The material for high temperature industrial valve

Working temperature is a key factor should be taken into consideration for valve design, manufacture and inspection. Generally, the operating temperature t > 425℃ valve is referred to as a high-temperature valve, but the number is difficult to distinguish the temperature range of high temp valve. High temp valve including high temp gate valve, high temperature globe valve, high temperature check valve, high temperature ball valve, high temperature butterfly valve, high temperature needle valve, high temperature throttle valve, high temperature pressure reducing valve. Among them, the most commonly used are gate valve, globe valve, check valve, ball valve and butterfly valve. High temp valves are widely used in petrochemical, chemical fertilizer, electric power and metallurgy industries. According to ASME B16.34, the material of the valve body and interior part are different in each temperature range. In order to ensure the valve in accordance with its corresponding high temp working conditions, it is absolutely necessary to scientifically and reasonably design and distinguish the high temp level of valve.

Some high temp valve manufacturers divide high temperature valves into five grades according to temp rating based on its production experience. That is, the valve operating temperature t>425~550℃ is grade PI, t>550~650℃ is grade PII, t>650~730℃ is grade PIII, t>730~816℃ is grade PIV, and t>816℃ is grade PV. Among them, PI~PIV valve mainly depends on the selection of appropriate materials to ensure its performance, PV valve in addition to material selection is more important to use special design such as lining insulation lining or cooling measures. High-temperature valve design should pay attention to the use of temperature shall not exceed the maximum allowable use temperature of the material. According to ASMEB31.3, the maximum temperature of common high-temperature valve materials is shown in the following table. Special note is that in the actual design of the valve also consider the corrosive medium and stress levels and other factors, the allowable temperature of the valve material is actually lower than the table.

Pressure-temperature rating for commonly used stainless steel:

Pressure – temperature rating of Cr – Mo high-temperature steel

In short, high temp valve with the operating temperature higher than 425℃, the main material of which is alloy steel or stainless steel or Cr-Ni heat resistant alloy. Actually, in practice application, the material WCB(or A105) is also widely used in the main body of the valve, such as high-temperature ball valve, check valve and butterfly valve. When the working temperature of the ball valve with PTFE and rubber as sealing ring is higher than 150 ~ 180℃, it is not recommended to use the counterpoint polystyrene seat (working temperature t≤320℃) or metal seat, that is proper “high-temperature ball valve”.