2.3 Verification: the step that is not a formality

1 The one-sentence requirement, and what it does not say

1910.147(d)(6) is the shortest step in the sequence: "Prior to starting work on machines or equipment that have been locked out or tagged out, the authorized employee shall verify that isolation and deenergization of the machine or equipment have been accomplished."

Notice what it does not say. It does not say to check that the lock is on — you just put it on. It does not say to confirm the disconnect is open — you just opened it. It says to verify that isolation and deenergization have been accomplished, which is a statement about the machine, not about your own actions. Everything up to step 5 was you doing things. Step 6 is the machine answering.

That distinction is why verification is the step most often reduced to a formality. Opening a breaker and then confirming that you opened it feels like verification and proves nothing. The question step 6 asks is whether the energy is gone from the place your hands are going.

2 The try step, and the caution that follows it

Appendix A gives the mechanical version in step 7, and it contains a caution most people have never read. The step: "Ensure that the equipment is disconnected from the energy source(s) by first checking that no personnel are exposed, then verify the isolation of the equipment by operating the push button or other normal operating control(s) or by testing to make certain the equipment will not operate."

Three things in one sentence. First, check that nobody is exposed before you try to start the machine — you are about to command motion on purpose, and if the isolation is incomplete the machine will move. Second, the try itself, using the normal operating control. Third, the alternative: "or by testing," which is what you do when trying the control is not meaningful.

Then the caution: "Return operating control(s) to neutral or 'off' position after verifying the isolation of the equipment." A control left in the run position is a machine that starts the instant power returns, which is precisely the moment when the crew is standing around it admiring the finished job.

3 The electrical version: test, and test for the surprises

Subpart S is far more specific, and its wording is the most useful in the whole body of standards for anybody who opens a panel. 1910.333(b)(2)(iv) says the requirements of that paragraph "shall be met before any circuits or equipment can be considered and worked as deenergized," and there are two of them.

(A): "A qualified person shall operate the equipment operating controls or otherwise verify that the equipment cannot be restarted." That is the try step, assigned to a qualified person.

(B) is the one to memorize: "A qualified person shall use test equipment to test the circuit elements and electrical parts of equipment to which employees will be exposed and shall verify that the circuit elements and equipment parts are deenergized. The test shall also determine if any energized condition exists as a result of inadvertently induced voltage or unrelated voltage backfeed even though specific parts of the circuit have been deenergized and presumed to be safe. If the circuit to be tested is over 600 volts, nominal, the test equipment shall be checked for proper operation immediately before and immediately after this test."

• A qualified person. Not whoever has the meter. The definition is in 1910.332(b)(3) — see Part 1, Chapter 3.
• The parts employees will be exposed to. Test where your hands are going, not at the panel you locked.
• Induced voltage and unrelated backfeed. The standard names the two failure modes explicitly: voltage induced from a parallel circuit, and voltage arriving from a source the drawing does not show.
• Over 600 volts: check the meter before and after. A meter that fails between two readings gives you a confident zero. Proving it live before and after is what closes that hole.

And the instrument itself is regulated. 1910.334(c)(1): "Only qualified persons may perform testing work on electric circuits or equipment." (c)(2): test instruments, leads, cables, power cords, probes and connectors are visually inspected for external defects and damage before use, and anything defective is removed from service. (c)(3): they "shall be rated for the circuits and equipment to which they will be connected and shall be designed for the environment in which they will be used."

4 Verifying each kind of energy

Every energy has a way of answering, and it is never the same answer twice. The table below is the shape of a good verification step in a written procedure — which is what 1910.147(c)(4)(ii)(D) requires the procedure to contain.

One line about the atmospheric case, because maintenance work runs into it constantly: 1910.146(c)(5)(ii)(C) requires the internal atmosphere to be tested with a calibrated direct-reading instrument "for oxygen content, for flammable gases and vapors, and for potential toxic air contaminants, in that order." Oxygen first, because every other reading depends on it. Part 4, Chapter 2 covers the rest.

5 Verification is not a signature

A recurring pattern in maintenance incidents is a procedure with a verification box that gets initialed at the desk. The paperwork side of this is real — 1910.147(c)(4)(ii)(D) requires the procedure to state the specific requirements for testing to verify effectiveness — but the paper is downstream of the act. A box initialed before the test is worse than no box, because it makes the next person believe a test happened.

The 8,000-volt fatality above is the shape of that failure at its worst: teardown after a test, a circuit presumed dead because the test was over, no visual verification, no instrument. And the detail that makes it a maintenance story rather than an electrical one is that he was doing mechanical work — loosening a nut on a lead — on equipment whose electrical state he had no evidence about.

6 Re-verification: the three moments

A verification describes a moment. Three things end that moment, and each of them starts the step over.

1. 1
   Reaccumulation. Where stored energy can build back to a hazardous level, (d)(5)(ii) requires verification of isolation to be continued for the duration of the work — not repeated once.
2. 2
   Any temporary removal of the devices. 1910.147(f)(1)(v) requires all systems to be deenergized and energy control measures reapplied "in accordance with paragraph (d)" to continue the work, which puts you back at step 6.
3. 3
   A shift or personnel change. 1910.147(f)(4) requires specific procedures for the orderly transfer of device protection between off-going and oncoming employees. The oncoming authorized employee is now the person exposed, and the verification is theirs.

The third one is the most commonly skipped and the easiest to fix: the oncoming tech puts a personal lock on before the off-going one comes off, and then verifies the machine themselves. Part 5, Chapter 3 covers how the group lockbox makes that mechanical rather than verbal.