Gaskets suitable for raised-face flanges
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Why do the practical flange manuals I’ve consulted, as well as the standards issued by the Ministry of Chemical Industry, specify that raised-face flanges should use those with an inner ring for alignment, while here we use basic gaskets with raised-face flanges. Is this correct?
The gasket having an inner ring is conditional. The inner ring can serve to reinforce it.
1. First, understand the structure and function of the gasket. The inner ring serves as a reinforcement gasket (to prevent crushing), while the outer ring (the centering ring) is used for positioning (it fits against the lower edge of the bolt hole, allowing for accurate positioning as the bolts are inserted). The remaining coiled part is the actual part used for sealing. 2. Standards generally stipulate that full-flat flanges are equipped with outer rings or wound gaskets of inner and outer ring types ； Raised-face flange with outer ring or inner and outer ring type gasket ； Rough-faced flange with inner-ring gasket ； Tenon-and-socket face flange with basic type wound gasket ； 3. Raised-face flanges are equipped with basic-type gaskets; firstly, it is difficult to achieve proper positioning, and secondly, when the bolt preload is high, there is a risk of the gasket being compressed. If you really have to use it, then there’s nothing can be done about it; it can only be said that you don’t meet the standard requirements, which is not good.
The basic type is generally used for tenon and mortise sealing surfaces. RF generally uses inner and outer ring gaskets. Use a gasket with an inner ring for uneven surfaces; use a gasket with an outer ring instead.
The correct answer is above: first, understand the function of the reinforcement rings, such as internal ring reinforcement and external ring positioning reinforcement; this information can be found in many resources. The basic types can be used as substitutes in situations where high requirements regarding temperature and pressure do not exist. However, safety comes first, so it is still necessary to choose the appropriate gasket for the corresponding flange surface.
Inner and outer ring metal wound gaskets: The inner ring is a reinforcing ring, while the outer ring is a positioning ring； Raised-face flanges generally use gaskets with inner and outer rings; metal wound gaskets with only an inner ring can also be used (although they are not convenient for alignment). The basic type is not entirely unsuitable, but it is not recommended for use in high-pressure (≥1.6 Mpa) or high-temperature environments. I’m not sure if you are using it at a lower specification level.