REMOVABLE COVERS TO PROTECT
THE BELLOWS DURING TRANSPORT
AND HANDLING

For a chemical plant in France, Belman has successfully designed and manufactured a special Pressure Balanced Expansion Joint with removable covers to protect the Bellows during transportation and handling. The design also included external tie rods to effectively control pressure thrust and absorb movements.

 

CLIENT ISSUE
The chemical plant, which produces nylon, needed a replacement for a worn-out Inline Pressure Balanced Expansion Joint on one of their liquid-carrying pipelines. The client therefore forwarded the technical specifications and requested Belman engineer a suitable replacement solution.

 

BELMAN SOLUTION – Removable covers on Expansion Joint for protection during transport
Belman designed and optimised the required Inline Pressure Balanced Expansion Joint, which was made entirely from stainless steel materials. The design featured one working Bellow at the inlet, a balance Bellow positioned centrally within the Expansion Joint, and two working Bellows at the outlet to accommodate both axial movement and lateral movement. At the inlet, the Expansion Joint is designed with a DN 500 diameter. Directly after the flange, a coned end reduces the diameter to DN 360 for the remainder of the Expansion Joint.

The existing Expansion Joint solution installed at the plant was already an approved design, but since Belman had introduced improvements, the client asked for clarification of the differences. When comparing the new solution with the previous one, the client noticed that the worn-out Expansion Joint had the coned end placed at the outlet. Belman relocated the coned end next to the inlet to reduce the overall size of the Expansion Joint. This optimisation resulted in significant cost efficiency for the client: the reduced dimensions required less material, allowed for smaller convolution sizes, and enabled the use of thinner layers of material on the Bellows. These changes also lowered the spring rates, contributing further to cost savings. After thorough analysis and benchmarking of the existing design versus Belman’s optimised design, the client decided to proceed with the improved solution. The coned end in the Expansion Joint is necessary because the Expansion Joint connects to equipment with a larger diameter than the pipeline. Increasing the pipeline diameter to match the equipment would not be practical or economical; therefore, the client required a coned transition to be integrated into the Expansion Joint. Incorporating the coned end into the Expansion Joint does not influence its functionality, only the physical dimensions and appearance.

The original worn-out Expansion Joint’s pipe ends, coned ends and flanges etc. were made from carbon steel, which were coated for durability. However, the client requested a full stainless steel solution to achieve an even longer service life. Although the material upgrade increased the initial cost, selecting a material with higher longevity is more economical and environmentally beneficial in the long term. Belman therefore designed the new Expansion Joint in full stainless steel as requested.

To ensure safe horizontal installation, lifting lugs were added to the design. Additional tie rods were strategically positioned to guarantee controlled and secure movement absorption.

External tie rods to control the pressure thrust and movement absorption
The strategic placement of the tie rods follows the classic pressure balanced design principle. The tie rods not only control the pressure thrust but also define which movements the Expansion Joint Bellows are able to absorb. In this design the Expansion Joint is engineered to accommodate both axial movement and lateral movement. The tie rods are positioned strategically so that they can take up the pressure thrust, while the axial movement is absorbed by the four Bellows – where the working Bellows contract while the balance Bellow expands. This construction ensures that the length of the Expansion Joint can be variable without the reaction force generated by the internal pressure affecting the connecting equipment.

Removable covers on each Bellow
The Expansion Joint is equipped with removable covers on each of the Bellows, which are manufactured from the material 1.4307 (AISI 304L). These covers are mounted as per client request to protect the Bellows during transportation, handling, storage and installation. Since the Bellows are a flexible element formed from thin layers of metal sheets, they are inherently delicate and susceptible to dents and damage if not properly safeguarded. The covers are fastened with screws onto the metal studs and provide effective protection. Once the Expansion Joint has been installed, the covers can be quickly and easily removed.

 

Belman – expertise on Inline Pressure Balanced Expansion Joint designs
Since 1994, Belman has engineered and manufactured numerous Inline Pressure Balanced Expansion Joints for clients across a wide range of industries worldwide. These solutions span from very small to extremely large diameters and are produced in many different materials and designs. Each Expansion Joint is custom-designed to meet the specific requirements of the client and its project. Among many specialised solutions, Belman has produced a large-diameter, four-metre-long DN 2500 Inline Pressure Balanced Expansion Joint with a DN 3800 balance bellow for use in a desalination and power plant. At a smaller end of the scale Belman has also manufactured small size solutions – for example, two 299-mm-long DN 50 Inline Pressure Balanced Expansion Joints for a research centre. These two examples demonstrate the full breadth of Belman’s capabilities in the design and manufacture of Inline Pressure Balanced Expansion Joints.