Question

A small changes in liquid will give a large change in metric. Which indirect liquid level measurement below, that detect a small changes in liquid and have a low cost? Briefly explain how the measurement works.

a) Capacitance level gauge

b) Hydrostatic pressure gauge

c) Bubbler

d) Ultrasonic level gauge

Answer 1

BUBBLER

A bubbler-type level sensor is a technology used in vessels that operate under atmospheric pressure. A dip tube having its open end near to the vessel open carries a purge gas (typically air, although any inert gas such as dry nitrogen may be used whenever there is a danger of contamination of or an oxidative reaction with the processing fluid) into the tank.

As gas flows down to the dip’s tube outlet, pressure in the tube rises until it overcomes the produced hydrostatic pressure by the liquid level at the outlet. The pressure equals to the process fluid’s density multiplied by its depth from the end of dip tube to the surface and is monitored by a pressure transducer well connected to the tube.

Bubbler-style liquid level measurement systems are mostly preferred when the process liquid in question is highly corrosive, prone to the plugging sample ports, or in any other way objectionable to have indirect contact with a pressure sensor.

AMONG ALL THESE PROVIDED METHODS, BUBBLER HAS LEAST COST AND EVEN DETECT A VERY SMALL CHANGE IN THE LIQUID. THE SETUP OF OTHER PROVIDED METHODS IS RELATIVELY COSTLY.

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