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The World‘s Only Clamp-On Steam Meter: FLUXUS ST

FLEXIM has been setting standards for 30 years, and with the FLUXUS ST steam meter series, boundaries for non-invasive measuring technology have been pushed again.

Non-invasive and efficient

FLUXUS ST measures steam flow non-invasively from the outside of the pipe. Non-invasive steam flow measurement means measuring without any interruption of operation and supply. Since clamp-on ultrasonic transducers are simply mounted on the outside of the pipe, it requires just minimal installation effort and no opening of the pipeline.

The acoustic measuring method proves to be impressive with its exceptionally high measuring dynamics, is highly sensitive even at very low flow velocities and functions independently of the flow direction. Due to this large flow range (flow velocities from 0.03 ft/s up to 200 ft/s), there is no need to reduce pipe diameter to fit an inline meter’s requirement of minimum flow velocity. Moreover, the non-invasive measurement does not cause any pressure loss. The transducer mountings can be completely insulated to reduce any heat loss to the environment.

With FLUXUS ST, for the first time ever, it is possible to capture all steam usage from very low to very high flow rates with one meter size.

Completely maintenance-free

Non-invasive steam flow measurement also means measuring without direct contact with the medium flowing in the pipe. FLUXUS ST has no moving parts. Therefore, FLUXUS ST is not subjected to wear and tear and does not require any maintenance.

FLUXUS ST measures volume and mass flow of saturated and super­heated steam at temperatures up to 356 °F. The clamp-on ultrasound system is available as both a stationary and a portable meter.

Fixed and versatile

FLUXUS G721 ST is a fixed installed flow meter for steam and offers a variety of digital communication interfaces such as Profibus, Modbus TCP and others.

100% process availability is guaranteed when using a FLEXIM solution – the installation of a FLUXUS G721 ST does not disturb the steam process itself at any time.


  • Reliable, non-invasive steam measurement
  • High dynamic flow range even at low flow velocities
  • no pipe diameter reduction – zero pressure loss
  • Integrated mass flow measurement
  • AMV Logo


Industry applications

Technical facts

Measurement uncertainty of the measuring system (volumetric flow rate)
±0,3 % of reading ±0.015 ft/s
Measurement uncertainty at the measuring point (volumetric flow rate)
±1..2 % of reading ±0.015 ft/s, depending on application
±0.15% of reading, ±0.015 ft/s
Flow channels
1 or 2
saturated steam, superheated steam
Process temperature
max. 356°F non Ex
max. 329°F ATEX Zone 2 / FM Class I Div. 2
max. 311°F ATEX Zone 1
Process pressure
min. 44 psig
Pipe diameter range
1,80 inch to 39,40 inch
Flow velocity range
0.03 ft/s…200 ft/s (depending on pipe size and transducer)
Explosion protection
Communication Protocol
Modbus RTU, Modbus TCP, Profibus PA, FF H1, BACnet MS/TP, BACnet TCP
Digital communication
USB Interface
Advanced Meter Verification
Additional Information
please have your specific application tested for feasibility