Selection of equipment flanges
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I saw a heat exchanger with a design pressure of 1.0/FV for the shell side, a design temperature of 260°C, with steam/condensate as the fluid, and the material used being Q345R. The pipe bank is designed for a pressure of 0.5/FV, a design temperature of 260°C; the medium is methanol, and the material used is 304 – it is a Class II vessel. In the diagram, the flanges for the tube box are those specified in NB/T47023-2012, specifically of type FM700-1.6 S30408Ⅲ. I’m not sure: can flanges from NB/T47022-2012 be used instead? And can such flanges be made with a 304 substrate covered with 20Ⅲ material? Are there any standards available for selecting equipment flanges?
For containers with vacuum conditions, lined flanges are not suitable.
Refer to the provisions of 5.3.3.2 in GB/T151-2014.
Vacuum, high temperature – not suitable for lining
I think type B flanges (NB/T47022) can be used, with a gasket ring structure; the reinforcement sections should be made of stainless steel, while the flanges can be made of carbon steel (either in sheet form or as forgings), along with spiral wound gaskets. A loose-lining structure with stainless steel linings is not suitable here; firstly, because vacuum operation is involved, and secondly, due to the high temperatures, the lining is prone to falling off. NB/T47023 flanges can also be used; these flanges are made of 20III material with a stainless steel surfacing.