Today we replaced our first rupture disc assembly due to exhaust leakage from the flange. The gasket had blown out, apparently due to the gasket material becoming wet, softening and losing it’s mechanical integrity. The material is Frezelit isoplan 500, and according to the Frenzelit website, is “based on biosoluble fibers”. This appears to mean “water soluble”, leading to failure after 2 years and about 5000 hours operation in a rainy climate. This is a HUG-supplied exhaust and SCR. We are making up rain shields for the flanges and coating the exposed edges of the replacement assembly with a high temp coating to help water proof this material. The replacement disc assemblies consist of two discs with several layers of the isoplan 500 sandwiched in-between in a bonded assembly.
Has anyone out there found a better alternative to these short-lived OEM assemblies? We also question why there are two discs sandwiched together, vs. a single disc with a single gasket on each side.
Dave Mordecai, Hopkins Generating Station