Massachusetts Wastewater Practice Exam

If a rotary screen is not turning, what could be the most likely cause?

1. Broken bearing

2. Screen clogged

3. Flow too high

4. Electrical failure

The correct answer is: Broken bearing

A rotary screen is designed to continuously rotate to filter out solids from wastewater, and if it fails to turn, one of the most likely causes is a mechanical problem such as a broken bearing. The bearings support the rotating mechanism, allowing it to move smoothly. If a bearing is damaged or broken, it can cause increased friction or even a complete halt in movement. Other issues, such as a clogged screen, high flow rates, or electrical failures could also interrupt the function of the rotary screen. However, these tend to manifest in different ways. A clogged screen might allow for some rotation but inefficient operation, while high flow could simply overwhelm the screening process without stopping rotation. An electrical failure might affect the motor that drives the screen but typically wouldn't prevent the screen from physically turning if the mechanical components are intact. Under normal operational conditions, a broken bearing presents as a specific failure that directly results in the screen not turning, making it the most likely cause in this scenario.