Do you make any of these seven assumptions?
1. It’s safe until there is a reason to suspect otherwise. You should consider it unsafe until you prove otherwise. This doesn’t mean extensive testing of each possible variable that could pose a danger. It means doing things like verifying a denergization attempt by measuring for voltage using the three-step system (measure a known voltage, the test point and a known voltage again). It means doing things like checking a ladder for mechanical defects, knowing the age and fall history of a harness before using it, and measuring the oxygen level in a confined space before entering it.
2. The job briefing covered all risks. It can’t possibly cover unknown risks. The solution is to be alert to your environment and any changes in it while you are working. For example, you’re 30 minutes into the job and you start to smell some kind of chemical. The person preparing the job briefing could not have anticipated a seal failure in a process line would produce a leak. Other problems such as grease dollops or smears on the floor, extension cords running across stairs, or somebody slopping gasoline while refueling a portable generator because he was too lazy to get a funnel, are all outside the scope of what can be reasonably expected to be covered in a job briefing.
3. If you can’t see it, hear it, or smell it, then it’s not there. A classic example is an invisible, odorless gas such as nitrogen that has pretty much filled a vessel. Or carbon monoxide that has slowly accumulated in a back area of a garage. Or carbon dioxide that has settled into the transformer vault after leaking out of the fire suppression system. Look for indirect signs of problems that may not be directly detectable.
For example, if an area is protected by a fire suppression system that uses bottles of suppressant (carbon monoxide or anything else), check the bottle gages against the value stated on the inspection tag. We have lockout/tagout procedures partly because you can’t see, hear, or smell current running through energized conductors (not at the normal distribution voltages for premises wiring), so it is necessary to deliberately deenergize them and then use a meter to verify they aren’t energized.
4. The crew before you correctly implemented lockout/tagout; to take over where they left off on this job, you simply replace their tags and locks with yours. The correct way is for you to review the drawings, then walk through lockout/tagout with the other crew to replace locks and tags. Both you and they should be able to explain, from the drawings, why this particular switch or breaker is being locked out and how doing so isolates the circuit/equipment in question.
5. An electrical lockout/tagout removes all energy sources you may encounter. A stamping machine is the classic example in teaching that this assumption is wrong. When the ram is all the way up, kinetic energy is at its peak. Locking out the breaker won’t stop that ram from falling on you. That prevention is achieved by blocking the ram mechanically or by lowering it completely.
6. Everybody in your crew is working in a safe manner and not making any safety mistakes. We all make mistakes. Crew members need to check each other. As the day wears on and fatigue sets in, concentration tends to wane and it’s easy to go on autopilot. One reason electricians typically work in pairs is so that one is checking the other.
If Ron is checking Barb’s lockout/tagout of breaker X, she needs to watch him do that. One reason is so Ron doesn’t shove two test leads at the breaker at the same time and cause an arc flash. Another reason is to ensure Ron is testing the right breaker. Ron, of course, would have also checked Barb’s tag against the drawing to make sure she was on the right breaker.
By doing this together, they catch what could have been a deadly mistake by either one of them. They could save time by just assuming the other person never, ever makes mistakes. But do you actually know any such person?
7. It was safe before lunch, it’s safe after lunch. Things happen while you’re gone. Someone takes a shortcut through your work area despite the yellow tape and accidentally kicks over a solvent can (but keeps going). An operator sees your crew is at lunch, so despite your tag puts the machine into RUN mode for “just a few minutes” so he can make an adjustment or load new blanks in for the next run. He gets interrupted, leaves, and forgets about the control switch.
While lockout/tagout is supposed to be sacroscant (you never operate a tagged-out control, locked or not), not everyone respects the rules. In an appliance plant, a maintenance crew spent more than an hour setting up a 750-ton press for a maintenance and repair task. They got called away on a critical equipment downtime call. When they came back, they walked through the isolation procedure from Step One. They discovered someone had “borrowed” two of the ram locking devices and one of the safety bars used as a backup to those devices.
If you’re going to make any assumptions about work safety, you will be safest if you assume the worst and then work your way forward from there.
About the Author
Mark Lamendola
Mark is an expert in maintenance management, having racked up an impressive track record during his time working in the field. He also has extensive knowledge of, and practical expertise with, the National Electrical Code (NEC). Through his consulting business, he provides articles and training materials on electrical topics, specializing in making difficult subjects easy to understand and focusing on the practical aspects of electrical work.
Prior to starting his own business, Mark served as the Technical Editor on EC&M for six years, worked three years in nuclear maintenance, six years as a contract project engineer/project manager, three years as a systems engineer, and three years in plant maintenance management.
Mark earned an AAS degree from Rock Valley College, a BSEET from Columbia Pacific University, and an MBA from Lake Erie College. He’s also completed several related certifications over the years and even was formerly licensed as a Master Electrician. He is a Senior Member of the IEEE and past Chairman of the Kansas City Chapters of both the IEEE and the IEEE Computer Society. Mark also served as the program director for, a board member of, and webmaster of, the Midwest Chapter of the 7x24 Exchange. He has also held memberships with the following organizations: NETA, NFPA, International Association of Webmasters, and Institute of Certified Professional Managers.