Oil refining device of stainless steel welded pipe, generally exist in the process of using the following questions:
(1) the stress corrosion cracking, transgranular fracture (mainly chloride), intergranular stress corrosion cracking (mainly sulfide).
(2) the pitting corrosion, intergranular corrosion,
(3) the naphthenic acid corrosion, mouth
(4) the carburizing embrittlement.
Corrosive factors mostly in oil refining crude oil into the together, the main for organic sulphur compounds (crude oil contains 0.01 5%) and inorganic salts (a few parts per million – 200 parts per million (PPM). Heating when they break down, may produce active substances, such as H2S and hydrochloric acid in the crude oil also contain so-called naphthenic acid organic acid, are too many content will cause the material corrosion, in addition to the crude oil into the corrosion factors, in order to improve the effect of refining, in addition to water, hydrogen, also using sulfuric acid and caustic alkali, ammonia, etc.
Therefore, according to the different corrosion of oil refining device with different materials. Such as high temperature sulfur system considering Al and Cr sulfur corrosion resistance and high temperature strength, use the Cr5 – Mo above materials; High temperature H2S – H2 system using 13 cr – Al, 18-8 ni steel; Cr – Mo steel is used in the high temperature and high pressure H2 system or surfacing 18 Cr – ni – Nb steel; Low-temperature H2S – H2O system chooses 00 cr18ni10, 00 cr17ni14mo2 or monel alloy lining, H2S – HCl – H2O system selects more than 00 cr18ni5mo3si pitting corrosion resistance, resistance to stress corrosion of stainless steel welded pipe; Naphthenic acid system, chooses 00 cr17ni14mo2 can low velocity case, high velocity it needs further research; Low temperature CO2 corrosion system, generally at about 200 ℃ can use 00 cr18ni10; Response H2 equipment modification in the furnace tube, high temperature heating furnace of steel tube and various fluid of hanger, stents can choose 25 cr – ni, 20 Incone alloy 800, etc.
Source: Zhejiang Yaang Pipe Industry Co., Limited (www.yaang.com)