The issue with the gauge flange surface that has plagued me for years
Thread Content
Some process media require that the flange connections on the equipment be of the MFM type; how should the instrumentation team communicate this requirement to the equipment team regarding the flange connections? Did they mention the MFM surface too? But if that’s the case, many instrument manufacturers only have instruments with an RF interface, and no ones with an MFM interface! If the flange opening of the RF face is considered, could there be safety hazards? I hope experts can help me figure this out!
An M/FM face flange refers to a flange with a concave and convex surface; generally, the flange surface on the equipment side is concave FM, and the corresponding instrument requires a convex M surface to match it. When the instrument data sheet is prepared, it will be indicated that the instrument is equipped with a convex flange. If they only have RF surface gauges, then check whether parameters such as the outer diameter of the protrusion on the RF surface and the protrusion height under the selected standards are consistent with those of the convex surface M.
If the device has a concave FM surface while the gauge has an RF surface, then it is necessary to add two flanges, one with a convex M surface and the other with an RF surface, so that they can be connected together as a transition.
On ordinary equipment, it is FM, which refers to the concave surface. MFM simply denotes the type of sealing surface for a set of flanges; there are two types, one being M and the other FM
The RF face is a raised-flange type; for process pipelines, the SH standard of 5.0 MPa requires the use of RF faces, so what’s there to worry about with your instruments? Just choose a pad with safety features for the inner and outer rings.
In many places where toxic substances are present, the MFM surface is used; it seems to them that using the MFM surface is safer than using RF. I’m not sure if it’s actually possible to use an RF surface !
The opinions on the 6th floor are quite reasonable. Firstly, MFM flanges offer relatively strong sealing performance. The use of MFM flanges in the equipment indicates that there are special requirements for this material; therefore, RF flanges cannot be used for the instruments. Secondly, flanges are not a difficult aspect in instrument manufacturing; as long as certain requirements are met during the design process, they can be fulfilled. Note: The use of gaskets or intermediate flanges for conversion is not recommended.