How are Flanges Classified?
A flange is an external or internal edge or rim (lip) for friction, such as an iron plate flange, such as an I-beam or a T-beam, or for attachment to another part, such as a pipe end flange, a steam ring, and so on. A flange can also be a plate or ring that is fastened to the pipe to shape a rim at the end of a pipe. A blind flange is a plate that is used to cover or remove a screw’s end. A flange joint is a pipe attachment with flanges that lock the components together.
A lot of common flange standards are to be found around the globe. These are designed to have standardized dimensions to allow easy interchangeability and functionality. ASA / ASME (USA), PN / DIN (EU), BS10 (British / Australian), and JIS / KS (Japanese / Korean) are General world standards. In 1996 ANSI stopped publishing B16.5 in the USA and the equivalent for this is ASME B16.5.
There are two pipe types of nomenclature: decimal, and metric. In the imperial system, they use pounds per square inch(psi) to refer to pressure or nominal pipe size(NPS) to refer to the size of the pipes. The pressure would usually be noted in kilopascal (kPa), while pipe diameter is noted in nominal diameter(DN) of the metric system depending on the international unit scale.
What does PN and DN stand for?
PN stands for “Pressure Nominal.” The PN is used as a prefix to the Flanges’ pressure rating. The PN16 flange, for example, is designed to operate at up to 16 levels. PN6, PN10, PN16, PN25, PN40, PN64, PN100 are normal scores. Following ISO 7005-1 or DIN 2501, PN10, PN16, PN25, and PN40 specify both pressure classes in pressure bars and metric flange dimensions that use the metric measuring system. Flanges developed to ANSI, AWWA, ASA, or old British specifications measured in inches will not always fit the flange specification.
It’s probably a good idea to specify the actual working pressure when defining a PN flange specification because it’s common to allow a similar PN, say PN16, flange drilling on a fitting or valve to suit neighboring flanges but the pressure level is lower than PN16.
The term nominal diameter refers to the internal diameter of a pipe. All piping board dimensions, as well as the approximate pressure level and type rating, e. g. The flange dimensions are specified in relation to the nominal diameter. Steel is not often defined as a commodity, but it is.
It should be noted that the true internal diameter varies by several millimeters in many cases. Only by specifying the nominal diameter DN in relation to the equivalent DIN norm can it be accurately concluded that pipes from various manufacturers can be mixed.
The nominal diameter is specified using the DN (Diameter Nominal) abbreviation in compliance with EN ISO 6708 followed by a dimensionless number equivalent to the real internal diameter in millimeters. For reference, a DN 50 pipe indicates a pipe with an external diameter of 60.3 mm and a wall thickness of 3.65 mm according to EN 10255 (resulting indoor diameter of 53 mm).
