Problem of support disengagement due to secondary stresses in pipelines
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I just started learning about pipe stress. When calculating secondary stress, C2 uses the operating condition minus the installed condition for verification. If the support is detached in the operating condition, would the verification of secondary stress then be inaccurate? Because the axial force within the allowable stress range has changed. Is it possible to define a load condition that includes only the operating temperature, so that the calculated secondary stress is not affected by the deflection of the support? Seeking advice from experts
The bracket coming loose is an abnormal operation; won’t you find a way to design it so that it doesn’t come loose? If you consider the main support displacement again, then this pipeline cannot be designed.
What a professional question. I’ve encountered similar issues with pipes that cross utility tunnels in the past: the hot water pipes are installed on steel structures, while the supporting structures for these pipes are located in the upper-level utility tunnels. Once steam is introduced, the pipes above end up hanging in mid-air
Identify which bracket is causing the void, and replace it with a spring bracket.
After the analysis, it should be checked to see if there is any support loss. If the support becomes unsupported, remove that support and analyze again. If further analysis shows that this support must be designed, it is then changed to a spring support.
Lift-off is an abnormal condition that can be addressed in two ways: 1. By adjusting the fixing points and strain release points to ensure even distribution of deformation and prevent lift-off; 2. By installing elastic supports at these locations and applying a certain amount of pre-tension in the cold state, which allows for greater counteracting stress on the pipeline when it is in the hot state, thus preventing lift-off.
L1:=W+P+T (operational state) L2=T (secondary stress) L3=L1-L2 (primary stress, regardless of whether the support is detached). If the support becomes detached under conditions of L1 and L2, then the value of L3 should represent the primary stress without that detached support. Is it appropriate to use L2 and L3 to verify the stress levels?
I use autopipe; it calculates (W+P) and T separately, and then adds them together to get W+P+T. (It doesn’t seem to calculate W+P+T directly, based on my own speculation.) If a gap is created, the program will issue a warning. My habit is to check the stress conditions of each SUPPORT. If a support becomes unsupported, I remove that support and run the process again until no supports are left unsupported. I suggest removing the empty supports and running it again before comparing the data.
Bracket deflation: Adjust the bracket position under the condition of satisfying the primary stress, or use a spring bracket