Considerations For Coriolis Mass Flow Meters Measuring Hydrogen

Recently, we installed three flowmeters for measuring hydrogen flow on hydrogenation reactors. The owner selected Coriolis mass flowmeters for accuracy and safety. However, measuring gases using a Coriolis mass flowmeter differs somewhat from measuring liquids. During installation and commissioning, we encountered some issues that we would like to share.
First, consider the installation orientation:
Coriolis mass flowmeters can be installed with the sensor facing downward, upward, or in a flag-like position. When measuring gases, it is recommended that the measuring tube be installed upward to prevent liquid from accumulating in the sensor's measuring tube. If liquid is present in the measuring tube, gas and liquid will mix, causing the flowmeter to malfunction.

Second, consider the flowmeter's range:
When measuring gases, the range of a Coriolis flowmeter is different from that used for measuring liquids. Generally, the manufacturer's label indicates the range for measuring liquids. For example, the flow range of the Zhonglong mass flowmeter we selected is 80-800 kg/h, which is the liquid range. Generally speaking, the measurement range for gases is generally one-fifth that of liquids, with the optimal measurement range being one-fifth of the lower limit to one-tenth of the upper limit, or 16-80 kg/h.

The density of the gas should also be considered:

At normal temperature and pressure, hydrogen is a highly flammable, colorless, transparent, odorless, and insoluble gas in water. Hydrogen is the world's smallest known gas, with a density only 1/14 that of air. That is, at 1 standard atmosphere and 0°C, its density is 0.089 g/L, making it the substance with the smallest relative molecular mass. (The above is quoted from Baidu Encyclopedia.)
Gases are compressible. Initially, the client specified a cubic flow rate, an operating pressure of 1.2 MPa, and an operating temperature of 26°C. Based on the flow rate, a DN15 mass flowmeter was selected. Later, on-site observation revealed that the standard cubic flow rate should have been used. The density difference between operating and standard conditions was over tenfold, so the DN15 was later replaced with a DN6. Finally, let's set the threshold flow rate:
Due to gas instability, low flow rates may occur when measuring gas flow. All brands of Coriolis mass flowmeters have a low-flow cutoff function. The threshold flow rate setting range is generally between 1% and 3% of the range, and it's recommended to set it lower initially. When setting the threshold flow rate, be sure to ensure the correct units are used. We've encountered situations where the meter display does not display flow rates due to incorrect units.