How to select valve material under high temperature condition?

Working condition of high temperature including high temperature, high temperature Ⅰ Ⅱ, high temperature, high temperature Ⅲ Ⅳ, high temperature, high temperature Ⅴ level, the following were introduced.

1, Sub-high temperature

Sub-high temperature refers to the valve operating temperature in the 325 ~ 425℃ region.If the medium is water and steam, mainly use WCB, WCC, A105, WC6 and WC9.If the medium is sulfur-containing oil, mainly with anti-sulfide corrosion of C5, CF8, CF3, CF8M and CF3M, etc.They are commonly used in oil refinery atmospheric and vacuum units and delayed coking units. At this time, the valves made of CF8, CF8M, CF3 and CF3M are not used for corrosion of acid resistant solutions, but for sulfur- containing oil and gas pipelines.In this working condition, the upper limit of the maximum operating temperature of CF8, CF8M, CF3 and CF3M is 450℃.
 

2, High temperature Ⅰ level   

Valve working temperature is 425 ~ 550 ℃ for high temperature when Ⅰ level (PI).Grade PI valve body material as the CF8 ASTMA351 standard as the fundamental form of "high temperature Ⅰ level of carbon chromium nickel titanium rare earth high quality heat resistant steel".Because PI grade is a specific name, here includes the concept of high temperature stainless steel (P).Therefore, if the working medium is water or steam, although high temperature steel WC6(T ≤540℃) or WC9(T ≤570℃) can also be used, although high temperature steel C5(ZG1Cr5Mo) can also be used in sulfur containing oil products, but here can not be called PI level.

3, High temperature Ⅱ level

Valve working temperature is 550 ~ 650 ℃, as the high temperature Ⅱ level (hereinafter referred to as the P Ⅱ level).P Ⅱ level high temperature valve is mainly used in heavy oil catalytic cracking unit of refinery, which contains three rotating nozzle used in the lining of parts such as high temperature wear gate valves.P grade Ⅱ valve body material as the CF8 ASTMA351 standard as the fundamental form of "high temperature level Ⅱ carbon chromium nickel and rare earth, titanium in tantalum type heat resistant steel".

4, High temperature Ⅲ level

Valve working temperature is 650 ~ 730 ℃, as the high temperature Ⅲ level (hereinafter referred to as the P Ⅲ level).P Ⅲ level high temperature valves are mainly used on large heavy oil catalytic cracking unit in the refinery.P Ⅲ level high temperature valve body material for the CF8M ASTMA351 standard for fundamental form of "high temperature Ⅲ carbon chromium nickel molybdenum in rare earth, titanium tantalum enhanced heat resistant steel".
 

5, High temperature Ⅳ level      

Valve working temperature is 730 ~ 816 ℃, as the high temperature Ⅳ level (hereinafter referred to as the P Ⅳ level).Will P level Ⅳ valve operating temperature limit at 816 ℃ because valve design chosen standard ASMEB16134 pressure - temperature rating provides a maximum temperature of 816 ℃ (1500 nu).In addition, after the working temperature exceeds 816℃, the steel is close to entering the forging temperature region, at this time the metal is in the plastic deformation region, the plasticity of the metal is good, it is difficult to bear the high working pressure and impact force and maintain the deformation.P grade Ⅳ valve body material as the CF8M ASTMA351 standard as the fundamental form "high temperature Ⅳ carbon chromium nickel molybdenum in rare earth, titanium tantalum enhanced heat resistant steel".CK-20 and ASTMA182 standard F310(including C content ≥01050%) and F310H and other heat-resistant stainless steel.

6, High-temperature Ⅴ level

Operating temperature of valve Ⅴ level above 816 ℃, referred to as P, P Ⅴ level high temperature valve (for cut off valve, rather than the external regulation butterfly valves) must be the use of special design method, such as lining insulation lining or water or air cooling, etc., can guarantee the normal work of the valve.So, level of P Ⅴ high temperature valve operating temperature limit does not make the rules, the working temperature of this is because the control valve is not only on the material, but with the special design method to solve, and the basic principle of design method is the same.P Ⅴ level high temperature valves according to the pressure of work and working medium and the special design methods and so on, choose reasonable, can meet the material of the valve.In P Ⅴ scale high temperature valve, normally the flue board flashboard valve or butterfly valve or butterfly plate often choose the HK - 30 ASTMA297 standard, HK - 40 high temperature alloy, they are able to under 1150 ℃ oxidation and corrosion in a reducing gas, but it can't withstand the impact and pressure load.