BS 4504 is an obsolete British Standard that specifies the dimensions and tolerances of flanges and bolting for pipes, valves, and fittings. It is now superseded by EN 1092-1, but it remains in use for the dimensions of light duty, economy stainless steel flanges in applications where corrosion resistance and hygiene, rather than high pressures and temperatures, are the primary considerations.

BS 4504 covers four types of flanges:

Plain flanges
Boss flanges
Integrally cast or forged flanges
Weld neck flanges
The flanges are available in a variety of materials, including carbon steel, stainless steel, alloy steel, and copper. They are also available in a variety of pressure ratings, from PN6 to PN40.

The technical specifications of BS 4504 flanges are as follows:

Nominal size: DN10 to DN400
Pressure rating: PN6 to PN40
Material: Carbon steel, stainless steel, alloy steel, copper
Finish: Plain, raised face, grooved
Bolting: DIN 2566 or BS 3692
BS 4504 flanges are used in a variety of applications, including:

Water and wastewater treatment
Chemical processing
Food and beverage processing
Pharmaceutical manufacturing
Power generation
Oil and gas