Hydrogen Mass Flow Meter

A hydrogen mass flow meter is a Coriolis-principle instrument that measures gaseous H2 mass flow directly without inferring from velocity, pressure, and temperature. Two parallel measuring tubes vibrate at resonance; hydrogen flowing through the tubes induces a Coriolis force proportional to mass flow that twists the tubes, and position sensors at the inlet and outlet read the phase difference. Mass flow, medium density, and medium temperature come out simultaneously on the 4-20 mA loop, with RS-485 Modbus and HART for station SCADA integration. The factory build for hydrogen refueling station service uses 9/16-18 UNF and 13/16-16 UNF threaded process connections to match international HRS dispenser fitting standards.

Thermal-mass works on clean dry H2 up to about 4 MPa and reads only mass; pressure capability falls short of dispenser service above 35 MPa. Ultrasonic transit-time on hydrogen is feasible at low pressure but acoustic impedance mismatch and small bore make custody-grade accuracy difficult at HRS pressures. Coriolis is the only mass-flow principle that delivers ±0.1 % of rate custody accuracy at H35 350 bar and H70 700 bar simultaneously, with density measurement built in for compressibility cross-check. For low-pressure clean H2 production and pipeline service, the hydrogen thermal-mass build and hydrogen swirl build are the picks; the Coriolis hydrogen build covers dispenser service those families do not reach.

H35 is the 35 MPa (350 bar) hydrogen refueling protocol used on heavy-duty fuel-cell vehicles (trucks, buses, forklifts) and many bus depots. H70 is the 70 MPa (700 bar) protocol used on passenger fuel-cell cars worldwide (Toyota Mirai, Hyundai Nexo, Honda Clarity). H35 dispensers use 13/16-16 UNF threaded fittings; H70 dispensers use 9/16-18 UNF threaded fittings. The CMASS hydrogen series covers both: DN3 and DN4 sensors are spec’d for H70 9/16-18 UNF service, DN8 and DN15 sensors for H35 13/16-16 UNF service, all with the same 100 MPa working pressure ceiling. Configure to the dispenser protocol and the meter ships factory-built for that side.

Standard ship-with-meter certifications are ISO 9001 calibration certificate (mass flow + density traceable), Ex d [ia] IIC T6 Gb hazardous-area certification, EMC 2014/30/EU Annex II, and IP67 ingress rating. OIML R 139 (compressed gaseous fuel measuring systems for vehicles) and CSA HGV 4.10 type approval for hydrogen dispenser custody are buyer-arranged with the destination-country notified body (PTB, NMi, NIST, MIIT etc.). The factory build supports the OIML R 139 type-approval pathway with the ±0.1 % of rate accuracy class, dual-pulse output, and density cross-check required by R 139 Annex. Factory does not hold the type approval directly; the buyer secures it for the deployment market.

This build covers gaseous high-pressure H2 above the vaporizer outlet only. Medium temperature range is −40 to +60 °C; the working pressure range is 10 to 100 MPa. Cryogenic LH2 at −253 °C is out of range for the CMASS hydrogen series. For LH2 terminal off-loading, ASU liquid-hydrogen vaporizer feed, and any service below −50 °C, go to the Cryogenic Coriolis build instead; that version uses the same Coriolis principle but with the −269 to +100 °C cryogenic tube and jacket system. Both families share the transmitter, output protocols, and Ex certification, so the SCADA integration is identical.

Standard lead time is 5 to 7 business days from order confirmation, factory direct. CMASS003 (DN3), CMASS004 (DN4), CMASS008 (DN8), and CMASS015 (DN15) sensor bodies are held on the production line in 316L wetted material with both 9/16-18 UNF and 13/16-16 UNF thread options pre-machined; the lead time covers transmitter configuration, factory calibration with traceable mass-flow rig, and Ex-zone documentation. Titanium, Hastelloy C, and tantalum wetted-part upgrades add 7 to 10 business days. Each meter ships with the ISO 9001 calibration certificate, transmitter configuration sheet, and the Ex d [ia] IIC T6 Gb certificate.