Rockwell Automation 440L GuardShield PAC Type 4 Safety Light Curtain - Manual (Page 11)

GuardShield™ PAC Safety Light Curtain Installation Instructions
9
Original instructions
Figure 5: GuardShield three-beam PAC and corner mirrors mounted
to pedestal floor stands
Figure 6: GuardShield two-beam PAC and corner mirrors mounted to
pedestal floor stands
Figures 5 and 6 show two- and three-beam GuardShield PACs
with two corner mirrors providing three-sided detection. Mirrors
are offered in either narrow or wide styles in heights to
accommodate two- or three-beam GuardShield PACs.
Response Time
The response time of the two- and three-beam GuardShield PAC
safety light curtain is 20 ms without beam coding or 30 ms with
beam coding.
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 mounting the light curtains around the
machinery. 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
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
90º position of the crankshaft rotation.
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.
ATTENTION
The GuardShield PAC safety light curtains
must be mounted at a sufficient distance
from the hazardous motion to ensure that the
machine stops before a person’s body reaches
the hazard.