REG NASA-LLIS-0005-1991 Lessons Learned - Inadequate Electrical Cable Strain Relief Design Leading to Shorts and Ignition.pdf

1、Lessons Learned Entry: 0005Lesson Info:a71 Lesson Number: 0005a71 Lesson Date: 1991-04-22a71 Submitting Organization: JSCa71 Submitted by: T MichaelSubject: Inadequate Electrical Cable Strain Relief Design Leading to Shorts and Ignition Description of Driving Event: A pair of shuttle orbiter telepri

2、nter 28 VDC power cable wires shorted together. A short section of wire and insulation ignited and burned releasing a small amount of contaminants within the crew cabin. The burn through produced an open circuit, but was of insufficient duration (150 milliseconds at 50 amps) to open the circuit brea

3、ker. The crew manually opened the breaker and removed the cable. An investigation determined the cause of the failure was inproperly designed strain relief at one end of the cable where mated. The resultant flexure of the cable caused 360 degree annular breaks in the insulation of the power wires ad

4、jacent to each other. The cable was redesigned to utilize a more effective 90 degree bend strain relief device. The wire insulation material was changed from kapton to the more flexible teflon. Other orbiter cables of similar design were inspected and designs reviewed to preclude problems in similar

5、 configurations. This incident involved a non-mission essential component and the crew was potentially exposed to voltages below human shock hazard levels. However, the failure produced an ignition source.Lesson(s) Learned: Inadequate strain relief design for electrical cables can result in electric

6、al shorts and subsequent ignition within closed environments such as the shuttle orbiter crew cabin.Recommendation(s): The orbiter teleprinter cable strain relief device was redesigned and the wire insulation was changed from kapton to teflon. Designs of other orbiter system cables were reviewed and

7、 existing cables inspected.Evidence of Recurrence Control Effectiveness: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N/ADocuments Related to Lesson: N/AMission Directorate(s): a71 Exploration Systemsa71 Sciencea71 Space Operationsa71 Aeronautics

8、ResearchAdditional Key Phrase(s): a71 Aircrafta71 Energya71 Flight Operationsa71 Flight Equipmenta71 Hardwarea71 Launch Vehiclea71 Parts Materials & Processesa71 SpacecraftAdditional Info: Approval Info: a71 Approval Date: 1993-09-09a71 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-,-,-