ng=0 width=100%>Yahoo! is not affiliated with the authors of this page or responsible for its content.
What safety requirements are there for an Optical Protective Device?
199
1-888-282-2123
www.jokabsafetyna.com
What safety requirements are
there for an Optical Protective Device?
Light Grid
for long distances.
Light Grid
with monitored
by-passing
during material
transport.
Light Curtain for
short safety
distances.
Light Curtain to
protect during
cycle initiation.
Light Curtain as area protection.
Light Curtain
for inner area limiting.
High safety demands are stated in the standards
EN 61 496-1 and prEN 61 496-2 which deal with
optical protective devices. The main demands are
on a safe stopping function and that light from light
sources other than the transmitter or other distur-
bances do not affect the safety function.
Depending on how the safety function is built up
there are safety components of type 2 and 4 accord-
ing to EN 954-1.
Type 4 which has the highest safety level, states
that a fault is not allowed to affect the safety function
and that the fault shall be detected by the outputs
opening immediately or that they do not reconnect
after being disconnected. Maximum allowed aperture
angle for the light is +
_ 2
�.
Type 2 states that a simple but monitored safety
function is required, which means that the safety
function shall be monitored through periodic tests
which open the output when a fault occurs. Between
the testing times there can be faults which result in
the safety component malfunctioning. The test func-
tion can either be built into the safety device or an
external unit (e.g. the machines control system) can
initiate a test. Maximum allowed aperture angle for
the light is +
_ 4
�.
Light curtains and light grids are included among
the products in the machine directives appendix 4,
which means that an external certifying procedure
with an officially recognized institution is called for.
Light Grids for
Passable Protection
Both light curtains and light grids can often be used
as passable protection into a risk area. This is called
passable protection because it is possible to get in
behind the safety device. Common applications are
robot installations, openings for in and out passage of
material, etc. The choice between light curtain or light
grid is often a question of available safety distance,
reach and price. Light curtains are often chosen for
short safety distances light grids are chosen for long
reach up to 50 m and for a low price.