Flow Meters and Liquid Level Meters in the Sewage Treatment Process

1. Flowmeters

The flowmeter is used to measure the flow of the measured medium, which is simply to measure the fluid flow in open channels or pipes. According to the working principle, common flow meters are divided into differential pressure type, liquid level type, ultrasonic type, electromagnetic type, etc. Taking the electromagnetic flowmeter as an example, based on the electromagnetic induction principle, the flow is measured according to the electromotive force generated when the conductive fluid passes through the external magnetic field. It can be seen that the electromagnetic flowmeter has high accuracy, no pressure loss, and excellent waterway form. The measurement is not affected by the change of fluid density, viscosity, temperature, pressure, and conductivity.

According to the working environment of the electromagnetic flowmeter, select reasonable sensor lining and electrode materials to ensure that the lining and electrode materials have strong corrosion resistance and wear resistance. In the sewage treatment process, the electromagnetic flowmeter is used at the inlet pipe of the sewage regulating tank. The magnetic poles at both ends of the electromagnetic flowmeter need to be cleaned regularly to ensure that the magnetic poles are not attached to the impurities in the sewage so that the flow into the sewage regulating tank can be measured. After the electromagnetic flowmeter is installed in a standardized way, the operator can judge the total amount of sewage treated according to the change value of the inlet flow of the sewage regulating tank. Moreover, the electromagnetic flowmeter has the advantages of simple installation and use, less maintenance work in the later period, etc.

2. Supmea sewage-type electromagnetic flowmeter

Sewage type electromagnetic flowmeter is also an indispensable instrument for measuring the discharge in the sewage treatment process. Now let's briefly understand some knowledge about Supmea sewage electromagnetic flowmeter:

The basic principle of the electromagnetic flowmeter is that a pair of magnetic poles N and S are installed outside the pipe made of general non-magnetic materials to generate the magnetic field. When the conductive liquid flows through the pipeline, the magnetic induction electromotive force is generated because the fluid cuts the magnetic line of force. The induced electromotive force is led out by two electrodes perpendicular to the magnetic pole. When the strength of the magnetic field is unchanged and the diameter of the pipeline is fixed, the magnitude of the induced electromotive force is only related to the flow rate. The magnitude of the induced electromotive force can be read by passing it to the display instrument.

Advantage:

1) There are no movable parts and blocking fluid in the measuring pipe, so the pressure loss is very small and there is no mechanical inertia, so the response is sensitive;
2) Wide measurable range: the measuring range ratio is generally 10:1, up to 100:1, and the flow velocity range is generally 1-6m/s, which can be extended to 0.5-10m/s; The flow can range from 90mL/h to more than 100000 m3/h; The pipe diameter can range from 2mm to 2400mm or 3000mm;
3) It can measure the volume flow of liquid containing solid particles, suspended solids or acid, alkali, and salt solution with a certain conductivity, and also can measure the pulsating flow, and can conduct two-way measurement;
4) There is a linear relationship between the flow signal and the fluid volume flow, so the instrument has a uniform scale; Moreover, the volume flow of the fluid is independent of the physical property and flow state of the medium, so the electromagnetic flowmeter can be used to measure the volume flow of other conductive liquids without correction after being calibrated with water;
5) Compared with most other flow meters, the requirements for the front straight pipe section are lower.

Disadvantages:

1) The operating temperature and pressure shall not be too high;
2) Due to its limited application scope, it can not be used to measure the flow of non-conductive fluids such as gas, steam, and petroleum products and fluids containing more large bubbles;
3) When the velocity and velocity distribution do not meet the set conditions, large measurement errors will occur;
4) When the flow rate is too low, it is difficult to amplify and measure the induced potential of magnitude opposite to the interference signal, and the instrument is prone to zero drift;
5) The signal of the electromagnetic flowmeter is relatively weak, and the measurement accuracy can be affected by slight external interference.

It can be said that the advantages of the sewage-type electromagnetic flowmeter outweigh the disadvantages because according to our understanding of Hangzhou Supmea in the sewage treatment industry for more than ten years and the use of the products, the disadvantages of the sewage-type electromagnetic flowmeter can be almost ignored on the site. Therefore, as long as there is a demand for electromagnetic flowmeter in sewage treatment, as long as you find our Hangzhou Supmea, you can properly provide a perfect solution.

3. Level Meters

The height of the liquid in the container is the liquid level, and the instrument for measuring the liquid level is the liquid meter. According to different principles, common liquid level indicators are differential pressure type, static pressure type, air blowing type, float type, ultrasonic type, etc.

Take the ultrasonic level meter as an example. During the measurement, the sensor sends out an ultrasonic pulse. When the sound wave reaches the liquid surface, it is reflected. The receiver receives the reflected signal and converts it into an electrical signal. The liquid level value is calculated by calculating the time difference between the transmission and reception of the sound wave. The ultrasonic liquid level meter has good accuracy when measuring liquid levels, does not touch liquid surfaces, and has a wide measuring range, which is almost applicable to all kinds of liquids; It has the suppression function of interference echo and strong anti-interference ability to ensure the authenticity of measured data.

The ultrasonic level transmitter has the advantages of low price, small volume, lightweight, long service life, and high-cost performance. However, it should be noted that the ultrasonic level sensor has a blind area, and the distance between the reserved installation position of the sensor and the measured liquid must be calculated during installation. In the water treatment process, an ultrasonic level gauge is installed on the top of the regulating tank, which can monitor the water level in real time and transmit the measured data to the DCS controller for data analysis, processing, and storage, so that the operator can adjust the process parameters according to the measured results.