i just wanted to know the difference between flange standards BS EN 1092-2 and BS 4504. Will these match?

Question

flanges for piping -

Answer 1

The two standards referred to are for round piping flanges and for flanged valves, both generally of the 10 bar pressure requirements. This would be equivalent to ANSI 125/150 nominal pressure rating.
If the flanges are of the nominal ANSI 125/150 pressure rating designation and of the same nominal pipe size, they should match dimensionally.
Cast iron flanges of the 125 pound classificattion usually have a flat face and so should usually be mated to other flat face flanges of the 125 (cast iron) or 150 (steel) ratings.

Answer 2

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