The cause and solution of the self rotation of the water meter

- Apr 07, 2018 -

1. Background:

As the State Ministry of construction requires the water supply enterprises to copy the meter to the household, one household and one table work in full swing in the national urban water supply enterprises, which reduces the old contradiction between many users and the water supply enterprises, such as the water leakage disputes and the low water pressure in the pipe network and the low water pressure of the users in the pipe network. A list of problems. However, with the continuous deepening of a household and one table, there are many new problems, such as the determination of the location of the household table, the heating of the winter, the charge of the meter reading and the rotation of the water meter, especially the problem of the self rotation of the water meter. In the early days, the screw pump was not directly connected with the water supply enterprise, and the direction of the indoor pipe and the installation position of the water meter were layered and installed. The distance between the table and the table was large and the layout of the pipe in the user's home was simple. The possibility of self rotation is less. Therefore, the user has never reflected the problem of water table rotation. With the continuous improvement of the living standard of the people, the multi-stage pump has more sanitary ware, the pipe layout is relatively complex, the water consumption is increasing, and the water cost is directly settled between the users and the water supply enterprises, the diaphragm pump and the water price are also rising. Therefore, users are also concerned about the operation of their own water meters. The problem of water meter rotation is highlighted.

Two, the cause of self rotation:

The rotation of water meter is caused by many factors, mainly for the following reasons.

1, pressure fluctuation, because water is a kind of liquid, in general, the physical characteristics are incompressible, but in the water pipe, the pipe pressure is higher, then water will show certain compressibility. In the water pipeline, the pressure fluctuation is unavoidable, and at present, the water meter we adopt is the mechanical meter, which is driven by the kinetic energy produced by the flow of the water in the water, thus achieving the purpose of measuring the amount of water. When the suction pump does not use water, there is a certain amount of fixed high pressure water in the pipe connected at both ends of the water meter. Therefore, when the pressure of the municipal pipe network rises, the volume of tap water in the back tube will be reduced because of the increase of pressure. At this time, there will be a trace of water passing through the water meter to produce a positive rotation; when the pressure is reduced, the back of the tube is compressed. The water expands due to the pressure drop, and there will also be trace water passing through the water meter. We all know that the general mechanical meter is up and up in the water when the water is inflow, and the gear pump pushes the gear forward, and when the water is poured into the water is up and down, the gear reverses, the resistance of the two phase water is different, although the two water intake is the same, the readings on the water meter are quite different. According to statistics, under the condition of no air, no amount of water is generated, which is about 0.5-1m3/ months. Usually, users will not pay attention to this water volume. At the same time, this is also a normal result at the current level of measurement.

2, the air bag causes a large amount of rotation. The production process of the water enterprise is all open in the open air. In the process of production, a large amount of gas will be dissolved in the water. At the same time, in the construction process, the gas will be brought into the pipe. If the exhaust valve on the pipe is not set, the gas of the oil bucket pump can not be well eliminated. In this way, if the family is not designed for a long time without water or pipeline design, the highest point or the starting point of the pipeline will produce air bags. As we all know, the compressibility of gas is very high, and if there is pressure fluctuation on the tube, the space expansion in the pipe will be very large after the table, so there is a lot of self rotation of the water meter. According to statistics, the resulting water volume is less than 2-3 m3/ months, and there will be more than a dozen cubic meters of water per month. According to the statistics of the report, 26 telephone calls for self rotation of the water meter are reflected by the existing users. Through the field investigation, 21 households, 80.8% and 5 leakage of water in the pipe after the meter are found. Therefore, most of the current household water meters are self rotating due to the air pocket in the rear tube.

3, the way of installation and installation quality: 1) as the water meter is mostly a unit, the household tables are concentrated in a box and installed on the first floor.  Considering the cold prevention and frost prevention in winter and the convenience of meter reading, 6 or 12 water meters are connected with a pipe of a diameter of 40mm- diameter 50mm. The distance between the table and the table is small and the straight pipe section of the water meter is few. This will also affect the normal measurement of the water meter, and cause the self rotation of the water meter. 2) installation quality. Pipeline engineering is basically buried in underground or walls, which is a hidden project. The national pipeline construction specification stipulates the installation requirements, construction procedures, acceptance criteria and notices of various pipe pipe construction, shielding the pump but in the field construction, some managers do not work according to the requirements of the standard, resulting in more or less quality problems in the pipeline.

Three. Solutions:

1, install check valve before the table, since the water meter rotation is due to pressure fluctuation, the water is compressed, can consider installing check valve, check valve can play the role of preventing water flow back flow. In this way, when the pressure rises, the water is compressed and the water meter is positively rotated. When the pressure is reduced, the check valve will automatically turn off, and the water meter will not rotate. When the pressure rises again, the water meter will not turn again as long as the pressure is not high over the inner pressure of the return valve. The self rotation of the water meter is mainly the water meter reciprocating many times before accumulating the large amount of water. The installation of the check valve can reduce the frequency of the self rotation of the water meter, and it can also solve the pressure well.

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