Abnormal causes of sewage flow meter and solutions

Abnormal causes of sewage flow meter and solutions:

Sewage flow meters are measuring instruments that measure the cumulative volume of water in a pipeline. At present, most of the company's sewage flow meters use electromagnetic flowmeters. It is a speed-type water meter and uses the principle of Faraday's electromagnetic induction law. There are many phenomena and causes of flowmeter metering anomalies. I will analyze the characteristics of the water supply pipe network and the flowmeter itself based on the actual work. The following phenomena and causes are mainly involved:
Phenomenon 1: Many users' water meters have slow rotation when they are not using water. The performance occurs when the water meter starts to move and stops, and sometimes it takes three rounds to retreat. This phenomenon is more obvious during the peak period of water use, which we call the phenomenon of water meter rotation.
Reason (1): Water pressure fluctuation According to the working principle of the water meter, we know that the water meter is driven by the kinetic energy generated by the flow of water in its surface to drive the rotation of the impeller to drive the metering device to measure. Without the use of water, the water pressure in the pipeline connecting the two ends of the water meter is balanced. After the implementation of the “one household, one surface” reform, the water meters of the same unit are basically installed in one place and are closely spaced. When the adjacent user's valve is momentarily opened, the original pressure balance is destroyed, the pressure in the front tube of the connecting main pipe is lower than the pressure in the back of the watch, and the water under pressure after the watch expands due to the pressure decrease before the watch, and there will be a small amount The water flows through the water meter and impinges on the impeller, forming a reversal, so that the pressure reaches equilibrium. When the valve is suddenly closed, the water pressure inside the tube will increase rapidly. At this time, the pressure before the watch is greater than the pressure behind the watch. After the watch water will shrink due to pressure, there will be a small amount of water flowing through the water meter. Turn to reach a new pressure balance. Due to the influence of the structure of the water meter, the resistances that flow through the water meter in different directions are different. Although the water intake is the same, the rotation speed of the impeller is different, and the forward rotation is faster than the reverse rotation. However, when there is no air in the pipeline, the resulting amount of water is less, generally no more than 1m3 per month.
In fact, the most fundamental reason for water meter rotation caused by water pressure fluctuations is the presence of air in the pipeline. We know that gas has a strong compressibility. When the water pressure increases, the air is squeezed by the water stream at the high points of the pipeline or water appliances to form a compressed gas. At this time, the water pressure equals the pressure and is in equilibrium; when the water When the pressure is reduced, the pressure is greater than the water pressure, the compressed gas expands, and the water is pushed back, so that the water flow moves to drive the rotation of the impeller. For most water meters, the positive rotation number is greater than the reverse rotation number, and the compressibility of the gas is very strong. If there is air in the pipeline behind the watch, the expansion space will be greatly affected by the water pressure fluctuations. The amount of water produced is relatively large; when neighboring users use water more frequently, the amount of water that is generated as a result is less (2 to 3) m3 per month, and as many as ten cubic meters.
In fact, there are many situations in which air is trapped in pipelines. For example, tap water will have a large amount of gas dissolved in the process of production and water supply. At the same time, in the maintenance of pipelines, replacing water meters and reforming pipelines will also bring in gas, and in addition, it will happen. There will also be gas left in the pipe network that stops the water area, as well as in the solar water heater and the end of the pipeline.
1. Installation of Check Valves In order to prevent water pressure fluctuations from affecting metering, installing a one-way check valve in front of the watch can prevent water backflow. When the water pressure before the watch is greater than the pressure after the watch, the water behind the watch is compressed and the water meter produces positive rotation; when the water pressure before the watch drops, the check valve closes automatically under the effect of the pressure behind the watch, and the water meter does not rotate. When the water pressure before the watch rises again, as long as the pressure does not exceed the pressure after the check valve, the water meter will not turn again. Therefore, installing a one-way check valve can reduce the frequency of rotation of the water meter, and it can also well solve the water metering anomaly caused by water pressure fluctuations.
2. The air in the tube is evacuated because the air in the tube has a great influence on the metering of the water meter. Therefore, it is necessary to exhaust the meter of the newly installed or modified tube. When exhausting, all the valves of the water equipment should be opened one by one, try to exhaust the air in the tube, reduce the air content in the water, and for users who are long-term out or unoccupied, close the rear valve of the user's water meter that does not live. Avoid mixing the gas into the pipe due to water stoppage, and cause the water meter to rotate due to the fluctuation of the pipe network water pressure.
Reason (2): The installation is not standardized Now, most of the “one household, one table” transformation will be the same unit of the household table installed in the same place on the first floor. Considering the beauty, economy, and convenience of meter reading, it is common to connect 6 to 12 water meters with a pipe of Φ40 mm to Φ50 mm, and the distance between the tables is small, and the straight pipe section connected to the water meter is also shorter [2]. When the water meter is too close to the supervisor, these conditions can easily cause the water meter to fluctuate due to the water pressure in the main pipe and a metering anomaly occurs.
Sewage flow meter measures:
1) Pay attention to the installation quality The quality of water meter installation will directly or indirectly affect the accuracy of metering. The installation of the water meter must comply with GB/T778.2-2007 "Measurement of Water Flow in Closed Full Pipes Part II: Installation Requirements for Drinking Water Meters and Hot Water Meters". When installing, care should be taken to remove water meter plugs and protect them. Good port of the pipeline to avoid impurities into the pipeline, if necessary, clean the pipeline before installation, install the water meter to keep the water meter end is not tilted; the water meter must be installed on the straight pipe section of the pipeline, the water inlet side, outlet side of the water line The length of the pipe segment shall not be less than 10 times and 5 times of the diameter of the water meter respectively. The pipe diameter on the inlet side of the water meter shall be greater than or equal to the inlet diameter of the water meter; when selecting the water meter, the water meter shall not be too close to the main pipe and be below the floor. For centralized safety monitoring, the water meter on the roof of the building should be connected to the front of the main pipeline, and the water meter on the downstairs should be connected to the back end of the main pipeline. This will reduce the impact of water fluctuation on the water meter.
Phenomenon 2: The user's water meter has continuous rotation when not using water. The performance of the water meter starts moving continuously and constantly when the pointer is not used. When the total valve is closed after the watch is turned, the rotation speed becomes slow or does not turn.
Cause: This phenomenon is mainly caused by leaking of water pipes or user equipment in the user's home. Leakage of water from faucets and pipes is relatively easy to spot, but most users will bury the pipe network in the wall or underground during the renovation. It is difficult to find if the pipe leaks. In addition, leaking water in toilets and pipes near the floor drain is not easily noticeable. Therefore, the leakage of water will cause the flow of water in the pipeline, causing the water meter to continuously and continuously rotate, and the amount of water used will rise substantially, which will cause metering anomalies.
Measures: Exclude leaks from the pipe network. Check the water leakage of the pipe network. Observe whether the water meter rotates. Turn off all the faucets in the house and observe the start pointer of the water meter. If the pointer moves steadily and continuously, it indicates that there is leakage in the pipe. Focus on the interface of the water heater, the connection between the washbasin, the laundry pool elbow or the living connection, and the elbow fitting near the floor drain. In particular, check the toilet for water leakage (this can be done from the water left in the toilet. Whether there is water ripples to see), it is found that there are leaks should be ruled out in time.

Extended reading: Ming Yu controlled flow meter

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