Ultra Sonic Flow Measurement

General Information
Measurement system and application

The fully digitized intelligent Ultrasonic Flow Measurement System, is excellently suited for the precise measurement, display and transmission of flow rate, volume flow and integrated flow of liquids in pipes and open channels. The system comprises

• Ultra Sonic Sensors
• Transducer-electronics
• Intelligent processing units

in the latest microprocessor technology.

Additional modules for special functions open up an exceptionally wide field of application:

• Flow measurement in storage and run-of-river power stations
• Pipe rupture monitoring of penstocks
• Flow measurements in open channels
• Flow measurement in water distribution networks of public water supplies
• Inflow and outlet measurements for sewage treatment plants

Transit-Time Measurement Principle

The sensors work alternately as transmitter or receiver. A piezo-ceramic oscillator is excited with a transducer voltage surge. The resulting ultrasonic sound pulse is propagated through the medium to be measured and is received at the oposite side where it is transformed back into an electrical signal. The transducer-electronics calculates the flow rate from the travel time difference of the ultrasonic pulses which are transmitted alternately with and against the flow.

Advantages:

Microprocessor controlled digital technology

• Sophisticated processing units
• Short measurement time
• High accuracy
• No moving parts
• High electromagnetic compatibility
• No impairment of the pipe or channel cross-section and therefore no pressure or head loss
• Large nominal diameter range
• Independent of liquid conductividty
• Multi-path measurements possible including crossflow correction
• Extremely flexible arrangement of transducer electronics and processing unit
• Proven operating concept in the languages English, German, French, Italian or Spanish
• Various additional modules, eg, for pipe rupture monitoring

Multi Path measurement: Proven technology

Several tests were carried out at the IMHEF hydraulic laboratory of the Swiss Federal Institute Of Technology Lausanne. The test conduit had a diameter of 444,6mm. Flowrates from 80l/s to 930l/s have been produced, which corresponds to velocities from 0,5m/s to 6m/s. It can be shown that multiple path technology extremely shortens the straight-run requirements for ultrasonic transit-time flowmeters.

Single Path (1 Plane) Two Paths (2 Planes)

Two Paths Crossed (1 Plane) Four Paths Crossed (2 Planes)

Application

Single path measurement at the Atatuerk power plant, Turkey

The Atatürk rockfill dam with a height of 184 m was completed in 1993. The associated power plant with a total turbine capacitiy of 2400 MW and an annual average energy generation of 8.9 TWh/year is the largest hydroelectric powerplant in Turkey. Eight penstocks lead the water from the reservoir to the turbines. The length of the penstocks vary from 530 for the inner one close to the dam, to 650 m for the outer one close to the abutment. The diameters vary according to the position of the penstocks, so that the same net head is available for each turbine, ranging from 6.6 m for the two innermost penstock up to 7.25 m for the two outermost ones. The wall thickness of the steel pipes vary form 22 mm to 43 mm. At each penstock, two single-path flowmeters were installed (see illustration), one for measuring the flow near the intake (Q-upstream), the other for measuring the flow at the powerhouse entrance (Q-downstream). In this way, a very efficient penstock leak detection system was established. The pipe rupture monitoring system enables the immediate recognition of pipe rupture and the calculation of leak losses in pipelines. Expensive consequential damage to material, the environment and individuals can thus be avoided.

Accessories

Plastic field housing large for wall mounting and more accessories are available.

Technical Data of the Transducer-Electronics MFUMUN

Transducer Electronics

Flow rate 0 ... 0.7 to 0 ... 20 m/s (0 ... 2 to 0 ... 60 ft/s) Accuracy in pipe: single path ± 6 mm/s at v < 0.6 m/s ± 1% at v > 0.6 m/s Accuracy in pipe: Multi-path ± 3 mm/s at v < 0.6 m/s ± 0.5% at v > 0.5 m/s Accuracy in channel 1...5%, depending on measurement arrangement Resolution 0.8 mm/s Temperature dependence 0.01 mm/s per ºC

Pipe Measurement

The RISONIC pipe measurement is used in fully floated closed conduits with liquids which are permeable to sound.

The RISONIC sensors used for pipe measurement comprise a transducer insert, pressure insert and welding neck. Measurement takes place without restricting the pipe cross-section and therefore causes no pressure loss. The transducer insert can be removed under pressure. Complete measurement pipes are also available as an option.

The fully digitized transducer-electronics calculates the flow rate and communicates with the intelligent processing unit via the two-wire leads of the SENSORbus. In parallel, the transducer-electronics also provides the acquired flow as an analog signal.

The user friendly processing unit enables the application-specific parameterization of the entire measuring installation. The processing unit has:

• 2 analog outputs 0/4 ... 20 mA
• 2 pulse outputs
• 1 flow direction output
• 1 OK output
• 1 DUAL PORT RAM connection

The DUAL PORT RAM connection, together with an interface, enables communication with a process control system.

Technical Data of Ultra Sonic Pipe Measurement Sensors "RISONIC"

Ultrasonic sensors

Pipe diameter 150 mm up to 8000 mm (6” up to 320”) Pipe wall strength 4 ... 60 mm (0.15 ... 2.36”) Material (pressure insert and welding neck) corrosion-resistant steel 1.4301 (316) Maximum allowable pressure 150 bar (2250 psi) Protection class IP67 (NEMA - 4X) Operating temperature -30ºC ... +70ºC (-20ºF ... 158ºF) Humidity 100% relative humidity Max. line length to transducer-electronics 150 m (450 ft), triaxial cable

Open Channel Measurement

The Ultra Sonic open channel mesurement system offers the same functionality as the pipe measurement. The processing unit is equipped with the same outputs:

• 2 analog outputs 0/4 ... 20 mA
• 2 pulse outputs
• 1 flow direction output
• 1 OK output
• 1 DUAL PORT RAM connection

For the flow measurement in an open channel, level H must also be taken into consideration. The processing unit therefore additionally provides 2 analog inputs 0/4 ... 20 mA.

With one or two pressure sensors (4-20 mA) or with an intelligent level measurement system (SDI-12) a single level or a level average is acquired. Measuring a level average, the accuracy of the flow calculation is further increased.

The processing unit can likewise communicate over the SENSORbus with several transducer-electronics. A multi-path measurement is thereby optimally supported.

Technical Data of Ultra Sonic Channel Measuremnt Sensors "Risonic"

Ultrasonic Sensor for submersible mounting

Channel forms rectangle, trapezoid, etc Assembly sensors adjustable, surface of buried type Max. channel width 15 m (600”) Max. allowable pressure 15 bar (225 psi) Protection class IP68 (submersible)

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