REG NASA-LLIS-1369-2003 Lessons Learned Functional Failures of Electrical Circuit Breaker Lock Out Tag Out (LOTO) Devices.pdf

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1、Lessons Learned Entry: 1369Lesson Info:a71 Lesson Number: 1369a71 Lesson Date: 2003-03-26a71 Submitting Organization: JSCa71 Submitted by: Bill CrittendenSubject: Functional Failures of Electrical Circuit Breaker Lock Out/Tag Out (LOTO) Devices Abstract: Investigation of a lockout device that did no

2、t perform its intended function discovered that the circuit breaker could still be operated even with the device in place.Description of Driving Event: While working on a lighting system in a JSC building, it was determined that a circuit breaker that had been properly locked and tag out in the de-e

3、nergized (open) position, had been repositioned to its energized (closed) position, with the lockout device still installed. INVESTIGATION FINDINGS: It was determined through experimentation that the breaker lever could be thrown to the energized (closed) position with the lock out device installed.

4、 Later investigations of TFE and TED breakers also found that another similar breaker thumb-screwed type lockout device had fallen off after it had been properly installed and locked 1. They must insure that the circuit breaker lock out devices reliably secure the breaker in a “Safe“ configuration,

5、and can support the weight of the lock and tag for the duration of the Lock Out Tag Out operation.2. They must carefully try out the locked and tagged out breaker to ensure that it is really secured in a “Safe“ position. This requires that the breaker lever to be physically pushed on in an effort to

6、 close the breaker after the device is properly installed, while no one is exposed to the hazards of the circuit. Some of the breaker lock out devices allowed enough play in the breaker lever, to close or energize the circuit with the lock out device in place.3. The importance of qualified personnel

7、 actually testing the electrical circuit with validated test equipment, to ensure that the circuit has been, and still is in a “Safe“ deenergize state before working on it. This must be done initially and upon returning from any absence or break in time when the “Safe“ condition of the circuit could

8、 have been re-configured. In short - lock out, tag out, try out, and test out the electrical circuits being locked and tagged.Evidence of Recurrence Control Effectiveness: PendingDocuments Related to Lesson: JPG 1700.1, “JSC Health and Safety Handbook“, Chapter 8.1, Electrical Safety, & chapter 8.2,

9、 Lockout/Tagout PracticesMission Directorate(s): N/AAdditional Key Phrase(s): a71 Configuration Managementa71 Energya71 Facilitiesa71 Ground Equipmenta71 Ground Operationsa71 Hardwarea71 Human Factorsa71 Human Resources & Educationa71 Industrial OperationsProvided by IHSNot for ResaleNo reproduction

10、 or networking permitted without license from IHS-,-,-a71 Personal Protective Equipmenta71 Policy & Planninga71 Risk Management/Assessmenta71 Safety & Mission Assurancea71 Securitya71 Test & VerificationAdditional Info: Approval Info: a71 Approval Date: 2003-10-01a71 Approval Name: Ron Montaguea71 Approval Organization: JSCa71 Approval Phone Number: 281-483-8576Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-