Pressure relief valve / safety valve in steam line of boiler

[nandu6630]

I have 2 safety valves / pressure relief valve coming in single line feeding steam to a turbine. One is set a lower pressure and other a slightly higher discharge pressure.
Is there any logic that first lower capacity / higher capacity should come from drum side.?
Any standard / code requirements in giving this configuration and positioning of safety valves.?

Kindly clarify

Thanks

[josefreitas]

see ASME B31.3 and the book:
Piping Calvulations Manual, by E. Shashi Menon