Common Faults of Ultrasonic Flowmeters
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Readings are unstable and change dramaticallyCause analysis: The pipeline where the ultrasonic flow sensor is installed vibrates greatly or there is a device that changes the flow pattern (such as the flow meter is installed downstream of the regulating valve, pump, or contraction hole).
Solution: Modify the flow sensor to a place away from the vibration source or move it upstream of the device that changes the flow pattern.
(II) Inaccurate readings and large errors
Cause analysis:
1. The ultrasonic flowmeter sensor is installed on the top and bottom of the horizontal pipe, and the sediment interferes with the ultrasonic signal. Solution: Install the sensor on both sides of the pipe.
2. The ultrasonic flowmeter sensor is installed on the pipe where the water flows downward, and the pipe is not filled with fluid. Solution: Install the sensor on the pipe section filled with fluid.
3. There are devices that cause the flow pattern to fluctuate violently, such as: Venturi tube, orifice plate, vortex flowmeter, turbine flowmeter or partially closed valve, which is just within the range of the sensor's transmission and reception, making the reading inaccurate. Solution: Install the sensor far away from the above device, 30D upstream of the sensor and 10D downstream of the sensor or move it upstream of the above device.
4. The input diameter of the ultrasonic flowmeter does not match the inner diameter of the pipeline.
Solution: Modify the pipe diameter to match it.
(III) The sensor is good, but the flow rate is low or there is no flow rate
Cause analysis:
1. The paint and rust on the outside of the pipeline have not been cleaned up. Solution: Re-clean the pipeline and install the sensor.
2. The pipeline surface is uneven or the ultrasonic flowmeter is installed at the weld. Solution: Grind the pipeline flat or keep it away from the weld.
3. The pipeline has poor roundness, the inner surface is not smooth, and there is pipe lining scaling. If the pipe is a cast iron pipe, this may occur. Solution: Choose a pipe material or lining with a smooth inner surface such as a steel pipe.
4. The measured medium is a pure substance or the solid suspended matter is too low. Solution: Choose a suitable other type of instrument.
5. The sensor is installed on a fiberglass pipe. Solution: Remove the glass fiber.
6. If the sensor is installed on the casing, the ultrasonic signal will be weakened. Solution: Move the sensor to the pipe section without casing.
7. The sensor is not well coupled with the pipeline, 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 rate 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 ultrasonic flowmeter actually measures the flow rate of the control valve's reduced diameter flow rate. The flow rate increases due to the reduction in diameter.
Solution: Move the sensor away from the control valve, 30D upstream of the sensor from the control valve, or move the sensor to the upstream of the control valve 5D from the control valve.