Selection of flange sealing surfaces for methanol equipment
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For methanol tanks at atmospheric pressure, should the flange sealing surfaces of the equipment be flat or raised (for pressures below 1.0 MPa)?
For pipelines using methanol as the medium, I use RF-type fittings with diameters of DN15 to DN40; for diameters over DN40, I use SW-RF type fittings or WN-RF type fittings
Are there any regulations that provide some guidelines on this?
Given your operating conditions, RF should work fine. For flammable and explosive media, planar FF is not suitable.
Since existing equipment is being used, the sealing surface of the pipe flange is of type FF, and the pressure rating is 0.6 MPa (G); is it feasible to use this for storing methanol at atmospheric pressure?； Also, are there any regulations regarding the flanges at the outlets of equipment used for storing toxic and hazardous substances?
I’m here mainly to ask if there are any regulations stating that for the storage of moderately hazardous medium methanol at normal temperature and pressure, the sealing surfaces of the equipment’s flanges (at 0.6 MPa) cannot use a flat FF design.
In HG20592, regarding the selection of seal face types, page 21 states that for flammable and explosive media, the recommended seal face types are RF, MFM, and TG. Generally, FF is only used in non-metallic pipes, cast iron pipes, and utility pipes.
In SH3059-2001, the design pressure for pipes is specified as follows (5.3.2): The nominal pressure of SHB and SHC grade pipes should not be lower than 2.0 MP. Methanol is classified as SHB-grade material, so a design pressure of 2.0 MPa (150 LB) or higher is recommended. In that case, the flange sealing surface should at least be RF. But this is a recommendation (preferred), not mandatory. Given the situation described by LZ, normal-pressure methanol tanks already have vents that lead directly to the atmosphere. In this case, using FF is also an option. It simply requires regular inspections during use to prevent leaks. Methanol is toxic! In terms of design, I wouldn’t choose FF. :)
For the selection of flange sealing surfaces, there are no FF surfaces available for media that are (flammable, explosive, highly hazardous, and extremely hazardous).
Agree with the opinion on floor 8; there is no mandatory requirement.
The sealing surface uses RF, but I have a question: which type of connection should be used? Please give me some advice.