On an MHI HAGC cylinder at Baosteel Shanghai, 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.
The Challenge: To eliminate leakage
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.
- −70°C Shrink-Fit Assembly: Sleeve chilled to cryogenic temperature, NBR o-ring becomes rigid and brittle
- Long Installation Travel: O-ring rolls and twists in groove during sleeve insertion
- Interference Fit Tolerance: Tight bore-to-sleeve fit leaves no room for seal compliance
The 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.
The 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.
- 0: - Bore Leakage
- −70°C - Cryogenic Step
- Increase Seal Reliability
