Why do domestic membrane gas meters need to be replaced with new ones instead of maintenance

2019.04.29 13:44:17

1、 The state stipulates that the service life of gas meters shall not exceed 10 years

In August 1991, the State Bureau of Technical Supervision issued the relevant provisions on the verification of work measuring instruments subject to compulsory verification, which stipulates that domestic gas meters shall only be subject to compulsory verification for the first time, use within a time limit and rotate at the expiration. The verification regulation of membrane gas meters (jjg577-2005) clearly stipulates the service life of gas meters: for gas meters (household meters) with maximum flow Qmax ≤ 10m3 / h and used for trade settlement, only the first compulsory verification shall be carried out, which shall be used within a time limit and replaced at the expiration. The service life of gas meters with natural gas as the medium generally does not exceed 10 years. The service life of gas meters with artificial gas and liquefied petroleum gas as the medium is generally no more than 6 years.

There is no follow-up verification for domestic membrane gas meters, but only the first compulsory verification. They shall be used within a time limit and replaced at the expiration of the time limit. There is only in-service inspection in the middle, and the requirement for the maximum allowable error is doubled, but the understanding of why to relax is different. Some people believe that the requirements for domestic membrane gas meters are relaxed because they have been used for a period of time; Some people think that the in-service inspection is carried out on site (the accuracy, installation conditions and verification control conditions of the standard are not as good as those in the laboratory); After the membrane gas meter is installed, the influencing factors of strong strain lead to the relaxation of the index. Different departments will have differences from different interests and functions. For example, a membrane gas meter that has passed the first inspection and has not been used for a long time is removed and returned to the laboratory for verification due to measurement disputes. Is this subsequent verification or "in-service inspection"? Since the requirements for the maximum allowable error of measurement in these two cases are twice the same, it is easy to have disputes. There shall be no cross between in-service inspection and subsequent verification. The national technical specification specifies that the purpose of in-service inspection is to check whether the verification mark or verification certificate of the gas meter is valid, whether the protection mark is damaged, whether the state of the gas meter after verification has been significantly changed, and whether the error exceeds the maximum allowable error in use (no verification certificate is issued for in-service inspection).

Hardware reasons why the error of in-service inspection is doubled after installation:

According to the bending moment requirements in 6.2.6.3.2 of membrane gas meters (GB / t6968-2011), the gas meter shall be able to withstand the specified bending moment. During and after the test, the tightness of the gas meter shall meet the requirements. After the test, the residual deformation of the pipe joint shall not exceed 5 °; Before the bending moment test, the indication error of the tested gas meter shall meet the requirements; After the bending moment test, the test value error of the tested gas meter shall be tested again. The indication error shall be within the specified maximum allowable error limit. The installation must bear the corresponding bending moment, which is caused by the fact that the threaded joint and pipeline are not in an absolute plane. Therefore, the membrane gas meter tested after installation must be unreasonable according to the first verification error requirements, and can only meet the maximum allowable error limit of durability (i.e. double the maximum allowable error) according to the requirements of GB / t6968-2011.

"In use inspection" needs a clear boundary. Since it is a regulation, it may not be 100% fair. Membrane gas meter, no matter installed for one day or several years, definitely belongs to "in-service inspection".

To sum up, we uniformly define that membrane gas meters belong to "in-service inspection" after installation, regardless of the length of installation time.

2、 Livelihood safety measurement

The replacement of gas meters according to the service life stipulated by the state is not only related to people's daily life, but also related to people's home safety. The expiration replacement of gas meter is more important than water meter and electric energy meter, because if the water meter and electric energy meter are used beyond the time limit, it only involves the problem of inaccurate trade settlement, and the gas meter also involves the problem of safety.

Overdue gas meters will not only cause inaccurate measurement, but also bring serious potential safety hazards to families. The extended service of the gas meter directly leads to the aging of the sealing filler of the gas meter body and the loss of mechanical firmware, resulting in inaccurate measurement of the gas meter, and is prone to gas accidents caused by the leakage of the gas meter body, which directly threatens the life and property safety of users. Therefore, the use of gas meters in extended service has great potential safety hazards.

Some people want to consider from the perspective of so-called "economy and economy": whether the membrane gas meter can prolong its service life and use it for another cycle after passing the test. Or repair it and continue to use it for 10 years. Is this really "saving"? Let's calculate the account: at present, an ordinary household membrane gas meter with qualified quality is about 100 yuan. According to the 10-year conversion, the depreciation expense apportioned to each year is about 10 yuan.

First, what is the maintenance value of membrane gas meter after 10 years? The aluminum of the aluminum case watch can be recycled, but the steel case watch has no recycling value, because after 10 years of use, the shell has almost rusted and can no longer be used, and the movement inside is almost unavailable. In addition, after 10 years of process progress, there is no maintenance value at all. The cost of maintenance is even higher than that of a newly manufactured membrane gas meter.

Second, a watch that saves 100 yuan cannot be compared with the life safety of several people in a family. The practice of prolonging the domestic membrane gas meter without authorization is to ignore people's life safety.

Compared with the accuracy of gas meters, the safety of gas meters is more important. Gas meters that have been used for more than years will bring serious potential safety hazards to families. Due to the gas impurities, humidity and salt spray corrosion resistance of the service environment, the sealant in the gas meter is aged, and the joint between the meter case and the joint is rusted, which will form internal or external air leakage. Once it is leaked, it may cause loss of family property, or personal injury and death, and the consequences are very serious.

According to the working principle of the gas meter, the inner membrane of the gas meter will age and deform after a certain service life, resulting in the reduction of the volume of the metering chamber and the error change. With the passage of time, this change is gradually accelerating, making the error of the gas meter bigger and bigger.

In fact, strictly following the requirements of the national verification regulations can ensure that each household can use a safe and accurate gas meter. If the newly installed gas meter is verified for the first time and replaced according to the service life specified by the state, the safety and accuracy of the gas meter are guaranteed.