Metal Expansion Joints

Metal Bellows Manufacture & Design


MACOGA Expansion Joints are designed, manufactured and tested in accordance with:

  • E.J.M.A. (Expansion Joint Manufacturers Association, Inc.)
  • ASME VIII, Div. I, App. 26
  • EN 14917, European Standard for Metal Expansion Joints.


If specially requested or included in the terms of the contract, the Expansion Joints can also be designed according to various international standards and codes, including AD-Merkblatter B13, Stoomwezen D 0901, Suomen SFS 2773 or CODAP.

Design control and modifications are set out in the latest version of our Quality Control Manual and the Quality Procedure "Design and Calculation".

Manufacturing Methods

MACOGA uses different methods for producing the metal bellows depending upon a range of different contributing factors (eg. diameters, the number of sheets used, the materials used, etc.), although in all cases the bellows are manufactured using seamless tubes or metal cylinders welded along their length. The methods used are as follows: Expanding, Elastomeric, Hydraulic and Roll forming.

Circular Expansion Joints are manufactured with single or multiple ply with a diameter ranging from 15 to 8000 mm.

Our manufacturing range includes Circular Expansion Joints of the following types:

  • Axial
  • Hinged
  • Gimbal
  • Lateral
  • Pressure Balanced
  • Jacketed
  • Externally Pressurized
  • Lens
  • Flanged & Flued

As well as Rectangular Expansion Joints which, with limitless dimensions, can be supplied with different convolution and corner types:

  • W-shaped, Camera Corner
  • V-shaped, Miter Corner (single or double)
  • U-shaped, Rounded Corner


The use of circular multiply bellows are the ideal solution for Expansion Joints which are exposed to high pressures. This system involves constructing a bellows using several thin sheets instead of one single thick ply. This technique considerably improves the flexibility of the bellows, its most important characteristic.

There are five main advantages to be gained from using multiply metal bellows:

  • They are highly resistant to high pressures.
  • They maintain a high degree of flexibility even when working under high pressures.
  • They have lower spring rates than the single thick sheet bellows.
  • They have a high absorption rate for movements across short lengths thus ensuring a longer working life.

They guarantee important savings:

  • Few units are required within any given system owing to their greater capacity to absorb movements.
  • The low spring rates reduce the costs incurred by anchorage and supporting structures.
  • To avoid corrosion, special materials (eg. Inconel, Incoloy, etc.) can be applied to the inner layer in order to protect against temperature and corrosion and austenitic steel can be used to cover the remaining layers in order to withstand high pressures.

Materials Used

The essential component of an Expansion Joint resides in the degree flexibility of its bellows and this depends upon the design of its convolution and the materials used during the production process.

The choice of metals to be used in manufacturing the bellows, being the basic component of the Expansion Joint, is made taking the following criteria into account:


  • Temperature resistance.
  • Resistance to corrosion.
  • Forming capacity.
  • Mechanical characteristics.
  • Resistance to fatigue.
  • Flexibility when in use.

The tables shows the materials mostly used to produce our bellows:

stainless steel grades
Stainless steel grades
254 SMO and 253 MA are trademarks of Outokumpu Stainless
nickel alloys
Nickel Alloys
Inconel, Monel & Incoloy are trademarks of Special Metals Corporation.
Hastelloy is a trademark of Haynes International, Inc.

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