[ Aerospace ]
[ Aerospace ]
Cryogenic pipes for aerospace
A recent order from the European aerospace industry required two flexible, vacuum-insulated cryogenic pipelines to expand a test infrastructure for innovative propulsion systems. Stainless Steel World spoke to Dr Jürgen Essler from BRUGG Pipes to find out more.
By Joanne McIntyre, Stainless Steel World
The order for vacuum-insulated cryogenic pipelines was won by BRUGG Pipes, a company which has developed deep expertise in highly demanding industrial and cryogenic applications. The two pipelines connect an elevated tank for cryogenic media with a lower-level engine test facility. In such applications, cryogenic media must be transported safely and with minimal loss, even under demanding thermal conditions. Two pipe systems had an outer diameter of 98 mm and 174 mm and a total length of 185 meters each. Segment lengths were 90 m and 95 m. Both systems are equipped with a redundant leak monitoring system and are designed for temperatures down to-200 ° C. A special feature of the project was the manufacture of the pipes: BRUGG Pipes produced individual lengths of 90 and 95 meters. This meant that only one connection point was required per pipe. The small number of connections simplified installation and, at the same time, reduced potential weak points. This is an important factor for tightness and operational safety, especially in cryogenic applications.
“ This design results in specific, demanding requirements for material selection” – Dr Jürgen Essler
Demanding requirements The special piping developed for the aerospace industry is designed to transport cryogenic media, such as liquid methane, at a temperature of −161.6 ° C.“ Our core products for these applications are stainless steel 316L corrugated pipe-in-pipe systems, incorporating a vacuum annulus between two corrugated stainless steel pipes for thermal insulation,” explains Dr Essler.“ This design results in
The special pipes are equipped with a leak monitoring system and are designed for temperatures down to-200 ° C.
specific, demanding requirements for material selection.”“ The material must be suitable for our welding and cold-forming processes, and it must also retain sufficient ductility after production. Furthermore, an austenitic material is required to ensure reliable performance at cryogenic temperatures. In addition, it must be guaranteed that the materials provide permanent leak tightness for the vacuum insulation, with leak rates in the range of 10-9 mbar /( l · s).”“ Based on these requirements, 316L( 1.4404) stainless steel is selected as the base material for the corrugated pipes. Stainless steel coils in accordance with EN 10028, with a maximum thickness of 1 mm, are used for this application. These coils are welded using TIG or laser welding without filler material, allowing the production of several hundred meters of pipe in a single manufacturing run.” The high ductility of 316L, even after cold forming, ensures that the pipes can be coiled and uncoiled on drums for transportation and installation without compromising their integrity.
“ The end terminations of the corrugated pipes are also manufactured from stainless steel,” continues Dr Essler.“ Here, market availability is taken into consideration, and either 316L( 1.4404) or 316Ti( 1.4571) is used, together with the appropriate filler materials for TIG welding.
X-ray inspection of weld seams Special attention was also paid to the project’ s cleanliness requirements. Although no classic clean-room production was available, the company complied with the project-specific specifications by adapting manufacturing processes and implementing strict quality assurance measures. All weld seams were X-ray inspected both at the factory in Wunstorf( Germany) and on the construction site. This non-destructive testing ensured that the requirements for tightness and safety were met. Dr Essler continues:“ While the welding of these materials does not present any particular challenges, one of the key factors for achieving consistently high weld quality is proper joint preparation
42 Stainless Steel World May 2026 www. stainless-steel-world. net