Eliminating Static Seal Failure in a Cryogenic HAGC Cylinder Bore
Introduction
On an MHI HAGC cylinder, leakage appeared between the cylinder sleeve and bore. Inspection found the o-ring twisted, extruded, and mechanically damaged, reducing reliability and adding cost to what was already an expensive cryogenic assembly process.
Failure analysis traced the damage to the installation process itself rather than the seal design. The sleeve is chilled to -70°C for a shrink-fit assembly, and at that temperature the standard NBR o-ring becomes rigid and brittle. Over the long installation travel required to seat the sleeve, the o-ring rolled and twisted in its groove, and the tight interference fit between bore and sleeve left no room for the seal to compress.
Challenge
To eliminate leakage in a static seal caused by installation damage during a -70°C cryogenic shrink-fit sleeve assembly, where the interference fit left no room for the seal to compress during insertion.
Solution
System Seals redesigned the seal geometry and the assembly process together. A custom profiled seal replaced the standard NBR o-ring, and the interference fit was changed to a clearance fit, removing the need for cryogenic chilling during assembly entirely.
Result
Bore leakage was completely eliminated, and the -70°C cryogenic step was removed from the assembly process. System Seals later applied the same redesign to a comparable mill application with a history of repeated bottom seal failures, with long-term reliability validated in the field.
