Lockout/tagout procedures should be used any time an electrical device or circuit is being serviced. Whether working alone or with others, locks and tags provide a visual reminder and physical barrier to prevent electrical circuits and devices from being unintentionally energized while service is performed. This is an important step in preventing potential injury or death caused by electrical shock. Lockout means to place a lock on a device, tool or cord to prevent energizing a circuit or starting a piece of machinery or equipment. The locking mechanism prevents the switch from being turned to the on position or a cord from being plugged in. Thus, the lock prevents the equipment from operating and prevents potential injury or death by disallowing the machine to start and/or disallowing a current to flow. Tagout means to place a warning tag on a switch or other shut-off device to warn others not to start or use the piece of equipment. Tagout should be used only with lockout, unless locking out the equipment is not possible.
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| Tool/Cord Protection | Switch Protection | Breaker Protection |
Application
All electrically-powered equipment, including but not limited to wood chippers, sharpening machines, soil mixing or filling equipment, limb or brush shredders, and other electrically powered devices should be locked out while being repaired.
In addition to lockout, any stored energy in the equipment should be blocked from release. For example, hydraulic equipment in a raised position should be lowered or securely supported in the raised position to prevent accidental lowering during repair. Electrical energy may be stored in a battery or capacitor and should be discharged or disconnected. Amputations, factures or even death could occur while cleaning or repairing equipment if it starts unexpectedly.
Suggested Lockout and Tagout Procedures
- Notify all affected employees or workers that a lockout/tagout procedure is ready to begin.
- Turn off power to the equipment at the control panel.
- Turn off or pull the main disconnect. Be sure all stored energy is released or restrained.
- Check all locks and tags for defects.
- Attach a safety lock or tag on the energy-isolating device.
- Try to restart the equipment at the control panel to ensure the lock is secured.
- Check the machine for possible residual pressures, particularly for hydraulic systems and reciprocating and conveying equipment.
- Test the circuit with a voltage-detecting instrument to verify the absence of voltage.
- Complete the repair or servicing work.
- Replace all guards on the machinery.
- Remove the lockout/tagout device.
- Verify proper operation of the repaired or replaced equipment or electrical supply.
- Let others know that the equipment is back in service.
Common Mistakes in Lockouts
- Leaving keys in the locks.
- Locking the control circuit and not the main disconnect or switch.
- Not testing the controls to make sure they are definitely inoperative.
References
NFPA 70E-Standard for Electrical Safety in the Workplace. Quincy, MA: National Fire Protection Assoc., 2009.
Reviewer: Kent McGuire, CFAES Safety and Health Coordinator, Food, Agricultural and Biological Engineering