Which of the problems listed will occur if...

🔍 Key Concepts

• Identify the function of diaphragm E in this pilot-operated pressure-reducing valve. • Think about how spring F and downstream pressure act on opposite sides of the diaphragm to position the auxiliary (pilot) valve. • Consider what happens to the force balance and flow path if the diaphragm can no longer separate the two chambers because of a large hole.

💭 Think About

• In normal operation, what pressure is applied to the underside of diaphragm E, and how does that pressure affect the position of the pilot valve and main valve? • If diaphragm E develops a large hole, will downstream pressure still be able to act effectively on the diaphragm, or will spring F dominate? What motion does that cause in the stem connected to the auxiliary valve? • When the auxiliary (pilot) valve moves in that direction, does it cause the main valve B to open more, close more, or stay about the same—and how will that affect downstream pressure relative to the set setting?

✅ Before You Answer

• Be clear on which direction the spring F force tries to move the diaphragm and stem, and which direction downstream pressure pushes. • Trace the flow path from inlet through the main valve B and the pilot passages to see how opening the pilot valve changes pressure above/below the main valve piston. • Verify whether a failed diaphragm would make the regulator go wide open or fail-closed, and then match that behavior to the listed consequences.

Which of the problems listed will occur if diaphragm "E", in the illustration shown, develops a significantly large hole? See illustration GS-0044.

The auxiliary valve will open wider due to the action of spring 'F'.

The main valve "B" will open wider compressing the main valve spring 'A'.

Downstream pressure will be greater than the desired setting.

All of the above.

🔍 Key Concepts

💭 Think About

✅ Before You Answer