External clamp type ultrasonic flowmeterIt is a non-contact flow measurement instrument based on ultrasonic detection technology, which achieves accurate measurement of fluid velocity and flow rate by clamping it outside the pipeline. The core principle is the ultrasonic propagation time difference method or Doppler effect: when the ultrasonic pulse penetrates the pipe wall and fluid, there is a difference in the propagation speed in the forward and backward directions. By measuring the time difference, the fluid velocity can be calculated, and the volumetric flow rate can be calculated based on the known pipe diameter. Some models also integrate Doppler shift technology, which is suitable for measuring fluids containing particles or bubbles.
This device has significant technological advantages. Non contact design avoids medium pollution and pipeline modification, and can be directly installed in operating pipeline systems, especially suitable for corrosive liquids or high-pressure environments. Its measurement range covers pipe diameters from DN15 to DN6000, with a flow rate range of ± 32m/s. It supports uniform media such as water, oil, and chemical liquids, and is suitable for pipelines made of metal, plastic, cement, and other materials. The high-precision time to digital conversion chip and real-time temperature compensation technology enable measurement accuracy to be better than ± 1%, effectively overcoming small flow errors and zero drift problems.
Scientific maintenance is crucial to ensure its long-term stable operation and measurement accuracy. Here isExternal clamp type ultrasonic flowmeterDetailed maintenance methods:
1、 Daily inspection and maintenance
Check signal quality
Signal Strength: Regularly (recommended daily or weekly) check the signal strength through the instrument display screen or accompanying software. The normal value should usually be greater than 80%, and if it is lower than 60%, it should be investigated immediately.
Transit Time Ratio: Check if the value is within the normal range (usually 0.98-1.02). Abnormal fluctuations may indicate installation issues or changes in fluid conditions.
Appearance and connection inspection
Check the sensor and transmitter housing for damage, corrosion, or water accumulation.
Confirm that the sensor is securely installed without any looseness, and that the fixing fixture or magnetic attraction device is intact.
Check if the cable connections are tight and if the sealing ring of the junction box is aging to prevent water or moisture from entering.
Cable protection
Avoid contact between signal cables and high-temperature, corrosive media or strong electromagnetic interference sources (such as frequency converters, high-power motors).
The cable should be shielded by a metal tube and kept at least 0.5 meters away from the power cable to avoid being laid on the same cable tray.
2、 Special maintenance of sensors (probes)
Regularly clean the surface of the sensor
Cycle: It is recommended to conduct it every 3 months, and the cycle should be shortened when the water quality or environment is poor.
Method:
Cut off the power supply to ensure safety.
Remove the sensor (if it is magnetic, it can be directly removed).
Dip a soft, lint free cloth into a small amount of alcohol or specialized cleaning agent and gently wipe the ultrasonic emitting/receiving surface.
It is strictly prohibited to use metal tools, sandpaper, or hard objects to scrape, in order to avoid damaging piezoelectric components.
Purpose: To remove oil stains, scale, dust, etc., which can severely attenuate ultrasonic signals.
Check and replace the coupling agent
Cycle: Check once every 6 months, and more frequently in high temperature environments (>60 ℃).
Method:
After cleaning the sensor and pipeline surfaces, apply a thin layer of specialized acoustic coupling agent (such as silicone grease) evenly.
Ensure that the coupling agent is not dry, has no bubbles, and has a thickness of less than 0.5mm.
High temperature pipelines require the use of high-temperature resistant coupling agents (such as ceramic filled silicone grease).
Purpose: Coupling agents can eliminate air gaps between sensors and pipelines, ensuring efficient transmission of ultrasonic waves.
3、 Electrical and Environmental Protection
Waterproof and moisture-proof
Regularly check the sealing of the transmitter junction box and ensure that there is no accumulated water inside after rain.
Even if it has a protection level of IP65 or above, it should be avoided from direct water flushing or long-term exposure to humid environments.
grounding protection
Ensure that the instrument is independent and well grounded, with a grounding resistance of less than 4 Ω.
Effective grounding can significantly reduce electromagnetic interference and improve signal stability.
Winter protection
When the temperature of the pipeline medium may be lower than 0 ℃, install a heat tracing strip locally on the sensor and pipeline.
Attention: It is prohibited to directly wrap the transmitter host in the heat tracing belt to prevent overheating and damage to electronic components.
4、 Regular calibration and verification
Real flow calibration
It is recommended to perform real-time calibration every 12 to 24 months to ensure high accuracy of ± 0.5%.
For situations with high precision requirements, it is recommended to calibrate once a year.
Comparison verification
Equipped with a portable ultrasonic flowmeter, regularly compare and measure online instruments.
When there are abnormal fluctuations or sudden changes in the readings of online instruments, portable instruments can be used to quickly calibrate and determine whether it is an instrument malfunction or a real flow change.
5、 Establish and maintain archives
It is recommended to develop a "Checklist for External Clamp Ultrasonic Flowmeters" and record key parameters such as signal strength and transmission ratio daily.
Analyzing data trends monthly can effectively prevent over 90% of potential failures.