Which valves are most often used where pressure is relatively high and positive shutoff is required, such as the discharge of a high lift pump?

• A. Gate valves
• B. Globe valves
• C. Ball valves
• D. Large plug valves

Answer: (D)

When a system needs reliable, high-pressure positive shutoff in a large-diameter line, the valve chosen should seal securely at full pressure and allow a straight-through flow. Large plug valves fit this need by using a cylindrical plug that rotates to shut off flow and seats tightly under pressure, giving dependable, bubble-tight shutoff even in high-pressure service. The flow path through a plug valve is essentially straight, so when open it passes with minimal resistance, which helps maintain predictable head and flow in a pump discharge. Other valve types either favor throttling with higher pressure drop (globe valves), require more effort or bulk at large sizes for full shutoff (gate valves), or can be less practical in large diameters and high-pressure service (ball valves). So for high-pressure, positive shutoff in a discharge from a high-lift pump, large plug valves are the best fit.