Measures to reduce the thrust on the fixing brackets of bellows expansion joints
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This post was last edited by lp3484 on 2021-10-9 09:57. The axial thrust exerted by the bellows expansion joint on the fixed support consists of two components: one is the elastic thrust resulting from the deformation of the expansion joint, and its value is equal to the degree of deformation multiplied by the stiffness of the expansion joint; the other component is the thrust due to internal pressure, and its value is equal to the internal pressure in the pipeline multiplied by the cross-sectional area of the expansion joint. For a DN300 steam pipe with a pressure of 0.6 Mpa, the internal pressure thrust can reach as much as 50 KN; the horizontal thrust exerted by the fixing brackets is very large, which results in high costs. The owner will be furious upon hearing this. Is there any way to reduce the internal pressure thrust? What I’m thinking of is using expansion joints that are tightened in a cold state, by stretching them by half of their maximum deformation amount during installation; this would allow us to account for only half of the elastic thrust, but it’s still far from enough ； Another approach is to adjust the position of the fixing bracket so that the thrusts on either side of it can balance each other out, thereby reducing some of the thrust. I’m not sure if there are any other methods.
1. Balanced bellows compensators are used, but their drawback is their large size and high cost. 2. A longitudinal beam type pipe rack is used, with the horizontal thrust being balanced by the longitudinal beams.
I would also like to ask: if there are multiple pipes, is the horizontal thrust on the fixed pipe rack equal to the sum of the horizontal thrusts of all the pipes? And in the case where there are both hot and cold pipes, how should it be calculated? Does the direction of the force also need to be taken into account?
Sections 4.1 and 4.3 of GB 51019-2014, \"Code for Design of Pipe Racks and Pipe Piers in Chemical Engineering\", provide detailed discussions on this topic.
I see that it mentions a restraint coefficient for the support structures listed above, but nothing is said regarding the horizontal thrust on the fixed support structures
4.3.3 The thrust calculation formula includes a restraining coefficient.
That’s a movable pipe rack; I’m talking about a fixed pipe rack
Refer to Standard Appendix C; the thrust formula for the fixture includes the friction force Fm, and the calculation of this friction force is provided in 4.3.3.
I’ve seen that formula. What I want to ask is: if there are multiple pipes on a fixed pipe rack, exerting both pulling and pushing forces on it, does it mean that each pipe needs to be calculated individually, and then the vectors are added together?
There is no need to calculate each one; simply use the restraint coefficient determined in 4.1.3.