About air pressure test and liquid column static pressure of medium during operation

This post was last edited by zjq1962 on 2018-12-29 08:09 During the air pressure test, the results of the vertical and horizontal tests are the same. My understanding is that the air pressure test does not need to consider the static pressure of the liquid column.

I don’t understand that your equipment is installed vertically. The liquid column pressure of the working medium is 03mpa, which means that the pressure of this equipment must be greater than 0.3mpa. On this basis, the maximum working pressure can be added according to the multiple of water pressure and air pressure. It will not be lower than the maximum working pressure. This is the macro explanation. For reference.

You have misunderstood several issues. Air pressure does not add liquid column static pressure. Even in hydraulic experiments, yours is wrong. The working liquid column static pressure is different from that in the experiment. You have confused them.

For this problem, the typical design pressure is 0.1 and the liquid column static pressure is 0.3. If the medium during equipment operation is liquid, there are two situations:: 1. If the medium fills the inner cavity of the equipment, the liquid column static pressure must be included in the design pressure, and there is no need to consider the liquid column static pressure in the vertical hydraulic test. ； 2. If the medium does not fill the inner cavity of the equipment, the static pressure of the liquid column should be increased when using vertical water pressure. The value is the difference between the liquid level and the total height of the equipment during normal operation. If the medium during equipment operation is gas, then there is no need to consider the static pressure of the liquid column during the air pressure test.

I have never encountered this problem before, it is quite interesting. I guess the poster thinks so.: When 0.11MPa is used for the test, there is no problem in checking the upper head. However, the calculated pressure of the lower head is already 0.4MPa. At this time, using 0.11MPa as a strength check for the lower head has no effect at all. GB/T 150.1 Medium 4.6.2.1 Clause b) of: “When the static pressure of the liquid column of the built-in medium is greater than the static pressure of the liquid column in the hydraulic test under working conditions, appropriate consideration should be given to increasing the test pressure accordingly." This is clearly a "hydraulic test", so when using pneumatic testing, should it be considered? Why not stipulate that "increasing the test pressure should be considered during the pressure test?" I think it is based on the danger of the pneumatic test. According to the regulations on the withstand voltage test, this is what it says: The minimum value of the pressure test pressure is as specified by the XXXXX formula ； So the standard is very clear that this is the minimum value, which can be higher but not lower. When the pressure is higher than the pressure calculated by the formula, stress verification of the pressure resistance test is required, which is the requirement of Article 4.6.3. Therefore, to sum up, the regulations do not mandate that it is not allowed to increase the test pressure of the air pressure test. When increasing the test pressure, all aspects should be considered, that is,: You can do it as long as the law does not prohibit it - you are not wrong, there is nothing wrong with you. I suggest that the landlord should seriously consider the following points:: 1. Is it necessary to conduct air pressure test? If hydraulic test can be used, try not to use air pressure test. ； 2. Is there a big thickness difference between the upper head and the lower head? If the air pressure test pressure is increased rashly, it may be difficult to pass the stress check of the upper head. ； 3. For the air pressure test, the risk is greater due to the compressibility of the medium. From this perspective, it is not recommended to increase the air pressure test pressure too much.

The pressure for air pressure test should be 0.41MPa

I have some questions about this poster's post, "The static pressure of the liquid column of the medium during operation is 0.3MPa" and the design pressure is 0.1MPa?

1. According to GB/T150, considering the static pressure of the liquid column during the test is for the hydraulic test. If the static pressure of the liquid column is considered in order to test the strength of the lower head and cylinder, then the stress level of each pressure component under the test conditions must be checked according to standard 4.6.3. 2. The second method is to increase the design pressure. Of course, this must take into account the manufacturing cost.

This post was last edited by zjq1962 on 2019-1-3 15:31. A question arises from this. For vertical equipment with relatively high heights, the working medium is gas phase. When performing vertical hydraulic tests, the actual pressure endured by the components exceeds the withstand pressure test value specified in GB/T150.1. Although the standard does not indicate it, in this case, the stress of each component should also be checked.

The first point is that you don't have a clear idea about design pressure and calculated pressure. What is the liquid column static pressure included in the design pressure? Second point, I still don’t know what the pressure value is? Because the density of the liquid medium is greater than water during normal operation, the static pressure generated at the bottom is greater than the static pressure during the hydraulic test. This part should be considered both in the vertical version and in the horizontal version.