??? A bubble level is either a curved tube, wherein the center portion represents level, or some sort of circular object, wherein the central circle marked on the sight glass represents level:
Thanks, but what I'm talking about is a level indicator for a tank, that features a long tube going almost all the way to the bottom. Air gets bubbled down the tube and somehow that results in a level measurement. I've looked all over the web, and I have failed to turn up any info. Any help would be appreciated. We're planning on using one on a sulfur pit, but I'm wondering if some kind of radar device wouldn't be better.
GPSA Engineering Data Book Section 4 (Instrumentation) speaks of "head-pressure level gauges."
"The true level of a liquid can be determined by dividing the measured hydrostatic head by the density of the liquid. This method requires a knowledge of the densities of all phases of the liquid. Some of these methods are: pressure gauge, bubble tube, and differential pressure measurement. The bubbler is used at vacuum and low pressures and is especially good for services such as molten sulfur and dirty liquids. In "boiling-liquid" service, a condensate trap must be used on the vapor leg. The level of trapped condensate in the vapor leg will usually be different than the vessel liquid level, requiring compensation of the transmitter."
MintJulep has it right. A low pressure stream of air is bubbled at a constant rate to the bottom of the tank. Back pressure on the bubble tube is measured and will be proportional to the tank level (head pressure). Note that a constant flow rate is required for accuracy. I have used one for level measurement in a flume. The flume was handling waste from a dairy factory, lost of fat, caustic and on occasion acid too. Hence propper material selection for other direct measurement was hard. Eventually replaced with an expensive radar or ultrasonic unit.
I have always thought a sight gauge and bubbler are different.
A sight gauge is a piece of "pipe" that is transparent (such as glass, plastic, "flippers", dial, etc.) and you can see the level within it's range.
A bubbler is as described above.
The two can both be used to determine/indicate level, but are different instruments.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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Just reread your original post, and you are also looking for a supplier. The unit I was working with was supplied by Taylor. Very good pneumatic instrumentation and control. Sadly I do not think they still exist or make the bubbler measurement system. However it would be possible to make a unit yourself. I am certain a constant flow device can be sourced from one of the compressed air valve manufacturers, compair, SMC or Festo. Link this with a pressure gauge or transducer and you will have the bubbler system.
