1. Sub-high temperature
Sub-high temperature refers to the operating temperature of the valve in the 325~425℃ range. If the medium is water and steam, WCB, WCC, A105, WC6 and WC9 are mainly used. If the medium is sulfur-containing oil, C5, CF8, CF3, CF8M and CF3M, which are resistant to sulfide corrosion, are mainly used. They are mostly used in atmospheric and vacuum units and delayed coking units in refineries. At this time, valves made of CF8, CF8M, CF3 and CF3M are not used to resist corrosion from acid solutions, but are used on sulfur-containing oil products and oil and gas pipelines. In this operating condition, the maximum operating temperature limit of CF8, CF8M, CF3 and CF3M is 450°C.
2. High temperature level I
When the working temperature of the valve is 425 to 550°C, it is a high temperature grade I (referred to as PI grade). The main body material of PI level valve is "high temperature grade I medium carbon chromium nickel rare earth titanium high quality heat-resistant steel" based on CF8 in the ASTM A351 standard. Because PI grade is a specific name, it 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 when sulfur-containing oil is used, but in We cannot call them PI level here.
3. High temperature level II
The working temperature of the valve is 550~650℃, which is designated as high temperature level II (referred to as PII level). PⅡ high-temperature valves are mainly used in heavy oil catalytic cracking units in refineries. They include high-temperature lined and wear-resistant gate valves used in three-rotation nozzles and other parts. The main body material of the PⅡ class valve is "high temperature class II medium carbon chromium nickel rare earth titanium and tantalum reinforced heat-resistant steel" based on CF8 in the ASTM A351 standard.
4. High temperature level III
The working temperature of the valve is 650~730℃, which is designated as high temperature level III (referred to as PIII level). PⅢ class high temperature valves are mainly used in large heavy oil catalytic cracking units in refineries. The main body material of the PⅢ grade high temperature valve is "high temperature grade III medium carbon chromium nickel molybdenum rare earth titanium and tantalum reinforced heat-resistant steel" based on CF8M in the ASTM A351 standard.
5. High temperature level IV
The working temperature of the valve is 730~816℃, which is designated as high temperature level IV (referred to as PIV level). The upper limit of the operating temperature of PIV class valves is 816℃ because the maximum temperature provided in the standard ASMEB16134 pressure-temperature class selected for valve design is 816℃ (1500υ). In addition, after the working temperature exceeds 816°C, the steel is close to entering the forging temperature range. At this time, the metal is in the plastic deformation range. The metal has good plasticity and cannot withstand high working pressure and impact force without deforming. The main body material of PⅣ level valve is CF8M based "high temperature level IV medium carbon chromium nickel molybdenum rare earth titanium and tantalum reinforced heat-resistant steel" in the ASTM A351 standard. Heat-resistant stainless steels such as F310 (with C content ≥01050%) and F310H in CK-20 and ASTM A182 standards.
6. High temperature level V
The working temperature of the valve is above 816℃, which is referred to as PⅤ level. PⅤ level high-temperature valves (valves used as cut-off valves, not regulating butterfly valves) must adopt special design methods, such as lining with thermal insulation lining or passing water or gas. Cooling, etc. can ensure the normal operation of the valve. Therefore, there are no regulations on the upper limit of the operating temperature of PⅤ-class high-temperature valves. This is because controlling the operating temperature of the valve is not determined by materials alone, but by special design means, and the basic principles of the design means are the same. PⅤ class high temperature valves can select reasonable materials that can meet the requirements of the valve according to its working medium and working pressure and the special design methods adopted. In PⅤ class high-temperature valves, usually the insert plates or butterfly plates of flue gate valves or butterfly valves are often made of HK-30 and HK-40 high-temperature alloys in the ASTMA297 standard. They can resist oxidation and reducing gases below 1150°C. Resistant to corrosion, but cannot withstand impact and high pressure loads.