A pressure reducing valve has two upper operating chambers sealed from each other by a

• A. Rigid piston
• B. Metal diaphragm
• C. Elastomeric seal
• D. Flexible, Reinforced Diaphragm

Answer: (D)

The valve uses a flexible, reinforced diaphragm to separate the two upper operating chambers. This diaphragm acts as a movable barrier that can flex as pressure on one side changes, translating that movement into valve stem adjustment to regulate downstream pressure. The reinforcement gives the diaphragm the strength to withstand repeated cycling without tearing, which is essential for reliable long-term operation.

A rigid piston wouldn’t allow the necessary flexing to modulate the valve properly, and a metal diaphragm would be too stiff for the precise, responsive movement needed. An elastomeric seal alone isn’t designed to separate two pressurized spaces in a continuously operating regulator and lose its shape under pressure. The reinforced flexible diaphragm provides both the isolation between chambers and the flexibility required for accurate pressure regulation.