Screwed flange are often used for small diameter, high pressure requirements. Screwed flanges with a hub have published specifications that range from 1/2 thru 24. Pressure class: Class 150 to Class 2,500, PN 2.5 to PN 250 and Facing: RF / RTJ. Screwed flanges are threaded in the bore which match an external thread on the pipe. Screwed flanges are used with pipes that have external threads. The benefit of these flanges is that it can be attached without welding.
