scope:

Description of Driving Event:

A rubber seal friction force was being measured in an altitude tank between a plate and an inlet flow duct when the mishap occurred. The failure occurred at an inlet test condition of 10.2 psia with a test cell pressure of 3.6 psia. As the inlet pressure was being increased, the mounting studs holding the seal together failed.

The investigating committee determined that improperly sized studs were used to hold the rig together. The structure had tapped 1/2-13 holes to mate with the plate mount pads. 7/16-14 studs were used for assembly because of the difficulty of getting the 1/2-13 studs into the tapped holes.

Further investigation revealed that the tapped holes contained rust and paint that did not allow the larger studs, designed for the assembly, to be installed.