Depth analysis of water meter use regulations and current situation analysis and solutions

by law

According to the relevant laws and regulations of the water meter, for the residential domestic water meter (the general nominal diameter is less than or equal to 50mm, and the commonly used flow rate does not exceed 16m3 / h), the "first mandatory verification, limited use, expiration rotation" method is implemented, and the period of use is implemented. It is 6 years (water meter with nominal diameter of 25mm and below) or 4 years (water meter with nominal caliber > 25mm to 50mm); the verification period of industrial water meter (generally nominal caliber is more than 50mm or common flow exceeds 16m3 / h) is generally 2 years.

Use status

Due to various reasons, the ordinary civil water meter can not perform the prescribed cycle rotation. Once it is put into use, it often works continuously for many years, which causes the metering performance of the water meter to deteriorate, and the measurement "misalignment" problem occurs. The water meter is a relatively precise measuring instrument. The internal gears and gears, the worm gear and the worm, the character wheel and the dial wheel are very precise. The wear of the parts during long-term use will affect the performance of the water meter. Problems such as fouling, water inlet holes, and clogging of the filter mesh holes and the position of the impeller space may cause the performance of the water meter to deteriorate, thereby causing measurement misalignment. The appearance of the new factory table is shown in Figure 1. After several years, the typical appearance is shown in Figure 2. The appearance is very dirty.

Error trend analysis

For the water meters in use in Guangzhou, the author randomly checks 100 of them for the indication error verification. The data summary results for 10 consecutive years are shown in Figure 3. It can be seen from Fig. 3 that with the increase of the service life, the probability of misalignment of the indication error of the water meter increases greatly, which affects the fairness of measurement. Taking the three error intervals of 0 < | E | ≤ 1* MPEV, 5* MPEV < | E | ≤ 10* MPEV, 15*MPEV < | E | ≤ 20* MPEV as an example, draw the water meter shown in Figure 4. Misaligned trend chart. For water meters (qualified) with 0 < | E | ≤ 1* MPEV, the proportion of qualified with the increase of years is decreasing year by year; for water meters with 5* MPEV < | E | ≤ 10* MPEV (general misalignment), It has hardly appeared in the first 2 years, starting from the third year and reaching a peak in the sixth year; for the water meter (severely misaligned) of 15 * MPEV < | E | ≤ 20 * MPEV, it has barely appeared in the first 5 years. It has risen year by year since the 6th year and peaked in the 10th year. It can be seen that with the increase in the number of years of use, the probability of water meter misalignment increases year by year, and measures must be taken to deal with it.

Influencing factor

According to the sampling analysis, the main causes of water meter misalignment are as follows. The probability distribution is shown in Figure 5. It can be seen that the selection of water meters, the quality of installation and the quality of water supply are important reasons for the water meter misalignment.

1

product quality

The misalignment of water meters during the life cycle can be divided into two categories: permanent and temporary. The permanent misalignment is to indicate that the water meter component is not up to standard when the factory is in the process, or that the water meter movement and the damage caused by the external movement cause the water meter to be misaligned, and can only be used after replacement or repair; and the temporary misalignment is Due to the accidental phenomenon caused by external factors, the internal movement of the water meter is not damaged. If it can be found in time, it can be corrected or restored by cleaning. Obviously, the product quality of the water meter directly affects the accuracy of the water meter. Therefore, it is necessary to select a water meter product produced by a regular manufacturer that has the national manufacturing measuring instrument license mark and has passed the qualification of the technical supervision department. The appearance of the water meter produced by a regular manufacturer is shown in Figure 6. The appearance of a typical product produced by a non-regular manufacturer is shown in Figure 7.

2

Water meter selection

The selection of water meters also directly affects the use of water meters. Selection includes the caliber (flow range), mechanical structure, material, and water quality of the water meter. The selection of the diameter of the water meter should ensure that the normal water flow rate of the user is between the commonly used flow rate and the minimum flow rate of the model; when the water quality is good, the volumetric water meter can be used, and vice versa, the rotary type water meter should be used. When the diameter is large, the screw type water meter should be used. Mainly; when the pipeline pressure is large, the water meter of engineering plastic material is not suitable, and the water meter of stainless steel should be considered when the water quality is poor.

3

Installation quality

The installation quality of the water meter includes the installation location, the environment, and the technical requirements of the installation process. The survey found that the problem of misalignment due to installation quality has accounted for more than 50%. The installation location is not easy to be selected, so that the water meter is affected by external vibration and pipe water pressure changes, which makes the water meter movement wear more intensive; the influence of installation inclination, the straight pipe section before and after the installation position is also very important; in addition, the water meter installation environment is too humid, Direct exposure to the sun, or by organic gas, will accelerate the rust of the water meter. Therefore, the installation location of the water meter and the scientific rationality of the installation method should be guaranteed.

4

Water supply quality

According to the survey, the worse the water quality of the urban water supply, the lower the accuracy of the water meter. There are two main situations in which the water supply quality adversely affects the accuracy of the water meter:

First, the solid impurity particles entrained in the water, such as sand, hemp, and the inner wall of the pipe, etc., block the internal pipeline of the water meter;

Second, the organic matter (such as iron, salt, etc.) contained in the water exceeds the standard, which is likely to cause corrosion inside the water meter. Both of these conditions can result in inaccurate metering.

Of course, the quality of the water supply also has a lot to do with the quality of the water pipe. As shown in Figure 8, this severely rusted old water pipe will obviously cause the water quality to deteriorate.

5

usage habit

Some of the user's water use habits will also indirectly affect the metering accuracy of the water meter. Some users will open the water to a small amount, and the flow will be dripping. At this time, the reading of the old model water meter that does not meet the standard flow rate will not move; some users have the habit of frequently opening and closing the faucet, which will also cause measurement. The error is mainly due to the large inertia of the impeller when it starts to rotate. It will only be eliminated when it is used continuously. In addition, the air is mixed with air, and the residual air is stuck in the upper adjustment plate, so that the adjustment plate counters the water. The effect is significantly weakened, and the effect is only eliminated when the air is discharged from the water meter.

Countermeasures

In order to ensure the fairness of production and domestic water consumption, the following countermeasures are proposed for reference.

(1) Strengthen the management of metering licenses for water meter manufacturing, and make access to good water meter production; conduct special inspections of water meter product quality at least twice a year, so that there is no living space for inferior water meters.

(2) According to the requirements of on-site water flow range, water quality, working environment, etc., carefully select the water meter, and ask the industry experts to check if necessary.

(3) The quality of the on-site installation of the good water meter is strictly controlled; the turbidity of the factory water is strictly controlled to prevent the filter pool and deep well from leaking sand, and the clear water pool is cleaned regularly; the regulations on flushing and sewage disposal in pipeline laying and repair are strictly implemented, and the inner wall coating of the pipeline is improved. The quality of the old water pipes should be replaced in time.

(4) Strengthen the implementation of JJG162 - 2009 "Regulations for the Calibration of Cold Water Meters", do the first verification and periodic verification of water meters; vigorously implement the system of strong inspection and filing to ensure the periodic verification of water meters according to law.

Conclusion

The problem of misalignment in the use of water meters has always been a focus of problems in the metering industry. Fortunately, there have been some targeted research work in the industry. Based on the experimental research data for ten years, the author puts forward five main factors affecting the metering performance of water meters, and gives corresponding solutions, which lays a solid foundation for reducing the probability of water metering misalignment.

At the same time, the viewpoint of this paper also has a high reference value for the technological innovation of urban water supply departments and technical management departments.