Level Measurement

Bubbler Level measurement system

What is Bubbler system?

A bubbler system is an accurate means of measuring the level of fluid in open or vented containers, particularly in harsh environments such as cooling tower sumps, swimming pools, reservoirs, vented fuel tanks, drain sumps or air washers.

A complete system consists of a compressed air source, an air flow limiting tube, and a pressure transmitter. The sensing tube is the only element that is subjected to the components. All others can be in a protected area remotely.

Where Bubbler level systems are used?

Bubbler-style liquid level measuring devices are particularly helpful when the method liquid in question is extremely corrosive, susceptible to plugging sample ports, or objectionable to direct contact with a pressure sensor in any other manner.

Using a bubbler system, where the pressure sensor can be located anywhere along the length of the dip tube and therefore easily located where maintenance personnel can access it,

level measurement applications where direct contact with the pressure sensor would make access to that sensor inconvenient or even impossible.

Construction of Bubbler level meter

Air bubbler systems do not contain moving parts, making them suitable for water level measurement, viscous fluids, liquids with large amounts of suspended solids, slurries, sewage, drainage water, and sludge.

Because the air flow tube is the only part of the bubbler that touches media, it can be used in applications where you don’t want the liquid to contact a sensor. And, because bubblers can be used in small pipes of diameter, they allow installations in tanks where other systems will not fit.

Working of Bubbler level system

A common construction uses either a rotameter or a sight feed bubbler to monitor purge gas flow rate, with a needle valve to restrict that flow:

  • Slowly purge gas is introduced into a “dip tube” that is submerged in the liquid process so that no more than a few bubbles per second of gas emerge from the end of the tube.
  • Gas pressure is (very nearly) equal to the hydrostatic pressure of the liquid at the submerged end of the tube within all points of the tube system.
  • Any pressure-measuring unit touched anywhere along the length of this tube scheme will feel this pressure and can infer the fluid depth in the process vessel without having to contact the fluid process directly.
  • As long as the material density remains constant, the pressure is proportional to the liquid level in the tank

Advantages of using Bubbler level system

  • Not affected by foam or turbulence
  • Can be used in small diameter pipes
  • Easy to understand/proven technology
  • Large installed base


Instrumentation Engineer

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