1.3 The vocabulary: authorized, affected, isolating device

1 Authorized, affected, and everyone else

Three levels of involvement, three levels of training, and only one of them gets to touch the lock.

The definition of authorized employee ends with a sentence people miss: "An affected employee becomes an authorized employee when that employee's duties include performing servicing or maintenance covered under this section." The label follows the task, not the badge. A machine operator whose job includes clearing jams under a lockout procedure is an authorized employee for that task — and has to be trained to (c)(7)(i)(A), not merely instructed to (c)(7)(i)(B).

1910.147(c)(8) closes the loop: lockout or tagout shall be performed only by the authorized employees who are performing the servicing or maintenance. A supervisor cannot hang a lock on behalf of a technician. A technician cannot hang one on behalf of a colleague who is running late.

2 Energy isolating device — and what is emphatically not one

1910.147(b) defines an energy isolating device as "a mechanical device that physically prevents the transmission or release of energy," and then gives examples: a manually operated electrical circuit breaker; a disconnect switch; a manually operated switch by which the conductors of a circuit can be disconnected from all ungrounded supply conductors, with no pole operable independently; a line valve; a block; and any similar device used to block or isolate energy.

The definition finishes with the sentence that decides most disputes: "Push buttons, selector switches and other control circuit type devices are not energy isolating devices."

That single sentence rules out the stop button, the e-stop, the HMI "maintenance mode," the mode selector key switch, the PLC output someone has forced off, and the interlocked gate. Every one of those interrupts a control signal. Every one of them can be defeated by a component failure, a stuck relay, a shorted conductor, a software state, or a colleague who does not know you are inside. A disconnect, a line valve or a block interrupts the energy itself.

3 Capable of being locked out

This definition decides whether your plant may run a tagout system at all, so it is worth quoting closely. 1910.147(b): an energy isolating device is capable of being locked out "if it has a hasp or other means of attachment to which, or through which, a lock can be affixed, or it has a locking mechanism built into it. Other energy isolating devices are capable of being locked out, if lockout can be achieved without the need to dismantle, rebuild, or replace the energy isolating device or permanently alter its energy control capability."

The second sentence is the demanding one. A valve with no hasp is still "capable of being locked out" if a bolt-on chain-and-clamp lockout, a gate valve cover, or a ball-valve clamp will hold it shut — because fitting one of those does not dismantle, rebuild, replace or permanently alter the valve. The bar for saying "we can't lock this" is much higher than "it did not come with a hole."

And it keeps rising. 1910.147(c)(2)(iii) requires that since January 2, 1990, whenever a machine gets a replacement, major repair, renovation or modification, and whenever new machines are installed, the energy isolating devices be designed to accept a lockout device. A plant running tagout in 2026 on equipment it has replaced since 1990 has a problem that no amount of tag training will fix.

4 Energized, energy source, and stored energy

The definition of energized is four words long and does a great deal of work: "connected to an energy source or containing residual or stored energy." A machine with its disconnect open and its accumulator charged is, by the standard's own definition, still energized. So is a press with a ram held up on trapped hydraulic pressure, a centrifuge coasting down, a jacketed vessel still at 300 °F, or a capacitor bank that has not bled off.

Energy source is defined just as broadly: any source of electrical, mechanical, hydraulic, pneumatic, chemical, thermal, or other energy. The words "or other" are doing real work there. Gravity is not on the list by name and is one of the most common killers in maintenance work — a suspended load, a raised platen, an unsupported dump body. It lands squarely inside "other," and 1910.147(a)(3)(i) speaks of "otherwise disabling" machines, which is where blocking and cribbing come from.

5 Lockout, tagout, and the devices themselves

Four definitions in 1910.147(b) form two pairs, and the difference between the pairs is the difference between physics and communication.

1. 1
   Lockout — placing a lockout device on an energy isolating device, in accordance with an established procedure, ensuring that the device and the equipment cannot be operated until the lockout device is removed.
2. 2
   Lockout device — a device using a positive means such as a key or combination lock to hold the isolating device in a safe position and prevent energizing. Blank flanges and bolted slip blinds are included.
3. 3
   Tagout — placing a tagout device on an energy isolating device, in accordance with an established procedure, to indicate that the device and the equipment may not be operated until the tag is removed.
4. 4
   Tagout device — a prominent warning device with a means of attachment, securely fastened to the isolating device, indicating that it may not be operated.

Notice that both lockout definitions use the words "cannot be operated," and both tagout definitions use "may not be operated." That is not a drafting accident. It is the entire distinction, written into the vocabulary.

Both pairs share one phrase: "in accordance with an established procedure." A lock hung without a procedure behind it is not lockout as the standard defines it. That is the bridge to the next chapter.

6 Two definitions people forget: setting up, and normal production operations

Setting up is defined as "any work performed to prepare a machine or equipment to perform its normal production operation." It is deliberately broad, and it is listed inside the definition of servicing and maintenance. Changeovers, die changes, tooling swaps, threading a new roll of film, dialing in a first article — all of it is setup, all of it is servicing, and all of it comes under the standard when an employee is exposed to unexpected energization.

Normal production operations, by contrast, is defined in a single line: "the utilization of a machine or equipment to perform its intended production function." Running parts. That is all it means. The moment the machine stops performing its intended production function and someone starts preparing, adjusting, cleaning or unjamming it, the vocabulary has changed and so has the standard that applies.