Biogas Roots Flow Meter

A biogas Roots flow meter is a positive-displacement (PD) volumetric instrument that measures gas through a pair of twin-lobe rotors sealed in the casing; each rotation displaces a fixed sealed-pocket volume, so the rotation count is the totalized volume. It sits at the biomethane outlet of the upgrading skid (post-amine or post-membrane H₂S scrubbing, post-PSA or post-membrane CO₂ separation, post-drying) where the gas is ≥95 % CH₄, ≤10 ppm H₂S delivered, ≤4 ppm H₂O, dry single-phase. The factory K-factor gives ±0.5 % of rate custody-grade billing and the PD principle holds accuracy at the low-flow tail where turbine cannot. Post-upgrade only; raw biogas at the digester outlet is outside the operating range.

No. Raw biogas at the digester outlet is water-saturated, carries 30 to 45 % CO₂ and 100 to 10,000 ppm H₂S, and is often pulsating; outside the Roots Series applicability (clean dry gas only). The Roots rotor will pit under wet H₂S service and the K-factor shifts under condensate carry-over. For raw biogas at the digester or pre-upgrading buffer, go to the biogas-swirl-flow-meter (LUXB Series) which uses Hastelloy C-276 wetted parts and tolerates H₂S to 10,000 ppm with water saturation. The biogas-roots page covers only the post-upgrade biomethane stream after the upgrading skid; that is where custody-grade billing happens.

Same site; different flow range. Biogas-roots (LQ Series) covers DN25 to DN150 small-skid RNG outlets where flow runs G16 to G1000 (1 to 1,000 m³/h) and the off-peak swing matters; PD wins the low end down to the published Qmin where turbine reads zero or biases low. Biogas-turbine (LWGQ Series) covers DN50 to DN200 grid-injection skids at higher steady flow with titanium body for residual H₂S excursions. A typical mid-size RNG plant might run a Roots meter at the off-taker delivery point and a turbine at the high-flow grid-injection skid. Pick by flow range, not by precision grade; both are ±0.5 % of rate at their service window.

Production G-classes are G16, G25, G40, G65, G100, G160, G250, G400, G650, and G1000 on DN25 through DN150. A small RNG plant in the 50 to 300 Nm³/h biomethane production range typically sizes a G65 (2 to 100 m³/h on DN50, 1.0 MPa) or G100 (2.5 to 160 m³/h on DN80, 1.6 MPa) at the upgrader outlet. A landfill-gas off-taker on a smaller upgrader uses G160 to G400 (3 to 650 m³/h) on DN80 to DN100. The 1:30 turndown on the top G-class lets one meter cover off-peak / shoulder / peak production swings without re-sizing. G16 to G25 covers very small WWTP biomethane-to-CHP service at DN25 to DN40.

The factory ships each meter with an ISO 9001 calibration certificate listing the G-class, K-factor, calibrated DN, and tested flow range across the published range. Hazardous-area cert is Ex ia IIC T6 Ga (intrinsically safe); EMC compliance is to EU Directive 2014/30/EU. Custody-transfer type approval per the local gas-meter metrology regime; OIML R 137 / R 138, EN 16723 biomethane quality, or country-specific equivalent; is buyer-arranged with a notified body in the deployment country. The meter is a candidate instrument that the buyer's metrology consultant submits to a witnessed type-test if the local tariff regime requires it. Engineering will share build documentation and calibration traceability records to support that submission.

Standard lead time is 5 to 7 business days from order confirmation, factory direct. Each meter ships with an ISO 9001 calibration certificate listing the G-class, K-factor, calibrated DN, and tested flow range; a mill cert for the aluminium alloy body; the build-coded serial plate with model string; and a daily-and-interval logger file pre-formatted for audit retrieval. Hazardous-area cert is Ex ia IIC T6 Ga (intrinsically safe) for classified RNG-skid delivery points. EMC compliance to EU Directive 2014/30/EU ships standard with IP65 ingress. The 3.6 V lithium battery option ships pre-fitted with a multi-year service life for off-grid AMR billing endpoints.