WPC 1000 User Manual 1125100
Initialization, Setup, and Checkout 3-25
Example: Calculating the Safety Distance for a Light Curtain Using the OSHA Formula
The OSHA formula is
Ds = K x Ts
The following value is a constant:
K = 63 inches per second
We will use the following values for the variables in the formula:
Stopping time of press + response time of press control = 0.190 sec. (result of the 90° stop-time
test)
Response time of light curtains = 0.059 sec. (Shadow 8 with 202 in. combined length including
extensions–see Table 3-4, page 3-22)
Additional time for brake wear = 0.035 sec. (see Example 2 in Stop-time Limit Calculation
Examples, page 3-16)
Putting these values into the formula, we get:
Ds = 63 x (0.190 + 0.059 + 0.035)
Ds = 63 x 0.284
Ds = 17.89 in.
The light curtain must be mounted 17.89 in. away from the pinch point.
When using the OSHA formula, be sure to do the calculations in this order:
(1) Add the factors involved in the stopping time Ts first.
(2) Multiply the result by 63. This is Ds.
If you do no follow this order, your safety distance calculation will be incorrect.
Adding to Safety Distance for Blanking Windows
When using fixed or floating blanking windows with your Shadow 8 light curtain, you must
add a factor to the calculated safety distance for each beam that is blanked. This applies
whether you use the ANSI or the OSHA formula. For a one-beam fixed blanking window,
you must add 5.38 in. (136.6 mm) to the calculated safety distance (ANSI formula). You
must add 5.76 in. (146.3 mm) to the calculated safety distance for a one-beam floating
blanking window (ANSI formula). See your Shadow 8 user manual for further details about
fixed and floating blanking.
If you are using another Shadow light curtain, refer the appropriate Shadow user manual for
the additional distance factor to add to the safety distance formula for each blanking window.
OSHA SAFETY DISTANCE FORMULA FOR USE WITH TWO-HAND CONTROL
The formula for safety distance when using a Two-hand Control as a safeguarding device is similar
to the formula above, but does not include the response time of the light curtain. Use the following
OSHA formula for calculating the safety distance for a Two-hand Control:
Ds = K x Ts
As indicated above, Ts must include all factors that are involved in stopping the press, including
the response time of the press control.
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