Current position >About Us
Clamp-on and Ultrasonic Flow Meters: High-Accuracy Non-Invasive Solutions
Quick Answer: A clamp-on ultrasonic flow meter measures flow from outside the pipe without cutting or welding. It works well for clean liquids such as water, chemicals, and light oils. Silver Automation Instruments supplies clamp-on ultrasonic flow meters for pipes from DN15 to DN6000 and can configure models for desalination, chemical dosing, and oil transfer.
What Makes a Clamp-on Meter Non-Invasive
No process shutdown, no drilling, no gaskets, and no pressure drop. The transducer pairs clamp onto the outside of the pipe. The liquid stays inside the closed line. This matters for chemical plants and water networks where cutting a pipe is expensive or dangerous.
Because there is no contact with the liquid, the meter does not add contamination risk. Food and beverage plants use this advantage for CIP return lines and sugar syrup batching. A dairy processor in Malaysia installed a clamp-on meter on a DN50 stainless steel line. The line handled hot water at 82 °C. The meter was installed in one afternoon while production continued.
Transit-time vs Doppler: Which One Fits
Silver Instruments supplies two main clamp-on types. Transit-time meters are used for clean water, chilled water, seawater, chemicals, and light hydrocarbons. Doppler meters are used for slurries, sludge, and liquids with bubbles or particles above about 100 ppm.
Here is the thing. Many engineers overspec a Doppler meter for river water. But a transit-time meter works if suspended solids stay low and pipe walls are not heavily scaled. We ask for your liquid type, solids content, and pipe material before recommending. For high-viscosity oils above 100 cP, a clamp-on ultrasonic meter is not always the best choice. A positive displacement oval gear meter may deliver better low flow performance.
Accuracy You Can Expect in the Field
Manufacturer data sheets often say ±0.5% of reading. In practice, a well-installed clamp-on ultrasonic meter on a straight pipe run can hold ±0.5% to ±1% repeatability. That is enough for water balancing, chemical transfer, cooling loop monitoring, and pump performance checks.
Straight run matters more than the meter head. We recommend 10D upstream and 5D downstream for transit-time clamp-on installations. For a DN200 pipe, 10D means 2 meters of straight pipe before the sensors. Valves, elbows, and pumps nearby create swirl. That swirl reduces accuracy quickly.
Do not expect high accuracy on very old pipes with internal scale or rust. The ultrasonic signal weakens. Last year, a water treatment contractor in Oman asked us to check a DN300 raw water line with heavy scale. The signal was unstable. We recommended a spool-piece insertion meter instead of a clamp-on unit. That saved the customer from a bad installation.
Pipe Sizes, Temperatures, and Outputs
Our clamp-on ultrasonic flow meters cover pipe sizes from DN15 up to DN6000. Liquid temperature range depends on the transducer. Standard clamp-on sensors handle -40 °C to 120 °C. High-temperature sensors extend the range to 180 °C. Pipe materials include carbon steel, stainless steel, PVC, HDPE, and copper. For HDPE and PVC, we supply coupling gel and sensor mounting blocks to improve signal transfer.
Outputs include 4-20 mA HART, pulse, and Modbus RTU over RS485. Some customers also request a PT100 temperature input for heat quantity calculations. The transmitter can show flow rate in m³/h, L/min, kg/h, or gpm. Accuracy on clean water with a straight run is typically 0.5% to 1% of reading. Repeatability is 0.2% to 0.3%.
Power options are 24 VDC or 85-265 VAC. The transmitter enclosure is IP65 or IP66. The clamp-on sensors can be IP68 for buried or flooded pits. This is useful in wastewater lift stations and seawater intake bays.