The Hierarchy of Protection for Machinery
Why design comes first, guards second and instructions last, and how to apply that order to a real machine.
11 min
Activities: 0 of 2
The order matters
Machinery safety follows a fixed order of thinking. First, remove the hazard by design, so there is nothing to protect against. Second, where a hazard remains, keep people away from it with guards and protective devices. Third, for what still remains, give information, warnings, training and personal protective equipment. Each step is weaker than the one before, because it depends more on people doing the right thing every time.
The existing lessons showed that injuries happen when people are inside the machine. The hierarchy tells you where to look for the fix.
The three steps
Change the machine so the hazard does not exist or cannot reach people: lower speeds or forces, rounded edges, enclosed drives, gaps too small to trap a finger or large enough not to crush a body, controls placed outside the danger zone.
Put the controls in order, strongest first
- 1Interlocked guard or protective device
- 2Warning sign and instructions
- 3Fixed guard
- 4Personal protective equipment
- 5Remove the hazard by design
An operator's hand comes near a cutting blade on every cycle. Which response follows the hierarchy best?