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Greyline Instruments, Inc.

Massena, NY 13662   map
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Doppler Flow Switch

Item #: DFS-II

Control Flow From Outside a Pipe
Flow Switch with Non-Contacting Sensor

Controls Flow with:
No pressure drop
No sensor fouling
No maintenance

Flow Sensor installs without cutting the pipe

Installs in Minutes No moving parts

Mount the DFS-II ultrasonic sensor on the outside of metal or plastic pipes. The sensor continuously injects high frequency sound through the pipe wall and into the moving fluid where acoustic pulses are reflected back to the sensor from particles or bubbles in the fluid.

Ideal for "difficult" liquids No contact, No maintenance

Flow rates of most liquids can be accurately controlled including acids, caustics, lubrication fluids, chemicals, abrasives, waste water and sludge. There are no moving parts and no sensor maintenance is required.

Easy Calibration

The compact, water tight electronics enclosure includes adjustable controls with separate ON and OFF switch set-points, sensitivity and time delay. Indicator lights for signal strength and relay status are included.

Installation can be made while the flow system is in full operation. No contact is made with the moving fluid and no holes are drilled in the pipe. There is no fouling or scale build-up on the sensor.

Easy-to-install, Automatic Flow Control
Recommended for Pump Protection and Flow Alarms

The DFS-II flow sensor installs without cutting the pipe. It takes just a few minutes to mount on the outside of any pipe. The switch/electronics enclosure can be mounted 20 ft (6 m) away from the sensor (optional up to 500 ft / 152 m) to simplify wiring to pumps, alarms, valves or other equipment.

Switch adjustments and electrical connections are fast and easy. The DFS-II relay time delay is adjustable from 0 to 60 seconds to prevent nuisance alarms and relay "chatter" in turbulent flow. Includes switch selectable "normal" and "failsafe" operating modes.

Choose DFS-II for:
  • No contact with the measured liquid
  • No obstruction to flow - No pressure drop
  • Sensor mounts easily on the outside of the pipe
  • Can be installed while pipe line is in use
  • Insensitive to pressure, specific gravity and conductivity
  • Does not require pipe metering sections
  • Does not require consideration of material compatibility with the liquid

Repeatable, Reliable Flow Control

Use the DFS-II for pump protection, valve control and flow/no-flow alarms. It is ideal for "difficult" liquids like wastewater, slurries, abrasives and chemicals, or any liquid which contains gas bubbles or solids. The standard Sensor mounts on any pipe 1" (25mm) diameter or larger.
Doppler Flow Switch

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Item #: DFS-II
Item #:DFS-II
Item Name:Doppler Flow Switch
Weight:8 lbs
3.6 kg
Enclosure:Watertight, dust tight NEMA4X (IP 67) polycarbonate with a clear shatter-proof face
Input Voltage:120 VAC
Frequency:50 to 60 Hz
Power:10 W
Control Relay:5 ampere DPDT
Set Points:ON/OFF adjustment from 0.25 to 10 ft/sec (0.075 to 3 m/sec)
Sensor:Single-head ultrasonic with 20 ft (6m) shielded cable
Pipe Size:Any pipe ID from 1/2" to 180" (12.5 mm to 4.5 m)
Sensor Operating Temperature:-40 to 200 ºF
-40 to 93 ºC
Electronics Operating Temperature:-10 to 140 ºF
-23 to 60 ºC
Accuracy:±2%, requires solids or bubbles minimum size of 100 microns, minimum concentration 75 ppm
  • Recommended for liquids containing suspended solids or bubbles minimum size of 100 microns, minimum concentration 75 ppm
  • Sensor mounts on Vertical or Horizontal pipes.
  • Sensor Mounting Location: 6-10 pipe diameters from elbows, tees (turbulence increasing devices) >30 pipe diameters from pumps, controlling valves and pipe discharge
  • Pipe Materials: steel, stainless steel, cast iron, PVC, fiberglass, any continuous pipe material that conducts sound, including lined pipes with liner bonded to pipe wall. Avoid pipes with loose insertion liners and pipe materials which contain air pockets (concrete, wood etc.)

Applications Support
Take advantage of Greyline's applications experience. Phone toll free 1-888-473-9546 for advice and information on applications, installation or service for Greyline instruments.
How to Order
Contact a Greyline sales representative in your area or phone one of our sales engineers. Describe your requirements and receive our prompt quotation.
No Risk Appraisal
The Greyline DFS-II Doppler Flow Switch must meet your requirements. Discuss your application with a Greyline representative to arrange a 30-day trial.
Non-Contacting Flow Control
Pump protection … Flow/No flow indication
Overfill alarm … High or Low flow control

Ideal for "difficult" liquids

The DFS-II Doppler Flow Switch is recommended for flow control of liquids containing gas bubbles or solids: chemicals, slurries, sludge, viscous liquids, wastewater, caustics and abrasives. The ultrasonic sensor injects high frequency sound through the pipe wall into the flowing liquid. Acoustic pulses are continuously reflected back to the sensor and the DFS-II measures a frequency shift to calculate flow velocity.

No pipe cutting, No pressure drop, No sensor fouling, No maintenance!

It takes just a few minutes to install and calibrate a DFS-II Flow Switch. The DFS-II controls flow of most liquids in closed pipes. The ultrasonic sensor mounts on the outside of any pipe from 1" to 180" (25 mm to 4.5 m) I.D.

Reliable and Repeatable

The DFS-II control relay can be set to turn ON and OFF at any flow rate between 0.25 and 10 ft/sec (0.075 to 3 m/sec). Repeatability is ±0.1% of full scale (0.1 ft/sec or 0.003 m/sec).

Standard features include signal strength indication, 5 ampere DPDT relay contacts, a non-contacting, strap-on Sensor and a remote watertight enclosure.

Durable Sensor...

Sealed in a stainless steel and epoxy housing, the DFS-II ultrasonic sensor withstands accidental submersion up to 10 psi (69 Kpa). It is also available with optional intrinsic safety barriers for Sensor mounting in hazardous rated locations.

Ideal for Pump Protection

Avoid expensive pump repairs and downtime The DFS-II strap-on Sensor can be installed in minutes without shutting down flow or cutting pipe. Use the adjustable relay time delay to eliminate relay "chatter" and reduce pump wear.

Self-tunes to Extended Sensor Cable

Up to 500 ft (152 m) extra sensor coaxial cable can be added. Extended cable and junction box can be ordered from Greyline. The cable can be cut or extended as required during installation. The flow switch automatically tunes to the cable length. No circuit adjustment or calibration is required.

Special Offer

Discuss your application with a Greyline sales representative to arrange a trial in your facilities. Test a DFS-II on your application for 30 days and return it for full credit if it does not perform satisfactorily. Contact Greyline Instruments or your local sales representative for more information, a quotation, or a demonstration.

Each DFS-II Includes adjustable
  • ON and OFF setpoints
  • Relay deadband
  • Time delay
  • Sensitivity
  • Failsafe mode

Installed in these Applications
  • Sewage
  • Viscous liquids
  • Acids
  • Slurries
  • Solvents
  • Treated wastewater
  • Sludge
  • Pulp stock
  • Food products
  • Oils
  • Chemicals
  • Aerated Water
  • Cooling Water

Hazardous locations:Intrinsically Safe Sensor
Sensor Cable:Up to 500 ft (152 m) shielded coaxial pair. Self tunes to extended cable
Sensor Mounting Clamp:Stainless steel, adjustable
Input Voltage (Optional):230 VAC
24 VDC
Frequency (Optional):50 to 60 Hz
Standard Features
Set-Point (Standard):Field-adjustable with separate ON/OFF set-points
Indication:Signal strength LED, relay status LED
Time Delay:Adjustable 0 to 60 seconds
Electrical Surge Protection:AC power input and sensor
Failsafe Mode:Switch selectable
Sensor Coupling Compound included
The Greyline Guarantee
Quality of Materials and Workmanship - Each instrument manufactured by Greyline is warranted against defects in materials and workmanship for a period of one year from date of purchase. Refer to our limited warranty included with each product.

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