Basic Wastewater Operator Practice Exam

What causes a centrifugal pump discharge pressure to increase while discharge quantity decreases?

1. Blockage in discharge line

2. Blockage in intake

3. Low power supply

4. Low flow into station

The correct answer is: Blockage in intake

A blockage in the intake of a centrifugal pump can lead to a situation where the discharge pressure increases while the discharge quantity decreases. When there is an obstruction at the pump's intake, the pump struggles to pull in the necessary volume of fluid. As the pump operates, it generates pressure in the discharge line, but due to the reduced flow rate resulting from the blockage, the quantity being pumped out diminishes. The centrifugal pump functions by creating a difference in pressure between the intake and discharge. When the intake is blocked, the pump may still create pressure at the discharge side, but since it cannot draw water effectively, the flow rate decreases. This results in higher pressure in the discharge line, indicated by the rise in discharge pressure, while the actual volume of liquid being discharged drops. Understanding this scenario is key for operators, as it underscores the importance of regular maintenance and monitoring of pump systems to prevent blockages that can disrupt operation and efficiency.