What are the criteria for selecting gasket materials for pipe flanges?
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Not long ago, a leak occurred at a flange of a hydrogen pipeline in that facility; after shutting down the system, maintenance personnel found that the copper gasket was defective, but there were no new gaskets of the same type available for replacement. So the maintenance supervisor found a PTFE gasket as a substitute. Although I had objections, I didn’t have any good reasons to convince them otherwise. For now, we will ignore the issue of pressure rating. I would like to ask, what were the considerations behind using copper gaskets in the original design? Is it feasible to replace the PTFE gasket now? Why?
HG/T20635-2009 Appendix A
The OP’s question description is too vague. At P10MPa: ribbed or trapezoidal groove flanges, grade 2 hard steel cardboard, annealed copper gaskets. The poster can choose the appropriate gasket by referring to the maximum pressure and temperature of your pipelines::lol:lol:lol:lol
Thanks for the tip! I’m really an amateur when it comes to pipes, flanges, and things like that. So it is always desirable to adhere to the original design or the standard configuration, especially for flammable and explosive substances like hydrogen; although the operating pressure isn’t extremely high, it still ranges from 17 to 20 MPa. Thank you again: handshake
Can’t use PTFE instead? For high-pressure flange surfaces, octagonal gaskets are generally used
Generally speaking, several factors need to be considered when selecting gaskets, such as operating conditions, temperature, pressure, and the medium. Then, factors such as the material of the sealing surface, its roughness, and the amount of pre-tightening force that the bolts can provide need to be considered. As you mentioned, if the pressure is between 17 and 20 MPa, it falls within the range of medium to high pressure, and in such cases metal gaskets are generally used for sealing. PTFE gaskets belong to the category of non-metallic gaskets and are commonly used in low-pressure applications. It is recommended that ordinary PTFE gaskets be used in conditions where the pressure does not exceed 16 Bar, or 1.6 MPa. The general recommendation for modified versions is no more than 80 Bar; in special cases, 200 Bar can be used. Ordinary polytetrafluoroethylene gaskets have low strength and a low coefficient of friction; if used to seal high-pressure gases, they can easily be blown out.
I missed something just now; we also need to consider the type of sealing surface.
I’m worried too, but I can’t find any convincing evidence. I don’t have either the time or the ability to study it now, so I have to ask everyone for advice: handshake
The fastest way is to consult the standards directly; each material has its own range of applications and operating conditions.
Strength, corrosion resistance, temperature
The PTFE gasket is for low pressure; check the hydrogen pressure