Tennessee Wastewater Operator Practice Exam

If there is a normal gas pressure but zero feed rate on the rotometer, what is the likely issue?

1. Clogged injector

2. Low gas pressure

3. Faulty rotometer

4. Leaking seals

The correct answer is: Clogged injector

In this scenario, a normal gas pressure but a zero feed rate on the rotometer indicates that gas is not flowing through the system as expected. The most plausible explanation is a clogged injector. When an injector becomes clogged, it obstructs the path through which gas must flow, leading to the inability of the gas to reach the rotometer. Since the pressure is normal, it supports the idea that there is gas available in the system; however, the blockage at the injector prevents it from being fed into the rotometer, resulting in a reading of zero. Other options would not sufficiently explain the situation. Low gas pressure would typically result in reduced flow rather than a complete blockage, a faulty rotometer could lead to inaccurate readings but wouldn’t normally manifest as zero flow if gas is present, and leaking seals would likely allow gas to escape, potentially resulting in reduced pressure rather than zero feed rate. Therefore, a clogged injector aligns perfectly with the conditions described.