Company Profile

Ultrasonic Flow Sensors: Clean Liquid Velocity Transducers for Zero Pressure Drop

Quick Answer: Ultrasonic flow sensors for clean liquids measure velocity with no wetted moving parts and no pressure loss. They fit water, chemical, food, and desalination lines from DN15 to DN50. Silver Automation Instruments supplies inline models with 4-20 mA HART, pulse, and RS485 Modbus outputs for process skids and batching systems.

What an Ultrasonic Flow Sensor Does in a Clean Liquid Line

An inline ultrasonic velocity transducer sends acoustic signals through the liquid. The electronics compare upstream and downstream transit time. Flow velocity is calculated from that difference. There is no impeller, gear, or paddle in the flow path. That means zero pressure drop and very low maintenance.

Most engineers skip this part. Pressure drop may look small on paper, but the loss becomes real when a pump runs near its curve limit. A turbine meter can lose 100 mbar or more at rated flow. An inline ultrasonic sensor does not add that loss. In a low pressure feed line, that saved head can protect the whole process.

Key Specifications for Clean Liquid Velocity Transducers

Silver Instruments offers inline ultrasonic flow sensors from DN15 to DN50. Wetted materials are 316L stainless steel and PTFE. The standard flow velocity range is 0.1 to 10 m/s. Accuracy is 1.0 percent of reading. Repeatability is 0.2 percent. The standard process temperature range is 0 to 90 °C and pressure rating is 16 bar. Output options include 4-20 mA, pulse, and RS485 Modbus. HART is available for process plants that need remote configuration.

We have seen this on customer sites many times. A skid builder in Malaysia needed a DN20 sensor for demineralized water. The pressure budget was tight. A small positive displacement meter was causing too much loss. The inline ultrasonic sensor removed that loss and kept the same 4-20 mA signal to the PLC.

Where These Sensors Work Best

Use an inline ultrasonic velocity transducer for clean water, RO permeate, cooling water, mild chemicals, and beverage process water. They are also suitable for desalination plant feed lines and pharmaceutical water loops. Do not use them for slurries, high viscosity oils, or liquids with entrained gas. Bubbles scatter the acoustic signal and create unstable readings.

For dirty water or wastewater, choose a full bore electromagnetic flow meter instead. For oils or fuels, check viscosity first. Clean diesel fuel often works with a transit time sensor. Heavy fuel oil will not work well. We can help you confirm based on your cP value and operating temperature.

Installation Notes That Save Time

Inline ultrasonic flow sensors need straight pipe upstream and downstream. For DN15 to DN50, plan 10 pipe diameters upstream and 5 downstream. Mount the sensor in a full pipe. Avoid the highest point of a line where air can collect. Install a degassing valve upstream if the liquid releases gas.

Because these sensors have no moving parts, routine maintenance is low. But a coated transducer face can reduce signal strength. Clean the transducer face during shutdown if the liquid leaves a film. This is common in sugar water lines and some cosmetic process water applications.

Recommended Models from Silver Instruments

For DN15 to DN25 clean water lines, choose the Silver Instruments UFS-15 or UFS-25 series. These compact velocity transducers provide a pulse output for local batching and a 4-20 mA signal for remote flow reading. For DN32 to DN50 process water, choose the UFS-50 series with PTFE transducer face.