Does the valve seat belong to the internal components of a valve?

The valve seat is an important component of a valve, and it is generally considered to be part of the valve’s internal components. In the API600 standard, the valve seat may not be explicitly listed in the internal parts table, but it is generally considered a key component inside the valve, responsible for creating a seal and controlling fluid flow. Therefore, it can be understood that the valve seat is part of the valve internals. .

The reason why valve seats are not listed in the internal parts table of API600 standard is that at the time the standard was formulated, valve seats were directly welded onto the valve body as part of its construction, and were not considered separate components; it was only later, with changes in manufacturing processes, that valve seats began to be manufactured and assembled as separate parts.

1. The understandings or statements from upstairs are all inconsistent with the actual situation. The material requirements for valve seats can be traced back to versions of API 600 from 1998 or even earlier, which contained clear specifications on this matter. 2. For the valve seat in Chinese, API 600 uses the term “SEAT RING”; the accurate translation should be valve seat ring. For example, in Appendix C of API 600-2021 version, item 19 in Figure C.1 is referred to as the valve seat (Seat Ring). 3. Requirements for the material of the valve seat ring. A very comprehensive description is provided in Table 7 of API 600-2021. The valve seat ring can be made as a single piece of the sealing surface material specified in Table 8, or it can have a hardened layer material specified in Table 8 welded onto it. When a hardened layer is used, the corrosion resistance of the matrix material of the valve seat must be no lower than that of the valve body. 4. Finally, discuss whether the valve seat counts as an internal component. Based on the classification method of whether it is in contact with a medium, the valve seat is one of the components in the broad sense. In other words, apart from components such as the valve body that represent specific pressure-bearing boundaries, those components that come into contact with the medium can generally be considered internal components, such as the gate, valve stem, and valve seat. The above is for discussion with everyone, meant to serve as a starting point for further insights.

2 questions: Since, according to Table 7 in Section 6.1 of API600 (2015), the valve seat ring is classified as a material other than the internal component materials, strictly speaking, per the definition in API600, the valve seat is not considered part of the internal components. But paradoxically, his material follows Table 8, and Table 8 is the material for the internal components. Thank you, big bro first

Discussion on internal component issues based on API 600-2015. 1. Which ones belong to the internal components, according to the definition in 6.2.1. 2. Table 8 specifies the material and hardness requirements for the sealing surface, valve stem, and upper sealing seat. The requirements for the relevant internal component materials are specified in 6.2.2. 3. Regarding the valve seat ring. There are 3 situations that need to be distinguished. In case 1, when the sealing surface of the gate valve is directly welded onto the valve body itself, or is formed by machining the valve body, then there is no such component as a seat ring ； 2 means that the sealing surface and the valve seat ring can also be integrally formed; 3 represents the most common scenario, in which the sealing surface is welded onto the valve seat ring and then combined with the valve body. So, in the second case, should the valve seat ring be labeled as a valve seat ring or a sealing surface in the BOM? 4. Since the standards specify requirements for all aspects of the valve seat ring, whether it counts as a valve internal component is something that needs to be clearly distinguished; perhaps it isn’t that important after all.

Discussion on internal component issues based on API 600-2015. 1. Which ones belong to the internal components, according to the definition in 6.2.1. 2. Table 8 specifies the material and hardness requirements for the sealing surface, valve stem, and upper sealing seat, but not for all internal components. The requirements for the relevant internal component materials are specified in 6.2.2. 3. Regarding the valve seat ring. There are 3 situations that need to be distinguished. In case 1, when the sealing surface of the gate valve is directly welded onto the valve body itself, or is formed by machining the valve body, then there is no such component as a seat ring ； 2 means that the sealing surface and the valve seat ring can also be integrally formed; 3 represents the most common scenario, in which the sealing surface is welded onto the valve seat ring and then combined with the valve body. So, in the second case, should the valve seat ring be labeled as a valve seat ring or a sealing surface in the BOM? 4. Since the standards specify requirements for all aspects of the valve seat ring, whether it counts as a valve internal component is something that needs to be clearly distinguished; perhaps it isn’t that important after all.

Thank you very much for your detailed and thorough understanding; respect