The principle behind flanges is that mechanical force needs to be exerted in order to preload the gasket.  The mechanical force is usually provided by bolts. The reason for this is that when internal pressure is applied, the flange – in conjunction with a gasket – is able to maintain a seal.

They allow for two pipes to be mechanically connected to one another.  They also allow for a pipe to be mechanically connected to a host of other equipment such as a valve or tee fitting.   A flange however needs to be first attached or connected to the pipe through either welding or threading.   They can be used either internally or externally for strength.  Their use allows for the easy assembly or disassembly of pipes.

Flanges are sized according to their nominal bore size, which for most pipes does not represent their actual outside or inside diameters.  For instance a pipe with a nominal diameter of say 1 inch is not indicative of the size of the pipe.  In this instance the outside diameter would be 1.315 inches. The inside diameter of any pipe is determined by the thickness of its wall.  For this reason it is imperative that manufacture of all and any pipe flanges is matched to the piece of the bore size of the matching pipe.

Industry Standards

The manufacture of flanges is subject to various industry standards, all of which are adhered to by us here at Chemipetro; a reputable, leading supplier worldwide of pipe fittings and flanges.

One such standard is the NORSOK standard.  This standard is intended to confirm or bear out the fact that a manufacturer has the experience, the qualifications and the necessary equipment and facilities to manufacture according to the acceptable properties of the materials being used.  The materials in question are Duplex SS, high alloyed austenitic SS, Nickel based alloys and Titanium and its alloys.