[Weekly Topic] Let’s discuss the practical problems everyone encounters in their daily work (2011.08.08~8.14)
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This post was last edited by wangjianwei86 on 2011-8-8 09:13. The topic here is quite good – it combines problems encountered in practice with the specific provisions outlined in texts. I believe such topics can help people gain a better understanding of written descriptions. Building on this theme, relevant practical issues are also discussed together, and I encourage everyone to share their opinions actively. 1. Regarding pressure vessels, the design pressure should be higher than the opening pressure of the safety valve. The pressure used for the airtightness test is equal to the design pressure. Regulatory requirements state that the safety valve must be installed during the airtightness test, and its opening pressure is lower than that of the airtightness test pressure; will it be possible to conduct such a test? I find this a bit contradictory. 2. There are several nouns here; let’s discuss the sequence of operations in practice: sandblasting for rust removal, anti-corrosion paint (primer), topcoat, hydraulic testing, welding repairs, heat treatment, airtightness testing, pickling and passivation, material cutting, welding, riveting, installation of nameplates, cold working, hot working, material procurement, third-party inspection, and so on. (It’s not necessary to include every item, but at least three should be mentioned along with an explanation of the sequence. Note: Do not repeat the sequence already provided by someone else.)
This issue has been discussed on the forum; it’s important to know how to use search effectively. The design must specify the maximum allowable operating pressure for this container; the setting of the safety valve should be a value greater than the design pressure but equal to or less than the maximum allowable operating pressure.
Reply to 2# liushen203: Thank you, user number 2. Why is it said that the operating pressure is greater than the design pressure? According to Appendix B6.2b of GB150-1998, the design pressure should be greater than or equal to the opening pressure.
Reply 3# zwj2009: Appendix GB150 does not address whether a leak test is required or not. In other words, it’s not required that the airtightness be greater than or equal to a certain value; instead, it’s sufficient that the airtightness be greater than that value, with the overall value being greater than or equal to the specified threshold.
Reply to 4# liushen203: It’s not correct either to use a pressure that is greater than the required value for airtightness. The value should be greater than the design pressure but less than the opening pressure of the safety valve. The pressure used for the airtightness test should equal the design pressure. According to regulatory requirements, the safety valve must be installed during the airtightness test; if its opening pressure is lower than the design pressure, won’t there be leaks during the test? What should be done?
Please read carefully my reply on the 2nd floor. Additional note: The maximum allowable operating pressure is generally higher than the design pressure. Do not repeat your question; it is recommended that you search for relevant posts now, and become a technical professional who can identify and solve problems.
Reply to 5# zwj2009: What was said above is already very clear – what’s required is that the designer specify the maximum allowable operating pressure for this device! ! When testing for airtightness, set the discharge pressure of the safety valve to a value higher than the design pressure, but lower than the maximum allowable operating pressure! Then a airtightness test is conducted.
Reply to 6# liushen203: It means that when a gas-tightness test is required, the opening pressure of the safety valve can be higher than the design pressure of the container, but it must be lower than the maximum allowable operating pressure. I have a container that needs to undergo a gas-tightness test. Its operating pressure is 2 MPa, the design pressure is 2.2 MPa, and the maximum allowable operating pressure is also 2.2 MPa. So what should be the appropriate setting for the safety valve’s opening pressure?
Reply to 7# wangjianwei86: It means that when a gas-tightness test is required, the opening pressure of the safety valve can be higher than the design pressure of the container, but it must be lower than the maximum allowable operating pressure. I have a container that needs to undergo a gas-tightness test. Its operating pressure is 2 MPa, the design pressure is 2.2 MPa, and the maximum allowable operating pressure is also 2.2 MPa. So what should be the appropriate setting for the safety valve’s opening pressure?
Reply to 9# zwj2009: Setting the pressure to 2.1 Mpa will work. However, during the actual airtightness test, the opening pressure of the safety valve can be adjusted to the maximum allowable operating pressure for the test
Reply to 10# yinmaizi: I’m quite satisfied with this answer. In other words, the setting for the safety valve’s opening pressure is determined separately for testing and actual use, and in practical use the opening pressure of the safety valve is adjusted to 2.1 MPa. Is that correct?