1、Lessons Learned Entry: 0080Lesson Info:a71 Lesson Number: 0080a71 Lesson Date: 1992-05-22a71 Submitting Organization: KSCa71 Submitted by: David PenningtonSubject: SRB Holddown Stud Detensioning Operation Description of Driving Event: During detensioning operations of a holddown post, while pressure
2、 of approximately 8K to 10K lbs was being applied, a loud “bang“ was heard. Pressure on the tensioner fell to zero. It was later determined that the loud “bang“ was the result of thread failure between the puller bar socket and the SRB holddown stud. With only 8 threads engaged, the shear stresses i
3、ncreased to 96,000 psi, as compared to 98,000 psi shear strength of the stud. Examination of the holddown stud revealed that 8 threads sheared on a 135 degree circumferential segment of the holddown stud.Lesson(s) Learned: Failure to fully engage the puller bar prior to detensioning a holddown post,
4、 resulted in failure of the puller bar socket-to-holddown post threads.Recommendation(s): Include a requirement in the OMI to take a measurement verifying that the puller bar is fully engaged prior to start of detensioning operation.Evidence of Recurrence Control Effectiveness: N/ADocuments Related
5、to Lesson: N/AProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Mission Directorate(s): a71 Space Operationsa71 Exploration SystemsAdditional Key Phrase(s): a71 Hardwarea71 Launch Processa71 Launch Vehiclea71 Packaging Handling Storagea71 Parts Materials & ProcessesAdditional Info: Approval Info: a71 Approval Date: 1994-06-02a71 Approval Name: James G. Klinea71 Approval Organization: KSC/HEIa71 Approval Phone Number: 407-867-7614Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
