🔍 Key Concepts

• How outlet pressure is fed back to the top of the diaphragm/auxiliary valve through passage C/H and how that force compares with the spring force from above (F). • Whether the auxiliary (pilot) valve D closes when the stem is pushed upward or downward, and what motion each condition (inlet pressure change, outlet pressure change, screw G adjustment) produces. • What happens to the main valve A/K when the auxiliary valve D is closed versus open in a spring-loaded pressure reducing valve.

💭 Think About

• For each option, ask yourself: does this make the force on the diaphragm from outlet pressure stronger or weaker compared with the spring above it? Then decide whether that force balance would move the stem toward closing or opening D. • Trace the flow path: when D is open, where does fluid go, and what happens to pressure above the main valve plug A/K? If that path is restricted by closing D, how must the pressures above and below the diaphragm change to make that happen? • Think about adjusting screw G: if you turn it to raise it, are you increasing or decreasing compression on spring F, and would that tend to let outlet pressure move the diaphragm more easily, or resist it and keep D more open?

✅ Before You Answer

• Identify which side of the diaphragm E is exposed to outlet pressure (look at ports C and H) and which side is acted on by the spring F adjusted by screw G. • Determine the direction of motion required to seat (close) the auxiliary valve D and what combination of pressure and spring force would create that motion. • For each choice, mentally follow the cause-and-effect chain: condition changes → force balance on diaphragm/spring changes → stem moves up or down → does that actually seat valve D? Eliminate any option where this chain does not plausibly end with D closing.