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Programmable Safety Controller SCR P
Safety Mat Safety Distance (Minimum Distance)
As a stand-alone safeguard, the safety mat must be installed at a
safety distance (minimum distance) so that the exterior edge of the
sensing surface is at or beyond that distance, unless it is solely used
to prevent start/restart, or solely used for clearance safeguarding
(see ANSI B11.19, ANSI/RIA R15.06, and ISO 13855).
The safety distance (minimum distance) required for an application
depends on several factors, including the speed of the hand (or
individual), the total system stopping time (which includes several
response time components), and the depth penetration factor. Refer
to the relevant standard to determine the appropriate distance or
means to ensure that individuals cannot be exposed to the hazard(s).
U.S. Applications
The Safety Distance formula, as provided in ANSI B11.19:
D s = K x (T s + T r ) + D pf
D s
the Safety Distance (in inches)
T r
the response time of the Safety Controller as measured from the time a stop signal from either hand control. The Safety Controller response
time is obtained from the Configuration Summary tab in the Software.
K
the OSHA/ANSI recommended hand-speed constant (in inches per second), in most cases is calculated at 63 in/sec, but may vary between
63 in/sec to 100 in/sec based on the application circumstances;
not a conclusive determination; consider all factors, including the physical ability of the operator, when determining the value of K to be used
T s
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 and measured at maximum machine velocity
T s is usually measured by a stop-time measuring device. If the specified machine stop time is used, add at least 20% as a safety factor to
account for brake system deterioration. If the stop-time of the two redundant machine control elements is unequal, the slower of the two times
must be used for calculating the separation distance
D pf
the added distance due to the penetration depth factor
equals 48 in, per ANSI B11.19
European Applications
The Minimum Distance Formula, as provided in EN 13855:
S = (K x T) + C
S
the Minimum Distance (in millimeters)
K
the EN 13855 recommended hand-speed constant (in millimeters per second), in most cases is calculated at 1600 mm/sec, but may vary
between 1600 to 2500 mm/sec based on the application circumstances;
not a conclusive determination; consider all factors, including the physical ability of the operator, when determining the value of K to be used.
T
the overall machine stopping response time (in seconds), from the physical initiation of the safety device to the final ceasing of all motion
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D s
D pf
K(T s + T r )
Hazardous
Zone
or
Area
Safety Mat
Figure 9: Determining safety distance for the safety mat