Tennessee Wastewater Operator Practice Exam

Which type of blower system relies on both positive displacement and internal compression?

1. Rotary lobe blower

2. Turbo blower

3. Rotary screw blower

4. Centrifugal blower

The correct answer is: Rotary screw blower

The correct answer focuses on the rotary screw blower, which operates on the principles of both positive displacement and internal compression. In a rotary screw blower, two intermeshing screws rotate within a casing, compressing the air as it moves through the blower. This mechanism creates a sealed chamber that traps the air, increasing the pressure as it advances through the rotation. The positive displacement aspect comes from the fact that this type of blower physically traps and moves air, while the internal compression aspect refers to the increase in pressure as the air is forced through the narrowing spaces created by the rotating screws. This combination makes rotary screw blowers particularly effective for applications requiring a constant and stable air supply at moderate to high pressures. Other types of blowers, such as turbo and centrifugal blowers, primarily utilize high-speed rotation to impart kinetic energy to the air, relying less on the positive displacement concept. Rotary lobe blowers also utilize positive displacement but do not achieve internal compression in the same manner as a rotary screw blower.