Selection of electrodes and lining
Standard electrodes are used for media that do not produce non-staining electrodes such as crystals, agglomerates, and scales. Otherwise, a doctor blade electrode is used. In addition to the pure alkaline solution, the dosing solution (crystallization of boron and magnesium double salt), the washing liquid and other electromagnetic flowmeters that use the scraper electrode, the other uses the electromagnetic flowmeter of the standard electrode. Since the process pipes in the workshop are basically made of plastic insulation material, if the electromagnetic flowmeter with two electrodes is selected, the grounding ring must be configured to ensure the measurement accuracy. However, the common grounding ring is easy to corrode, and the corrosion-resistant titanium or 钽 grounding ring is high in cost, so the three-electrode electromagnetic flowmeter is selected to ensure measurement accuracy, reduce cost, and convenient installation and maintenance.
Flowmeter type selection
The types of electromagnetic flowmeters are divided into: integral type and split type. In Qinghai, the coldest temperature in winter is up to -30 °C. Many metered electromagnetic flowmeters are outdoors, and the environmental humidity of magnesium-lithium separation, pressure filtration and washing processes in lithium and boron systems is large. Exquisite, evaporation, conversion and other processes up to 90 °C. Therefore, the humidity of the high temperature, low temperature, high temperature fluid, vibration source and other working conditions select a split flow meter to effectively prevent the impact on the measuring components, to ensure measurement accuracy and the life of the electromagnetic flowmeter. However, it should be noted that the signal cable between the electromagnetic flowmeter sensor and the transmitter should not be too long, and the manufacturer-specific cable should be used, otherwise the measurement accuracy will be affected. The rest of the working conditions are more ideal.
The correct selection of ultrasonic flowmeters can ensure better use of ultrasonic flowmeters. The type of ultrasonic flowmeter to be selected should be determined according to the physical properties and chemical properties of the fluid medium to be tested, so that the diameter, flow range, lining material, electrode material and output current of the ultrasonic flowmeter can be adapted to the properties of the fluid to be measured. And flow measurement requirements.
1, precision function check
Accuracy levels and functions are based on measurement requirements and usage scenarios to select instrument accuracy levels for cost-effectiveness. For example, in the case of trade settlement, product handover and energy measurement, the accuracy level should be higher, such as 1.0, 0.5, or higher; for process control, select different accuracy levels according to control requirements; It is to detect the process flow, no need to do precise control and measurement, you can choose a lower accuracy level, such as 1.5, 2.5, or even 4.0, then you can use a low-cost plug-in ultrasonic flowmeter.
2, measurable medium
Measuring medium flow rate, meter range and caliber When measuring a general medium, the full flow rate of the ultrasonic flow meter can be selected within the range of 0.5-12 m/s of the measured medium flow rate, and the range is relatively wide. The selection of the meter specification (caliber) is not necessarily the same as the process piping. It should be determined according to whether the measured flow range is within the flow rate range. That is, when the pipeline flow rate is too low to meet the requirements of the flow meter or the measurement accuracy is not guaranteed at this flow rate. It is necessary to reduce the gauge diameter, thereby increasing the flow rate inside the tube and obtaining satisfactory measurement results.
Some experiences on using ultrasonic flowmeter
1. The flowmeter has two modes, diagonal and reflective. When the reflection mode is not detected, it can be measured in diagonal mode, so that we have been using the reflection mode.
2. The flowmeter requires a relatively high pipe, and the insulation layer must be scraped off, otherwise it cannot be measured. When we measured the air conditioning water system, we cut the insulation layer with a knife to prevent the sensor. After the measurement, the cut insulation layer was glued. The surface of the pipe should be as bright as possible. If it is too rough, it must be sanded.
3. It is difficult to measure when the fluid in the pipeline is not full, so the measuring position should be as straight as possible, away from elbows, valves and other places.
4. The authenticity of the flowmeter reading depends on the signal strength. When the signal is too low, the result is basically unreliable, generally more than 60% or even more.
5. Since the readings may vary greatly, the approach we take is to have the flowmeter read continuously, such as continuously recording one minute of reading and then taking the average.
6. Measuring hot water lines is more difficult than cold water lines. Because the wall temperature of the hot water pipe is high, the coupling agent is easily formed at a high temperature. In addition to the product's own coupling agent, we have tried toothpaste.
The summary of ultrasonic flowmeter measurement accuracy and accuracy needs to be improved.