Used in critical applications. These are circumferentially welded onto the system at their necks which means that the integrity of the butt-welded area can easily be examined by X-ray radiography. The bores of both pipe and flange match thus reducing turbulence and erosion.
This is slipped over the pipe and then fillet welded. Easy to use in fabricated applications.
Sometimes called a blanking flange, this is used for blanking off pipelines, valves and pumps and as an inspection cover.
This is counter-bored to accept the pipe, which is then fillet welded. The bore of both the pipe and the flange are the same to ensure good flows.
This requires no welding and is used to connect other threaded components in low pressure noncritical applications.
These are always used with either a stub end or a taft which is butt-welded to the pipe with the flange loose behind it. Thus the stub end or the taft always provides the sealing face. Easily assembled and aligned, it is favoured in low pressure applications. To reduce cost these ‘backing’ flanges can be supplied without a hub and/or made from coated carbon steel.
Ring Type Joint
This can be employed on weld neck, slip on or blind flanges for leak-proof connection at high pressures. The seal is made by a metal ring being compressed into a hexagonal groove on the flange face.