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Metal Expansion Joints

The bellows of a metal expansion joint is made up of one or more convolutions. The bellows provide stable, long-lasting solutions to many problems involving harmonics, vibration, and high temperature expansion. The joint must be designed strong enough to accommodate the system design pressure as well as flexible enough to accept the design deflections for a calculated number of cycles.

Metal expansion joints are being successfully utilized in refineries, chemical plants, fossil and nuclear power systems, heating and cooling systems, and cryogenic plants around the world. Service conditions have ranged from pressures of 25 microns to 1,000 PSIG and -420°F to +1800°F. These types of expansion joints are a highly engineered product and can perform their intended function safely and reliably.

Unlike most commonly used piping components, bellows are constructed of a relatively thin gauge material in order to provide the flexibility needed to absorb mechanical and thermal movement expected in service.

For selection of the proper metal expansion joint, the following steps should be followed:

  1. Select applicable pipe size

  2. Select applicable pressure range.

  3. Determine type and amount of movement to be absorbed.

  4. Select bellows (single or dual and number of convolutions) to satisfy deflection requirements.

  5. Determine end fittings and hardware required.


Expansion joints may operate in pipelines or equipment carrying fluids and/or gases at elevated temperatures and pressures. Precaution should be taken to insure proper installation and regular inspection. Care is required to protect personnel in the event of leakage or splash.

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