Written by JD Cattel, the President of Digital Control Company.
There are many methods to measure the level in a municipal lift station. Some of these devices are bubblers, submersible transducers, ultrasonics, radar, floats, capacitive tapes, and so on. All of the technologies have been used with varying degrees of success.
Digital Control Company has specialized in the manufacture of bubblers for level measurement.
There are many advantages of using bubblers over the other devices in municipal lift stations. The environment in a municipal lift station is exceedingly harsh to say the least. Anything and everything detrimental to instrumentation has found its way into them. Add to that the effects of weather, specifically lightning, and reliably measuring level in a lift station is an arduous task.
Mechanically, a bubbler operates much like the aerator on a tropical fish tank. Air from either on board compressors or a standard plant instrument air system is pumped or “bubbled” into the lift station. The pressure in the bubbler line is proportional to the water level in the lift station. That is, if we can believe Archimedes and his famous principal.
There are many advantages of this configuration over other technologies. The only thing in the lift station wet well is a relatively inexpensive ¼ inch tubing weighted or fastened to the wall to anchor it near the bottom of the well. The expensive electronics are safely ensconced, usually in a NEMA 4x enclosure, with the other control components. This isolates the electronics from coming in contact with the extremely adverse substances in a wet well. Additionally the bubblers are inherently intrinsically safe as the probes are not powered at all. Finally, they are virtually immune to lightening strikes as again all of the electronics are safely housed in an electrically isolated enclosure away from the wet well.
They are cost effective because once set up, they do run for years. The on board compressors have a history of lasting upwards of 5 years and are readily replaceable.