Guards >>
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Guards are barriers which prevent access to danger areas.
There are four general types of guards:
| Fixed |
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As its name implies, a fixed guard is a
permanent part of the machine. It is not dependent
upon moving parts to function. It may be constructed
of sheet metal, screen, wire cloth, bars, plastic, or
any other material that is substantial enough to
withstand whatever impact it may receive and to endure
prolonged use. This guard is usually preferable to all
other types because of its relative simplicity.
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Safeguarding Action |
Advantages |
Limitations |
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Can be constructed to suit many specific
applications
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In-plant construction is often possible
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Can provide maximum protection
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Usually requires minimum maintenance
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Can be suitable to high production, repetitive
operations
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May interfere with visibility
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Can be limited to specific operations
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Machine adjustment and repair often require its
removal, thereby necessitating other means of
protection for maintenance personnel
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| Interlocked |
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When this type of guard is opened or
removed, the tripping mechanism and/or power
automatically shuts off or disengages, the moving
parts of the machine are stopped, and the machine
cannot cycle or be started until the guard is back in
place.
An interlocked guard may use electrical.
mechanical, hydraulic, or pneumatic power or any
combination of these. Interlocks should not prevent
"inching" by remote control if required.
Replacing the guard should not automatically restart
the machine. To be effective, all removable guards
should be interlocked to prevent occupational hazards. |
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Safeguarding
Action |
Advantages |
Limitations |
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Shuts off or disengages power,
stops the moving parts and prevents
starting of machine when guard is open; should
require the machine to be stopped before the
worker can reach into the danger area
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Can provide maximum protection
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Allows access to machine for removing jams
without time consuming removal of fixed guards
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Requires careful adjustment and maintenance
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May be easy to disengage
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| Adjustable |
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Adjustable guards are useful because they
allow flexibility in accommodating various sizes of stock.
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Safeguarding
Action |
Advantages |
Limitations |
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Provides a barrier that may be adjusted to facilitate
a variety of production operations
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Can be constructed to suit many specific applications
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Can be adjusted to admit varying sizes of stock
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Hands may enter danger area - protection
may not be complete at all times
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May require frequent maintenance and/or adjustment
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The guard may be made ineffective by the operator
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May interfere with visibility
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| Self-adjusting |
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The openings of these barriers are
determined by the movement of the stock. As the
operator moves the stock into the danger area, the
guard is pushed away, providing an opening which is
only large enough to admit the stock. After the stock
is removed, the guard returns to the rest position.
This guard protects the operator by placing a barrier
between the danger area and the operator. The guards
may be constructed of plastic, metal, or other
substantial material. Self-adjusting guards offer
different degrees of protection.
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Safeguarding
Action |
Advantages |
Limitations |
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Provides a barrier that moves according to the
size of the stock entering the danger area
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Off-the-shelf guards are often commercially
available
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Does not always provide maximum protection
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May interfere with visibility
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May require frequent maintenance and adjustment
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