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.
Vortex flowmeter installation requirements for straight pipe sections:
It is very important that the vortex flowmeter installation meets the requirements for straight pipe sections. Its detailed requirements are as follows:
The flowmeter has certain requirements on the upstream and downstream straight pipe sections at the installation point, otherwise it will affect the measurement accuracy.
If there is a tapered pipe upstream of the installation point of the flowmeter, there should be a straight pipe section of not less than 15D (D is the pipe diameter) upstream of the flowmeter, and a straight pipe section of not less than 5D in the downstream.
If there is a diverging pipe upstream of the installation point of the flowmeter, the upstream of the flowmeter shall have a straight pipe section of not less than 18D (D is the pipe diameter), and the downstream shall have a straight pipe section of not less than 5D.
If there is a 90° elbow or down joint upstream of the installation point of the flowmeter, there should be a straight pipe section of not less than 20D upstream of the flowmeter, and a straight pipe section of not less than 5D downstream.
If there is a 90° elbow on the same plane upstream of the installation point of the flowmeter, there should be a straight pipe section of not less than 25D upstream of the flowmeter, and a straight pipe section of not less than 5D downstream.
The flow regulating valve or pressure regulating valve should be installed as far as possible downstream of the flowmeter 5D. If it must be installed upstream of the flowmeter, the upstream of the flowmeter should have a straight pipe section of not less than 25D, and the downstream should have a straight pipe section of not less than 5D. .
If there is a piston type or plunger type pump in the upstream of the flow meter, a piston type or a Roots type fan and a compressor, the upstream of the flow meter should have a straight pipe section of not less than 25D, and the downstream should have a straight pipe section of not less than 5D.
Special attention: If the valve is installed near the upstream of the installation point of the vortex flowmeter, the valve is continuously opened and closed, which has a great influence on the service life of the flowmeter, and it is very easy to cause permanent damage to the flowmeter. The flowmeter should be avoided to be installed on the very long pipelines in overhead. After a long time, the leakage of the flowmeter can easily cause the leakage of the flowmeter to the flange. If it has to be installed, it must be in the upstream and downstream of the flowmeter. Pipe fastening devices are provided separately.
Vortex flowmeter analysis and solution
6. The connection problem between the secondary instrument and the subsequent instrument. Due to the problem of the subsequent instrument or the maintenance of the subsequent instrument, the mA output circuit of the secondary instrument is interrupted. For this type of secondary instrument, this part is mainly related to the problem 2. Especially for the subsequent recorders, in the case that the recorder cannot be repaired for a long time, it is necessary to pay attention to shorting the output of the secondary meter.
7. The circuit always has no indication due to the failure of the secondary instrument flat-axle cable. Due to long-term operation, coupled with the influence of dust, the flat-axle cable is faulty, and the problem can be solved by cleaning or replacing the flat-axis cable.
8. For the problem 7, the main problem is that the secondary instrument shows that the fixing screw of the meter head is loose, causing the head to sink, the pointer and the case friction are large, the movement is not working, and the problem is solved by adjusting the meter head and re-fixing.
9. Use environmental issues. In particular, the sensor part installed in the well is affected by the humidity of the environment, which causes the circuit board to be damp. This part is mainly related to questions 2 and 2. Through the corresponding technical improvement measures, the sensor part with large humidity is re-separated from the probe part and the conversion part, and the separate type sensor is used. Therefore, the working environment is good, and the instrument has been running well.
10. Due to the poor adjustment of the site, or due to the actual situation after the adjustment. Due to the on-site vibration and noise balance adjustment and sensitivity adjustment is not good. Or because of the re-allocation of the situation after a period of operation after the adjustment, causing the indication problem, this part of the reason is mainly related to questions 4 and 5. Use an oscilloscope, plus the combined process operation, and re-adjust.