Seven application steps
- Preparation for isolation and notification of the affected functions
- Shutting the machine down
- Isolating every energy source
- Tagging
- Locking
- Releasing stored energy
- Trying — verifying the absence of energy
Five steps back
Inspect, check, remove the locks and refit the guards, notify, restore energy. Skipping the return steps happens more often than skipping the locking, and is talked about far less.
Why the last step is counted separately
Fitting a lock does not prove the energy is gone. The try step is the only one that catches a wrong line locked, a dual fed machine, or an unlocked standby source. That is why the record says "tried", not "locked".
Forgotten energy types
| Type | Typical omission |
|---|---|
| Mechanical — gravity | A suspended load or a raised cover |
| Mechanical — spring | A compressed spring, a counterweight |
| Hydraulic and pneumatic | Pressure trapped in the line |
| Thermal | A surface that has not cooled |
| Chemical | Product left in the line, back flow |
The energy map
In the system we measured, every item of work equipment had a hazardous energy map and a visual instruction; energy points were coded and signed on the machine, and the map and the instruction had to carry the same codes. Codes that do not match mean the wrong point gets locked on site.
Training levels
The system recognised four levels: affected worker, authorised worker (with examination and certificate), other workers, and contractors. The list of authorised workers was posted in the relevant areas, and lock and tag equipment was issued personally against signature.