Sierra Instruments, Inc.

- Model 780i - Inline Thermal Mass Flow Meter



The QuadraTherm 780i is the most accurate inline thermal mass flow meter for air / gas mass flow rate measurement on the market today, achieving gas mass flow rate accuracy never before possible, +/- 0.5% of reading above 50% of full scale. The QuadraTherm rivals accuracies of Coriolis technology for measuring gas mass flow rate with a breakthrough thermal dispersion technology achieving “percent of reading” accuracy.

Change Gas Mixtures in the Field-No Recalibration Needed 

QuadraTherm thermal flow meter equipment comes with on board qMix(tm) gas mixing software that allows you to create custom gas mixtures in the field to compensate for gas compositional changes—no costly recalibration needed. Perfect for managing changes in flare gas composition in the field for upstream oil & gas flare gas measuring applications and other applications in which gas composition frequently changes.

Boiler MACT Certified

QuadraTherm air flow measurement devices are also ideal for compliance for Boiler MACT regulations for inlet fuel measurements for area source boilers (40 CFR 63, subpart JJJJJJ) and for major source boilers (40 CFR 63, subpart DDDDD). Learn More.

QuadraTherm introduces a patented four-sensor thermal mass air flow meter design—three precision platinum temperature sensors and one patented DrySense mass velocity sensor backed by a lifetime warranty. This precision flow meter for air and gas measurement is available in the 640i air/gasflow meter insertion version and this 780i inline version.

Four sensor technology provides the critical inputs for Sierra’s proprietary Raptor OS™ that manages changes in gas and pipe selection, gas temperature, gas pressure and outside temperature for precision air flow velocity measurement.

  • Patented DrySense sensor backed by lifetime sensor warranty
  • In-Situ calibration for in the field validation
  • Built-in flow conditioning to reduce straight run requirements
  • qMix gas mixing software to change gases in the field-no recalibration required

Operating Principle: Thermal dispersion technology provides direct mass flow measurement featuring: no pressure or temperature compensation needed; no moving parts; low-pressure drop; and high turndown.

  • Achieve the highest accuracy +/- 0.5% of reading
  • Eliminate drift with DrySense sensor
  • Reduce straight-run requirements with built-in flow conditioning
  • Needs only 1-diameter up and zero downstream diameters
  • Validate in the field for easy in-situ calibration
  • Backed by lifetime sensor warranty
  • Boiler MACT certified for area source boilers (40 CFR 63, subpart JJJJJJ) and for major source boilers (40 CFR 63, subpart DDDDD)
  • Part of Sierra's Big-3 iSeries family of flow meter technologies

  • Patented breakthrough QuadraTherm 'Quad' 4-Sensor thermal sensor technology
  • Patented zero drift DrySense™ velocity sensor
  • Lifetime warranty on sensor
  • 'Percent of reading' accuracy, which for the first time rivals accuracies of Coriolis technology
  • Sierra's state-of-the-art ISO 9000 closed-loop calibration facility matches each application for best accuracy
  • Greenhouse Gas (GHG) certified to meet EPA (40 CFR Part 98)
  • Ideal for high accuracy applications like custody transfer, wastewater treatment, hazardous areas, facilities management and general process control applications
  • Built-in flow conditioning elements drastically reduce upstream straight-run requirements
  • Features our proprietary Raptor OS operating system (formerly known as qTherm)
  • ValidCal™ Diagnostics: Field calibration validation and meter diagnostics to assure operating performance.
  • Multivariable outputs - gas mass flow rate, temperature and pressure
  • Total of four gases onboard; capability to change gas (Dial-A-Gas) in the field; Download Flare Gas Mass Measuring Tech Note
  • Capability to change pipe size (Dial-A-Pipe®) in the field
  • Unique multi-gas flow totalizer and alarms
  • High flows up to 60,000 scfm (305 smps)
  • Range of process connections
  • Very low pressure drop
  • No moving parts
  • Free computer interface software
  • Free Raptor software to create custom gases or mixtures to compensate for compositional changes; upload mixtures to the unit in the field  
  • Connected to the most up-to-date gases in our proprietary Raptor Gas Library, update the instrument via the web
  • An insertion version for pipes/ducts up to 72 inches (2 m) available - Model 640i
  • Large LCD display and pushbutton interface, remote enclosure mounting available
  • Multi-language display interface: English, German, Chinese, Spanish, Dutch
  • Certified for Boiler MACT measurement meeting EPA regulations for area source boilers (40 CFR 63, subpart JJJJJJ) and for major source boilers (40 CFR 63, subpart DDDDD)

  • Accuracy: +/- 0.5% of reading above 50% of full scale*
  • Repeatability of +/- 0.15% of full scale
  • Pipe sizes from 1.0' to 8.0'  (1.3cm to 20.3cm)
  • Flow range 0 to 60,000 sfpm (305 smps)
  • Turndown: 1000:1 
  • Measure all inert gases and all non-condensing clean gases
  • Flammable gases: methane, propane, hydrogen, digester gas, natural gas
  • Corrosive gases compatible with 316L stainless steel
  • 100:1 turndown
  • Gas/ambient temperature -40°F (-40°C) to 392°F (200°C) *Verified by an independent NIST & NVLAP accredited lab

  • Response time is three seconds to achieve 63% (one time constant) of final value
  • Power supply 100 to 240 VAC (0.4 Amps RMS at 230 VAC); 24 VDC +/- 10%, 1 Amp
  • 316 stainless steel construction
  • Output Signals: RS-232, 4-20 mA flow, 4-20 mA temperature, 4-20 mA pressure (optional)
  • Alarm output (contact SPST/opto relays)
  • User definable pulse output for totalized flow
  • Digital communications: Foundation Fieldbus, HART, Modbus RTU, and Profibus DP
  • Hazardous-Area Location Enclosure (IP66)
  • Approvals:
    • cFMus–Explosion proof for Class I, Div I, Groups B,C,D
    • CE–European Conformity
    • ATEX/IECEx

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