Which valve feature helps reduce the effort required to operate a main valve by lowering the pressure across the valve disk?

• A. Bypass valve
• B. Gate valve
• C. Globe valve
• D. Check valve

Answer: (A)

Reducing the hydraulic force the operator must overcome to move a main valve is achieved by lowering the pressure difference across the valve disk. A bypass valve provides an alternate path for water around the main valve, so when the bypass is opened, flow is redistributed and the upstream and downstream pressures become more equal. That diminishes the differential pressure acting on the valve disk, which directly reduces the torque or effort needed to open or close the main valve. This is especially helpful with large valves or high system pressures, where even a small reduction in differential pressure translates into a noticeable ease of operation. The other valve types don’t perform this pressure-relief function: a gate valve, globe valve, or check valve either don’t provide a bypass path to equalize pressures or don’t focus on decreasing the pressure differential across the main valve disk.