NFPA 70E provides a terse directive on employee involvement. It says, “Each person who could be exposed directly or indirectly to a source of electrical energy shall be involved in the lockout/tagout procedures” [120.2(A)].
It then provides an example of direct exposure and another of indirect exposure [Informational Note]. The first example is an electrician who is working on the motor starter control. It’s a direct exposure situation because the electrician could come into direct contact with the electricity present on the motor starter control terminals.
The second example is who is working on the coupling between the motor and the compressor. This person isn’t exposed to the electrical energy, but they are exposed to the mechanical energy produced by the motor due to the presence of the electrical energy. The way you protect this person in the second example is by de-energizing the circuit supplying the motor and motor starter.
This principle of protecting not only against shock from direct contact with electricity but also against injury from electrically driven equipment is a core principle in lockout/tagout. To fulfill this principle, you must start lockout/tagout with an assessment of the entire system you’re working on. In so doing, you should also look for where you may be the direct or indirect recipient of non-electrical energy sources.
Some questions to answer:
- Who else will also need their lock and tag on specific equipment? That is, who else may be directly or indirectly exposed?
- Who else (including operators) may be affected by de-energization or operation of this circuit/panel/machine even if not directly or indirectly exposed?
- What are the operational implications, as deduced from the drawings? What are the operational implications, according to the operators? Resolve any discrepancies.
- Are there any emergency devices (e.g., pressure valves, annunciators, fire protection) that are presumably operational? What happens if one operates while the area is occupied? Do any of these need to be rendered temporarily inoperable, and, if so, what is the exact procedure for that?
- Which equipment must be prepared in advance for shutdown (e.g., by removing work in process)?
- Are there any time limits or other restrictions or conditions of lockout to consider?
- What other energy sources must be addressed? Consider kinetic (e.g., punch press ram position), pneumatic, hydraulic, process pressure, etc.
- What non-electrical means should or must be used in addition to electrical lockout?
Not everyone who is “involved” will necessarily be aware of being involved. If you are performing the lockout/tagout, part of your job is to determine who may be directly or indirectly affected by your work on the equipment and then involve them in the lockout/tagout process. In many plants, discussing the project with the production superintendent or designated supervisor is part of the process, and it will give you answers to those questions posed above.
