Why are bypass valves often included within large gate valves?

• A. to equalize the pressure on the two sides of the gates
• B. to vent air from the line during operation
• C. to isolate the valve during maintenance
• D. to reduce turbulence in the valve body

Answer: (A)

When a gate valve is large and operating under line pressure, there can be a significant pressure difference across the gate. A bypass path around the gate provides a way to balance pressure on both sides of the gate, which greatly reduces the differential load the actuator or operator must overcome. This makes the gate easier to move and helps prevent binding or damage to the gate and seats that could occur from high opposing forces. It’s not primarily about venting air, isolating the valve for maintenance, or reducing turbulence, though those factors are addressed in other designs or procedures.