Sealing of convex and concave surfaces in large-diameter heat exchangers
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Recently, a heat exchanger was manufactured with a diameter of DN1600 and a design pressure of 6.0 for the tube side; a male-female wound gasket was used for sealing, but the seal failed during the hydrostatic test. . I don’t know what the reason is? The flange sealing surface is made of 16MnⅡ with S30408 surfacing; I would appreciate some guidance from the experts.
Is the gasket of reliable quality? What is the parallelism of the sealing surface? Is the installation proper?
Based on my limited experience, gasket materials with a pressure rating of less than 6.4 MPa are more suitable for use in internal combustion engines; for the heat exchanger in question, I would recommend using metal octagonal gaskets, metal lens gaskets, or metal elliptical gaskets.
This post was last edited by Shutong on 2021-1-20 21:33. What is the medium? It is recommended to provide further information
Was stress relief performed followed by further machining of the entire assembly after welding the flange sealing surfaces?
Check the annular gap after full wheel alignment
Try using a wavy tooth composite gasket; it’s also possible that the sealing surface is not flat. If the machining capabilities permit, re-machine the sealing surface
This post was last edited by ftxswb on 2021-1-21 at 09:00. Reasons include: 1) deformation of the parallel surfaces of the flanges, 2) incorrect sequence of tightening the studs, and 3) issues with the gaskets. The designed pressure is 6 MPa, but the minimum pressure required for a hydrostatic test is 7.5 MPa; using wound gaskets is somewhat risky in this case. Also, for such a large diameter, I’m not sure what standard flange to use?
As asked above, when it comes to the sealing of large-diameter equipment flanges, various factors need to be taken into account: the manufacturing and assembly processes of the flanges, the welding processes used for joining them to the cylinder body, as well as the type and material of the gaskets.
First, carefully determine whether the flange seal is satisfactory. Second, note that in such cases the gasket should have an inner ring. Additionally, for flanges of this size, it is necessary to increase the thickness of the weld on the sealing surface; check whether there are any defects on the flange sealing surface that could affect sealing, and also check whether the gasket has any defects. With such high pressure, and considering the large size of the flanges, it is recommended to use aluminum or copper gaskets in the design.
Flanges whose parameters exceed the standards of NB/T47023 cannot have their strength determined solely using SW6; the main mode of failure for such flanges is leakage, and their stiffness is crucial for ensuring a proper seal. Provided that there is no excessive deformation of the flange and the flatness of the sealing surface is satisfactory, it is recommended to try using a wavy tooth gasket