Which type of guard is a permanent part of the machine and is generally preferred because it has no moving parts?
- An adjustable guard
- A fixed guard
- A self-adjusting guard
- An interlocked guard
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B. A fixed guard
A fixed guard is a permanent barrier that does not depend on moving parts or on the operator to work, so it is usually the first choice. An interlocked guard also protects well but relies on a mechanism that can fail or be defeated.
Reference: 29 CFR 1910.212(a)(1); OSHA machine guarding guidance (OSHA 3170)
What should happen when an interlocked guard is opened while the machine is running?
- The machine stops, then restarts by itself as soon as the guard is closed again
- Power is shut off or disengaged, and the machine cannot cycle until the guard is back in place
- An alarm sounds, and the machine keeps running at its normal operating speed
- The machine slows to half speed so the operator can reach in to clear a jam
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B. Power is shut off or disengaged, and the machine cannot cycle until the guard is back in place
An interlocked guard automatically shuts off or disengages power when opened, and the machine cannot be cycled until the guard is replaced. Closing the guard should not restart the machine by itself; the operator must start it deliberately.
Reference: OSHA machine guarding guidance (OSHA 3170); 29 CFR 1910.212(a)(1)
A press uses a light curtain that stops the stroke when a hand breaks the beam. What kind of safeguard is this?
- A fixed barrier guard
- A pullback device
- A two-hand control
- A presence-sensing device
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D. A presence-sensing device
A light curtain senses when part of the body enters the danger zone and stops the machine, so it is a presence-sensing device. A pullback device uses cables attached to the wrists to withdraw the hands as the ram descends.
Reference: 29 CFR 1910.217(c)(3)(iii); OSHA machine guarding guidance (OSHA 3170)