Glossary · Safe work, maintenance and competence
Zero-energy state
Also known as: zero energy state, de-energized state
In machine safety, a zero-energy state is a verified condition in which hazardous energy has been isolated, dissipated, restrained or otherwise controlled, so it cannot cause harm during the work.
- Machine safety
- Maintenance
In one sentence
A zero-energy state is the verified condition in which all hazardous energy is isolated, released or restrained before work starts.
Example
Before clearing a jam in a baler, the operator locks out the power, bleeds the hydraulic accumulator, lowers the platen onto blocks and confirms zero pressure on the gauge.
How it applies
- Machine safety: “Zero” means controlled, not always absent. Gravity and spring energy often cannot be removed and must be restrained with blocks or pins. Stored energy that can re-accumulate needs continued verification.
- Technical documentation: Procedures list every energy source, how it is controlled and how the controlled state is verified. The machine manufacturer’s information on residual energy is essential input.
- Evidence: The tryout is the verification that the zero-energy state was reached. Without it, the state is assumed, not verified.
- Design: Gauges, test points and bleed valves at accessible locations make verification practical.
Zero-energy state vs. safe state
A safe state means risk is acceptable for the situation and may include energized functions. A zero-energy state is the specific condition required for servicing work under lockout/tagout.