MT91 Mass Flow Meter

Mass Flow Meter Summary

The MT91 is an insertion type multipoint, averaging thermal mass flow meter. It is designed for aplications inlarge pipe and duct applications such as stacks, flues, power plant air feeds and HVAC systems. The MT91 is QAL 1 certified by TUV for installation in European emissions monitoring and reporting applications. There are no moving parts flow element design to foul, and unlike multi-point DP flow meters, with MT91 there are no ports or orifices to clog, which results less maintenance and un-schedule service needs to save significantly on installed opearting cost. 


  • Stack monitoring for CEMS and QAL 1 compliance
  • Primary air flow monitoring
  • Combustion air flow monitoring
  • Flue gas recirculation monitoring
  • Scrubber and precipitator balancing
  • Air monitoring to low NOX burners


Flow Range: 0.25 SFPS to 150 SFPS [0,08 NMPS to 46 NMPS] in air at standard conditions of 70°F [21,1°C] and 14.7 psia [1,01325 bar (a)].

Flow Accuracy: (at calibrated conditions)
  • ± 2% of reading or ± 0.2 SFPS [± 0.06 NMPS]

Temperature Coefficient:
  • With optional temperature compensation; valid from 10% to 100% of full-scale calibration
  • Flow: Maximum ± 0.015% of reading/ºF up to 850ºF [±0.03% of reading/ºC up to 454ºC]

Flow Repeatability: ± 0.5% reading

Temperature Accuracy:
  • From 32°F to 212°F [0°C to 100°C]: ± 0.9°F [± 0.5°C]
  • < 32°F and > 212°F [< 0°C and > 100°C]: ± 1.8°F [± 1°C]

Temperature Repeatability:
  • From 32°F to 212°F [0°C to 100°C]: ± 0.2 % reading
  • < 32° and > 212° F [< 0° and > 100° C]: ± 0.5% reading

Turndown Ratio: From 5:1 to 100:1 within the calibrated flow range

Temperature Compensation: 
  • Standard: ± 30°F [± -1°C]
  • Optional: ± 100°F [± 38°C]

Enclosure: (Available in remote configuration only)
  • Standard: Powder coated aluminum enclosure is rated for NEMA/CSA Type 4 (equivalent to IP66); an optional explosion-proof enclosure is available
  • Optional: 19 inch rack in accordance with DIN 41494 Part 1, ANSI/EIA-RS-310C.

Agency Approvals: Contact FCI

N.I.S.T. Certified Test Lab Calibration: Standard

Flow Element

Materials of Construction: 
  • Standard: 316 stainless steel with nickel braze per specification AMS 4777 for all wetted surfaces
  • Optional: Hastelloy-C with corrosion-resistant alloy braze

Number of Flow Sensing Points per System: Up to 16 points total

Process Connection: 
  • Standard: 2" MNPT or 3" 150 lb. raised face carbon steel flange
  • Optional: Other flange sizes and material types

Insertion Length: Variable insertion lengths, customer specified

Operating Temperature:
  • Standard: -50°F to 350°F [-45°C to 177°C]
  • Optional: -50°F to 850°F [-45°C to 454°C]

Operating Pressure: To 50 psig [3.4 bar(g)]; design pressure to 500 psig [34 bar(g)]

Optional Coatings: Electroless nickel, chromium carbide, Hastelloy-C

Flow Transmitter

Operating Temperature: 
  • With LCD Display Activate: 32°F to 140°F [0°C to 60°C]
  • With LCD Display Inactive: 0°F to 140°F [-18°C to 60°C]

Input Power: 100 Vac to 240 Vac (47 Hz to 63 Hz), 3.5 amp fused; 24 Vdc (18 Vdc to 36 Vdc).

Relay Outputs: 2 DPDT alarm relays rated at 2 amps and field progammable for flow, temperature or sensing point failure.

Digital Communication Port: RS-232C, RS-422 or RS-485 field selectable and programmable

Display: 4 lines, 20 characters per line LCD display

Keypad: 20 keys for input provide easy touch programming to change zero, span, switch points, and units of measurement for instrument verification, troubleshooting and other critical instrument functions

Interconnecting Cable: 10' [7,6 m] PVC cable (standard), custom lengths are available

Optional Remote Enclosure: Powder coated aluminum enclosure is rated for NEMA/CSA Type 4 (equivalent to IP66); an optional 19 inch DIN rack is available.