How to make equipment safe to work on. Controlled equipment has several energy sources at once, and each one must be isolated, locked, and verified before you touch anything.
Isolate every energy source, not just the obvious one. A pump can be electrically dead and still full of pressurized, hot chemical. It can also be re-energized by a controller, a timer, or someone using the app miles away.
| Source | Examples | Isolate by |
|---|---|---|
| Electrical | Controller supply, relay boards, wireless switches and relay strips, pumps, drives | Breaker or disconnect, locked off; plug removed and kept under your control. See Electrical Safety. |
| Pressure | Process piping, injection lines, closed loops, expansion tanks, accumulators | Isolation valves closed and locked, then drained or vented to zero. See Pressurized Systems. |
| Thermal | Boiler water, hot loops, steam lines, motor housings | Time. Let the section cool before opening it. |
| Chemical | Dosing lines, day tanks, sensor housings | Supply valves closed, lines depressurized and flushed where possible. See Chemical Handling. |
| Automatic control | Control modes, schedules, interlock resets, remote commands | Physical isolation of the actuator. Disabling software is not enough. See Automatic and Remote Operation. |
| Mechanical | Motors, rotating pump parts, spring-loaded valves | Electrical isolation, and waiting for rotation to stop. |
Only then begin work. Remove locks in reverse order when the work is finished, after tools are cleared and everyone is clear of the equipment.
Never trust a switch position, an indicator lamp, or an app screen as proof of isolation. Measure.
Lockout/tagout is regulated in most jurisdictions: for example OSHA 29 CFR 1910.147 in the United States and CSA Z460 in Canada. Follow your site’s written procedure where one exists.