🔍 Key Concepts

• Operation of a self-actuated steam pressure reducing valve shown in GS-0044 • Relationship between upstream (supply) pressure, valve spring setting, and controlled downstream pressure • Role of the diaphragm and pilot/auxiliary valve in sensing and controlling outlet pressure

💭 Think About

• Look at where the sensing line from the outlet connects to the underside of the diaphragm. How does a change in outlet pressure make the main valve open or close? • Which of the choices describes a condition that would prevent the valve from ever reaching the set outlet pressure, even if the valve were fully open and working correctly? • Which options actually describe parts of the normal control action (how the valve is supposed to work) rather than a fault or failure?

✅ Before You Answer

• Identify on the illustration which side of the diaphragm sees reduced (downstream) pressure and which side sees spring force. • Decide whether frictional losses downstream change the pressure right at the valve outlet, or only farther in the line. • Ask yourself: if the supply pressure entering at the inlet dropped, could the valve still deliver the same reduced pressure at the outlet, even wide open?