OSHA Definition
Per OSHA 1910.147(b), energized means connected to an energy source or containing residual or stored energy.
Understanding the Risk
Equipment is considered energized any time it is connected to an energy source or retains stored energy. This includes obvious cases like a machine connected to electrical power, but also less obvious situations: a spring under tension, a hydraulic system holding pressure, an elevated load held by a mechanism, or a chemical process with residual heat.
Stored Energy
Even after isolation, equipment may remain energized due to stored or residual energy. Capacitors retain electrical charge, springs retain mechanical energy, hydraulic accumulators retain pressure, and elevated components retain gravitational potential energy. The LOTO procedure must address the dissipation or restraint of all stored energy.
