Landfill Gas Thermal Mass Flow Meter
Landfill Gas TMF Build
Accuracy of ±1.5% of rate
Temperature service −10 to +80 °C
Turndown ratio of 1:1200
- Line sizes DN25 to DN300
- Working pressure ≤ 1.6 MPa standard
- Sensor wetted parts Hastelloy C-276 (option for sour-gas service)
The Landfill Gas Thermal Mass Flow Meter measures raw landfill gas on flare-stack feeds, LFGTE collection headers, and RNG (Renewable Natural Gas) upgrade-skid outlets. Hastelloy C-276 wetted parts (optional) handle H₂S sour-gas service, with siloxane and wet-gas condensate tolerated by the no-window CTD sensor geometry.
Outputs Nm³/h directly with on-board CH₄ rolling correction. The 0.2 Nm/s low-flow detection catches idle-leak drift on standby flare heads. Lead time stays 5–7 business days.
Benefits
- Direct mass flow: thermal-dispersion outputs Nm³/h or kg/h; replaces ultrasonic + siloxane-cleaning + flow-computer stack.
- ±1.5 % of rate: standard build on variable LFG; tightens to ±1.0 % with 4–20 mA composition-analyzer input across 35–55 % CH₄.
- Hastelloy C-276 option: corrosion-resistant probe handles sour-gas LFG across the full landfill lifecycle; 316L pits early on aged-cell H₂S.
- 0.2 Nm/s low-flow detection: resolves wellfield trickle and small-flare idle that ultrasonic drops below 1–2 m/s; 12–18 % under-reporting on legacy installs.
- 1:1200 velocity turndown: one model covers the 30× swing from wellfield trough to LFGTE peak; no parallel-meter bypass piping.
- Hazardous-area: CNEX Ex d IIC T6 Gb (flameproof, Zone 1) standard; IP65/66/67 and EMC 2014/30/EU.
- Lead time: 5–7 business days from the factory.
Configure your build.
Select your specs; we’ll generate a TMF 12-position model code and ballpark price. Submit to engineering for verified sizing against your LFG wellfield / flare / LFGTE / RNG profile, cell age and CH₄ composition range, H₂S profile, and reporting regime within 4 business hours.
Your Configuration
TMF-200-U-A-EX-4-P-M4-2-1-Q-S
Pipe sizeDN200
TransmitterIntegral
Accuracy±1.5 % of rate
CH₄ composition45 % (mature cell)
ConnectionFlanged ANSI 150 LB
Wetted partsHastelloy C-276 · sour-gas LFG
Reference20 °C / 101.325 kPa (GB/T)
Output4-20 mA + HART
EnclosureCNEX Ex d (flameproof, Zone 1)
Estimated unit price
Verified after engineer review
Quote
Subtotal (× 1)Engineering quote
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✓ PTFE + Hastelloy material certificate + H₂S / siloxane tolerance report
✓ CNEX Ex d (flameproof, Zone 1) certificate + Zone 1 declaration
✓ Factory calibration certificate with each meter
✓ Reply within 4 business hours
✓ CNEX Ex d (flameproof, Zone 1) certificate + Zone 1 declaration
✓ Factory calibration certificate with each meter
✓ Reply within 4 business hours
Typical applications
Active LFG Wellfield
Vacuum-side wellfield trunks at −10 to −50 mbarg with composition input across 40–55 % CH₄. DN200 Hastelloy C-276 typical, Nm³/h to SCADA.
Flare Stack Destruction
Regulator-mandated CH₄ destruction reporting on enclosed and candlestick flares. Mass-of-methane output via 4-20 mA + HART or Modbus RTU.
LFGTE Engine Feed
Fuel-line metering upstream of LFGTE gas-engine and CHP skids. Dual-compartment Ex d handles engine vibration; 1-s response catches load swings.
RNG Upgrader Inlet
Raw-LFG inlet on RNG-upgrader skids at ±1.5 % with composition input. Switch to TMF-NG post-upgrader.
Specifications
Performance
| Accuracy | ±1.5 % of rate standard across 35–55 % CH₄ · ±1.0 % of rate with composition-analyzer input locked · ±0.5 % repeatability |
|---|---|
| Velocity range | 0.2 to 120 Nm/s (1:600 practical, 1:1200 across product line) · aged-cell trickle to active peak |
| Low-flow detection | 0.2 Nm/s; resolves aged-cell wellhead trickle, low-yield vacuum-tuned wells, night-time flare-stack minimums |
| Temperature measurement | Pt1000 reference RTD, integrated · ±0.3 °C |
| Response time | 1 second; fast enough to log CH₄ swings during flare valve modulation and engine load transients |
| Pressure loss | Negligible > DN80 (< 1 kPa at rated flow) · critical under vacuum-side wellfield collection where pressure drop directly reduces yield |
| Power supply | 24 V DC or 220 V AC · ≤ 18 W maximum · solar-panel option for remote wellhead service |
Process & Environment
| Medium | Raw landfill gas (LFG) · active wellfield collection · flare-stack destruction feed · LFGTE engine fuel · RNG upgrader inlet feed · post-blower main trunk |
|---|---|
| Composition range | 35–55 % CH₄ / 35–50 % CO₂ / 1–15 % N₂+O₂ air intrusion / sour-gas H₂S service via Hastelloy C-276 wetted parts / water-saturated · siloxanes (D4/D5/D6) acceptable · trace VOCs and mercury vapor tolerated by no-window CTD sensor |
| Pressure range | −50 mbarg to +0.25 MPa standard (vacuum-side wellfield to post-blower flare/engine line) · +1.6 MPa on request for RNG upgrader compressed-feed designs |
| Medium temperature | -10 to +80 °C (landfill ambient to post-blower discharge) · flare pilot-line service up to +120 °C with high-temp option |
| Ambient temperature | -20 to +65 °C · 5 % to 100 % RH (outdoor wellfield service) · 86 to 106 kPa atmospheric · solar-radiation shield recommended above +45 °C |
| Enclosure rating | CNEX Ex d (flameproof, Zone 1) standard (Zone 1) · NEC Class I Div 1 Group D for US landfills · dual-compartment with barrier seal for LFGTE engine rooms |
| Signal distance | Sensor to remote display: up to 1000 m · suited to wellhead-to-flare-panel, wellhead-to-SCADA cabin runs |
Hastelloy C-276 Wetted-Parts Package
| Standard probe (LFG default) | Hastelloy C-276 wetted parts (optional) for sour-gas LFG service. Specify the cell H₂S range at order so wetted material matches the service. |
|---|---|
| Bare Hastelloy option | Hastelloy C-276 without PTFE · 0–5,000 ppm H₂S continuous · for fresh-cell service or well-managed wellfields with scrubber preconditioning |
| Economy option | SS316L · ≤ 200 ppm H₂S only · suitable for desulfurized RNG upgrader outlet, post-polishing pipeline-grade biomethane downstream of the H₂S scrubber |
| Compatibility testing | Sour-gas qualification per the wetted-parts option · LFG composition compatibility verified against typical landfill GC reference data |
| Siloxane / mercury tolerance | No transducer face, no orifice edge; siloxane mist and mercury vapor cannot concentrate on a flow-disturbing surface; CTD heater is thermally stable across siloxane D4/D5/D6 range · quarterly probe inspection recommended |
| Water-vapor handling | thermal-dispersion physics insensitive to water-vapor fraction within ±1–2 % range · top-mount probe option rejects liquid slugs · knock-out pot + coalescing filter upstream mandatory on LFG · condensate drain bypass required |
Materials/NEC & Approvals
| Sensor wetted parts | Hastelloy C-276 standard for sour-gas LFG (optional) · 316L economy build for desulfurized RNG service only |
|---|---|
| Body material | SS304 standard · SS316L for coastal / leachate-rich service · aluminium-bronze for aggressive hydrogen-sulfide-saturated wellheads |
| Sensor pair | Two Pt-class RTDs: one temperature reference, one heated at fixed ΔT · PTFE overcoat shared between both for LFG build |
| Elastomers | FKM (Viton) standard · HNBR for H₂S-rich LFG service · Kalrez on request for VOC/mercury exposure |
| Housing | CNEX Ex d (flameproof, Zone 1) flameproof aluminium · Zone 1 · NEC Class I Div 1 Group D (US) · dual-compartment with barrier seal for LFGTE engine-room vibration |
| Approvals | CE · CNEX Ex d (flameproof, Zone 1) · EMC 2014/30/EU (Annex II) · ISO 9001 calibration certificate with each meter · GB/T 32201-2015 |
| Net weight (DN200) | 14.6 kg integral, PN16 flange · 17.2 kg dual-compartment · 9.8 kg DN100 threaded |
Flow range by pipe size.
Landfill-gas flow range in Nm³/h referenced to a typical 45 % CH₄ composition. Reference conditions are user-selectable on the local display or HART so the meter output matches the regulatory regime the operator reports under. The engineering team validates each sizing against the wellfield profile.
| Pipe size | Minimum (Nm³/h) | Typical range (Nm³/h) | Maximum (Nm³/h) | kg/h typical |
|---|---|---|---|---|
| DN50 (2″) | 3 | 55 – 380 | 550 | 73 – 502 |
| DN80 (3″) | 6 | 140 – 950 | 1,360 | 185 – 1,254 |
| DN100 (4″) | 10 | 210 – 1,460 | 2,100 | 277 – 1,927 |
| DN150 (6″) | 20 | 470 – 3,300 | 4,720 | 620 – 4,356 |
| DN200 (8″) | 36 | 820 – 5,720 | 8,180 | 1,082 – 7,550 |
| DN250 (10″) | 56 | 1,320 – 9,220 | 13,180 | 1,742 – 12,170 |
| DN300 (12″) | 80 | 1,900 – 13,280 | 18,980 | 2,508 – 17,530 |
| DN350 (14″) | 108 | 2,560 – 17,920 | 25,610 | 3,379 – 23,654 |
| DN400 (16″) | 140 | 3,340 – 23,400 | 33,440 | 4,409 – 30,888 |
| DN400 HV (16″) | 188 | 4,500 – 31,500 | 45,000 | 5,940 – 41,580 |
Installation
Five rules separate a 10-year LFG install from a probe lost in one aged-cell season.
- Match probe to cell-age H₂S log; Hastelloy C-276 standard for raw sour-gas LFG; 316L only for desulfurized RNG.
- Vacuum-side of the blower; vacuum-rated to −50 mbarg. Downstream of moisture separator; never upstream of blower drain.
- KO-pot + 5-micron coalescing filter upstream; raw LFG is water-saturated and siloxane-loaded. KO-pot ≥ 2 m upstream; inspect probe quarterly year one.
- Spec CH₄ nominal at order; locked curves 35/40/45/50/55 % at ±1.5 %. Analyzer input gives ±1.0 % as cell-age distribution shifts.
- Match CNEX to drawing; Ex d IIC T6 Gb covers Zone 1 wellheads, flare panels; dual-compartment near engines.
Frequently asked questions
How does the LFG TMF differ from the biogas TMF; can I use one model for both?
The LFG TMF and the biogas TMF share the same chassis but spec out differently on three points. (1) Wetted material: the LFG model specifies Hastelloy C-276 wetted parts standard for sour-gas LFG service; the biogas model runs bare Hastelloy on cleaner anaerobic-digester service. (2) CH₄ range: the LFG model calibrates 35-55 % to handle the full landfill lifecycle; the biogas model calibrates 50-65 % for AD service. (3) Pressure: the LFG model is vacuum-rated standard for active wellfield extraction; the biogas model is positive-pressure only. For an LFG-to-RNG plant, use the LFG TMF on the raw front end and the natural-gas TMF on the post-upgrader grid side.
How does CH₄ composition vary across the landfill lifecycle, and does that matter for accuracy?
LFG composition is structurally variable in a way natural gas and digester biogas are not, and handling that variability is the main reason to spec a thermal-mass meter with composition-input over a fixed-curve thermal meter. Fresh cells run higher CH₄, mature cells settle around 50/45, aged cells drift lower as air intrusion rises. The TMF holds ±1.5 % of rate across the 35-55 % CH₄ range on the stock firmware curve; for tighter accuracy, wire a CH₄ analyzer to the 4-20 mA composition input and the meter recomputes mass flow against the live CH₄ reading in real time. Multi-cell wellfields should always spec the analyzer input; manifold blending shifts trunk CH₄ hour-to-hour. Send us your wellfield analyzer history and we will recommend the right approach in the quote.
What about siloxane, VOC, and mercury vapor; will those foul the probe?
No without accuracy drift, which is the main advantage of thermal-mass measurement over ultrasonic on LFG. Siloxanes (D4/D5/D6) deposit as silica glaze on any heated optical surface; that is the standard ultrasonic-transducer failure mode on landfill gas. The CTD sensor is a pair of RTDs in the pipe wall: no transducer window, no optical path, no flow-restricting bluff body. Siloxane vapor passes without depositing on the sensing element. Inspect the probe visually every 12-12 months. Mercury vapor at trace level is unreactive with Hastelloy C-276. A KO-pot and coalescing filter upstream is mandatory and handles the heaviest mist before it reaches the probe.
Can the meter be installed on the vacuum side of the wellfield blower?
Yes; this is the standard service. Active extraction pulls the trunk to mild vacuum (typically −10 to −30 mbarg). The meter is vacuum-rated and handles the same hardware on positive-pressure service post-blower, so one meter covers both cases. The installation rule: place the meter downstream of the wellfield moisture separator and KO-pot on the vacuum manifold; never upstream where condensate slugs can hit the probe. Thermal-dispersion physics is agnostic to absolute pressure in this range. By comparison, TMF-BG is positive-pressure only.
Need help sizing the landfill-gas build?
Send pipe size, application, CH₄ range, H₂S range, working pressure. Engineer replies with sized Nm³/h, model code, wetted-parts recommendation, price in 4 hours.