Metal Expansion Joints

Thermal growth, equipment movement, vibration or pressure pulsation may generate movement in a piping system. When this movement is not absorbed by the piping system itself, an expansion joint is the perfect solution.

An expansion joint is a device primarily formed by flexible bellows used to absorb movements in a piping system while containing pressure and a medium running through it.

The most important part or main element of any expansion joint is the bellow. The bellow is a flexible element consisting of one or more corrugation and the end tangents.

The most standard types of connection parts are welding ends and flanges. Metal Expansion Joints are connected to pipes, machines and apparatus either by welding them to the pipes or by flanging them. In some cases, screwed nipples or clamps are used.

The basic advantages to be gained from using Expansion Joints are:


  • Little space required for installation
  • Absorption of movements in multiple directions due to their inherent flexibility
  • They require no maintenance
  • They reduce load and temperature loss to a minimum


There are three basic movements that can be absorbed by an Expansion Joint:

Axial Movement is the change in dimensional length of the bellows from its free length in a direction parallel to its longitudinal axis.

Angular Movement is the rotational displacement of the longitudinal axis of the bellows toward a point of rotation.

Lateral movement is the relative displacement of one end of the bellows to the other end in a direction perpendicular to its longitudinal axis.

Metal expansion joint example 1 Metal expansion joint example 2

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 other international standards and codes (AD-Merkblatter B13, CODAP, etc.).

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:

304 304 S30400 1.4301 Austenitic
General Service
304L 304L S30403 1.4306
316 316 S31600 1.4401
316L 316L S31603 1.4404
316H S31609 1.4401/1.4919 -
316Ti 316Ti 1.4571 1.4571
321 321 S32100 1.4541
904L 904L N08904 1.4539
254 SMO S31254 S31254 1.4547
304H 304H S30409 1.4948 Austenitic
Heat Resisting
321H 321H S32109 1.4878
309S 309S S30908 1.4833
310S 310S S31008 1.4845
253 MA S30815 S30815 1.4835
Stainless steel grades

254 SMO and 253 MA are trademarks of Outokumpu Stainless

Inconel 600 N06600 2.4816
Monel 400 N04400 2.4360, 2.4361
Inconel 625 N06625 2.4856
Inconel 625LCF N06625 2.4856
Incoloy 800 N08800 1.4876
Incoloy 800H N08810 1.4958
Incoloy 825 N08825 2.4858
Hastelloy C4 N06455 2.4610
Hastelloy C-22 N06022 2.4602
Hastelloy C-276 N10276 2.4819
Nickel Alloys

Inconel, Monel & Incoloy are trademarks of Special Metals Corporation. Hastelloy is a trademark of Haynes International, Inc.