Which of the following is NOT an example of a level control device for a pump station?

A pressure vessel is not considered a level control device for a pump station because its primary function is to hold gases or liquids at a pressure substantially different from the ambient pressure. Level control devices, on the other hand, specifically monitor and control the level of liquid in a tank or reservoir.

Devices like bubbler level gauges, mercury or mechanical float switches, and ultrasonic sensors are all specifically designed to measure liquid levels, relay information to control systems, and help maintain desired levels in the pump station. These sensors work by different mechanisms, such as measuring the displacement of floats, using sound waves to determine distance, or gauging the pressure exerted by a column of liquid. In contrast, while a pressure vessel may play a role in the overall system by managing pressure, it does not perform the function of monitoring or controlling liquid levels directly. This distinction makes the pressure vessel unsuitable as a level control device in the context of pump stations.