Analysis on the application of electromagnetic flowmeter in water supply industry

Flow rate is a commonly used process control parameter in industrial production and an important production technology indicator in the water supply industry. The accuracy of flow measurement will affect the correct calculation and credibility of important indicators such as the cost accounting and energy consumption of the enterprise. Therefore, it is crucial to choose a flow meter with high quality, stable operation and accurate measurement.

With the development of science and technology, new flow meters are constantly emerging, with various varieties and different performances. Their use conditions and technical parameters are also different. We have carefully analyzed, compared and demonstrated the actual application of various flow meters used in the past, the existing problems, the difficulty of installation, the performance-price ratio and other issues. We believe that the electromagnetic flow meter has the advantages of sensitive response, good linearity, high accuracy, and is not affected by the temperature and viscosity of the measured medium during the measurement process. Therefore, in the selection of flow meters, the electromagnetic flow meter produced by Chengde Decheng Electronics Co., Ltd. is mainly selected.

After years of practical application, we have realized that in order to make the electromagnetic flow meter run safely and stably, we should create better on-site conditions, and strictly follow its technical requirements for correct installation and commissioning, and implement centralized management to ensure the normal operation of the electromagnetic flow meter and achieve continuous and accurate measurement. The following is the specific practice of our company in the application of electromagnetic flowmeter (taking the electromagnetic flowmeter of Chengde Cheng Electronics Co., Ltd. as an example) for discussion.

1. Selection of the installation location of the electromagnetic flowmeter

The installation location of the electromagnetic flowmeter should meet the requirements of the electromagnetic flowmeter for the front and rear straight pipe sections, that is, the length of the upstream straight pipe section of the electromagnetic flowmeter is greater than 5D (D is the pipe diameter), and the downstream straight pipe section is greater than 2D, so as to ensure the axisymmetric distribution of the flow velocity and eliminate the measurement error caused by it.

The installation location of the electromagnetic flowmeter should avoid strong vibrations, avoid strong interference sources, and the pipe should be filled with water.

2. Correct installation of the electromagnetic flowmeter

1.

Installation of the sensor The installation of the electromagnetic flowmeter is divided into the installation of the sensor and the installation of the converter. In particular, the installation of the sensor requires water stoppage, pipe cutting, water pumping, welding or punching, which makes the installation work more difficult and requires long-term water stoppage, resulting in certain economic losses. In response to this situation, when we installed the flowmeter on the cast iron pipe, we adopted a new process method, replaced the traditional short pipes A and B with two single-disc compensators, cancelled the punching process and the maintenance time of the pipe mouth, especially when the valve is not closed too tightly, it can be operated with water. After the water supply is cut off, it only takes half a day to install a sensor to restore the water supply, thus shortening the installation time, reducing the economic losses caused by the water outage, and achieving certain social benefits.

2. Good grounding of the sensor housing is a necessary condition to ensure the normal and stable measurement of the flowmeter.

People generally believe that the sensor is installed on a metal pipe, and the pipe is buried underground, and the pipeline is very long. It is a large grounding electrode in itself, and the instrument does not need to be grounded. However, two problems are ignored. One is that the pipeline is generally treated with anti-corrosion, and the other is that the connecting flange and the pipeline are separated by a hole or a rubber pad, which greatly increases the grounding resistance of the sensor and affects the normal operation of the electromagnetic flowmeter. In

actual application, we once had an electromagnetic flowmeter that did not work properly after it was put into use. The flow display was sometimes there and sometimes not, and even an empty pipe alarm prompt appeared. At that time, there was no result in finding the cause according to the fault phenomenon. Later, a separate grounding electrode was made for the sensor, and the fault phenomenon disappeared immediately, and it has been running normally since then.

Therefore, after the electromagnetic flowmeter is installed, the grounding resistance should be measured. If the resistance is too large, it is best to make a grounding electrode to reduce the interference potential caused by stray current.

3. Usage

After several years of actual operation and observation comparison, we believe that the operation of the electromagnetic flowmeter in our company's production is better than the working conditions of other instruments used before.

1. The electromagnetic flowmeter has high precision, good linearity, and stable operation, which improves the accuracy of measurement and the credibility of data, and overcomes the problem that some instruments are not stable, resulting in unreliable measurement data. After many on-site comparisons, the errors are all within the control range, which enhances the degree of trust in the instrument, ends the unscientific measurement method of calculating the water volume according to the performance curve of the water pump, and actually takes the instrument collection data as the standard, avoiding human factors.

2. The electromagnetic flowmeter has a simple structure, the sensor has no moving parts, and there is no measurement error or instrument failure caused by mechanical movement wear or impurity entanglement. Therefore, the failure rate is very low, and the maintenance volume is greatly reduced, thereby saving a lot of manpower and material resources.
3. The electromagnetic flowmeter has a variety of interface circuits, which can be easily connected to the data acquisition terminal or computer to realize the automation of data collection, analysis and management.

IV. Management of electromagnetic flowmeter

1. Establish an electromagnetic flowmeter operation file, which includes the manufacturer, model, production date, installation location, pipe diameter, calibration time, etc. of the flowmeter, in order to facilitate the maintenance and management of the meter.

2. Strengthen patrol inspections and conduct regular testing and calibration. We mainly use two methods. One is to use a relatively high-precision portable flowmeter to measure and compare with the electromagnetic flowmeter; the other is to use a flow meter calibrator to calibrate the flow converter, check whether the various technical indicators are correct, and archive the test data.

3. Compare the test data with previous test results, carefully analyze and study the suspicious data, find out the possible causes, deal with and solve them in a timely manner, and make an analysis report on the operation of the flowmeter. (end)