scope:

Description of Driving Event:

All inventory SRM case o-rings were reinspected during the STS 51-L investigation. When reinspected using original inspection equipment (mechanical micrometer), very few out-of-tolerance conditions were identified. However, when reinspected with a laser micrometer with a 0.007-inch measuring beam, numerous small localized out-of-tolerance conditions were detected. All inventory o-rings were also x-rayed, indicating numerous o-ring inclusions. Although tests proved that these conditions did not affect the sealing capability, this does indicate a potential problem and a need for processing and inspection improvements. It was also learned during this investigation that the o-ring material manufacturer had changed material formulations and processing numerous times since starting to produce srm o-ring material. While all these formulations resulted in o-ring material that was in compliance with MIL-R-83248, this lack of standardization could possibly result in application problems and is unacceptable for such a critical item