The ultrasonic flow meter for operation in hazardous areas with intrinsically safe process inputs

The FLUXUS F831 is FLEXIM's dual channel ultrasonic clamp-on flow meter for bi-directional flow measurement of liquids in hazardous areas (ATEX, IECEx Zone 1 and FM Class I, Div. 1 approved).

With its explosion proof housing, intrinsically safe inputs and the corrosion resistant transducers residing outside the pipe wall, but inside the rugged VARIOFIX C mounting fixture, ensuring a permanent contact pressure and high mechanical stability, the FLUXUS F831 series is perfectly suited for every demanding industrial application in and out of the oil field and the chemical industry. The connection and electronics compartments of the FLUXUS F831 are hermetically sealed, so that the measurement system provides maximum operational reliability and safety.

With faster processing capabilities, the meter offers significantly improved accuracy and response time between measurement channels which results in better representation of flow profile and high accuracy. In addition, the FLUXUS F/G831 comes with carefully matched and temperature compensated transducers (fully ANSI / ASME MFC 5M compliant) providing unmatched zero-point stability and precise bi-directional flow measurement over a wide range of conditions.

The FLUXUS F831 bi-directional flow meter can be applied on inner pipe diameters ranging from 10 mm to 6500 mm (no limitations on pipe wall thickness or material) and media temperatures from -190°C up to +630°C (by use of the high temperature mounting fixture WaveInjector).

With up to two measurement channels, the FLUXUS F831 explosion-proof flow meter is also ideal for difficult measurement points with non-ideal flow profiles. Even liquid streams with high solids content or gas bubbles are not a problem due to the innovative HybridTrek mode and the unique signal processing implemented into the flow computer.


  • Bi-directional flow measurement of liquids and gases in FM Class I, Div. 1 and ATEX / IECEx Zone 1 areas
  • Very cost effective: No pipe work, No process shut-down, Virtually maintenance-free
  • Matched, paired and wet calibrated flow transducers (traceable certification to national standards)
  • Excellent zero-point stability and drift-free
  • Wide turndown ratio
  • Independent of pipe size, material, operating pressure, medium and temperature (from as low as -170 °C up to +630 °C)
  • High tolerance to entrained solids and gases
  • Free of wear and tear and abrasion
  • Not prone to clogging or corrosion
  • No pressure loss or risk of potential leaks and fugitive emissions
  • AMV Logo


Industry Applications

Technical Facts

Measurement uncertainty of the measuring system (volumetric flow rate)
±0,3 % of reading ±0.005 m/s
Measurement uncertainty at the measuring point (volumetric flow rate)
±1,0 % of reading ±0.005 m/s
0.15 % of reading ±0.005 m/s
Flow velocity range
0.01...25 m/s
Ex zone transmitter
FM Class I/Div. 1, FM Class 1/Div. 2, ATEX/IECEx Zone 1
Power supply
100-230VAC, 24DC
Available transducers
Shear Wave
for Ex zones
FM Class I/Div. 1, FM Class 1/Div. 2, ATEX/IECEx Zone 1
for pipe sizes range
10mm ... 6500mm
for temperature range
-40°C ... +240°C / WI: -200°C ... +630°C
4-20mA active/passive
4-20mA HART active/passive
4-20mA passive (Ex ia)
Temperature (Ex-ia)
4..20mA (Ex-ia activ)
Digital communication
Foundation Fieldbus-Ex-ia
Profibus PA-Ex-ia
4..20mA HART (Ex-ia passiv)
Advanced Meter Verification (AMV)
Additional Information
For more detailed Information please download the Technical Specifications