Typical Causes of Metal Expansion Joints and Metallic Compensators Failure
Most common sources of failure or malfunctioning in metal expansion joints and metallic compensators
The metal expansion joints and metallic compensators are those parts of the piping that can provide many years of reliable service, as long as they have been designed and manufactured in well manner in accordance with the project specifications.
Our know-how designing and manufacturing metal expansion joints and compensators since 1978, has shown us that certain breakdowns rest most of the time with the same mistakes or incidences, such as those set out in the following sections.
Damages during transportation and handling of the expansion joints
Dents and deformation of the bellows due to the impact of objects and structures (tools, chains, conveyors, surrounding constructions, etc.)
Wrong stacking on site for storing or prior to transportation.
Inadequate protection against poor weather conditions.
Improper installation and insufficient protection during and after the setting-up of the expansion joints
Expansion joints with inner sleeves that are placed opposite to flow direction.
Placement of the metal expansion joints or compensator in a different location to that stated on the erection drawings.
Early dismantling of the transportation and packaging accessories and protections.
Twisting of the bellows to accommodate misalignments of the piping.
Inadequate protection against mechanical damages coming from the surrounding area.
Insufficient protection against welding tasks carried out in the area around the bellows.
Premature removal of shipping devices and packing.
Anchorings, guiding and piping supports that are unsuitable for the expansion joint
Failure of the anchorage during operation
Corrosion of the bellows
Inappropriate choice of the material of the bellows to be in contact with the fluid and/or external environment. In particular, one of the most common sources of corrosion in the stainless steel bellows is the presence of chlorides leaking from the insulation.
Stress corrosion cracking.
We recommend you to contact with the materials supplier in order to do the right decision about the choice of materials.
Overpressure of the system (during normal operation or hydraulic test)
Vibration of the bellows (of mechanical origin or caused by the flow stream) that can lead to fatigue failure
Thermal expansion exceeding the expected design figures
Erosion of the bellows
This can be observed in expansion joints that are placed in high-speed pipings having no inner sleeve in the bellows.
Accumulation of undesired particles in the waves of the bellows, hindering a proper functioning of the expansion joint
The service life of a metal expansion joint or metallic compensator can be drastically reduced due to corrosion issues. The design and operation conditions can influence meaningfully, in such a way that the bellows may be affected by corrosion issues whilst the surrounding pipes and supports may not, even though they are made of similar materials.
Design, manufacturing and test procedures are a key factor for metal expansion joints manufacturers. In this technical article we explain briefly how are the most important factor to take into account.
There are many design alternatives, depending on the elements that make up the metal expansion joint or compensator.