How to choose the material of petrochemical valve?

In the petrochemical industry, valve material selection is directly related to the safe operation and service life of the device. In the face of complex working conditions such as high temperature, high pressure and corrosive media, how to scientifically select the valve material is a problem that engineers must face.

Why should we pay attention to valve material selection?

The media transported by petrochemical pipelines are often corrosive, toxic or flammable and explosive, accompanied by high temperature and high pressure conditions. The data show that the cost of pipeline engineering in petrochemical plant is about 10%~30% of the total engineering cost, and the cost of valve is about 30% of the cost of pipeline engineering, which is the main part of the cost of pipeline equipment. Once the valve is improperly selected, it will lead to media leakage and pollution of the environment, and it will cause the device to stop production and even vicious accidents, so the selection of materials must be cautious.

Different parts of the valve have different emphasis on material requirements: valve body cover is the main pressure bearing parts, need to have sufficient strength and toughness; To ensure the sealing performance of the valve, the sealing surface needs to have high strength, corrosion resistance, abrasion resistance and other characteristics; As an important force part, the valve stem must have sufficient strength and toughness, and corrosion resistance and abrasion resistance.

Common valve materials and application scenarios

Carbon steel is the most basic material choice for petrochemical valves. Data show that carbon steel valves in oil refining units account for about 90% of the total number of valves, which is the absolute dominant material. The applicable temperature of the representative brand WCB does not exceed 425℃, with excellent strength and processing performance, economic price, widely used in general oil and gas pipeline system. When the temperature exceeds 425℃, the risk of graphitization of carbon steel should be noted.

Stainless steel is the first choice for dealing with corrosive media. 304 stainless steel is suitable for general corrosion environment, and 316/316L stainless steel due to the addition of molybdenum elements, resistance to pitting corrosion and crevice corrosion ability is stronger, especially suitable for sour oil, seawater and other strong corrosive media. It is necessary to be alert to the risk of stress corrosion cracking of stainless steel under the condition of chloride.