Civil Engineering Reference
In-Depth Information
designed to permit a flow of parts in and out of the working envelope. Access doors must
be interlocked.
TABLE 18.6
Current Safety Devices
Safeguarding Devices
Description
Typical Application and
Restrictions
Fencing
Guards with interlocked gates
Heavy material handling
Guard rails
Awareness barriers with interlocked
gates
Light material handling
Chains and posts
Passive guard
Small assembly; lightduty
applications
Curtain
Flexible screen
Protection from welding and heat
in addition to safety
Photoelectric beams
Photocell/optical
Often used in combination with
other devices
Pressure-sensitive mats
and surfaces
On floor or attached to machine; can
sense walking or touching
Often used in combination with
other devices
Floor markings
Painted floor warnings
Indicates robot/machine work
envelope
CHAINS
Chains are passive guards that work as awareness barriers. They can be easily overcome
by intruders. However, they are appropriate for small robots and machines used for light
duty work, and the main function is to remind the operator.
WELDING CURTAIN
The main purpose of a welding curtain is to protect operators from radiation and
ultraviolet light from welding. They also have a secondary purpose, since they are in
effect physical barriers.
PHOTOELECTRIC BEAMS
Photo cells can be used for outlining the work barrier. Alternative devices such as light
curtains and magnetic curtains are also sometimes used to detect personnel intruding into
the working envelope.
PRESSURE-SENSITIVE MATS
These are used to detect a person walking towards the work envelope. Their use is
impractical if parts have to be rolled in and out of the work envelope. Pressuresensitive
surfaces or skins may also be attached to a critical work surface or a machine, so if an
operator presses against or touches this area, the robot or machine is stopped.
