+640/-0 MM
AXIAL MOVEMENT
ABSORBED BY UNIQUE
EXPANSION JOINT DESIGN

For a power plant in Europe, Belman has designed and manufactured five special Expansion Joints for the absorption of very large axial movements.

 

CLIENT ISSUE
The client had some worn-out Expansion Joints that had performed reliably for many years but had now reached the end of their long service life. Satisfied with their design, performance and operation, the client sought an identical replacement solution to maintain trouble-free operation. Despite the original Expansion Joints having been manufactured by a different supplier, the client turned to Belman – a manufacturer known for its ability to customise and thereby produce the exact design according to the client’s and application’s requirements. For that reason, Belman was able to help supply this client with some replacement units.

 

BELMAN SOLUTION : +640/-0 mm axial movement absorbed by a unique Expansion Joint design 
The Expansion Joints are specifically engineered to absorb large axial movement – a +640 mm extension along the longitudinal axis to be precise. Accommodating such extensive movement requires a specialised design to ensure both stability and flexibility. To absorb these large axial movements, the Expansion Joint features two bellows, each designed to absorb half of the total movement. Typically, a Pantographic Gimbal would be required to ensure uniform movement absorption between the bellows. However, in this case, a design incorporating a tie rod system as movement limiters was sufficient for effective movement control. Therefore, with the tie rod system, the front bellow absorbs more movement than the other bellow – a factor that has been accounted for in the design. When designing a functional bellow that allows optimum absorption of movement, it is always a question of balancing stability and flexibility. In this case, in order to ensure stability while also maintaining the required degree of flexibility, the Bellows were made from 2-ply 0.5 mm material and consist of 14 convolutions. The bellow convolutions allow full flexibility and, because they are high as well as fully compressed, they can absorb the full axial extension.

To ensure optimal protection of the Bellows, the Expansion Joints are equipped with inner sleeves, consisting of two inner sleeves mounted on each Bellow. This position of the inner sleeves provides maximum flexibility. The inner sleeves are very long, meaning that they are placed very close to each other when in neutral position. This design ensures that, even at full extension during operation, the inner sleeves continue to provide full coverage and protection of the Bellows.

 

Tie rods to control the highly flexible Bellow design
The Expansion Joints are designed to absorb extremely extensive axial movement of +640/-0 mm in combination with lateral movement of +/-5 mm. As the Bellows are very soft and flexible, a tie rod system of control bars is required to precisely regulate movement absorption. The tie rods ensure that each Bellow absorbs only the intended amount of movement. While the Bellows are engineered to handle more than half of the total movement, real-world operation may result in one Bellow absorbing +400 mm axial movement while the other takes on +240 mm axial movement. If completely equal movement distribution had been required, a pantographic gimbal system would have been used instead of the tie rod system. To ensure balanced and controlled movement absorption, the system incorporates four tie rods, effectively controlling the movements absorbed and maintaining stability while allowing the necessary flexibility within the Expansion Joint. After installation the lugs marked with black/yellow tape are removed to allow full movement absorption, as these are only mounted for transport/installation purposes.

 

Belman – unparalleled expertise in customised Expansion Joints for absorbing large movements
Certain piping system layouts and operating data require Expansion Joints that can absorb very large movements. Accommodating these large movements requires a very special Expansion Joint design. Belman has unparalleled experience in such designs and has a long track record in engineering remarkable Expansion Joints that have provided industries all over the world with optimum movement absorption. One of the most notable designs included a 5-metre-long Expansion Joint with 11 bellows in sequence, enabling it to accommodate an impressive +/-450 mm axial movement (a total of 900 mm). By integrating multiple Bellows in series, Belman’s Expansion Joints efficiently handle large-scale movements while ensuring system stability and long-term durability.