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Faults and solutions of ultrasonic flowmeter

Ultrasonic flow detection technology is a new technology which develops rapidly in recent years. It uses the information of fluid velocity carried by ultrasonic wave to measure fluid flow.

I. unstable reading changes dramatically
Cause analysis: the pipeline installed with ultrasonic flow sensor has large vibration or there is a device to change the flow state (such as flowmeter installed in the downflow of regulating valve, pump and shrinkage orifice).

Solution: refit the flow sensor away from the vibration source or move it upstream of the flow changing device.

Ultrasonic Flow Meter

Ultrasonic Flow Meter

II. Inaccurate reading and large error
Cause analysis:
1. The ultrasonic flowmeter sensor is installed at the top and bottom of the horizontal pipeline, and the sediment interferes with the ultrasonic signal. Solution: install the sensor on both sides of the pipeline.
2. The ultrasonic flowmeter sensor is installed on the pipeline with water flow downward, and the pipeline is not full of fluid. Solution: install the sensor on the pipe section full of fluid.
3. There are devices that make the flow state strongly fluctuate, such as venturi, orifice, vortex flowmeter, turbine flowmeter or partially closed valve, which are just within the range of sensor transmitting and receiving, making the reading inaccurate. Solution: install the sensor far away from the above device. The upstream of the sensor is 30d away from the above device, and the downstream is 10d away from the above device or move to the upstream of the above device.
4. The input pipe diameter of ultrasonic flowmeter does not match the inner diameter of pipeline.

Solution: modify the pipe diameter to match.

III. the sensor is good, but the flow rate is low or there is no flow rate
Cause analysis:
1. The paint and rust outside the pipeline are not removed. Solution: clear the pipe again and install the sensor.
2. The pipe surface is uneven or the ultrasonic flowmeter is installed at the welding joint. Solution: grind the pipe flat or away from the weld.
3. The roundness of the pipe is not good, the inner surface is not smooth, and there is pipe lining scaling. If the pipe is cast iron, this may happen. Solution: select the place with smooth inner surface such as steel pipe or lining.
4. The measured medium is pure or the solid suspension is too low. Solution: choose other suitable instruments.
5. The sensor is installed on the fiberglass pipe. Solution: remove the glass fiber.
6. If the sensor is installed on the sleeve, the ultrasonic signal will be weakened. Solution: move the sensor to the pipe section without casing.
7. The coupling between the sensor and the pipeline is not good, and there are gaps or bubbles on the coupling surface.

Solution: reinstall the coupling agent.

IV. when the control valve is partially closed or the flow is reduced, the reading will increase
Cause analysis: the sensor is installed too close to the downstream of the control valve. When the valve is partially closed, the flow rate measured by the flowmeter is actually the flow rate that controls the valve to reduce the diameter and increase the flow rate due to the reduction of the diameter.

Solution: keep the sensor away from the control valve, 30d upstream from the control valve or 5D upstream from the control valve.

V. normal operation, but no flow measurement
Cause analysis:
1. The measured medium changes. Solution: change the measurement method.
2. The measured medium will be gasified due to too high temperature. Solution: cool down
3. The measured medium temperature exceeds the limit temperature of the sensor. Solution: cool down
4. The coupling agent under the sensor is aged or consumed. Solution: reapply coupling agent
5. Due to high-frequency interference, the instrument exceeds its filtering value. Solution: keep away from interference sources
6. The data in the computer is lost. Solution: reenter the correct parameters
7. The computer crashes.



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