Expansion Joints

According to their physical properties, most metals expand with increasing temperatures and contract with decreasing temperatures. In pipeline systems, this phenomenon causes a variation in the length of the individual sections of the pipeline.

As pipelines are normally anchored at least on two connection points, any variation in length will result in thermal strain in the material and enhanced forces and moments at these terminal points.

As far as possible, one will utilize the inherent flexibility of a pipeline to compensate the pipe expansion (natural compensation).

Should the expansion, however, exceed the inherent flexibility of the pipe, expansion joints are necessary to compensate these movements.

Additionally, mechanical vibrations of pumps, compressors, turbines and motors should be dampened to avoid any damage to adjoining pipelines, their supports or any installed instruments.

Forces and moments on nozzles of compressors, turbines, vessels and other plant components are limited and must not be exceeded.

In all these cases, expansion joints can be utilized.

The central component of each expansion joint is the metal bellows (*) that, due to its shape and thin wall, acts like a spring. The bellows however has to meet the following basic criteria to qualify for its use as an expansion element.

It must

- withstand the operating and test conditions (pressure, temperature) of the pipe system,

- ensure corrosion resistance against internal (flow) and external (atmospheric) conditions,

- provide sufficient flexibility to compensate thermal expansion and mechanical vibrations with the requested durability (life expectancy)  

- include sufficient squirm stability.

(*) Exceptions are rubber expansion joints.

Expansion joints with stainless steel bellows

The BOA Group offers a wide range of expansion joints, suitable for numerous specific applications.

The BOA expansion joints portfolio basically consists of three main series:

- Standard series: expansion joints up to DN 150 (6")

- Industrial series: expansion joints up to DN 1.000 (40")

- Special series: expansion joints >DN 1.000

The heart of all expansion joints is the metal bellow. Thanks to modern design and manufacturing facilities, all BOA expansion joints offer the following advantages:

- High flexibility

- Short build length

- Large movement capacity

- Durability and excellent chemical resistance

The BOA Group uses almost every type of bellows forming to offer the best possible solution to its customers: Hydraulic and elastomer forming, punching as well as mechanical rolling.

Please contact Mr. Xie for business 13818451931.