Tennessee Wastewater Operator Practice Exam

What can cause a surge in a centrifugal blower?

1. The motor speed is increased excessively

2. The inlet valve is throttled too much

3. The air filter is cleaned

4. The discharge pipe is shortened

The correct answer is: The inlet valve is throttled too much

A surge in a centrifugal blower occurs when there is an imbalance in airflow and pressure. When the inlet valve is throttled too much, it restricts the airflow into the blower. This restriction can create a situation where the blower cannot move air efficiently, leading to fluctuations in pressure and flow that cause the blower to surge. The surge condition often manifests as an oscillating or unstable operation, where the blower may alternate between periods of high flow and low flow, potentially damaging the system if not addressed. In contrast, increasing the motor speed excessively typically increases airflow and pressure, which can lead to different types of operational issues but not necessarily directly cause a surge. Cleaning the air filter usually enhances airflow through the system, enhancing performance rather than causing instability. Shortening the discharge pipe should ideally improve performance by reducing friction losses, again not leading to a surge condition. Understanding the impact of throttling the inlet valve provides crucial insights into maintaining stable operations in centrifugal blowers.