Lockout procedures commonly lock the energy isolating device using which component?

• A. Breaker
• B. Disconnect switch
• C. Mainline switch
• D. Fuse holder

Answer: (C)

Lockout work centers on locking the device that actually isolates the power source from the equipment. That energy-isolating device is the mainline switch, which is the primary disconnect that fully cuts or stops the supply to the circuit or machine. By placing a padlock on the mainline switch, you prevent someone from closing the switch and re-energizing the equipment while work is being done.

While a circuit breaker can also be an isolating device, and lockout practices may involve breakers in some setups, the mainline (disconnection) switch is the standard isolation point used for lockout in many facilities. Fuse holders aren’t typically locked with standard lockout devices because fuses are protective components that are removed or bypassed rather than securely locked in place for isolation.