Even after equipment is locked out and tagged, why might it still be unsafe to repair?

• A. Equipment parts can still move
• B. The person who tagged the equipment might not be at the plant
• C. Stored energy in gas, electricity, air, water, steam, and hydraulic systems
• D. Only a qualified maintenance worker can repair the equipment

Answer: (C)

Lockout and tagging stops a machine from starting, but it doesn’t remove all the energy that might be stored in the system. That stored energy can be in many forms—electrical charge, compressed air or hydraulic pressure, steam, gas, or even springs and gravity—that can be released suddenly when you open a valve, disconnect a line, or disturb a component during repair.

Electrical energy can remain in capacitors or energized parts even after power is cut. Pressure in lines or vessels can snap or spray if valves are opened or fittings are disturbed. Steam, gas, or water under pressure can release with dangerous force. Springs or heavy rotating masses can snap back or move if not properly blocked. Because of these possibilities, the work should only proceed after confirming that all energy sources have been safely dissipated or isolated and that there is zero residual energy, not just after the control has been de-energized. This is why stored energy hazards are the reason repair may still be unsafe even with lockout and tagging.