LPG Vapor Roots Flow Meter

An LPG vapor Roots flow meter is a positive-displacement instrument that meters LPG in the gas phase; propane, butane, or propane-butane mix downstream of a vaporizer. A pair of twin-lobe rotors sealed in the meter casing trap a fixed volume of vapor each revolution; the rotation rate gives instantaneous flow and the totalizer gives cumulative volume. The Roots principle is independent of velocity profile, so the meter holds ±0.5 % of rate accuracy down to the low-flow tail of the range where a turbine meter loses signal. Outputs include pulse, 4-20 mA, RS-485 Modbus, HART, and 4G for unmanned vapor-return stations.

For liquid-phase LPG; storage-tank loading, road-tanker filling, cylinder bottling plant feed lines, and inter-storage transfer at pressurized liquid (8 bar propane, 2 bar butane at ambient); go to the LWGY LPG Turbine flow meter counterpart. The LWGY build covers DN15 to DN150 for liquid LPG (propane 0.18 cSt, butane 0.27 cSt) under storage pressure up to 25 MPa. This Roots build is binding to LPG vapor only (post-vaporizer, gas phase, low pressure). 2-phase service or wet vapor with droplet carryover exceeds the Roots range; route through a knockout drum first or order Coriolis.

Yes. The 3-wire pulse output is frequency-proportional to vapor flow with the calibrated K-factor on each meter's certificate. Gas-station pre-pay controllers (single-board PLC, Allen-Bradley MicroLogix, Siemens LOGO) read the pulses through the K-factor and convert to liters or kilograms on the dispenser display, with batch-end shutoff at the pre-paid limit. For unmanned stations, the 4G wireless option pushes meter readings plus a tamper-detect flag to a central billing endpoint, and the 3.6 V lithium battery option runs the meter and 4G modem for a multi-year service interval.

LPG vapor distribution after a vaporizer typically runs at 0.6 to 1.0 MPa with flow demand sized to the dispenser fleet or vaporizer bank. G16 (1 to 25 m³/h, DN25) and G25 (1 to 40 m³/h, DN40) cover small forecourt vapor return at independent service stations. G40 to G100 (2 to 160 m³/h, DN50 to DN80) cover commercial vaporizer outlets feeding apartment clusters and industrial estates. G160 and G250 (3 to 400 m³/h, DN80 to DN100) cover LPG depot vapor recovery from storage tanks and loading-arm vapor lines. DN125 and DN150 are supported by quote for high-throughput depot service.

Each meter ships with an ISO 9001 calibration certificate listing the G-class, calibrated DN, K-factor, and tested flow range; the calibration is performed on a bell-prover or sonic-nozzle gas rig at the factory before shipment. Custody-transfer type approval to the local gas-meter metrology regime is buyer-arranged with a notified body; the factory provides build documentation and traceable calibration records to support the buyer's type-test submission. For witness calibration at a third-party metrology institute (NMi, PTB, NIM equivalent), the buyer can specify the witness arrangement at order entry.

Standard lead time is 5 to 7 business days from order confirmation, factory direct. Hazardous-area certification is Ex ia IIC T6 Ga (intrinsically safe); mandatory for LPG vapor service because any leak path produces ignitable atmosphere at ambient. Gas group IIC and surface-temperature class T6 cover propane and butane ignition characteristics for Zone 0, 1, and 2 classified areas typical of gas-station forecourts and LPG depot terminals. IP65 ingress ships standard. EMC compliance to the EU Electromagnetic Compatibility Directive 2014/30/EU (Annex II) ships standard. The 3.6 V lithium battery option arrives pre-fitted for AMR billing.