Recora Neptune NF-2 Foot Switch - Manual (Page 5)

SERIES 12, 15 & 30 Switchmats have been designed for presence sensing applications
for stand alone operator detection in smaller areas.
Depending on how these Switchmats are combined with the machine control wiring,
these models can require the operator to step on the Switchmat, or off the Switchmat
before the machine will cycle or operate.
Calculating safe distances
According to ANSI B11.19-1990, “the size of the safety mat should be large enough to
prevent entry into the hazardous area.” In some cases, this may require the use of more
than one mat or additional guards.
The safety mat must be of sufficient size to detect entry by an operator or others into a
hazardous area. Switchmats are available in a variety of sizes. Knowing the distance that
must be covered with the safety mat is important in building a safe installation.
The minimum distance calculated is the minimum horizontal distance from the outer edge
of the Switchmat detection zone to the nearest part of the hazard.
The prEN 999 formula for floor mounted safety mats is:
S = (1600 x T) + 1200mm
S is the minimum safety distance in millimeters
The factor of 1600 is based on the standard assumption
of 1600mm/s as the approach speed.
T is the overall stopping time in seconds
The added 1200mm takes into account stride length and arm reach
The overall stopping time T is made up of two parts: T = t1 + t2
t1 is the maximum time between actuation of the sensing function and the
output signal switching devices being in the OFF state.
For the Switchmat, t1 = 35mS
t2 is the response time of the machine i.e. the time required to stop the
machine to remove the risks after receiving the output form the
Switchmat.
The response time of the machine used in the calculation needs to be the worst case time.
Some machines have inconsistent response times which are dependent upon mode of
operation, nature of the workpiece and point in the operation cycle at which stopping is
initiated. An allowance should be made for wear in brakes etc., if this can affect the
response time. An allowance for further delays in the machine control system may be
required in some circumstances.
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