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Underground gas storage in salt caverns starts out with the leaching of the cavern by solution mining. This process requires flow measurement of the injection water as well as the produced brine.

Wetted meters are a problem because anything that is touching the brine is subject to corrosion and because of the scaling nature of the salt that collects on surface, it plugs orifices, and degrades other signals. An operator that was in the process of solution mining was aware of these problems and thus looking for an alternative with non-invasive metering technology - one that can also accurately measure slurries as well as the brines concentration.

One of the major benefits of non-invasive ultrasonic flow meters is that, unlike traditional meters, they contain no moving parts and do not need frequent calibration and maintenance. Further, they are not affected by density, which make them ideal for brine measurements. They automatically compensate for variations in viscosity. Also, because the salt tends to plate, the meter can detect any buildup on the interior of the pipe, compensate for decreased diameter, and send an alert that the pipe needs cleaning.        

But for the process of in-situ leaching it is not only neccesary how much brine is flowing out, but to also know its the concentration to then calculate how much salt has been removed and hoch mich storage space has been cretaed.

FLEXIM' ultrasonic mass flow and concentration meter, PIOX S, infers the concentration by measuring what the speed of sound of the liquid is. Since the geometry of the pipe is known, it can directly measure the speed of sound of the moving liquid.  Since the meter measures the speed of sound of the liquid, and normalizes for the effect of temperature, the meter puts these two variables into the equation and the resulting change of sound speed is correlated to the salt concentration in the brine. Speed of sound is a very active variable when it comes to brine concentrations. So, with this technique one gets quite good resolution and repeatability. Besides that, the technique also works with many other applications such as sulfuric acid and nitric acid.

When it comes to measuring heavy slurries, FLEXIM's non-invasive ultrasonic meters automatically switch to their built-in Hybrid Trek Mode, which also allows for an accurate and reliable masurement of slurries.

Non-invasie gas flow measurement

FLEXIM's meters are very versatile.
When the caverns are complete, the ultrasonic meters work won’t be done as they are capable of measuring almost any kind of flow when properly equipped. It means, that the brine meters can easily be upgraded to measure gas flow and then complete the full measuring cycle when the underground gas storage field is developed.

Many operators of gas storage facilities realize, that when they combine the decreased maintenance cost and the continued use of the meters in their gas distribution operation, that this technology is exceptionally cost-effective.

FLEXIM’s ultrasonic clamp-on technology allows for non-intrusive, highly accurate measurement of water and brine flow. By measuring the sound speed, the same instrument can be used to determine the density of the produced brine at the same time. FLUXUS is also used for blanket measurement.


  • Simultaneous non-intrusive flow and density measurement with one instrument
  • Pressure independent
  • Not subject to corrosion through salt
  • No wear and tear, not affected by solid particles (i.e. sand and stones in the brine)
  • No risk of leakages
  • Installation without process downtime
  • Possibility to be upgraded into a gas flow meter for further measurement at the developed gas storage field