8 Safe Mounting Distance
8-2 US Safe Distance Formulas
15
<Calculation example>
Under the conditions of T
m
= 0.05
s
, Ts=0.02
s
and d=30 mm,
S = 2000 mm/s x (0.05
s
+0.02
s
) + 8 (30 mm-14 mm)
= 268 mm
This formula applies for all minimum distances of S up to and including 500 mm. The minimum value of S shall
not be less than 100 mm.
If S is found to be greater than 500 mm using the formula above, then the formula below can be used. In this
case the minimum value of S shall not be less than 500 mm.
S = (1600 mm/s x T) + 8(d – 14 mm)
8-1-2 Safety Distance Formula for Systems with a Minimum Object Resolution Great-
er Than 40 mm
When the minimum object resolution of the system is greater than 40 mm, use the following formula:
S = (K x T) + C
where:
S = the minimum distance in millimeters, from the danger zone to the detection point, line, plane or zone.
K = 2000 mm/s
T = the overall system stopping performance in seconds.
T = t
m
+ t
s
t
m
= maximum stopping time of the machine is seconds.
t
s
= response time of the safety light curtain in seconds.
This response time is given in Section 2-2—Technical Specifications.
C = 850 mm.
i.e.:
S = (1600mm x T) + 850mm
8-1-3 Factors Affecting the Safety Distance Formula
When light curtains are used for machine initiation, their minimum object resolution must be 30 mm or smaller
(based on EN 999, other standards may vary). In this case the formula given in Section 8-1-1 applices except
that the minimum distance S shall be greater than 150 mm./
For parallel approach the formula for C becomes:
C = 1200 mm – (0.4 x H), but not less than 850 mm
H = the height of the detection zone above the floor in mm.
8-2 US Safe Distance Formulas
In the United States two formulas exist to properly determine the safety distance. OMRON recommends the for-
mula provided by the American National Standards Institute (ANSI) which incorporates additional factors when
compared to the formula required by OSHA.
The ANSI formula given below is for a normal approach to the light curtain.
D
s
= K x (T
s
+ T
c
+ T
r
+ T
bm
) + D
pf
Where:
Ds = minimum safety distance, in inches, between the F3SL detection zone and the nearest point of operation
hazard.
K = hand speed constant in inches per second. The ANSI standard value is 63 inches/second which assumes
the operator starts a hand motion toward the point of operation from rest. According to ANSI B11.19-1990, “The
value of the hand speed constant, K, has been determined by various studies and although these studies indi-
cate speeds of 63 in./sec. to over 100 in./sec., they are not considered conclusive determinations. The user
should consider all factors, including the physical ability of the operator, when determining the value of K to be
used.”
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