Flange selection
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I would like to ask fellow sailors: Two atmospheric-pressure vessels are to be designed, with ethylenediamine and cyclohexylamine as the media, both of which are flammable substances. Can plate flat-welded flanges be used?
The flange is selected based on the nominal pressure
When the toxicity of the medium inside the container is classified as extremely hazardous, highly hazardous, or moderately hazardous due to its high permeability, and when the medium is liquefied petroleum gas, the flanges on the connections should be of the necked butt-welded type. —HG/T20583 (P437) 7.2.4 But it’s not clear whether this applies to pressure vessels at normal pressure
Flammable media refer to substances such as methane and ethane with a flash point of ≤45°C... For equipment, valves, and piping flanges, plate flat-weld flanges (PL) are strictly prohibited...
This is likely a flammable liquid; you need to consider whether a leak of this substance could lead to an explosion. Also, check whether the operating temperature is close to the flash point. If so, it is recommended to use a butt-welded flange with a neck. When a plate flat-weld flange is connected to a pipe, corner welds are used, which cannot ensure a tight seal.