One thing that many find confusing regarding the control of hazardous energy is the actual hazard they are trying to render to a Zero Energy State (ZES). This is a simple concept, but many get it wrong in their programs and machine-specific procedures. Let’s take compressed air as an example. Many compressed air systems in manufacturing facilities will operate around 120 psi. We have a machine that uses this compressed air to move a guillotine cutting blade. To get the blade to a ZES, the air must be locked out and bled down to 0 psi (e.g., ZES).
But the HAZARD is the guillotine-cutting blade, and the hazardous energy is this blade’s actions/movements. The air is NOT the hazard we are attempting to control; it is simply how we will control the hazard associated with the guillotine-cutting blade. Sometimes, we lock out an energy source that may not be hazardous, but what it does in the machine creates a hazard. In some situations, simply locking out the air to a machine may NOT be sufficient to achieve a SAFE STATE (i.e., ZES). We may need blocks/cribbing to manually hold up a part of the machine, which air usually does for us. We need the device to be in the UP position, but once we ISOLATE the air, the device will fall due to gravity (another energy source that needs to be addressed). So we ISOLATE the air so the device will NOT function (e.g., no longer a hazard to the workers), but now we have to ensure the device stays in the UP position during our work – this will require some official blocks/cribbing that is IDENTIFIED as an ISOLATION device and is SECURED in place via a Lock Out or Tag Out.