Episode 142 focuses on the role, limitations, and common misconceptions surrounding machine interlocks. Dr. Ayers explains that many organizations assume interlocks provide full protection, when in reality they are only one component of a larger safeguarding system—and often a weak one if misunderstood.
This episode is all about accurate hazard identification and ensuring leaders understand the true function of interlocks.
Machine interlocks do not eliminate hazards. They simply detect access and trigger a control response. Their effectiveness depends entirely on the machine’s stopping behavior, control reliability, and proper application.
Dr. Ayers emphasizes that:
Interlocks sense when a guard or gate is opened
They do not physically prevent access
They rely on the machine to stop quickly enough
They are often mistaken for physical protection
This misunderstanding leads to serious risk gaps.
Interlocks only protect workers if:
The machine stops before a person can reach the hazard
Stopping distance is measured and verified
The interlock is placed far enough from the danger zone
If stopping time is long, an interlock alone is insufficient.
Common issues include:
Using interlocks on high‑speed or high‑inertia equipment
Installing them too close to the hazard
Failing to validate control‑reliable circuits
Assuming “interlocked” means “safe”
Many incidents occur because the interlock was technically functioning—but the system design was flawed.
The episode highlights that interlocks are often:
Defeated with magnets or tools
Overridden for convenience
Misaligned or damaged
Ignored during maintenance
If workers can easily bypass an interlock, it’s not a safeguard—it’s a decoration.
Interlocks are appropriate for:
Low‑inertia hazards
Tasks requiring frequent access
Systems with verified fast stopping times
They are not appropriate for:
Whole‑body access hazards
High‑speed rotating equipment
Situations requiring containment or physical barriers
Choosing the wrong safeguarding method is itself a hazard.
Machine interlocks only work when engineered, validated, and applied correctly. They do not stop hazards by themselves, and they do not replace physical guards. Safety leaders must understand their limitations and ensure interlocks are part of a complete, verified safeguarding strategy.
