REG NASA-LLIS-0563-1997 Lessons Learned Electrical Connectors.pdf

1、Lessons Learned Entry: 0563Lesson Info:a71 Lesson Number: 0563a71 Lesson Date: 1997-09-08a71 Submitting Organization: SSCa71 Submitted by: Charles BoppSubject: Electrical Connectors Description of Driving Event: A routine hookup and pump testing was being attempted on LOX barge #5 by Test Complex te

2、chnicians. They were working under a process plan and standard operating procedure as required. The testing was necessary to functionally check the system after repair was performed.The technicians encountered difficulty in making a threaded electrical connection between the 480 VAC shore power cabl

3、e connector and the LOX barge receptacle. The cable was insufficient in length to make a comfortable hookup. They pulled on it attempting to gain range by decreasing the slack in the line. Although they were successful in mating the connectors, the weight and angle of the cable applied undue stresse

4、s. The lead technician was under the impression the connection was adequate due to the fact the associated retaining nut felt to tighten by hand. A strap wrench was therefore used to further tighten the nut.When power was applied to energize the system, a high current arc was produced within the con

5、nection. The forces exerted by this arc resulted in the connector plug being forcefully ejected free from the receptacle. This action caused the connector plug to come in contact with the barge access ramp. The chain holding the associated aluminum connector plug moisture/dust cap was severed. The c

6、ap was then propelled and struck a technician working nearby behind the ear.Lesson(s) Learned: By not having ample cable length, excessive stress was applied to the threaded electrical connections causing misalignment. This left a false impression of thread engagement to be observed. Proper mating o

7、f the connection was wrongly assumed when tightening due to a cross-threading effect.Recommendation(s): Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-1. Implement electrical and/or mechanical modifications that will ensure proper electrical connect

8、ion.2. Emphasize in the work authorizing documents specific procedures including verification steps to follow to prevent electrical connection mismating.3. Technicians performing tasks involving 480 VAC should not attempt to energize such a circuit unless they are absolutely sure the connection is p

9、ositively made.4. Technicians should contact the responsible engineer, supervisor, safety engineer, etc., for back up verification if and/or when any doubt should arise concerning integrity of the connection.5. Issue a shop safety bulletin regarding the potential hazards associated with 480 VAC syst

10、ems.6. Technicians should be educated on high voltage hazards and proper electrical connection techniques.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): N/AAdditional Info: Approval Info: a71 Approval Date: 1997-09-10a71 Approval Name: Mark McCalmana71 Approval Organization: QA00a71 Approval Phone Number: 601-688-2150Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-