Wednesday, December 10, 2014

Improving Maintenance and Reliability of Bubbler Systems


According to Wikipedia "an air bubbler system uses a tube with an opening below the surface of the liquid level. A fixed flow of air is passed through the tube. Pressure in the tube is proportional to the depth (and density) of the liquid over the outlet of the tube."

A common problem with many bubbler systems used in water and wastewater systems is long term accuracy and reliability issues. The need for scheduled maintenance is required because of the possibility of  tampering, failed solenoids, changing air flow rates, or clogged downpipes due to crystal formation - particularly in wastewater applications with high entrapped solids.

A better approach is to use a level transmitter for purge control. This solution offers a highly engineered single component that is easily retrofitted to bubbler installations. These purge transmitters automatically maintain an extremely low flow continuous purge (less than 0.02 scfm) regardless of liquid depth, and minimizing formations of crystals in the downpipe. The lag time during dynamic level changes is also eliminated. Furthermore, bubbler operation is tamperproof because there is no external regulator or needle valve (or rotameter) – internally a fixed differential is maintained over a precision flow orifice.

Transmitter purge (or bubbler) technology works reliably in the presence of vapors, and, unlike ultrasonics, can be used in media temperatures of more than 350°F. Bubblers are normally used in applications where foam, solid debris, sewage sludge, or turbulence make ultrasonic, radar, or float switch devices ineffective. The purge transmitter is relative compact in size and allows for installations in tanks where other systems won’t fit.

The purge control transmitters require a compressed air supply (35-150 psig/2.4-10.3 bar) and provide a two-wire 4-20mA output that can be transmitted over substantial distances. The transmitter can be mounted directly outdoors or within small enclosed spaces at the measuring point or up to a hundred feet away.

More information on the purge transmitter may be download here.