Expansion joint nut installation standards
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What are the installation standards for expansion joint nuts? Is the nut on the inside loose or tight, and how tight is it? Are there any standards? Let’s exchange ideas
This bolt can also be considered a limit bolt. The specific procedure should involve using positive-pressure pipes as the standard; the inner bolts should be fully loosened to the maximum extent, while the outer bolts are used for limiting and locking in place. It depends on the pipe diameter; visually assess the maximum stretching distance of the expansion joint, or adjust and lock it during pressure testing. If it is a negative-pressure pipeline, the inner limit should be controlled. This is a makeshift understanding for reference only.
The bolts of expansion joints come in two types: those that are designed to withstand the internal pressure thrust of the pipeline are called large tie rods, and these cannot be removed; even if the nuts loosen, they still need to be tightened； Another type is the transport tie rod used for fixing in place; it is usually painted yellow. This rod must be removed after the expansion joint is installed. In some cases, the nut on this rod is also painted yellow, and it is necessary to loosen the nut to the specified position.
This nut is used for setting limits; the position at which the nut is tightened depends on the compensation amount designed for the pipeline’s expansion joint, and this is determined through calculations, in accordance with GB/T 12777
Such tie rods can function at most as tie rods to accommodate axial displacement; they cannot withstand blind plate forces； The pull rods shown in the images are usually transport pull rods, and the ear plates of the larger pull rods are much thicker
I’m not entirely sure about the details, but I remember that one end needs to be fixed, while the other end seems to be calculated based on expansion joints; the image showing it in an upright position is definitely incorrect