The precautions for using external card type (external clip type) ultrasonic flowmeter can be divided into the following key points:
1、 Installation environment requirements
1. Pipeline adaptability: Metal pipes (such as carbon steel and stainless steel) have high acoustic impedance and strong signal penetration; Plastic pipes (such as PVC) require low-frequency sensors (≤ 50kHz) to be selected. If the inner lining of the pipeline is too thick (such as cement lining>5mm), it needs to be calibrated through actual measurement or selected as the "penetrating lining" mode.
2. Requirements for straight pipe section: Upstream must be ≥ 10 times the pipe diameter (10D), downstream must be ≥ 5D, otherwise turbulence may cause an error of ± 5% or more.
3. Fluid state: It must be full tube flow to avoid half tube, gas-liquid stratification or vortex, otherwise the installation position needs to be adjusted or a rectifier needs to be added.
2、 Key points for installation and debugging
1. Sensor installation:
The surface of the pipeline needs to be polished to Ra3.2 μ m or below (similar to a mirror) to remove rust and oil stains.
2. Coupling agent selection: Silicone grease is used for ordinary environments, and high-temperature resistant coupling agents (such as zinc oxide based) are required for high-temperature environments.
The torque of the fixture should be controlled between 10-15 N · m to avoid damaging the sensor due to over tightening or causing signal fluctuations due to over loosening.
3. Parameter settings:
Accurately input the outer diameter, wall thickness, and material of the pipeline (such as carbon steel density of 7.85g/cm ³). Incorrect input may result in a ± 3% error.
The fluid type needs to distinguish between "clean water" and "sewage" modes, and the gas needs to be equipped with temperature compensation.
3、 Maintenance and safety
1. Daily maintenance:
Check the status of the coupling agent monthly, and conduct weekly inspections in high-temperature environments.
Check the fixture fastening every quarter to prevent sensor displacement.
2. Environmental monitoring: Record temperature and humidity changes, and add moisture-proof measures when they exceed the equipment range (such as humidity>90%).
3. Electromagnetic interference: Keep away from strong vibration sources such as pumps, motors, and frequency converters (distance ≥ 2m), and use a metal shielding cover if necessary.
4、 Common problem handling
1. Low signal: It may be due to excessive pipe diameter or severe scaling. It is recommended to use an insertable probe or the "Z method" for installation.
2. Reading fluctuation: Check if the signal strength is stable (>80%), or reselect the installation point to meet the requirements of front 10D and back 5D.