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The Clamp-on Ultrasonic meter for Standard Volume Flow Measurement and API Determination in the Hydrocarbon Processing Industry

FLUXUS H721 is FLEXIM’s flow and analytical measuring system for the hydrocarbon processing industry (HPI). This sophisticated and highly accurate non-intrusive flow meter combines very precise ultrasonic flow and sound speed measurement with advanced calculation features and diagnostics. The H721’s nonintrusive flow meter built-in HPI computer calculates API gravity, operational density, density at base conditions and kinematic viscosity. Volumetric flow rates reported by the meter are automatically compensated for temperature and pressure within the meter according to industry standards ASTM1250, GPA TP25 and D4311 thus allowing for precise and dynamic standard volume flow measurement of liquid hydrocarbons.

In addition to these advanced and sophisticated measurement capabilities, the FLUXUS H721 flow meter is equipped with a hydrocarbon-specific database for a wide range of applications and process conditions ranging from light hydrocarbons to crude oils/refined products to heavy hydrocarbons at refineries, tank farms, oil terminals and transport liquid pipelines. Since Oil and Gas processes and operations vary from location to location, application-specific parameterization is also easily possible via a user-friendly editable table residing in the transmitter and allowing customization of liquid names and physical properties (density, API).

Typical applications for the FLUXUS H721 are leak detection and product identification in tank farms and oil terminals, quality check measurements and verification or temporary replacement of stationary measuring devices.


  • Accurate & Reliable - Cutting-edge ultrasonic non-intrusive flow measurement
  • Advanced Flow and Analytics - Automatic Fluid Identification and Interface Detection
  • Standard Volume Flow Compensation – Pressure & Temperature Inputs
  • Superior temperature stability - Zero drift.  Temperature compensated transducers
  • Robust - “Fit for Purpose” durable mounting fixtures and ATEX/IECEx Zone 2, FM Class I /Div 2 transducers
  • High turndown range - capability of measuring at very low flow rates
  • Bi-directional flow metering


Industry Applications

Technical Facts

Measuring quantities
flow: operating volumetric flow rate, standard volumetric flow rate according to ASTM 1250/TP25/4311, flow velocity, mass flow rate

HPI: API gravity, density, normalised density

interface detection: slope of the HPI physical quantities

fluid detection: according to fluid table
Measurement uncertainty at the measuring point (volumetric flow rate)
±1,0 % of reading ±0.005 m/s
Measurement uncertainty of the measuring system (volumetric flow rate)
±0,3 % of reading ±0.005 m/s
Transit time (HPI functions)
repeatable: 1/(50 • fα) ±10-4 • t
absolute: 1/(5 • fα) ±10-4 • t

fα – transducer frequency
t – total transit time e.g. for transducers with transducer frequency M (fα = 1 MHz):

repeatable: 20 ns ±10-4 . t
absolute: 200 ns ±10-4 . t
Explosion protection
Transmitter: ATEX/IECEx zone 2
Transducers: ATEX/IECEx Zone 2, FM Class I /Div 2
Power supply
100 ... 230 V AC / 50 ... 60 Hz
12 / 24 V DC
4 - 20 mA active
4- 20 mA HART active / passive
pulse / frequency / binary
Pt100 / Pt1000
4 - 20 mA active / passive
Digital communication
Modbus RTU/TCP
Profibus PA
Foundation Fieldbus
Pipe diameter range
6 mm ... 6500 mm
Temperature Range (pipe wall)
-40 °C ... +240 °C
Additional Information
For more detailed Information please download the Technical Specifications