High temperature conditions mainly include sub high temperature, high temperature level I, high temperature level II, high temperature level III, high temperature level IV and high temperature level V, which are introduced below.

 

1. Sub high temperature

 

Sub high temperature refers to the working temperature of the valve in the area of 325 ~ 425 ℃. If the medium is water and steam, WCB, WCC, A105, wc6 and wc9 are mainly used. If the medium is sour oil, C5, CF8, CF3, CF8M and cf3m with sulfide corrosion resistance are mainly used. They are mostly used in atmospheric and vacuum units and delayed coking units in refineries. At this time, CF8, CF8M, CF3 and cf3m valves are not used to resist acid solution corrosion, but for sulfur-containing oil products and oil and gas pipelines. Under this working condition, the maximum operating temperature of CF8, CF8M, CF3 and cf3m is 450 ℃.

 

2. High temperature class I

 

When the working temperature of the valve is 425 ~ 550 ℃, it is high temperature level I (referred to as PI level for short). The main material of PI valve is "high temperature grade I medium carbon chromium nickel rare earth titanium high quality heat resistant steel" based on CF8 in astma351 standard. Because PI grade is a specific name, the concept of high temperature stainless steel (P) is included here. Therefore, if the working medium is water or steam, although high-temperature steel wc6 (t ≤ 540 ℃) or wc9 (t ≤ 570 ℃) can also be used, and high-temperature steel C5 (zg1cr5mo) can also be used in sulfur-containing oil, they cannot be called PI grade here.

 

3. High temperature class II

 

The working temperature of the valve is 550 ~ 650 ℃, which is determined as high temperature grade II (hereinafter referred to as grade P Ⅱ). Grade P Ⅱ high temperature valve is mainly used for heavy oil catalytic cracking unit in refinery. It includes high temperature lining wear-resistant gate valve used in three rotating nozzle and other parts. The main material of grade P Ⅱ valve is "high temperature grade II medium carbon chromium nickel rare earth titanium tantalum strengthened heat-resistant steel" based on CF8 in astma351 standard.

 

4. High temperature class III

 

The working temperature of the valve is 650 ~ 730 ℃, which is determined as high temperature grade III (hereinafter referred to as grade P III). P Ⅲ high temperature valve is mainly used in large heavy oil catalytic cracking unit in refinery. The main material of grade P Ⅲ high temperature valve is "high temperature grade III medium carbon chromium nickel molybdenum rare earth titanium tantalum reinforced heat resistant steel" based on CF8M in astma351 standard.

 

5. High temperature level IV

 

The working temperature of the valve is 730 ~ 816 ℃, which is determined as high temperature grade IV (hereinafter referred to as grade P IV). The upper limit of the working temperature of class P Ⅳ valve is set at 816 ℃ because the maximum temperature provided in the standard asmeb16134 pressure temperature class selected for valve design is 816 ℃ (1500 ℃) υ)。 In addition, after the working temperature exceeds 816 ℃, the steel is close to entering the forging temperature area. At this time, the metal is in the plastic deformation range, and the metal has good plasticity, which is difficult to withstand high working pressure and impact force without deformation. The main material of grade P Ⅳ valve is CF8M in astma351 standard, which is based on "high temperature grade IV medium carbon chromium nickel molybdenum rare earth titanium tantalum reinforced heat-resistant steel" Heat resistant stainless steels such as F310 (with C content ≥ 01050%) and f310h in CK-20 and astma182 standards.

 

6. High temperature class V

 

The working temperature of the valve is more than 816 ℃, which is referred to as grade p V and grade p V high-temperature valves for short (used as cut-off valves rather than regulating butterfly valves) Special design means, such as heat insulation lining or water or air cooling, must be used to ensure the normal operation of the valve. Therefore, the upper limit of the working temperature of grade p v high temperature valve is not specified, because the control of the working temperature of the valve is not only based on materials, but is solved by special design means, and the basic principle of the design means is the same. Grade p v high temperature valve According to its working medium, working pressure and special design method, the temperature valve can select reasonable materials that can meet the requirements of the valve. In grade p V high-temperature valve, the plug plate or butterfly plate of flue plug valve or butterfly valve usually adopts hk-30 and HK-40 high-temperature alloys in astma297 standard. They can resist corrosion in oxidation-resistant and reducing gases below 1150 ℃, but can not withstand impact Impact and high pressure loads.