EXPANSION JOINTS FOR
SPACE ROCKET
LAUNCH PAD

For a French producer of aerospace rocket launch pads, Belman designed and manufactured a total of six Pressure Balanced Expansion Joints for installation in a cryogenic section of the fuel system, supplying LOX/Methane as well as nitrogen to the aerospace rocket engine.

 

CLIENT ISSUE

The client had already gained positive experience with customised Pressure Balanced Expansion Joints in other locations on its launch pads. For a different section of the launch pad – specifically at the engine interface – the client wanted to implement a similar Pressure Balanced Expansion Joint solution but with a simpler design. Given Belman’s strong reputation for customised solutions combined with our extensive experience in cryogenic Expansion Joints, the client approached Belman with an initial request outlining key parameters such as size, media and operating temperature.

 

BELMAN SOLUTION

Cryogenic Expansion Joints for a space rocket launch pad

Based on the submitted specifications and the request for a specific type of Expansion Joint, Belman initiated a dialogue with the client to fully understand the application requirements and operating conditions. Through this process, it became clear to Belman that the requested Pressure Balanced Expansion Joint was the optimum solution for the client. Both the provided data and subsequent discussion confirmed that selection. Accordingly, a customised Expansion Joint design was developed to match the specified operating parameters. The application did not impose any extreme constraints in terms of installation length, significant pressure drops, high dense fluids or fluid speed, further supporting the suitability of the Pressure Balanced design. Based on the technical design specifications submitted by the client for quotation, along with a sketch indicating the preferred Belman type and installation arrangement, Belman engineered a tailored solution. The design principle of the supplied Expansion Joints corresponds to this Belman type: Animation of Belman Pressure Balanced Expansion Joint

All Expansion Joints are installed in cryogenic piping, but in different locations on the launch pad system. The following units were supplied:

• 2 x DN 100 for LOX/Methane service
• 2 x DN 50 for LOX/Methane service
• 2 x DN 25 for Nitrogen service

Although DN 25, DN 50 and DN 100 are very small sizes for Pressure Balanced Expansion Joints, Belman’s wide product range enables both design and manufacturing of such solutions without issue. The client specifically evaluated this design as the most suitable solution, and Belman was pleased to support and supply accordingly.

 

Why design the Pressure Balanced Expansion Joints with external limiters?

The system operates at 10 barg under cryogenic conditions. This pressure level does not impose additional design requirements compared to operation at ambient temperatures (+20°C). The Expansion Joints are designed for 10 barg and can accommodate axial and lateral movements in combination. Because Pressure Balanced Expansion Joints are intended to absorb both axial and lateral movements, it is designed with two working Bellows. This configuration also reduces the lateral spring rate. In contrast, a design intended only for axial movement would require a single working Bellow.

As per client request, the Pressure Balanced Expansion Joints are designed with external tie rods to control the movements by transmitting forces and movements between the Bellows. This is a well-considered solution, as an alternative design with internal limiters (Finger Type) would result in excessive stiffness for the lateral movements in the client’s application.

Due to the critical nature of the application, full traceability as well as comprehensive testing were required. This included a tightness test, pressure test and penetrant test as well as dimensional and visual inspection. Given the specific line of service, special cleaning procedures were implemented for the project. This is standard practice for Belman on these types of applications, for which Belman has extensive experience.

 

What Expansion Joint materials are durable enough for cryogenic applications?

Due to the cryogenic nature of the application and the conveyed media (LOX/Methane and nitrogen, all at -196°C), the client specified using 1.4541 (AISI 321) material for the Bellows and materials 1.4404 (AISI 316L) and 1.4307 (AISI 304L) for the middle pipe, flanges, pipe ends, etc. These materials are all well-suited for cryogenic services (down to approximately -270°C). In many cases, carbon steel types are not suitable for such applications because they can become brittle and prone to cracking at low temperatures. In contrast, the selected stainless steel materials retain ductility and exhibit high fracture toughness under cryogenic conditions. The low carbon ‘L’ materials are therefore generally preferred for cryogenic applications. In certain cases, particularly for achieving light weight and heavy duty (high pressure), higher alloyed materials, mostly Inconel 625, may be used as an alternative.

 

Do Belman send 3D models for design verification?

As requested by the client, Belman developed detailed 3D models of the Expansion Joint solutions and provided them to the client for integration into their overall system model. This enables the client to maintain a complete and accurate representation of the pipeline and its components, allowing for verification and optimisation of the design. By incorporating the Expansion Joints into the full 3D model, potential issues, such as collisions, can be identified and resolved at an early stage. This is particularly important in compact systems where space is limited. In this case, the importance of 3D verification is further increased, as cryogenic pipelines are typically insulated or installed within larger vacuum pipes. Therefore, ensuring a proper fit and clearance through 3D modelling is essential for a reliable and efficient design.

 

Belman – highly experienced in Expansion Joints for the aerospace industry

Belman is a globally recognised manufacturer with more than 30 years of experience in the design and manufacture of high-performance Expansion Joints for demanding industries. Within the aerospace sector, Belman has developed a strong expertise through numerous projects across critical applications such as rocket feedlines, pressurisation systems, cryogenic pipelines and vacuum environments.

Belman’s solutions are engineered to meet stringent safety requirements, particularly in cryogenic applications, while ensuring reliable and efficient performance. With capabilities ranging from full vacuum to very high pressures, and operating temperatures from -269°C to +1000°C, Belman delivers solutions for some of the most challenging environments. All Expansion Joints are manufactured using high-grade materials to ensure durability and a long service life. Each solution is tailored to the specific application, combining proven design principles with advanced engineering. This approach has established Belman as a trusted partner within the aerospace industry.