7 installation mistakes
- Misalignment and offset. The joint is pulled into place to hide misaligned pipes. The convolutions work unevenly and crack. An axial joint does not fix a crooked pipeline.
- Shipping restraints removed at the wrong time. Removed before the pipeline is fixed on anchors — the joint is stretched during installation. Forgotten — the joint cannot work, and expansion goes into the anchors and equipment.
- Welding current through the bellows. The welding ground is clamped on the other side of the joint, and current flows through the thin convolutions. An arc strike or spatter burns through the bellows — such a joint must be replaced at once.
- No pipe guides. Without them an axial joint buckles sideways under pressure. Per EJMA recommendations, the first guide is placed within 4 pipe diameters of the joint, the second within 14.
- Weak anchors. They carry the pressure thrust and the bellows spring force. An anchor designed only for the pipe weight is simply torn off.
- Installation length ignoring temperature. The joint is installed at its delivered length without allowing for the installation temperature. As a result it lacks movement for heating or for cooling.
- Wrong flow direction. A joint with an internal liner is installed against the arrow on the body. The liner causes turbulence and vibration, and the convolutions wear out.
How to install correctly
- Check pipe alignment before fitting the joint — not with the joint.
- Install and fix the anchors and guides.
- Set the installation length for the installation temperature — per the joint data sheet.
- Weld with the bellows protected, with the ground clamp on the same side of the weld.
- Remove shipping restraints after the pipeline is fixed and before testing — per the manufacturer's instructions.
- Check the flow arrow on the body.
- Pressure test with the anchors fixed.
We will select the joint and anchors and send a data sheet with the installation length.
Expansion joints catalogueTesting and start-up
Hydrotesting is done only with all anchors fully fixed: otherwise the pressure thrust stretches the joint beyond its rated movement. Test pressure must not exceed the joint rating. During the first heat-up it is worth walking the route and checking that the joint compresses evenly, without tilting.
FAQ
When should shipping restraints be removed?
Can an expansion joint correct misaligned pipes?
Why must the welding ground not go through the bellows?
Where should pipe guides be placed?
Can a hydrotest be done without anchors?
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