Pressure relief valve / safety valve in steam line of boiler

nandu, what I think is these two releif valves used is to ensure double safety. If first doesnt works then 2nd can do the job. Its just conservative thinking by designer. Actually he is right because sometimes these valves get chocked. when u r using 2 safety valves then its obvious that first safety valve must be set at lower pressure than next otherwise it will be meaningless.But my point is why he used 2 safety valves near usage point (in your case its may be turbine) ?? Because there must be pressure reducing station after Boiler which must consist safety valve.