How do you install an expansion joint?

December 1, 2011

The necessary steps for installing all expansion joints shall be pre-planned. The installers shall be made aware of these steps as well as the installation instructions furnished by the manufacturer. The most critical phases of the expansion joint installation are as follows.

  • Care shall be exercised to prevent any damage to the thin bellows section, such as dents, scores, arc strikes and weld spatter.

  • No movement of the expansion joint (compression, extension, offset, rotation and especially torsion) due to piping misalignment, for example, shall be imposed which has not been anticipated and designed into the movement capability of the expansion joint. If such movements are imposed, they can result in system malfunction, damage to the bellows or other components in the system. Specifically, cycle life can be substantially reduced, forces imposed on adjacent equipment may exceed their design limits, internal sleeve clearances may be adversely affected, and the pressure capacity and stability of the bellows may be reduced.

  • Any field pre-positioning shall be performed in accordance with specific instructions which include both the direction and magnitude of the movement.

  • Anchors, guides and pipe supports shall be installed in strict accordance with the piping system drawings. Any field variances from planned installation may affect proper functioning of the expansion joint and must be brought to the attention of a competent design authority for resolution.

  • The expansion joint, if provided with internal sleeves, shall be installed with the proper orientation with respect to flow direction.

  • After the anchors or other fixed points are in place and the piping is properly supported and guided, the expansion joint shipping devices should normally be removed in order to allow the expansion joint to compensate for changes in ambient temperature during the remainder of the construction phase.

How does a toroidal expansion joint work?

December 1, 2010

A toroidal convolution consists of a circular tube (or totus) wrapped around weld ends or pipe ends having a gap at the I.D. to permit axial stroke. A toroidal expansion joint may consist of one convolution, or multiple convolutions. This joint is also known as an Omega bellows expansion joint for it resembles the Greek letter Omega. Most toroidal bellows are hydraulically formed which requires high pressure. Others are free formed, similar to blowing up a balloon. More accurate convolution shapes may be formed into toroidal dye cavities. Since this forming pressure is high, pressure resistance is also high.”U” shaped bellows cause a bending stress due to the pressure load on the convolution side wall. This generally determines the maximum pressure, however the toroid contains only membrane stress thus determining the maximum pressure. Due to the toroidal shape, deflection is limited. With “U” shaped convolutions, more deflection can be achieved but allowable pressures are lower.

Toroidal Bellow Expansion Joint
Toroidal Bellow Expansion Joint

How many expansion joints should be used in a pipe?

The number of expansion joints used on a pipe depends on the length of the pipe, the pressure, the temperature, and the size. Upon knowing these design conditions, we can inform you of the number of expansion joints the pipeline requires.

Where do we use expansion joints in piping?

Using expansion joints on piping depends upon the configuration of the piping where you will place the expansion joint to absorb thermal expansion or contraction.

How do you service test an expansion joint?

Expansion joints are maintenance free. They can only be tested if the expansion joint is supplied with 2-ply testable bellows using vacuum or air pressure testing.

How do you perform a burst test?

The burst test is primarily conducted on bellows. Normally, hydraulic pressure is slowly increased until failure occurs. Based on the burst test results, a safety factor is applied. This establishes the ultimate pressure rating.

Burst Testing
Burst Testing

What is burst testing?

The objective of the burst test is to determine the ultimate pressure resistance. This test is primarily conducted on bellows. Normally, hydraulic pressure is slowly increased until failure occurs. Based on the burst test results, a safety factor is applied. This establishes the ultimate pressure rating.

Burst Testing
Burst Testing
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