Badger Meter Dynasonics DFX Clamp-On Doppler Flow Meter

Badger Meter Dynasonics DFX clamp-on Doppler ultrasonic flow meter for dirty and aerated liquids

The Badger Meter Dynasonics DFX is a clamp-on Doppler ultrasonic flow meter for liquids that contain suspended particles or air bubbles, such as sewage, sludge, mud slurries and process water with solids. Its DT9 series transducers strap to the outside of the pipe, so there is no cutting, no flanged spool piece and no process shutdown. It complements the transit-time meters of the same Dynasonics family, which need clean liquid. Seven Star LLC supplies the DFX in Oman and the GCC as an independent supplier in Muscat, and this page explains how Doppler measurement works, what the data sheet specifies and what to check before ordering.

How the DFX measures flow

The transmitting transducer sends ultrasonic sound at 625 kHz through the pipe wall into the liquid. Particles or bubbles in the liquid reflect the sound, and the receiving transducer picks up the echo. If the reflectors are moving, the echo frequency is shifted by the Doppler effect, and the difference between the transmitted and received frequency is directly proportional to the reflector speed, from which the meter calculates flow. The meter therefore needs something in the liquid to reflect the sound; the data sheet states a minimum of 100 ppm of useful sonic reflectors larger than 35 microns, with at least 25 percent of the particle volume larger than 100 microns. Dissolved solids do not reflect sound and do not count.

Technical specifications of the DFX

Application constraints given by the manufacturer

• Enough reflectors: clean water with no particles or bubbles will not give a Doppler signal; use a transit-time meter instead.
• Good acoustic coupling: the transducer is coupled to the outside of the pipe with grease or RTV couplant, and the pipe wall must pass ultrasound without heavy attenuation. Most solid, homogeneous pipes qualify, while concrete pressure pipe, wood stave pipe, Teflon-lined pipe and fibreglass-reinforced pipe are listed as difficult.
• Full pipe: the meter assumes the pipe is completely full when it calculates flow, so partial filling gives inaccurate readings.

Installation benefits and limits

The manufacturer states that the DFX can be installed and operational within minutes on a full, active pipe, with no need to break into the line and no moving parts to wear. This saves flanges, fittings, strainers and filters. The automatic gain control and in-field linearisation help adapt to varied applications. Accuracy of ±2 percent of full scale is typical of clamp-on Doppler technology and is not comparable to a magnetic flow meter, so a DFX is chosen for convenience, for monitoring and for liquids where an in-line meter is not practical, rather than for custody transfer. The standard transducers are Standard Temperature (up to 90 °C), so very hot lines are outside the range.

Selection and ordering checklist for the DFX

• Pipe outside diameter, wall thickness and material, plus liner and scale condition.
• Liquid solids or bubble content: confirm at least 100 ppm of reflectors in the stated size range.
• Transducer set: standard (DT94) or small pipe (DT95), and cable length.
• Power supply: AC mains or 12…28 V DC.
• Outputs: 4…20 mA, relays or rate pulse into the control system.
• Mounting: wall or panel mount of the monitor.
• Whether several meters will share one pipe or manifold.

Commissioning notes

Enter the pipe data and the units, choose the response time, clean the pipe surface, apply the couplant and fix the transducers with the mounting brackets. Because the Doppler signal depends on particles, readings should be checked against a known flow, a tank fill test or another meter after installation, and the calibrated span adjusted accordingly. A flow profile disturbed by bends, valves or pumps close to the transducer can affect the reading, so allow straight pipe where practicable. Inspect the couplant at intervals, because dry couplant is a common cause of lost signal.

Typical applications in Oman and the GCC

The DFX suits sewage and sludge lines at treatment plants, return activated sludge and mixed liquor lines, mud and slurry lines, dredging and tailings lines, produced water with solids and cooling water with particles. Clamp-on installation is an advantage where lines run through existing plant and shutdowns are costly, and the wide ambient range of -40 to +85 °C is helpful in hot outdoor installations.

Information to send with an RFQ for the DFX

• Pipe size, material and wall thickness
• Liquid, solids content and temperature
• Transducer type and cable length
• Power supply and outputs
• Quantity and delivery site

Documents and quotation

The Badger Meter DFX product data sheet is attached on this page. It includes the specification table and the transducer options.

Send the pipe and liquid data and Seven Star LLC will confirm availability and prepare a quotation.