1、Lessons Learned Entry: 0564Lesson Info:a71 Lesson Number: 0564a71 Lesson Date: 1997-09-10a71 Submitting Organization: SSCa71 Submitted by: Dale LarsonDescription of Driving Event: An electrical mishap occurred on January 30, 1997, at the Water Deluge Pumping Substation 202 at the Cryogenic Transfer
2、Area at the Stennis Space Center (SSC). Electrical Technicians were working under a Troubleshooting Incident Report (TIR) and standard operating procedures as required. The troubleshooting was necessary to determine why the “Run“ indicating lights for Deluge Pumps No. 2 and No. 3 (of four) were reve
3、rsed from actual pump operation.While attempting to also check Pump No. 4, the mishap occurred when the technician jumpered terminals at a field wiring terminal block in the rear of the north switchgear section, believing they were the “Pump No. 4 Run“ contact. An electric arc caused second degree b
4、urns on the hands and third degree burns to the left index finger of the technician. The arc occurred because the two terminals were a 480 VAC tap from the switchgear incoming bus. When the terminals were shorted with the jumper, fault current flowed, and the electric arc formed as the circuit was i
5、nterrupted.Lesson(s) Learned: 1. The electrical technician believed he was jumpering a status contact in a 28 VDC control circuit. He didnt check every terminal for hazardous voltage before jumpering the contact.2. Personal Protective Equipment (PPE) gloves suitable for 480 VAC were not worn.3. Wiri
6、ng revisions had been made that were not documented, either on site drawings or on readily available red-lined working prints.4. Hazardous voltage (480 VAC) was mixed on the terminal block with low voltage (28 VDC) control signals.Recommendation(s): 1. Provide troubleshooting refresher training to:
7、verify the electrical potentials involved in any Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-troubleshooting operation before intentional or accidental contact; recognize patterns and consistency; identify when “live“ troubleshooting is appropria
8、te, and how to perform “live“ troubleshooting safely; review PPE training; and review Lockout and Tagout requirements. Properly rated test equipment must be used.2. Issue a Shop Bulletin on Safe Troubleshooting Practices, including a warning that all configurations should be verified before working
9、around hazardous energy sources.3. Include notation on the TIR Procedure to: obtain verified documentation and drawings for the troubleshooting; warning about high potential hazards; specify PPE requirements; and specify if “live“ troubleshooting is required. Identify which circuits may be energized
10、 if multiple sources are involved.4. Revise the “Facility Engineering Documentation Standard“, to require Engineering Modification Instruction drawings, Engineering Orders, installation red-lines, and configuration change red-lines for critical electrical systems be promptly updated after receipt.5.
11、 Review the Documentation Procedures to assure open or pending equipment configuration changes are identified whenever drawing copies are obtained from Central Engineering Files (CEF).6. Review SSC NASA and contractor policies and procedures to require the prompt forwarding of all red-line configura
12、tion changes to CEF for prompt updating.7. Working drawings with all red-line configuration changes should be maintained at a defined location near the equipment, for reference and use by all parties for troubleshooting purposes.8. All configuration changes to equipment shared by contractors should
13、be reviewed and approved by a single Change Control Board.9. Revise the “Facility Electrical Design Standards“ to require terminal block connections carrying significantly different and hazardous voltage (such as 480 VAC) should require warning labels and separation or barriers from other voltages.1
14、0. Review the drawings and inspect the equipment in all substations, switchboards, motor control centers, and other equipment where 480 volt power circuits and low voltage control circuits are used. Determine if hazardous voltages are mixed with low voltage wiring. Add barriers or separation to redu
15、ce the risk of personnel contact to hazardous voltages. Add labels at hazardous voltage terminals to alert personnel to the hazard.Evidence of Recurrence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): Provided by IHSNot for ResaleNo reproduction or networking permi
16、tted without license from IHS-,-,-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-,-,-
