New Mexico Pipe Fitter Journeyman (JPF) Practice Exam

Why are gate valves advised against being used in partially open or closed systems?

1. They do not seal properly

2. Excessive vibration and wear occur

3. They are prone to corrosion

4. They have slower response times

The correct answer is: Excessive vibration and wear occur

Gate valves are advised against being used in partially open or closed systems primarily due to the excessive vibration and wear that can occur in such configurations. When a gate valve is not fully open or closed, the fluid flow can create turbulence and induce vibrations in the valve. This is particularly problematic because gate valves are designed for either full open or fully closed positions, where the flow is either unrestricted or completely blocked. When left partially open, the valve may struggle to maintain a consistent seal, leading to increased wear on the gate and seating surfaces. Over time, this can result in significant performance issues, including leakage and reduced lifespan of the valve. The adverse effects of this excessive vibration can lead to mechanical failure, making gate valves unsuitable for throttling applications or in systems where they will not be fully opened or closed. Therefore, it's crucial to use valves designed for throttling, such as globe valves, in applications requiring frequent adjustments to flow rates.