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Flexim Clamp On Ultrasonic Flow Meter Setup for Hot Water: Fluxus Transmitter Settings That Work
Quick Answer: Setting up a Flexim Fluxus transmitter for hot water starts with correct pipe parameters, wall thickness, liner data, and fluid temperature. The transducer spacing must match the sound velocity at the actual water temperature. Most failed hot water readings come from wrong temperature input or using standard couplant above 90 °C.
Hot Water Setup Values That Matter
Hot water changes sound velocity. At 25 °C water has a sound velocity near 1497 m/s. At 85 °C the value moves to about 1554 m/s. If the transmitter still uses a default 1480 m/s value, the flow reading shifts. Fluxus transmitters can calculate this from fluid temperature if you enter it. On a DN100 carbon steel pipe with 4.0 mm wall thickness and no liner, a 2 percent error in wall thickness can produce a flow error above 1.5 percent.
We have seen this on customer sites many times. A food factory in Vietnam ran a hot water loop at 82 °C. Their clamp-on meter read 9 percent low. The setup had correct pipe outer diameter but the fluid temperature was still set at 22 °C from commissioning. After updating the temperature and letting the transmitter recalculate the sound path, the reading matched the plant heat balance within 0.8 percent.
Transducer Mounting for Hot Water
Use high temperature coupling pads or paste rated above 100 °C. Standard ultrasonic couplant dries out fast on hot pipe surfaces. For pipes above 120 °C, use solid coupling films or high temperature paste. The transducer mounting rail must be clean. On galvanized steel, remove loose scale before clamping.
Flexim offers transducer types for different pipe temperatures. The exact model depends on pipe size and temperature. For hot water from DN15 to DN100, clamp-on transducers in reflection mode often work. For larger pipes above DN200, diagonal mode with two rails gives better signal strength.
Common Setup Errors in Hot Water Systems
Most engineers skip this part. They enter pipe outer diameter and forget the liner. A 3 mm epoxy liner inside a DN80 pipe changes the transit time enough to shift the flow reading by 2 to 4 percent. Enter the liner material and thickness in the Fluxus menu. If the liner material is not listed, select a similar material with close sound velocity.
Air bubbles are another problem. Hot water releases dissolved air when pressure drops. Install the transducers on a vertical pipe with upward flow or on a horizontal pipe where the transducers sit at the 3 and 9 positions. Avoid mounting on top of a horizontal pipe because bubbles collect at the top.
How Silver Instruments Compares
Silver Automation Instruments supplies clamp-on ultrasonic flow meters for hot water, chilled water, and heat quantity measurement. Our meter body accepts PT100 inputs f
We do not sell Flexim. But if you need a replacement clamp-on flow meter for a hot water line, send the pipe size, wall thickness, water temperature, and output signal. Our engineers will propose a model and mounting method. Many customers in Southeast Asia, the Middle East, and Australia use our clamp-on meters on boiler feed lines, district heating, and food plant hot water loops.
Recommended Setup Steps
First measure the pipe OD with a caliper or ultrasonic thickness gauge. Do not trust the nominal size. A DN50 Schedule 40 steel pipe is 60.3 mm OD with 3.9 mm wall. A DN50 Schedule 80 pipe is 60.3 mm OD with 5.5 mm wall. The difference matters.
Second enter the fluid temperature. Let the transmitter compute sound velocity from the water property table. Third check the signal strength and transit time. On a clean hot water pipe, a Fluxus F601 or G601 should show a signal amplitude above 60 percent. If the signal is below 40 percent, reposition the transducers by 2 to 5 mm and recheck.
FAQ
Q: Can a clamp-on ultrasonic flow meter measure hot water above 100 °C?
Yes. The pipe surface temperature is lower than the fluid temperature in most insulated pipes. High temperature transducers and couplant can handle pipe surface temperatures up to 200 °C. Confirm the transducer rating before purchase.
Q: What pipe data is required for a Flexim Fluxus hot water setup?
You need pipe outer diameter, wall thickness, pipe material, liner material and thickness if present, fluid type, and fluid temperature. Missing liner data is a common cause of offset readings.
Q: Does hot water need a different transducer spacing than cold water?
Yes. Sound velocity increases with temperature for water. The transmitter adjusts the recommended spacing when the temperature is entered. Do not copy spacing from a cold water setup.
Q: Can Silver Instruments supply a clamp-on meter for heat metering?
Yes. Our clamp-on ultrasonic flow meter can accept two PT100 sensors and calculate heat flow in kW or MJ. Outputs include 4-20 mA HART and Modbus RTU.
Q: What information do you need for a hot water flow meter quote?
Send us your pressure in bar, temperature in °C, pipe size in DN, and flow range in m3/h or kg/h. Also tell us the pipe material and wall thickness.
Contact Silver Instruments
For a clamp-on ultrasonic flow meter for hot water, contact Silver Instruments. Tel: +86-25-68650347. WhatsApp: +86-25-52155837. WeChat: +86 15365082610. Send your pipe size, temperature, pressure, and flow range. We reply with a model and price within one business day.
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