1、Lessons Learned Entry: 0021Lesson Info:a71 Lesson Number: 0021a71 Lesson Date: 1991-08-29a71 Submitting Organization: JSCa71 Submitted by: S. MartinSubject: Use of Particle Impact Noise Detection Test to Detect Contamination Description of Driving Event: During various shuttle orbiter missions, seve
2、ral anomalies occurred which were subsequently attributed to particle contamination within limit switches. In three such instances the particles were metallic substances and of a sufficient size (greater than 0.015 inches) to create a premature state change. In a fourth instance, the particle contam
3、ination was non-metallic which resulted in a high contact resistance and the loss of a “closed“ indication. These switch failures were attributed to contamination from metallic (weld expulsion, less than 0.010 inches), glass from headers, ceramic from insulators, rubber from back-filling equipment,
4、polymers, and polyesters. Limit switches are often used to: (1) prevent systems or components from reaching damaging stress levels and, (2) inhibiting unwanted events or conditions. The primary corrective action to prevent recurrence of these failures was to impose Particle Impact Noise Detection (P
5、IND) testing on all future limit switch manufacturing. additional techniques included improved cleaning processes and the addition of filters to purging and drying fluids to preclude particle introduction into the components.Lesson(s) Learned: Use of particle impact noise detection test will detect
6、metallic and non-metallic particles that remain from fabrication processes.Recommendation(s): Suppliers perform a Particle Impact Noise Detection (PIND) test on all limit switches prior to delivery.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Evid
7、ence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Space Operationsa71 Aeronautics ResearchAdditional Key Phrase(s): a71 Flight Operationsa71 Flight Equipmenta71 Hardwarea71 Launch Vehiclea71 Parts Materials & Processesa71
8、Spacecrafta71 Test Articlea71 Test & VerificationAdditional Info: Approval Info: a71 Approval Date: 1993-09-10a71 Approval Name: Ron Montaguea71 Approval Organization: JSC/NS3a71 Approval Phone Number: 281-483-8576Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
