Tennessee Wastewater Operator Practice Exam

What may cause the discharge pressure to suddenly increase and the discharge quantity to decrease in a pump station?

1. A discharge valve was closed

2. A pump was turned off

3. The power supply was interrupted

4. The motor overheated

The correct answer is: A discharge valve was closed

When a discharge valve in a pump station is closed, it can lead to a sudden increase in discharge pressure because the pump is still working to push the fluid through the system, but the closure of the valve restricts flow. As the valve closes, the impeller continues to operate at its designed speed, generating pressure, but with limited or no flow due to the valve restriction, this creates a condition of increased pressure at the discharge side of the pump. At the same time, the discharge quantity decreases significantly because the closure of the valve effectively stops any movement of fluid out of the system or reduces it drastically. This is a common scenario in pump operations and can lead to potential issues such as cavitation or equipment damage if the high pressure persists without relief. Understanding this mechanism is crucial for operators to troubleshoot issues in wastewater systems and ensure proper operation and maintenance of pumps and valves. Other factors listed, like a pump being turned off or power interruptions, lead to different outcomes where pressure would typically drop, or the system would cease to function entirely rather than increasing pressure.