Step 5: Release/Block Stored Energy

There may be hazardous energy stored within the machine (e.g. trapped heat in a thermal system, gases that need vented, tension in a spring assembly). All potentially hazardous stored or residual energy must be released, blocked, disconnected, restrained, or otherwise rendered safe.

• Ensure the area is clear before releasing any stored energy.
• Ensure all parts have stopped moving.
• Relieve trapped pressure.
• Block or brace parts that could fall.
• Bleed lines and vent valves open.
• If stored energy can re-accumulate, then monitor conditions to make sure it stays below hazardous levels.

Examples of releasing/blocking stored energy:

• Mechanical: Carefully release energy from springs that are still compressed. If this is not possible, use blocks to hold the parts that may move if the energy is released.
• Gravitational: Use a safety block or pin to prevent movement of parts that may fall or shift. If feasible, lower the part to a height where falling is impossible.
• Electrical: Capacitors store electrical energy. In some cases, capacitors hold a charge and may release energy very rapidly (similar to the flash of a camera). In other cases, capacitors are used to remove spikes and surges in order to protect other electrical components. Capacitors must be discharged in the lockout process in order to protect workers from electrical shock. Contact the manufacturer for guidance. Many systems with electrical components, motors, or switch gears contain capacitors.
• Hydraulic and Pneumatic: Setting the valves in the closed position and locking them into place only isolates the lines from more energy entering the system. In most cases, there will still be residual energy left in the lines as pressurized fluid. This residual energy can be removed by bleeding the lines through pressure relief valves. Contact the manufacturer for more specific details, or if no pressure relief valves are available, what other methods are available.
• Chemical: If available, bleed lines and/or cap ends to remove chemicals from the system.