How do I tighten the bolts of this expansion joint?
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The expansion joint is welded to the pipeline and comes with two types of bolts. One is a long bolt that runs through the entire structure, and the other is a short bolt used to connect the two ends of the bellows. Could an expert please explain the functions of these two types of bolts, and whether they should be removed or tightened before operation?
Control bolts for pipes under internal pressure prevent the pipes from stretching, while control bolts for pipes under external pressure prevent them from shortening.
This post was last edited by wanlirn on 2019-12-30 08:44. This is the horizontal type with a long tie rod; there’s no need to move the nut of the long screw – just loosen the nut of the short screw
This post was last edited by Forgetting = Forgetting on 2019-9-3 09:03. After welding, the bolts are loosened or removed; these bolts are used to introduce pre-deformation, so that when subjected to tensile or compressive stresses, the expansion joint can counteract the deformation stresses through changes in its length
When testing the wave expansion joint under pressure, it is generally not necessary to loosen the tie rod bolts; simply loosening the nut on the inner side of the tie rod ear piece is sufficient. If stretching is the main force at play, then the nut on the outer side should also be loosened to a certain extent. Under no circumstances should the tie rod be removed. However, there are also some expansion joints that come equipped with pull rod mechanisms which need to be removed (those that can be removed are usually painted yellow). The function of these pull rods is to prevent the corrugations in the bellows from deforming or being crushed due to severe impacts during transportation, thereby serving to protect the corrugations. Once installed, it needs to be removed immediately in order for it to function properly; otherwise, the bellows cannot be compressed or stretched, and it will fail to provide protection for the pipeline.
Learn to read the design documents; the expansion joint data sheet indicates the amount of expansion, and adjustments should be made accordingly.
It should be released before operation, but it’s also possible that it has guiding and positioning functions; it’s best to check the instructions