What type of flange seal should be used for an autoclave with a temperature of around 300 degrees and a pressure of 10 MPa?
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I work in research at a chemistry school, and I need to conduct some experiments that require reaction vessels. This reactor is designed for a temperature of around 300 degrees, with an operating pressure of 10 Mpa. The preliminary design idea is to use a 316 stainless steel tube with its bottom welded shut. A long-neck butt weld flange is welded to the upper part, and the upper section is then sealed with graphite gaskets and a flange cover. Is this plan feasible? If possible, what type of flange with sealing surface should be used? Concave and convex surfaces, or convex surfaces only? ? I would be very grateful if you could all give me some advice!
I can introduce a friend who works with reaction vessels to you; you can discuss things with each other. His WeChat ID is 13248079212
See HGT 20592~20635-2009 for steel pipe flanges, gaskets, and fasteners
I’m not sure what size flange you’re using; for 10 MPa, it’s better to use an RJ flange for safety. An FM flange can also be used
HG/T 20592-2009: The highest pressure class is PN160. At operating temperature, the pressure-bearing capacity of 316 material is 9.89 MPa, while that of 316L is 7.9 MPa. So chemical process flanges cannot be used. Considering the use of GB/T 9124-2010, for national standard flanges with PN160 rating, the pressure-bearing capacity of 316 material at operating temperature is 11.88 MPa, while that of 316L is 11.04 MPa. The difference between the two standard temperature-pressure ratings is significant; considering that the design parameters should be higher than the operating parameters, it is recommended to use flanges of the PN250 grade. Therefore, GB/T 9125-2010 wafer-type butt weld flanges WN PN250 should be used, with a sealing surface of type RJ and an octagonal gasket. The flange cover uses an RJ octagonal ring gasket with a circular joint surface as specified in GB/T 9123-2010. For stainless steel flanges, gaskets are required. Ring gaskets, fasteners, and gaskets should preferably be selected by the manufacturer, as national standards can be a bit confusing.
The 304 stainless steel reactors we use currently can handle a maximum pressure of 45 Mpa (with threading and PTFE gaskets for sealing); why then does the flange of 316L only have a bearing capacity of 9.89 MPa?
Industrial standard flanges are manufactured in accordance with standards, but different industries have various requirements, such as those related to national standards, the chemical industry, petrochemicals, oil, machinery, light industry, shipbuilding, railways, and so on. The two flange standards I provided to you, HG/T 20592-2009 and GB/T 9124-2010, show the differences in the temperature-pressure ratings of the flanges under certain operating conditions. To be precise, it should be HG/T 20592-2009; flanges made of 316L with a PN160 rating have a pressure resistance of 7.9 MPa at 250°C and 7.48 MPa at 300°C. I’m sorry for the mistake in my previous response. Your reactor has a pressure rating of 45 Mpa (sealed using threads and PTFE gaskets). I would like to know where these connections are located For flanges that can handle 45 MPa, as far as I know, the standard is JBT 1308.13-2011, which is the flange standard for PN2500 valves; it applies only to sizes from DN15 to DN25. It can only be non-standard connection components designed specifically for equipment.
It is our own designed sealing solution; no professional flange standards were referenced. . But these reaction vessels were indeed sealed and used safely for several years. . We have dozens of such reaction vessels in total, and none of them have leaked
Our current reaction vessels do not use flange sealing; instead, a large bolt is screwed in from one end of the vessel to press down on a PTFE gasket, thereby sealing the titanium liner inside. Since we now want the new reactor to be able to reach temperatures above 300 degrees, PTFE gaskets may not be suitable for use at such temperatures; therefore, we want to replace them with graphite gaskets. .
So you’re using non-standard seals; you should go to the equipment area to discuss this issue. The design of non-standard seals is handled by the equipment specialists. The piping discipline generally does not consider the design of non-standard seals.