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".
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 Branchconnections.
On the website of Promat BD you can find more information about the various performances, dimensions etc.. Furthermore, they have an expanded range of special flanges, fittings and 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.