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Lock-out / Tag-out
8 questions By Tony R. Kuphaldt
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Question 7 of 8
Suppose you are finishing a maintenance project where an electric motor was locked out and tagged, and now the work is complete. Your lock is the last one to be removed from the circuit breaker, everyone else already having taken their locks and tags off. What should you do before removing your lock and turning the circuit breaker back on?
Reveal answerYou should check the equipment site to be sure no one is still working on it, unaware of the impending startup.
Notes:Real-life story here: I was once asked to place an electric motor back in service after it had been locked out for a few days, for routine maintenance. I removed my lock and tag, and was just about to turn the breaker back on, when better judgment prevailed and I decided to first check the job site. Lo and behold, there, still working on the motor coupling, were two contract employees completely oblivious to the situation. They had not been told there was a circuit breaker to secure power to that electric motor, nor were they aware that they needed to lock it out in addition to everyone else on the project! Had I turned that circuit breaker back on, the motor could have started up and severely injured at least one of them!
Lesson to be learned: if you are performing work on a piece of equipment, you need to have your lock and your tag securing energy to that equipment. Never, ever trust someone else to lock-out and tag-out a circuit breaker for you!
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Question 8 of 8
Large power distribution circuit breakers look nothing like the small breakers seen in residential and commercial electrical systems. They are large units, which “plug” into cubicles so as to facilitate removal and replacement for routine maintenance.
When securing an electrical system in a zero energy state prior to commencement of maintenance work, it is common practice to “rack out” any large circuit breakers feeding power to the system. What exactly does this term mean, and what is the procedure for “racking out” a circuit breaker?
Reveal answerTo “rack out” a circuit breaker means to unplug it from its cubicle so that it cannot conduct electric power to the circuit where work is being performed, even if someone were to close its contacts.
Notes:Ask your students whether the circuit breaker should be opened (turned off) before or after racking it out of the cubicle. Does this sequence matter? Why or why not? Also, ask your students where they think the standard locking and tagging procedures apply in a breaker that it racked out. What, exactly, should the lock prevent someone from doing?
