What does the sealing type of a valve flange depend on?
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What determines the sealing type of a valve flange? Or rather, it is something related to the valve that determines what type of sealing mechanism will be used for the valve’s flange. For flanged valves that are currently in use, those operating at pressures of 1.6 MPa or less generally use the RF type, while those operating at pressures of 2.5 MPa or higher use the raised-and-recessed type. The valve models do not include any parameters indicating the type of flange sealing; for example, Z41H-16C DN200 – it’s a bit confusing
According to the flange standards, the relevant flange standards can be found.
It is included in HG/T20592
It is determined based on the characteristics of the process medium, pressure level, etc. Each project at the design institute comes with a unified material control manual that specifies parameters such as pipeline materials of various grades and sealing types.
Related to pressure, temperature, and the medium in use
I really appreciate it; could you be more specific? Under what parameters or medium conditions are raised face flanges used, and when are recessed and raised face flanges employed?
I really appreciate it; could you be more specific? Under what parameters or medium conditions are raised face flanges used, and when are recessed and raised face flanges employed?
The flange face is generally selected in accordance with the HG20592 standard; it can be considered a conventional practice. An RF face is used for pressures below 1.6 Mpa, while an FM face is used for higher pressures
I mean the type of sealing surface on the valve body flange, not the type of sealing surface on the flange that comes with the valve. HG20592 is merely the sealing type for the accompanying flange.
First, it is necessary to clarify which flange you are referring to. Valve flanges are divided into the valve cover flange (middle flange) and the valve body connection flange (end flange). In the case of valve cover flanges, in accordance with Clause 4.6 of \"GBT12234-2007 Steel Gate Valves with Bolted Valve Covers for Use in the Petroleum and Natural Gas Industry\", for gate valves with a nominal pressure greater than PN25, the connection flanges between the valve body and the valve cover cannot be flat flanges (including FF and RF); instead, male-female flanges, tenon-and-socket connections, or ring-shaped groove connections may be used. Gate valves with a nominal pressure not exceeding PN25 can use flat flanges. For end flanges, in accordance with clause 6.2.2 of \"GBT12224-2005 General Requirements for Steel Valves\" and clause 3.1 (Table 1) of \"GBT9113-2010 Integral Steel Pipe Flanges\", flat flanges (FF face and RF face) are generally used for pressure conditions of PN25 and below; for pressure conditions of PN40 and above, ribbed faces, tongue-and-groove faces, O-ring faces, or ring-connected faces are usually selected. I don’t know why, but I can’t upload my pictures; you can go and check out these standards yourself. Of course, some customers choose flange standards such as HG20592-2009 or ASME B16.5, but the principle of selecting the sealing surface based on the pressure level is generally applicable in all cases.