Sanitary Flange Fittings Introduction
Flange fittings are generally used for connections to valves, inline instruments or equipment nozzles. Two surfaces are joined tightly together with threaded bolts, wedges, clamps, or other means of applying high compressive force. Although a gasket, packing, or O-ring may be installed between the flanges to prevent leakage, it is sometimes possible to use only a special grease or nothing at all. Although flange sanitary fittings are bulky, they perform well in demanding applications such as large water supply networks and hydroelectric systems.
The flanges have a nominal pressure of 150, 300, 400, 600, 900, 1500 and 2500 lbs or 10, 15, 25, 40, 64, 100 and 150 bars. Different types of flanges are available, depending on the construction. The flanges used in the piping (orifice, threaded, slip-on, blind, weld neck, bushing, lap joint and reducer) are available with a variety of facings, such as raised, flat and O-ring.
A weld neck flange is joined to a piping system by butt welding. Although its long neck (or hub) makes it expensive, it reduces mechanical stress on piping by distributing stress between the base of the flange and the wall at the weld. Turbulence and erosion are reduced due to the matching size of the pipe and flange.