High-temperature Grade III
When working temperatures of
valves are between 650℃ and 730℃, the
valves are called the high-temperature Grade III valves, also named the high-temperature PIII Grade valves. They are mainly used for the heavy oil catalytic cracking units of refineries. The main material of the PIII Grade
valve is the strengthening high temperature Grade III heat-resistant steel containing carbon, chromium, nickel and rare earth titanium, which is based on CF8M in ASTM A351 Standard.
High-temperature Grade IV
When working temperatures of
valves are between 730℃ and 816℃, the valves are called the high-temperature Grade IV valves, also named the high-temperature PIV Grade valves. The reason for the highest working temperature of high-temperature Grade IV being 816℃ is that the highest temperature stipulated in the ASME B16.34 Standard is 816℃. In addition, when the working temperature exceeds 816℃, steel will be in the forging temperature status, in other words, the plastic deformation status. Due to owning good plasticity, steel cannot stand the high working pressure as well as the large impact force and it will deform. The main materials of the PIV Grade
valves are the strengthening high temperature Grade IV heat-resistant steel containing carbon, chromium, nickel and rare earth titanium, which is based on CF8M in ASTM A351 Standard, the F310 and F310H heat-resistant stainless steel in CK-20 Standard and ASTM A182 Standard.
High-temperature Grade V
When working temperatures of
valves are higher than 816℃, the valves are called the high-temperature Grade V valves, also named the high-temperature PV Grade valves. The high-temperature PV Grade valves such as the butterfly valves used for cutting off the media in the pipelines must be designed specially, or the
valves may be unable to work properly. For example, the valves must be lined with the thermal insulation lining. There are no stipulations about the maximal working temperatures of high-temperature Grade V valves, because the working temperature control of these valves is realized by the special design of the valves instead of the valves’ materials only. The design principles of this kind of valve are almost the same. The materials of the high-temperature Grade V valves should be well and reasonably selected based on the media, the working pressure and the special design adopted.
Conclusion
With the rapid development of technologies, the main materials of
valves are becoming diversified with a variety of parameters. The working medium of valves also get more and more complex, which puts higher requirements on the working temperatures of valves. It is of great necessity for technicians and operators related to the designing, manufacturing, purchasing as well as using of valves to learn about the main materials of
valves and the properties of the main materials. What must be paid great attention to is that the working temperatures of the materials should not exceed their appropriate working temperatures, or terrible accidents may be triggered.
