a simple and convenient acid pickling technology with low cost and good pickling effect is introduced here. Pickling technology, so far this technology has been successfully applied to the cold-rolled plant 2 # galvanizing unit, rail beam cooling and finishing the second phase, two cold-rolled pickling, rail beam finishing steel two and 100m waste heat quenching, steel 2 # billet new RH vacuum and other major projects in the hydraulic, lubrication system, a total of nearly 500,000 meters of carbon steel pipe construction, and achieved a good pickling effect and economic benefits.

Before the line pickling hydraulic carbon steel pipe is generally used hydrochloric acid, hydrochloric acid pickling effect is good, but if not pay attention to is prone to quality and safety accidents, because although hydrochloric acid corrosion of iron slower, but with the The dissolution of rust, more and more iron will be directly exposed to hydrogen ions, the rate of dissolution of iron will gradually accelerate. With the dissolution of iron, the relative increase in the carbon content of steel pipe, steel pipe brittle; reaction of hydrogen will penetrate the wall, resulting in hydrogen embrittlement phenomenon; the other iron dissolved too much, wall thinning, pressure decreased. With the pipeline to reduce the performance of various, will eventually affect the normal use and life, or even occurred in the pipeline burst accident, and hydrochloric acid on the operator's injury is particularly large, very inconvenient in operation, acid discharge on the surrounding environment great influence. Therefore, in the construction of the theoretical knowledge and practice repeated demonstration and access to large amounts of information found in citric acid in water solubility, its aqueous solution is a strong organic acid, with the rust (FeO and Fe2O3) chemical reaction, remove the rust. It is not easy to cause over pickling, the construction of the harm to the operator is small, conducive to safe operation. The required equipment, equipment is simple, but also to ensure the quality of pickling rust. Therefore, in Panzhihua Iron & Steel Cold Rolling Plant 2 # galvanized unit engineering hydraulic system, we began to use hydrochloric acid instead of hydrochloric acid pickling carbon steel pipe, after a long period of experiment, found that the effect is very good, and the pipeline next process - oil cycle washing Saving a lot of time, under normal circumstances within 20 hours of oil circulation system can achieve cleanliness above the NAS5 level. The implementation of the new technology saves a lot of manpower, material and financial resources, reduces the difficulty of construction and shorten the construction period, the market economic benefits significantly, more importantly, breaking the conventional hydraulic, lubrication pipeline pickling technology, To shorten the construction period to lay a solid foundation and conditions.

The purpose of pickling carbon steel pipe is to chemically remove the oxides, rust and oil from the inner surface of the pipe and vessel to obtain the glossy metal surface, to ensure the cleanliness of the inner wall of the pipe, and to prevent rust after pickling But also makes the bottom of the pipe wall metal to be protected to prevent further corrosion, pipeline acid pickling is a key link in the construction of the pipeline. Pipeline pickling methods are more, the current construction site used by the acid pickling tank acid washing and cycle pickling, acid pickling and sub-line pickling and acid pickling line.

Circulation pickling method is to pipe with a hose or union joints constitute a loop, with acid pump acid into the pipeline for acid pickling. It can be installed pipe is not removed, as long as the hydraulic components disconnect with a hose can be connected, which is the so-called online cycle pickling. Such as some of the shorter pipe or not in the installation position of the loop to remove the pipe, in situ with a hose or connector connected to the loop for acid pickling, which is called the line outside the pickling.