Location of the corrugated expansion joint between the fixed supports
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I have always had doubts regarding the layout scheme for the wave compensators in the low-pressure pipelines of the plant’s integrated pipeline network; I’m not sure whether these compensators should be placed right in the middle of the two fixed supports, or closer to the main fixed support or the secondary fixed support (The examples or illustrations of compensators shown in the manual are all arranged near the side of the secondary fixing bracket). Here are the three options depicted: Option 1: the compensator is located near the main fixing bracket; Option 2: the compensator is located near the secondary fixing bracket; Option 3: the compensator is situated in the middle of the fixing brackets. I would like to hear the opinion of professionals – which option would be more suitable? ? ? Furthermore, before using CAESARII, manual calculations were carried out. According to Table 7-30 in Page P496 of the Power Piping Manual, the thrust on the fixing bracket of a wave compensator is calculated as follows: Fx = Elastic force of the compensator + Thrust due to internal pressure in the compensator + Back-friction force of the pipe = FA + FB + μqL, where L represents the distance between the wave compensator and the fixing bracket. Therefore, the placement of the compensator must have a significant impact on the thrust exerted on the main fixing bracket But after I built the model using CAESARII, the calculation results for all three options were the same. So, I would like to ask the fellow sailors: does the position of the compensator actually have an impact on the thrust exerted by the fixing frame? Which is correct, the software’s result or the manual calculation?
Assumptions: The pipe has a diameter of φ1020x10; the material of the pipe is temporarily specified as 20# steel. The vertical load on the pipe is 500 kg/m. The medium flowing within the pipe is gas, at a pressure of 50 kPa, with a maximum temperature of 100°C℃； For the wave compensator, an axial internal pressure type compensator is selected. The axial compensation amount is 70 mm, the effective area is 9043 cm2, the axial stiffness Kx = 845 N/mm, and the lateral stiffness Ky = 80954 N/mm. The thrusts acting on the primary and secondary fixed supports are to be determined. Additionally, models for three different scenarios were created using CAESARII, along with the calculation results
As a beginner using Caesar II, if there are any parts I haven’t expressed clearly, I kindly ask fellow users to point them out; I will then provide the relevant information
In my design, I chose the first option: one arranged symmetrically near the main fixing bracket.
I also chose Option 1, but I don’t understand it: if Option 2 or Option 3 is chosen, according to the formulas in the manual, the calculated thrust on the main fixing frame should be greater. Why are the calculation results in CAESARII all the same?
In an axial-type compensator pipeline, the main fixing bracket must take into account the static pressure thrust exerted by the bellows as well as the elastic forces resulting from deformation. The pipeline can be designed to use an intermediate fixing bracket, and this intermediate bracket does not need to consider any thrust forces. Only one axial-type compensator can be installed between the two fixing brackets of the pipeline; the first type of fixing arrangement is generally recommended, with a recommended distance of 4D from the fixing bracket
I understand what you mean, but why does the power pipeline manual still provide a calculation for the thrust of the intermediate fixing bracket, which is one side minus 0.7 times the other side?
Well, I’m not entirely sure about this either. I’m merely providing a response based on years of experience with the products manufactured by my company, Jiangsu Baixin Bellows Co., Ltd. As for the specific design aspects, I don’t dare to offer opinions on those; I can only help resolve any minor issues that arise during the use and installation of the products
Thank you for your answer; it’s still very helpful to me
When using software for calculations, friction is not taken into account; you need to set the MU value so that the results are different
There are not enough brackets; add a few more. The difference must lie in the friction force~