1、Lessons Learned Entry: 0294Lesson Info:a71 Lesson Number: 0294a71 Lesson Date: 1993-07-23a71 Submitting Organization: LERCa71 Submitted by: S. PapellSubject: Studs and Tapped Holes Description of Driving Event: A rubber seal friction force was being measured in an altitude tank between a plate and a
2、n 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
3、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
4、paint that did not allow the larger studs, designed for the assembly, to be installed.Lesson(s) Learned: When studs sized to fit into tapped holes are difficult to install, the use of smaller sized studs in test facility assemblies can cause test rig failure.Recommendation(s): Inspect tapped holes f
5、or contamination such as rust or paint prior to making repetitive assemblies and chase threads with taps if necessary to make studs (which are designed for the job) fit.Evidence of Recurrence Control Effectiveness: Provided by IHSNot for ResaleNo reproduction or networking permitted without license
6、from IHS-,-,-N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 HardwareAdditional Info: Approval Info: a71 Approval Date: 1994-06-15a71 Approval Name: Maria Havenhilla71 Approval Organization: LERC/EBASa71 Approval Phone Number: 216-977-1483Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
