Hard (fixed) Guarding
Reset Switch
Nearest Hazard Point
Robot
Turn-
Table
Hard (fixed)
Guarding
Safety Light Curtain/Screen
Figure 8. Safety distance (minimum distance) and hard (fixed) guarding
Formula and Examples
U.S. Applications
European Applications
The Safety (Separation) Distance formula for U.S. applications:
Ds = K × (Ts + Tr) + Dpf
The Minimum Distance formula for European applications:
S = (K × T) + C
Ds
the Safety Distance, in inches
K
1600 mm per second (or 63 in per second), the OSHA
29CFR1910.217, and ANSI B11.19 recommended hand-speed
constant (see Note 1 below)
Ts
the overall stop time of the machine (in seconds) from the initial
stop signal to the final ceasing of all motion, including stop times
of all relevant control elements (for example, IM-T-.. Interface
Modules) and measured at maximum machine velocity (see Note 3
below)
Tr
the maximum response time, in seconds, of the EZ-SCREEN LS
Basic emitter/receiver pair (depending on model)
Dpf
the added distance due to the depth penetration factor as
prescribed in OSHA 29CFR1910.217, and ANSI B11.19 for U.S.
applications. See Depth Penetration Factor (Dpf) table below or
calculate using the formula (in mm): Dpf = 3.4 × (S - 7) where S is
the resolution of the light curtain (for S ≤ 63 mm).
Table 3: Depth Penetration Factor (Dpf)
23 mm System
54 mm (2.14 in)
S
the Minimum Distance, in mm, from danger zone to light screen
center line
K
hand-speed constant (see Note 2 below); 2000 mm/s (for Minimum
Distances < 500 mm) 1600 mm/s (for Minimum Distances > 500
mm)
T
the overall machine stopping response time (in seconds), from the
physical initiation of the safety device and the machine coming to
a stop (or the hazard removed). This can be broken down into two
parts: Ts and Tr where T = Ts + Tr
C
the additional distance, in mm, based on intrusion of a hand or
object towards the danger zone prior to actuation of a safety
device. Calculate using the formula (in mm):
C = 8 × (d - 14)
where
d
is the resolution of the light curtain (for
d
≤ 40 mm).
Table 4: Intrusion Factor (C)
23 mm System
72 mm (2.8 in)
EZ-SCREEN
®
LS Basic Safety Light Screen
www.bannerengineering.com - Tel: 763.544.3164
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