You must know how to install corrugated expansion joints correctly

1. Selection of corrugated expansion joint

a. The corrugated expansion joint is only undergoes axial deformation, the stress on both ends is large, the middle part tends to deform to the side at any time. The compensation amount of each wave is generally only about 5-20mm, so the wave of the expansion joint is generally about 4 convolutions,not more than 6 at most.

b. Permissible deviation of the perimeter of the bellows expansion joint:

When DN> 1000mm, it is ± 6mm;

When DN≤1000mm, it is ± 4mm;

Convolution top diameter deviation is ± 5mm;

2. Installation of corrugated expansion joint:

a. The corrugated expansion joint should be pre-tensioned (at the time of thermal expansion) or pre-pressed (at the time of cold contraction) during installation, and its value is half of the pipeline compensation amount.

    The pre-tensioning of the corrugated expansion joint should be carried out in two to three times, and the force should be gradually increased to ensure that the peripheral surface of the node is uniformly stressed.

 b. Installation of corrugated expansion joint in pipeline:

     <a> The corrugated expansion joint is divided into that with sleeves and without sleeves according to the node structure. Pay attention to the direction when installing. The end of the inner sleeve with welds should be installed facing the medium flow on the horizontal pipeline; The pipeline should be placed above.

    <b> When the corrugated expansion joint is hoisted, the rope cannot be tied to the node, and the support cannot be welded to the node.

     <c> The corrugated expansion joint should be installed in accordance with the centerline of the pipeline strictly, and must not be deflected to avoid damage.

     <d> If a temporary support is provided, it shall be removed after the pipeline is installed and fixed.

     <e> During the hydraulic test of the pipeline, it is strictly forbidden to exceed the specified test pressure,to avoid damage the expansion joint. Clamp the bellows expansion joint firmly during the pressure test so as not to make it stretch free.

     <f> When the pipeline is purged with steam, the warming pipe should be slowly raised first. When the pressure rises to 0.3-0.4 MPa, the pipeline should be thoroughly inspected while the expansion amount, leakage, For fixing and other conditions, when the requirements are met, continue to raise the warming tube until the purge requirements are reached. After the purge is completed, when the pipeline is cooled to normal temperature and the pressure is increased to the purge pressure for the second time, the expansion, contraction, leakage, and fixing of the expansion joint should be carefully checked to confirm whether the expansion joint is working properly.