Application limits of raised face flat welding flanges and loose sleeve flanges
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Dear experts, I would like to hear your opinions on the use of raised face butt-weld flanges and loose-flange types. Is it necessary to use butt-weld flanges for all raised face flanges with a diameter of DN50 or less? What are the advantages and disadvantages of the raised face butt-weld flanges and flat face butt-weld flanges as specified in (GB/T9119-2000)? Thank you very much!!
The only difference between raised face welding flanges and flat face welding flanges is the pressure rating they can handle: raised face welding flanges are suitable for pressures ranging from 0.25 MPa to 2.5 MPa, while flat face welding flanges are suitable for pressures ranging from 0.25 MPa to 1.6 MPa. Loop flanges are generally used for pipes that need to be prefabricated and cannot be welded on-site; adjustable sections can also be used as a substitute for loop flanges.
What is the pressure range suitable for the loop flange? The intensity doesn’t feel strong enough
There shouldn’t be such a rule; the slip flange is used to save stainless steel material, and the pressure should not exceed 300#
According to HG20600-97, slip-on flanges are suitable for pressure ranges of 0.6MPa to 1.6MPa, and the applicable pipe diameters range from DN10 to DN600; therefore, not all pipes with a diameter smaller than DN50 require plate butt weld flanges. These two types should be referred to as plate butt weld flanges and slip-on butt weld flanges respectively (there is also a type of weld-on slip-on flange, with a pressure range of 0.6MPa to 4.0MPa). Thus, your terminology for these two types of flanges seems incorrect as well.
The scope of application is different, I think the convex type is used more often
The convex surface is the flange sealing surface, while loose sleeve and plate butt welding, as well as necked butt welding, are the methods used to connect pipes to flanges; they represent two different concepts that need to be distinguished from one another. In terms of voltage resistance and the toxicity and corrosivity of the working medium, butt welding with a neck is superior to plate butt welding ； Convex surfaces are superior to fully flat surfaces ； Butt-welded loose-flange fittings are superior to flat-welded loose-flange fittings. For specific details, refer to the specifications in the chemical industry flange standard (HG20592-2009).