Special Flanges are basically identical to standard flanges, but have a number of special features.
Long Neck Welding (abbreviated LWN) flanges are similar to a standard Welding Neck flange, but the Neck is considerably longer. This type is often used as a nozzle for a barrel or column. In addition, there are the type LWN Heavy Barrel (HB) and the Equal LWN Barrel (E); they have a different shape and a thicker Wall thickness.
Pad Flanges or Studding Outlets
Studding Outlet Flanges are usually designed to be installed outside of vessels, tanks and pipes. The curving of the outlet should be ordered to fit the curvature of the shell, head, or pipe. These flanges can come in sizes from 1/2 inches to 24 inches, and the pressure ratings of Class 150 to Class 2500. In Pressure Classes 150 and 300, the height of raised face is approximately 1.6 mm (1/16 inch). In Pressure Classes above, the height of rf is approximately 6.4 mm (1/4 inch).
They can be ordered in Carbon Steel, Stainless Steel, and alloy steel. A common alternative name for studding outlets is 'Pad Flange.' To clarify, the pad flange and the studding outlet are the same part and pad flanges are not a variation of studding outlet.
For example..Pad flanges allow the shortest possible projection outside and inside the vessel. This is critical in some applications for mounting certain equipment to the vessel. With a sight glass mounted on the pad flange, equipment operators or engineers can look inside a vessel to observe mixing processes or other internals. Those kinds of sight glasses with special glasses are designed to hold pressure and are temperature resistant.
Dimensions of Pad Flanges
The Weldoflange and Nipoflange is a combination of a Welding Neck flange and a supposedly Weldolet or Nipolet. The 2 components are manufactured in one piece, and not welded. These flanges are primarily in Branch Connections.
Expander Flanges is a Welding Neck pipe flange where the nominal size of the non-flanged end is larger than the nominal size of the flanged end. They can be used to change the size of a pipe run. These are usually used to increase the line size to the first or second larger size. This is an alternative to using a separate reducer and weld neck flange combination. The expander flange can be used to connect pipe to pumps, compressors and Valves.
Reducing Flanges are suitable for changing line size, but should not be used if abrupt transition would create undesirable turbulence, as at pump connections. A reducing flange consists of a flange with one specified diameter having a bore of a different and smaller, diameter. Except for the bore and hub dimensions, the flange will have dimensions of the larger pipe size.