Operating pressure, design pressure, nominal pressure, and test pressure of pipelines
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Regarding menstrual pads, I searched the forum again before posting. There are two common viewpoints on the forum, which I’ll summarize as follows: 1. The design pressure should be greater than or equal to the operating pressure; the test pressure is calculated based on this design pressure (taking temperature effects into account), and the nominal pressure is selected accordingly. 2. The design pressure should be greater than or equal to the operating pressure; the test pressure is calculated based on this design pressure (taking temperature effects into account), and the nominal pressure is determined by rounding off the value based on the design pressure. The main difference between these two viewpoints lies in whether the nominal pressure is determined based on the test pressure or the design pressure. Without the need to raise the pipeline grade due to specific operating conditions, the first approach is certainly more conservative, resulting in a higher flange grade – this is what our company used to do. However, after reading some replies from experts on the forum, I realize that since the selection of allowable stress already takes into account factors such as tensile strength and yield strength margins, the second approach is more reasonable. Now I tend to favor the second approach as well. I would appreciate any advice from experts out there
Thank you for the advice! Firstly, the test pressure is included because there are situations where the ultimately determined test pressure for a pipeline ends up being higher than its nominal pressure; in such cases, one feels worried and decides to increase the nominal pressure rating. Secondly, after calculating the pipe wall thickness using a formula and then determining the test pressure as 1.5 times that value, one again feels worried and uneasy, which is why this issue persists
It is normal for the test pressure to be higher than the design pressure, especially common in pipelines operating under high temperature and pressure conditions. In fact, there’s no need to worry too much if the test pressure is higher than the design pressure, as the allowable stress used in the wall thickness calculations is at least taken as (yield strength / 1.5); in other words, the allowable stress must be multiplied by 1.5 to reach the material’s yield strength.
I have a question: in the second point, why does the value taken from the temperature and pressure table in the ASME standards need to be multiplied by 0.8? Is it also needed in HG20592? Is it needed in HG20615 as well? Is there any regulation?
Ha, the data from this department states that it’s an empirical value. Well, my supervisor told me that HG/T 20615 is the same as B16.34 and B16.5 – as long as it’s a temperature and pressure value, and the temperature, pressure, and nominal pressure are all the same, then it should be identical. HG/T 20592 is indeed different, after all, the classification of nominal pressures varies.
http://bbs.hcbbs.com/thread-1244862-1-1.html； http://bbs.hcbbs.com/thread-1245585-1-1.html ； This is an earlier post; combining it with the replies should help clarify things for you
Does that specification provide a detailed explanation of the “P-T values at the hydrostatic test temperature”?
Detailed data on the P-T values of these materials are available in both HG/T 20615 and ASME B16.5.
Please make sure to read the original poster’s post carefully before answering the question. The pressure used in strength tests must be greater than the design pressure; generally, the hydrostatic test pressure is set at 1.5 times the design pressure. What the original poster is asking is whether it is reasonable for the test pressure to be higher than the nominal pressure rating of the pipeline. For example, in the case of steam with an operating pressure of 1.0 MPa and flanges rated at 16 kg, if the design pressure is set at 1.1 MPa, then the hydrostatic test pressure will be 1.65 MPa. In this situation, is it still reasonable to use flanges rated at 16 kg? ? I think it’s unreasonable; the level should be increased. Otherwise, what’s the point of strength tests?
Could you please avoid posting content about digging graves? If you have your own thoughts, just reply to the original poster directly; there’s no need to reply to me. Thank you!
Okay, let’s just discuss the issue