Nitrogen Thermal Mass Flow Meter
N₂ Purge & Inerting Build
Accuracy of ±1.0% of rate
Temperature service −40 to +120 °C
Turndown ratio of 1:1200
- Line sizes DN10 to DN300
- Working pressure ≤ 1.6 MPa standard, up to 6.3 MPa on request
- Sensor wetted parts 316L stainless or Hastelloy C
The Nitrogen Thermal Mass Flow Meter measures industrial N₂ on inerting headers, blanket-gas feeds, purge service, and bulk LN₂ vaporizer outlets; DN10 to DN300, direct from heater power.
Outputs Nm³/h or kg/h on 4-20 mA; no external T+P. 0.2 Nm/s low-flow detection catches off-shift purge drift that vortex misses. CNEX Ex d IIC T6 Gb on every config. Lead time 5–7 business days.
Cost structure
One audit standard meter replaces the rotameter + cylinder-count stack
Most plants measure nitrogen with a rotameter on each branch and reconcile monthly against bulk-tank deliveries; a workflow that misses leaks and quietly over-consumes N₂ by 15-25 % on the typical site. The TMF-N2 replaces this with a single meter per branch that produces a validated flow record. Below is a typical DN50 process-inert service priced out at factory-direct level over a 3-year horizon, not including installation labor.
Rotameter + Cylinder-Count Workflow
Visual flow only, no audit record, invisible below rotameter dead-zone; the status-quo approach at most Chinese plants.
- VA rotameter (DN50, ±5 %) $280
- Annual rotameter calibration (×3 yrs) $540
- Unseen purge drift: 18 % N₂ overconsumption × $2,400/yr × 3 yrs $1,296
- Untracked leak loss + bulk-tank over-delivery $800+
- Monthly manual reconciliation labor (2 h × $30 × 36 mo) $2,160
- No leak-attribution capability; guesswork n/a
3-year cost of ownership$5,076
TMF-N2 Single Instrument
Reads mass flow directly from heater power. Audit standard record, 0.2 Nm/s low-flow detection, cylinder-reconciliation totalizer.
- TMF-N2 DN50, ±1.0 %, 4-20 mA HART $1,820
- SS316L + Tri-clamp sanitary-style upgrade $420
- Material cert traceability package $320
- Integrated totalizer for bulk-tank reconciliation included
- Single calibration certificate, ISO 9001 traceability included
- Continuous audit standard flow log (128 MB, 7 yr) included
3-year cost; saves $2,516/point$2,560
Benefits
- Direct mass flow: thermal-dispersion outputs Nm³/h on 4-20 mA; replaces vortex + T + P + flow-computer stack.
- ±1.0 % of rate: standard build with ±0.5 % repeatability; sufficient for blanketing, ASU sub-measurement, tube-trailer fill verification.
- 0.2 Nm/s low-flow detection: resolves overnight blanket-gas idle and small leak drift that vortex (3–4 m/s minimum) reads as zero.
- 1:1200 velocity turndown: one model spans low-load standby through ASU peak; no parallel-meter bypass piping.
- Hastelloy C option: 316L for clean industrial N₂; Hastelloy C for chloride or moisture carry-over from upstream packing or membrane skids.
- 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.
Quick specifications.
| Measurement Principle | Thermal dispersion (constant-temperature-difference / CTD mode); two RTDs, direct mass flow from heater power |
|---|---|
| Execution Standard | GB/T 32201-2015; Gas Flow Meters (Chinese national) |
| Line Sizes | DN10 – DN250 (3/8″ – 10″) inline full-bore |
| Direct Mass Output | Yes; Nm³/h or kg/h on 4-20 mA + Modbus · zero external T+P compensation |
| Accuracy | ±1.0 % of rate grade A standard · ±1.5 % of rate grade B economy · ±0.5 % repeatability |
| Velocity Range | 0.2 to 120 Nm/s; 1:600 practical on low-flow config, 1:1200 across the product line |
| Low-flow detection | 0.2 Nm/s; five times below typical rotameter dead-zone |
| Response Time | 1 second |
| Pressure Loss | Negligible above DN80 (sensor in pipe wall, no bluff body, no orifice) |
| Pressure | 0.1 – 1.6 MPa standard · 2.5 MPa / 4.0 MPa / ANSI 300–600 LB on request |
| Medium Temperature | -40 to +120 °C (covers vaporizer outlet, reactor headspace, dryroom ambient) |
| Reference Conditions | Selectable: IUPAC STP (0 °C) · GB/T 3102.8 (20 °C) · ISO 13443 (15 °C) · NIST (25 °C) |
| Sanitary-style option | SS316L wetted parts with ISO 2852 Tri-clamp connections; geometry suitable for installations that include CIP / SIP cleaning loops. Mill cert traceable to heat number ships with the meter |
Configure your build.
Specify your N₂ service, line size, and material. Submit to engineering for verified sizing against your vaporizer / PSA output, branch demand profile, and lead-time requirement within 4 business hours.
Model codeTMF-50-S-EX-4-6-2-Q
DN sizeDN50
FormIntegral
Accuracy±1.0 % of rate
ConnectionFlanged PN16 / ANSI 150
MaterialSS316L stainless
Output4-20 mA + HART
HazardousStandard
Quantity1
Estimated unit price
Verified after engineer review
$1,820
Subtotal$1,820
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Typical applications
Four service zones where N₂ thermal-mass measurement replaces the rotameter + cylinder-count stack.
Inerting & blanket-gas feeds
Plant N₂ inerting on tanks, transfer skids, reactor headspace. 0.2 Nm/s catches off-shift purge drift.
Sanitary-style purge
SS316L wetted parts, ISO 2852 Tri-clamp DN15–DN80. Mill cert traceable to heat number ships with the meter.
Semiconductor N₂ curtain
Wafer-fab load-lock purge, vacuum-chamber vent. Butt-weld SS316L; totalizer reconciles to LN₂ invoices within 1–2 %/month.
Bulk LN₂ Vaporizer Outlet
Vapor-phase distribution at vaporizer outlet; direct mass flow, no external T+P stack.
Specifications
Performance
| Accuracy | ±1.0 % of rate grade A · ±1.5 % of rate grade B · ±0.5 % repeatability |
|---|---|
| Velocity range | 0.2 to 120 Nm/s (1:600 practical, 1:1200 across product line) |
| Low-flow detection | 0.2 Nm/s; five times below typical rotameter dead-zone |
| Temperature measurement | Pt1000 reference RTD, integrated · ±0.3 °C |
| Response time | 1 second |
| Pressure loss | Negligible > DN80 (< 1 kPa at rated flow) · wall-mounted probe, no bluff body |
| Power supply | 24 V DC or 220 V AC · ≤ 18 W maximum |
Process & Environment
| Medium | Gaseous nitrogen 99.9 % industrial ·, N₂/CO₂) on request |
|---|---|
| Pressure range | 0.1 – 1.6 MPa standard · 2.5 / 4.0 MPa / ANSI 300–600 LB on request |
| Medium temperature | -40 to +120 °C |
| Ambient temperature | -35 to +65 °C · 5 % to 90 % RH · 86 to 106 kPa atmospheric |
| Enclosure rating | IP66 standard · Ex d flameproof flameproof option (transit zone only) |
| Signal distance | Sensor to remote display: up to 1000 m |
Sanitary-style connection option
| Wetted surface | SS316L; smooth bore; no bluff body, no orifice edge |
|---|---|
| Connection | ISO 2852 Tri-clamp · DN15 to DN80 range |
| Process compatibility | Geometry suitable for installations with CIP / SIP cleaning cycles in the loop |
| Material traceability | SS316L mill cert traceable to heat number ships with the meter |
| Documentation | ISO 9001 K-factor calibration certificate. Pharma / food / dairy / battery cert packages are NOT shipped from this factory; buyer sources those separately if a regulated facility needs them |
| Pre-shipment | Cleaned and bagged for transit |
Materials & Construction
| Sensor wetted parts | SS316L standard · Hastelloy C-276 optional |
|---|---|
| Body material | SS304 standard · SS316L · SS316L for sanitary-style option |
| Sensor pair | Two Pt-class RTDs: one temperature reference, one heated at fixed ΔT |
| Electrical entry | M20 × 1.5 internal thread or ½″ NPT |
| Housing | Aluminium alloy IP66 · stainless option · Ex d flameproof flameproof for transit zones |
| Net weight (DN50) | 6.4 kg integral, PN16 flange · 4.2 kg Tri-clamp · 2.8 kg DN25 threaded |
Flow range by pipe size.
Nitrogen flow range in Nm³/h referenced to GB/T 3102.8 industrial conditions (20 °C, 101.325 kPa). N₂ at the reference condition has density 1.165 kg/Nm³; multiply the Nm³/h column by 1.165 to read kg/h. Column “kg/h typical” uses the typical-range midpoint. Pharma / battery dryroom purge lines typically operate in the lower half of the range; semiconductor N₂ curtains and large inerting loads in the upper half. Engineering validates your sizing against the vaporizer / PSA output and branch demand profile.
| Pipe size | Minimum (Nm³/h) | Typical range (Nm³/h) | Maximum (Nm³/h) | kg/h typical |
|---|---|---|---|---|
| DN10 (3/8″) | 0.2 | 3 – 22 | 40 | 3.5 – 26 |
| DN15 (½″) | 0.4 | 5 – 40 | 65 | 5.8 – 46 |
| DN25 (1″) | 1 | 15 – 120 | 175 | 17 – 140 |
| DN40 (1½″) | 2 | 40 – 320 | 450 | 47 – 373 |
| DN50 (2″) | 3 | 60 – 420 | 600 | 70 – 489 |
| DN80 (3″) | 6 | 150 – 1,050 | 1,500 | 175 – 1,223 |
| DN100 (4″) | 10 | 230 – 1,610 | 2,300 | 268 – 1,876 |
| DN150 (6″) | 22 | 520 – 3,640 | 5,200 | 606 – 4,240 |
| DN200 (8″) | 40 | 900 – 6,300 | 9,000 | 1,049 – 7,340 |
| DN250 (10″) | 62 | 1,450 – 10,150 | 14,500 | 1,689 – 11,825 |
Installation
Five steps to a clean N₂ install.
- Downstream of vaporizer or PSA outlet, before branch manifold; 5 m past the LN₂ vaporizer so N₂ is at stable +10 °C or higher.
- 10×DN upstream, 5×DN downstream; low-flow N₂ is more sensitive to asymmetric profiles than high-flow air (sensor closer to noise floor).
- Tri-clamp or butt-weld on CIP/SIP loops; Tri-clamp (ISO 2852) for fermenter blanket, formulation feed, dairy transfer; butt-weld for semiconductor high-purity.
- Pick reference condition to match procurement; “Nm³” is ambiguous; different buyers use different reference conditions.
- Do not retrofit sanitary-style after shipment; surface finish is factory-only; field re-polishing voids calibration and material traceability.
Frequently asked questions
Why specify a thermal mass meter for nitrogen when a rotameter is much cheaper?+
A rotameter reads ±5 % at best and cannot see flow below 10-15 % of span; weekend purge drift, overnight blanket bleed, and valve leakage sit under its detection floor. A DN50 header losing 2 Nm³/h to a leak is ¥1,400-2,800/month per branch. TMF-N2 delivers ±1.0 % mass flow on 4-20 mA, a continuous audit log, and 0.2 Nm/s low-flow detection. For display-only uses (weld-shield shroud, seal-pot purge) a rotameter is still the right answer.
What does 0.2 Nm/s low-flow detection actually buy me on a nitrogen system?+
It exposes the slow leaks and drift that kill your N₂ budget without showing up as a process fault. On a DN50 line, 0.2 Nm/s velocity is about 1.4 Nm³/h flow; small, but 1.4 Nm³/h × 24 × 30 = 1,008 Nm³/month of wasted nitrogen per branch, at ¥5/Nm³ bulk LN₂ that’s ¥5,000/month per branch of money leaving the plant with zero product to show for it. A rotameter sized for the branch’s normal 20-40 Nm³/h working range has a dead zone roughly below 4-6 Nm³/h; 1.4 Nm³/h is invisible. A vortex meter‘s 1:10 turndown would need the line to run 35-50 Nm³/h minimum to register, so anything quieter is also invisible. TMF-N2 reads 0.2 Nm/s as approximately 2 % of scale on a 100 Nm/s rated meter; solidly above the noise floor and a valid, auditable reading. For battery dryroom operators running 24/7 low-rate purge to maintain -60 °C dew point, this is the single most valuable feature: you finally see the night-shift drift and can size the PSA correctly instead of over-provisioning.
Why is there no Ex rating standard for TMF-N2 when the natural-gas version ships Ex d flameproof?+
Because nitrogen is inert and non-flammable; there is no ignitable atmosphere to protect against inside a pure-N₂ header. Most N₂ installations (pharma reactor blanket, battery dryroom, food packaging, semiconductor curtain) sit in general-purpose areas. Where the meter does sit in a hazardous-area zone, the hazard is the surrounding process side (solvent vapor, battery electrolyte fumes), not the N₂. For those cases; where the meter physically sits inside a Zone 1 or Zone 2 area even though nitrogen itself is not the hazard; specify the Ex d flameproof option at order; it is the same housing used on the natural-gas model. Asphyxiation risk is the real N₂ hazard and is an engineering / SCBA issue, not a flameproof-meter issue; the meter’s role there is to detect and log abnormal flow (a broken seal releasing N₂ into a confined space shows up as a flow spike). Both IP66 and Ex d flameproof versions ship in 5–7 business days.
Can TMF-N2 measure the total N₂ drawn from a bulk LN₂ tank for inventory reconciliation?+
Yes; this is one of the most common TMF-N2 applications. Install a single meter at the vaporizer outlet and the cumulative Nm³ reading reconciles directly to the bulk-tank truck-delivery manifests. Typical accuracy is within 1-2 % of the tank-level-gauge reading across a month, audit-quality for procurement reconciliation. Convert Nm³ to kg with 1.165 kg/Nm³ at standard reference, or output kg/h directly. Pair the totalizer with a 4G GPRS output for cloud-based reconciliation against delivery records.
Need help sizing the nitrogen build?
Send pipe size, source, service, typical purge/blanket range. Engineer replies with sized Nm³/h, model code, price in 4 business hours.