Industrial Gas Roots Flow Meter

A Roots gas flow meter is a positive-displacement (PD) volumetric instrument. A pair of twin-lobe rotors turns inside a sealed casing; each rotation displaces a fixed-volume pocket of gas from the inlet to the outlet, so the rotation rate gives instantaneous flow and the totalizer gives cumulative volume. The principle is independent of velocity profile, which is why Roots holds its accuracy down to the low end of the published range where velocity-type turbine meters fade. Output options are pulse, 4-20 mA, RS-485 Modbus, HART, and 4G for off-grid AMR billing endpoints.

The two families cover different flow zones. LWGQ turbine is the pick for high-flow industrial-gas custody at DN50–DN300 and 1.6–10 MPa; chemical-park bulk N2 / O2 distribution, refinery fuel-gas headers. LQ Roots is the pick for low-flow tenant sub-billing at DN25–DN150 and 0.05–1.6 MPa; per-tenant fence inlet inside an industrial park, chemical-park tenant N2 inerting takeoff, low-flow compressed-air audit branches. Below the turbine bottom-of-range, turbine accuracy fades; Roots holds ±0.5 % of rate across 1:30 turndown. Above 1.6 MPa or DN150, go to LWGQ turbine.

LWGQ compressed-air turbine is the pick for plant-air main-distribution measurement and tenant sub-measurement at DN25–DN300 where line velocity stays inside the turbine working range. LQ Roots is the pick for low-flow compressed-air audit branches where idle / off-shift / leak-detection flow drops below the turbine bottom-of-range and turbine pulse-output starts to drop pulses. Roots is positive-displacement and counts volume per rotation regardless of velocity, so it captures the leak-drift flow that an ISO 50001 energy audit targets as recoverable savings. Pre-dryer wet compressed air is out of scope for both; go to vortex.

The 3.6 V lithium battery (selection code V) powers the meter and its 4G modem without permanent mains supply, which suits unmanned per-tenant sub-meters on industrial-park fence inlets, remote chemical-park N2 takeoff valves, and outdoor compressed-air audit branches where pulling 24 VDC service is impractical. The integrated 4G modem (output code 7) streams instantaneous flow, totalizer, temperature, and pressure to a billing back-office or energy-management system. Battery service life depends on logging interval and signal strength; specify the duty cycle at the configurator stage for a service-life estimate.

The factory ships an ISO 9001 calibration certificate with each meter listing the G-class, calibrated DN, K-factor, and tested flow range. Fiscal / custody-transfer type approval per the local gas-meter metrology regime (notified-body pattern approval, periodic verification, sealing) is buyer-arranged with the local metrology institute or notified body; the factory provides build documentation and traceable calibration records to support the buyer's type-test submission. ISO 50001 energy-management-system certification (if required for the buyer's plant) is a site-level audit arranged through the buyer's certification body and is not an ex-factory meter cert.

Standard lead time is 5 to 7 business days from order confirmation, factory direct. Each meter is calibrated at the factory on a gravimetric or bell-prover gas rig per the selected G-class, tested across the published flow range, and shipped with the ISO 9001 calibration certificate listing K-factor, calibrated DN, tested range, and accuracy class. Witness calibration at a third-party metrology institute (NMi / PTB / NIM equivalent) before shipment can be arranged on request; specify the witness requirement at quote so the lead time can accommodate the booking. EMC compliance to EU Directive 2014/30/EU ships standard.