Specific Applications

Expansion Joints for Heat Exchangers

Thick-wall bellows & Reinforced MRR Series

Thick-Wall Bellows

Thick-wall bellows are singleply and generally manufactured in thicknesses ranging from 2 mm up to 20 mm for Lens and Flange & Flued types and up to 6 mm for MUX Series. In most cases, the material used for the bellows matches the heat exchanger shell itself.

These designs are primarily used in fixed tube sheet shell and tube heat exchangers.

Thick wall bellows are highly durable and, in many cases, easily repairable in case of leaking but they’re also very stiff and have limited flexibility. They usually have a small number of convolutions (two or three), but the convolutions are exceptionally tall compared to thin wall bellows.

Standard materials include: Carbon steel, Austenitic Stainless Steels and Nickel Alloys: Inconel, Incoloy, Hastelloy, etc.


High convolution profile and thick ply construction. Welded in the upper part of the corrugation.

More information Metal expansion joint - Thick Wall Lens


High convolution profile and thick ply construction.

More information Metal expansion joint - Thick Wall MUX

Flanged & Flued MFF Series

A special case of the thick wall type. Flanged and Flued expansion joints are made in two halves from flat annular plates. The outside edges of the plates are formed in one direction (flanged), and the inside edges are formed in the other direction (flued). The two halves are welded together and then welded into the heat exchanger shell. Because of the higher wall thickness, this type of expansion joint is rugged and the most durable from the standpoint of abuse, but it has the disadvantage of limited flexibility.

MACOGA Flange & Flued Expansion Joints are designed as per ASME VIII-1 mandatory Appendix 5 guidelines for the design of flanged and flued expansion joints and ASME Appendix 26 and EJMA that provide methods of calculating the stresses, fatigue life and spring rate.

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Metal expansion joint - Thick Wall Flanged and Flued

Reinforced MRR Series

Thin-walled MRR Series can be singleply or multiply and are usually manufactured in thicknesses from 0.5 mm to 2 mm each ply.

They are much more flexible than thick wall bellows and they incorporate more convolutions but the height of the convolutions is shorter.

The system involves the use of reinforcement or equalizing rings located around the outside of the convolution thus preventing the bellows being forced out of shape due to the high pressures.

Equalizing and Reinforcing Rings are devices used on some expansion joints fitting snugly in the roots of the convolutions. The primary purpose of these devices is to reinforce the bellows against internal pressure and equalize the movement among all the corrugations.

Equalizing and reinforcing rings are made of carbon steel, stainless steel or other suitable alloys.

Reinforcing rings are usually "T" shaped in cross section and equalizing rings are generally fabricated from tubing or solid round bars of carbon steel, stainless steel, or other suitable alloys.

Standard materials include: Austenitic Stainless Steels and Nickel Alloys: Inconel, Incoloy, Hastelloy, etc.

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Metal expansion joint - Reinforced MRR

Quality Control and tests

All MACOGA Expansion Joints for Heat Exchangers and Pressure Vessels undergo a comprehensive and rigorous quality control and testing programme run by qualified and experienced personnel including:

  • Review of Drawings
  • Advanced Review of Calculations
  • Check Material and welding consumables certificates
  • Review and update WPS, PQR and WQR
  • Review NDE Procedures & Operator Qualification
  • Radiographic Examination
  • Liquid Penetrant Examination
  • Magnetic Particle Examination
  • Hardness Testing of Welds
  • Pressure Test
  • Leak Detection Test
  • PMI - Positive Material Identification
  • Surface Preparation & Paint System
  • Check Packing & Marking
  • Etc.

ASME Code inspection and ASME Certification Mark


All Heat-Exchangers required to be manufactured under ASME Section Div 1 with ASME Stamp containing an Expansion Joint must incorporate an Expansion Joint manufactured by a ASME Stamp holder approved manufacturer authorized by the American Society of Mechanical Engineers

MACOGA is an ASME Stamp authorized manufacturer since 1997.

Since then, MACOGA has been designing and supplying expansion joints in accordance with ASME Section VIII, Div 1 Appendix 26 providing ASME Stamp and U-2 Manufacturer's Partial Data Reports.

The ASME International Boiler and Pressure Vessel Code establish rules governing the design, fabrication, and inspection of boilers and pressure vessels. The ASME Boiler and Pressure Vessel Code is in a class of its own and it is internationally renowned.

On-Site Services

Expert assistance when and where you need it.

If an Expansion Joint installed in the shell of an exchanger is damaged and begins to leak, it can cause significant operation and safety problems.

If the leak is not repairable, replacing the leaking Expansion Joint by a new one is an extremely laborious and costly process as the internal tubes must be removed to replace the bellows.

There is the possibility of replacing the leaking or damaged bellows without removing the internal tubes and it is through the use of a MACOGA Clamshell Expansion Joint.

If a bellows is leaking or damaged, or if a bellows must be changed with a target to having the minimum down time, this is where a clamshell should be considered.

MACOGA Clamshell bellows is the best solution when a quick and unexpected replacement of the bellow is necessary. Clamshell bellows is a two-piece bellow which is welded around the existing unit.

The bellows is split in half longitudinally in our works. The halves are match-marked to ensure the bellows halves are aligned correctly. The clamshell is fitted accurately in position. A purge gas is set up to minimize oxidizing of the weld to ensure a good quality weld. The clamshell halves are then welded back together.

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Metal expansion joint - Heat Exchanger Metal expansion joint - Heat Exchanger

Same Size Clamshell

The heat exchanger must be shut down to install a same-size clamshell and the current bellows to be replaced is removed and discarded.

More information Metal expansion joint - Clamshell samesize

Oversize Clamshell

Installed on top of the current bellow while the system operates.

More information Metal expansion joint - Clamshell oversize

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