How to select flanges
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The sealing surface type is the same (RF); I’m not quite sure whether to use a flanged joint with a neck or a plate-type butt weld flange. I would appreciate your advice. .
The pressure used is not high; generally, plate-type face weld flanges are used, with raised face flanges being the most common； Waisted butt-weld flanges are generally used in medium and high-pressure applications, where higher requirements are placed on the sealing surface.
The welding quality of flanges with a certain diameter is easy to ensure; they are often used in relatively important pipelines. For ordinary pipelines, such as cooling water pipes, butt-welded flanges can be used
Of course, it’s better to use a flange with a neck, but the cost is also higher. For less critical areas, a flat weld flange will suffice. However, the current trend is to use flanges with necks more often.
A pipe with a larger diameter is definitely better. If you want to use a plate-type pipe, then it depends on the medium flowing through it, as well as the pressure considerations
I remember that for one of our liquefied gas storage tanks, the low-point drain line used flat-welded flanges, and this was considered a potential hazard by the head office
Currently, virtually all projects use necked butt-weld flanges; flat-weld flanges may be used for certain process media, after all, it doesn’t cost much more!