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Hugong Valve is a well-known brand valve supplier that integrates research and development, manufacturing, sales, and service
How to choose valve materials under high temperature conditions?
Release time:
2024-08-14
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Sub high temperature refers to the working temperature range of valves between 325~425 ℃.
1. Sub high temperature
Sub high temperature refers to the working temperature range of valves between 325~425 ℃. 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 have resistance to sulfide corrosion, are mainly used. They are mostly used in the atmospheric and vacuum distillation units and delayed coking units of refineries. At this time, valves made of CF8, CF8M, CF3, and CF3M materials are not used to resist acid solution corrosion, but are used for sulfur-containing oil products and oil and gas pipelines. In this operating condition, the maximum operating temperature limit for CF8, CF8M, CF3, and CF3M is 450 ℃.
2. High temperature level I
When the working temperature of the valve is 425-550 ℃, it is classified as high temperature level 1 (referred to as PI level). The main material of PI grade valves is CF8 based "High temperature Grade 1 medium break chromium nickel rare earth titanium high-quality heat-resistant steel" according to the ASTMA351 standard. As PI grade is a specific term, it includes the concept of high-temperature stainless steel (P). Therefore, if the working medium is water or steam, although high-temperature steel WC6 (ts540C) or WC9 (ts570C) can also be used, and high-temperature steel C5 (ZG1Cr5Mo) can also be used in sulfur-containing oil products, they cannot be called PI grade here.
3. High temperature level II
The working temperature of the valve is 550~650 ℃, designated as high temperature level I (referred to as PI level). PII grade high-temperature valves are mainly used in heavy oil catalytic cracking units of refineries, which include high-temperature lined wear-resistant gate valves used in three-way nozzles and other parts. The main material of PI grade valves is "high temperature grade II medium carbon chromium nickel rare earth titanium tantalum reinforced heat-resistant steel" based on CF8 in the ASTMA351 standard.
4. High temperature level III
The working temperature of the valve is 650-730 ℃, designated as high temperature level III (referred to as P III level). PI grade high-temperature valves are mainly used in large heavy oil catalytic cracking units in refineries. The main material of the P Ⅲ high temperature valve is a "high-temperature dish grade medium carbon chromium nickel molybdenum rare earth titanium tantalum reinforced heat-resistant steel" based on CF8M in the ASTMA351 standard.
5. High temperature level IV
The working temperature of the valve is 730-816 ℃, designated as high temperature level IV (referred to as PIV level). The upper limit of the working temperature of PIV grade valves is set at 816 ℃ because the highest temperature provided in the standard ASMEB16134 pressure temperature grade selected for valve design is 816 ℃ (15000). In addition, after the working temperature exceeds 816 ℃, the steel approaches the forging temperature zone, and the metal is in the plastic deformation zone. The plasticity of the metal is good, and it is difficult to withstand high working pressure and impact force without deformation. The main material of P1V grade valves is CF8M based "high-temperature grade IV medium carbon chromium nickel molybdenum rare earth titanium tantalum reinforced heat-resistant steel" according to ASTMA351 standard. Heat resistant stainless steels such as F310 (with a C content of 201050%) and F310H in CK-20 and ASTMA182 standards.
6. High temperature Class V
The working temperature of the valve is above 816 ℃, abbreviated as PV grade PV grade high-temperature valve (used as a cut-off valve, not a regulating butterfly valve), which must adopt special design methods, such as lining insulation or water or air cooling, to ensure the normal operation of the valve. So, there is no regulation on the upper limit of the working temperature of PV grade high-temperature valves, because controlling the working temperature of valves is not solely based on materials, but is solved through special design methods, and the basic principles of design methods are the same. PV grade high-temperature valves can be selected with appropriate materials that meet the requirements of their working medium, working pressure, and special design methods. In PV grade high-temperature valves, HK-30 and HK-40 high-temperature alloys from the ASTMA297 standard are commonly used for flue plug valves or butterfly valves. They can resist oxidation and corrosion in reducing gases below 1150 ℃, but cannot withstand impact and high-pressure loads.
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