For vacuum equipment where the medium is flammable, explosive, and toxic, what type should be used – flanges with sealing surfaces?
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The working pressure is negative; the vacuum level is not high. The medium is flammable, explosive, and toxic. So, which type of flange should be chosen: PL, SO, WN? What type of sealing surface is used: RF, FF, MFM, or another type? The company has been using MFM, but in my opinion, under negative pressure, the gaskets (non-metallic gaskets) will be drawn into the container, losing their sealing ability!
There is no problem using flanges with uneven surfaces; the flange connection type should be WN. You can use metal wound gaskets, which will also provide sufficient strength.
If the medium properties are not extreme or high, either SO or WN will work; it is recommended that the pressure rating be no less than 1.0 MPa, and an RF sealing surface is sufficient.
The flange type should be at least a high-neck welded flange; the sealing surface can adopt the RF style, and the gasket should be a metal wound gasket with an external reinforcing ring. Also, this issue should be raised in writing by the process team or the client. How can the equipment specialty determine it on its own?
Does the type of sealing surface used by our company’s silicone gaskets have any relation to the strength of the flanges?
When the company faces high vacuum conditions, it uses MFM sealing surfaces. Does the type of sealing surface have an impact on the strength of the flange?
The type of gasket is related to both the temperature and pressure of the medium; the use of non-metallic gaskets is not recommended for toxic media, as such gaskets tend to age and cause leaks
The medium is flammable and explosive; therefore, a high-neck flange connection must be used. For the sealing surface, either RF or MFM types are acceptable, and metal wound gaskets must be used as packing. This is stipulated by the tolerance standards. However, since the takeover flange needs to be connected to the external piping, this must be coordinated properly with the owner and the process team.
It is recommended to use WN flanges, gaskets with reinforcing rings, and preferably a corrugated design for the sealing surfaces...