4.3 Lockout/Tagout (LOTO) & Electrical Safety

Energy isolation is not an administrative exercise; it is a physical constraint applied to a kinetic or potential force. A plastic "Do Not Operate" tag offers zero mechanical resistance to a breaker being flipped. Therefore, the safety of the technician relies entirely on the Zero Energy State—a condition where all energy sources (electrical, pneumatic, thermal, gravitational) are mechanically blocked and verified as dissipated.

LOTO Execution Logic

The procedure is binary: either the equipment is physically incapable of energization, or it is "Live." There is no intermediate "Safe" state based on trust.

• If Personnel bodies enter a machine danger zone -> Then apply a personal padlock to the energy isolation point (Breaker/Valve).
  • Constraint: 1 Person = 1 Lock. Never share keys. Never rely on a supervisor's lock.
• If Isolation is applied -> Then execute the "Try" step.
  • Action: Attempt to start the machine using the operator controls. If it starts, the isolation failed.
• If Shift change occurs during LOTO -> Then apply the incoming lock before removing the outgoing lock.
  • Constraint: The chain of custody on the energy block must never be broken.

Pro-Tip: "Live-Dead-Live." When verifying zero voltage, test your meter on a known live source first, test the target circuit (Dead), then re-test on the known source. This confirms your meter didn’t fail during the critical measurement.

Electrical Safety & Arc Flash

Electricity is invisible until it fails. Treat all conductors as energized until measured.

• If Voltage is > 50V AC/DC -> Then Arc Flash boundaries apply.
  • Requirement: Establish a Limited Approach Boundary (typically 1 m for low voltage) where only qualified personnel may enter.
• If Measuring Voltage -> Then use CAT III / CAT IV rated instruments only.
  • Physics: CAT II (Appliance) meters cannot withstand the transient spikes found in industrial distribution panels; they will explode in your hand.
• If Work requires "Hot" troubleshooting -> Then specific Energized Work Permit and Arc Flash PPE (Face shield, Balaclava, Rated Gloves) are mandatory.

Final Checklist

Parameter	Metric / Rule	Critical State
Isolation verification	"Try" Step	Machine Does Not Start
Lock Ownership	Key Custody	1 Person = 1 Key
Voltage Verification	Meter Test	Live-Dead-Live
Meter Rating	Category	CAT III (Min)
Approach Boundary	Unqualified Persons	> 1 Meter
LOTO Device	Type	Physical Lock (Not Just Tag)