A 2004 study by the U.S. Department of Energy shows continued global growth for the like Liquefied Natural Gas (LNG) industry as one of the sources to meet global energy demand. Our Micro Motion division recently announced that Coriolis technology is ideal in cryogenic mass flow metering applications like LNG (-153.1 degC). LNG can be stored and transported much more efficiently in a liquid state than in a gaseous state.
I came across a Chemical Engineering magazine article entitled, Flow Measurement in Bitter Cold: How to Use Coriolis Meters in Cryogenic Service which better describes why Coriolis technology works well in the bitter cold of more than -100 degC.
The authors, Emerson’s Tim Patten and Keven Dunphy describe how harsh temperatures pose problems for many flow measurement technologies. These problems are related to mechanical parts, wetted seals, and materials of construction with poor impact strength. And from a measurement standpoint, it’s expensive to keep the cryogenic fluids cold, so they are kept slightly below their boiling points. As the fluid flows past an obstacle such as a valve, flashing can occur. Pockets of gas form in the liquid making flow measurement difficult at best.
Tim and Keven point out that Coriolis technology is well suited since it has no moving wetted parts, nor temperature sensitive materials, and it has the accuracy required to satisfy custody transfer regulations. They recommend careful attention be paid to the pressure drop across the meter to avoid flashing by increasing the meter size. Their rule of thumb:
…the difference between the discharge pressure and liquid vapor pressure at the fluid temperature should be maintained at a factor of at least three times the pressure drop across the meter.
The article also provides tips on density measurement limitations, insulation best practices, and non-linear compensation. These tips apply not only to LNG but other cryogenic applications like liquid helium.