The effect of valve operation on pipeline stress
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Valve opening and closing should correspond to different operating conditions; the pipeline stress and the thrust on the supports must be different in these two states. Should CaesarⅡ be used to perform calculations separately for these two conditions? When CaesarⅡ calculates the operating conditions during valve closure, does it automatically account for the thrust on the valve? Should an equivalent thrust be artificially applied at the end of the pipe?
Personally, I don’t think it’s necessary to consider things in such detail, but if it’s a safety valve, then the backforce exerted by its discharge mechanism must be taken into account.
The purpose of our use of CII is not only to check the pipeline stress itself; the loads exerted on the pipeline from external sources are also part of what is calculated. Therefore, the external loads under different operating conditions need to be determined, such as the opening and closing of valves. Otherwise, the thrust you apply to the structure will be too low or too high.
1 The response time of valve closure affects pipeline stress. Closing too quickly can cause a water hammer effect. It needs to be calculated specifically. 2 The thrust at shutdown will not be added automatically.
It is not considered automatically; what the original poster is referring to falls within the scope of dynamic analysis. C2 is mainly used for static analysis, though it also has some modules for dynamic analysis
It seems like the original poster has a misunderstanding of the concept. Do you mean the thrust exerted on the valve by the pressure inside the pipeline when the valve is closed? This is likely not balanced by the horizontal thrust of the bracket, but rather by the thrust generated by the internal pressure in the pipe against the closed end on the other side of the pipe. With the valve closed, the pipeline becomes a balanced system… It can be considered a container with a rather strange shape.
The standards specify two scenarios for calculating the bracket thrust: valve opening and valve closing. After the valve is closed, the pipeline still experiences strain; isn’t it so small that it doesn’t generate any thrust? When expansion joints are present, this must definitely be taken into consideration; when expansion bends are available, it may not be necessary to consider valve operation. . .
What are the standards? I hadn’t really thought about this issue before. I agree quite a bit with the view from the 6th floor.