What type of gasket should be used for molten salt pipeline flanges?
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One of the DN200 flanges on the molten salt pipeline in our company keeps leaking; we have replaced the gaskets many times. There are also leaks in other places, but they’re not severe. The gaskets used were 2mm thick aluminum plates that I processed myself; graphite wound gaskets were also tried, but neither of them worked and failed to solve the problem. Could it be that the wrong type of gasket was chosen, or is there a better way to address this issue? I hope experts can offer some guidance. Thank you.
The leakage is not solely due to the gasket; it could also be caused by high stress in this area
We used metal wound gaskets before, but it’s better to use those with reinforcing rings. Once, the melting salt got blocked because the wrapping pads came loose
What’s the temperature? What material is the bolt made of, and has it suffered from creep?
The gasketing with steel rings used by us does not perform well; the molten salt penetrates it too easily, which is why aluminum gaskets are always chosen. A clog in the molten salt pipeline is a real hassle.
Use a D-type metal wound gasket; perform cold tightening first and then hot tightening after the temperature rises, which will allow it to last for some time. The sealing structure can also be changed to use a metal octagonal gasket; in this case the flange needs to be replaced, but it still requires tightening under both cold and hot conditions.
The normal temperature of the molten salt is around 355 degrees. All the bolts purchased are high-strength bolts. It was tightened too, and now the bolts can’t be screwed in anymore.
For high-strength bolts (35crmoA), the fact of tightening them in cold or hot conditions doesn’t really make much difference; what’s more important is the selection of gaskets and flanges!
It is sometimes also related to damage to the flange sealing surface.