Rockwell Automation 445L GuardShield Micro 400 Safety Light Curtain User Manual - Manual (Page 10)

R
GuardShield™ Micro 400 Safety Light Curtain User Manual
8
Original instructions
Figure 3: Additional label for blanking. After configuring blanking, the label must be
attached and clearly visible on the receiver portion of the light curtain
Determining the Safety Distance
The light curtain must be mounted with proper safety distance
• From the point of danger
• From reflecting surfaces
US Safety Distance Formula
This distance, referred to as the safety distance, must be properly
calculated prior to determining the safety light curtain’s
protective height and mounting the light curtains on the
machine. Failure to properly calculate this safety distance may
result in operator injury.
In the United States there are two formulas that are used to
properly calculate the safety distance. The first, the OSHA formula,
is the minimum requirement for the calculation of the safety
distance. The second formula, the one recommended by Rockwell
Automation, is the ANSI formula, which incorporates additional
factors to be considered when calculating the safety distance.
OSHA Safety Distance Calculation Formula
The OSHA safety distance formula as specified in CFR Subpart O
1910.217 is as follows:
Ds = 63 X T
S
Ds Safety Distance in inches
63 Is the OSHA recommended hand speed constant in inches
per second
Ts Is the total stop time of all devices in the safety circuit,
measured in seconds. This value must include all
components involved in stopping the hazardous motion of
the machinery. For a mechanical power press it is the
stopping time measured at approximately the 90° position
of the crankshaft rotation.
Note: The T
S
number must include the response times of all
devices, including the response time of the safety light
curtain, the safety light curtain controller (if used), the
machine’s control circuit and any other devices that react
to stop the hazardous motion of the machinery. Not
including the response time of a device or devices in the
stop time calculation will result in insufficient safety
distance for the application. This may result in operator
injury.
The ANSI Safety Distance Formula
The ANSI safety distance formula, which is the Rockwell
Automation recommended formula, is as follows:
D
S
= K x (T
S
+ T
CS
+ T
r
+ T
bm
) + D
pf
Ds Minimum safety distance between the safeguarding device
and the nearest point of operation hazard, in inches.
K Hand speed constant in inches per second. The ANSI
standard value is 63 inches per second when the operator
begins reaching toward the point of operation hazard from
rest. NOTE: ANSI B11.19 1990 E4.2.3.3.5 states “The value of
the hand speed constant, K, has been determined by
Fixed blanking From beam................to beam.....
Floating blanking Resolution................................mm
Reduced resolution Reaction time...........................ms
IMPORTANT
With the blanking function, the resolution and
the response time of the GuardShield Micro 400
light curtain system will be changed. If the
"Blanking" function is activated, a new, longer
response time and a new, larger resolution will
be present, which must be applied to the
calculation of the safety distance. The minimal
safety distance of the light curtain must always
be adapted to the actual operating mode. The
corresponding reaction time of a light curtain
without blanking is stated on the label of each
system. If blanking is configured, the new
reaction time, and the new resolution,
according to the configuration control
document must be entered in the appropriate
spaces on the supplied label, and attached to
the GuardShield Micro 400 light curtain (see
Figure 3). The labels are provided with the
GuardShield Micro 400 mounting kit.
IMPORTANT
Further information on "Blanking" may be
found in the “Configuration and Diagnostic
Tool” manual for the corresponding safety
controller (e.g. MSR42).
IMPORTANT
The GuardShield Micro 400 safety light curtains
must be mounted at a sufficient distance from
the pinch point or point of operation hazard to
ensure that the machine stops before a person’s
finger, hand, arm(s), or body reaches the hazard.
IMPORTANT
Regardless of the calculated safety distance,
GuardShield Micro 400 safety light curtains
should never be mounted closer than six inches
from the point of operation or pinch point
hazard.
IMPORTANT
Determining Stop Time: The measurement of
stopping time (Ts) must include the stopping
times of all devices in the stop circuit. Not
including all device and control system
elements when calculating Ts will result in an
inaccurate safety distance calculation.