Bellow Expansion Joints

The heart of a metal or rubber bellows expansion joint is the bellows.  Some people or designers may call it a bellows expansion joint. What is the function of the bellows expansion joint? We must first define what an expansion joint is. There are several types of expansion joints. The most common is an expansion joint used to relieve stress on concrete so it will not crack what it is up against. It also, helps to level the concrete pour.  The expansion joint is usually a strip of woos that can compress.  The concrete expansion joint is not related to the bellow expansion joint. The only similarity is the name.  The search engines have a difficulty of differentiating between the two. We will do our best to explain what the differences are, and what a bellow expansion is.

The bellows expansion joint is used to contract or expand when place in a piping system.  Pipe can expand when heated or contract when cold.  The bellows can be welded in the piping system, and anchors to protect structures, pumps, tanks or equipment from thermal pipe growth.  An expansion joint in the industrial industry is defined by Wikipedia, as are compensating elements for thermal expansion and relative movement in pipelines, containers and machines. They consist of one or more metal bellows, connectors at both ends, and tie rods that depend on the application.  The bellow can be one single arch in rubber expansion joints or several convolutions to absorb movement and help with axial and lateral movements.  The bellows constrict when the pipe system warms and expands when the system cools. The rubber bellow expansion joints are also excellent to ais the stresses of vibration and axial movement and small lateral offset.

Applications for the bellows type expansion joint include cryogenic services to steam and flow lines. Service includes wastewater, flares, pumps, or ant equipment that is in a piping system. The bellows of the expansion joint can be made of many different materials. The includes carbon steel, stainless steel, and many other exotic materials. Hastelloy, Inconel, and titanium is also used on a as need basis.

The expansion bellows, was part of the original patent, filed in 1920, by Emil Witzenmann in Germany. The expansion bellows was referred as a flexible metal tube. Some may have called his Metal expansion joint compensators. The hydroforming or roll forming of these bellows follow the guidelines of EJMA, (Expansion Joint Manufacturers Association) and ASME codes. It is important to know the expansion bellows limits has expressed in cycle life and fatigue limits. The bellows expansion joint can have thin walls with multiple layers. There is also, the issue of pressure thrust that must be contained and protect the system. While the metal bellows expansion joint is the weak point in the piping system, if engineered correctly, the bellows expansion joint can save the system and process.