Scenario:
You’re out and about, and you come up on two workers working on a piece of equipment. You stop and engage the two workers on their energy isolation for their work. One of the workers operates the machine and has it locked out as part of his end-of-shift cleaning tasks. The other worker is a maintenance worker and he is replacing the 480V motor on the machine.
The Operator has all of his LOTO points locked out per the machine-specific procedure and has the keys to his locks in his pocket.
The maintenance employee has his personal lock on the electrical disconnect, along with the Operators lock.
Everything looks good, but do you go deeper or shake hands, say thank you, and go about your way?
If you walk away from this arrangement, you may be missing a very common error/shortcut in LOTO that is NOT allowed even by OSHA’s minimum electrical safety standards.
The scenario happens hundreds of times a day across the USA. A maintenance worker recognizes a machine is down and needs to take advantage of this downtime. He/She asks the Operator if they can use the time to do their work, which involves isolating electrical energy. But in these situations, the maintenance worker simply applies their lock to the electrical disconnect along with the Operator who has already locked out the disconnect.
Do you see where this is going?
For the Operator, who is NOT actually doing electrical work, he/she will simply use the ON/OFF or START/STOP buttons to verify that he/she locked out the correct electrical disconnect. Can the qualified electrical worker who is actually going to be disconnecting the 480V wires from the motor rely on this means to verify ZES?
ABSOLUTELY NOT!
A qualified electrical worker who is performing LOTO for the means to perform “electrical work” under an “electrical safe condition” can NOT use the ON/OFF or START/STOP buttons as their means to verify ZES. This is a requirement under BOTH OSHA and NEC requirements; however, many safety professionals may not be aware of this significant difference in the means to verify a Zero Energy State.
This is what is REQUIRED for the Qualified Electrical Worker ON TOP of what the Operator has already done for him/her…
(emphasis by me)
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1910.333(b)(2)(iv)(A) A qualified person shall operate the equipment operating controls or otherwise verify that the equipment cannot be restarted. 1910.333(b)(2)(iv)(B) 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. |
So it is clear that the qualified electrical worker may be able to rely on the Operator’s use of the ON/OFF or START/STOP buttons as step A, but ONLY they can do step B.
The last sentence of the OSHA standard can be debated, as I have required this practice in my ESRWPs to be done on ALL voltages. But take notice, OSHA only requires the volt meter be checked for proper operation immediately before and immediately after this test when the voltage involved is over 600 volts.
This comes from NFPA 70E…
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110.4 Test Instruments and Equipment … (E) Operation Verification When test instruments are used for testing the absence of voltage on conductors or circuit parts operating at voltages equal to or greater than 50 volts, the operation of the test instrument shall be verified on any known voltage source before and after an absence of voltage test is performed. |
So at least NFPA requires this testing procedure for voltages equal to or greater than 50 volts.
But here is the issue… how many facilities require this, train on this, and audit this SAFETY CRITICAL step when work involves electrical work?
Have we defined and quantified our expectations within our ESRWPs?
You may be surprised at what you find when you begin to ask questions about how qualified electrical workers are verifying ZES before they begin work on electrical energy sources. The traditional means of verifying a ZES, as unqualified electrical workers do to clean a machine or clear a jam on their machine, is ONLY step 1 for a qualified electrical worker to verify ZES.
And for those who have qualified electrical workers who state they do this practice, take it to the next level as have them demonstrate their use of their volt meter in doing so.
Are they testing their meter on a KNOWN SOURCE, then testing the ISOLATED SOURCE to verify ZES, and then testing the KNOWN SOURCE again before starting work?
Do they do this regardless of the voltages involved?
Or do they follow OSHA’s limits of greater than 600 volts or NFPA’s 50 volts?
What do your ESRWPs require?
Does your facility even have an ESRWP that defines and quantifies this SAFETY CRITICAL practice for qualified electrical workers?
Maybe you learned something from this posting – let me know in your comments below.