A qualified electrical worker is performing maintenance on a de-energized 480V motor control center. After de-energizing the equipment and verifying the absence of voltage, the worker needs to prevent accidental re-energization during the work. Which of the following is the most effective and compliant method to achieve this according to Cal/OSHA?
- AApplying a lockout device with a personal tag to the disconnect switch.
- BRemoving the fuses from the circuit and keeping them nearby.
- CPlacing a 'DO NOT OPERATE' tag on the disconnect switch.
- DAssigning another worker to stand guard at the disconnect switch.
Show answer & explanationAnswer & explanation
Correct answer: A. Applying a lockout device with a personal tag to the disconnect switch.
According to Cal/OSHA and NFPA 70E lockout/tagout procedures, applying a physical lockout device with a personal tag is the most effective method to prevent accidental re-energization and is a mandatory step for ensuring worker safety on de-energized equipment. This practice physically prevents the operation of the energy isolating device.
Why the other options are wrong
- B. Removing fuses can de-energize the circuit, but it is not the primary or most compliant method for preventing re-energization during maintenance, as fuses can be reinserted. Lockout/tagout on the main disconnect is preferred.
- C. While tagging is part of the procedure, a tag alone does not physically prevent re-energization, making it less effective than a lockout device.
- D. Standing guard is a less reliable method and is generally only used as a temporary last resort when lockout devices cannot be applied, which is not the case here. It does not meet the full requirements of a lockout/tagout program.
Lockout/Tagout (LOTO)
A safety procedure used to ensure that dangerous machines are properly shut off and not able to be started up again prior to the completion of maintenance or servicing work. It involves isolating energy sources and physically locking them in an 'off' or 'safe' position.
- Mandatory for control of hazardous energy according to Cal/OSHA and NFPA 70E.
- Involves physical lockout devices and personal tags.
- Prevents accidental re-energization during maintenance or service.
Memory trick: Lock Out, Tag Out, Stay Safe, No Doubt!