Everything you need to know about the EN-ISO 13855 standard
The standard EN-ISO 13855 standard, within the scope of Industrial Safety, establishes the following methods for calculating the minimum safety distance for each type of safety device, based on the stopping time of the hazardous movement, which must be determined using a stopping time analyser and periodically verified through testing.
The units used in the formulas for calculating safety distances will henceforth be:
S: millimetres
T: milliseconds.
Each type of safety device has its own formula:
Safety Distance: Photoelectric Curtain
When determining the minimum safety distance, the resolution or detection range of the curtain’s smallest object must be taken into account:
Resolution d=<40 mm
The following formula will be applied:
S=(2000 x T) + 8(d – 14)
Where:
S = Safety distance between the detection plane and the hazardous area, in mm.
T = Total downtime in seconds: includes machine downtime + the response time of the photoelectric sensor.
d=Curtain resolution in mm.
The minimum distance between the detection plane and the dangerous area must in any case be 100 mm (min.).
If the distance obtained is S > 500 mm, the standard permits the use of the following formula, provided that the minimum distance of 500 mm is observed:
S=(1600 x T) + 8(d – 14)
Photoelectric curtains used to detect the start of hazardous movements must have a resolution of 14 mm or less and a minimum safety distance S of 150 mm, calculated using the following formula:
S=2000 x T
Resolution 40mm<d<70 mm
The standard classifies them as discrete-beam photoelectric devices and does not consider them suitable for detecting hand intrusion. The formula to be used in this case is:
S=(1600 x T) + (1200 – 0,4H)
H = height of the upper beam in mm.
In addition, the height of the lower beam must be 300 mm or less.
Single-beam or multi-beam photoelectric barrier
They should only be used for detecting bodies or body parts in the direction of the dangerous area.
The following formula will be applied:
S=(1600 x T) + (1200 – 0,4H)
H= height of the upper beam in mm.
Depending on the number of beams, the heights at which they must be placed are reflected in the following table:
No. of beams Ground height mm
4 300, 600, 900, 1200
3 300, 700, 1100
2 400, 900
Single-beam photoelectric barrier
This option can only be used for detecting people. The device must be positioned at a height of 750 mm above the reference plane.
The minimum safety distance is given by the following formula:
S=(1600 x T) + 1200
Safety Distance: Sensitive Mat
The EN ISO 13855 standard for pressure-sensitive devices states that the minimum width for a safety-sensitive carpet is 750 mm.
The safety distance S in mm must be measured between the danger zone and the outer edge of the carpet that is sensitive to touch. This distance must be calculated using the formula:
S=(1600 x T) + (1200 – 0,4H)
H = Height of the carpet above the floor in mm.
Floor-mounted
If the carpet is laid directly on the floor surface, the height H will be zero, and the following formula applies:
S=(1600 x T) + 1200
Installation on steps
If the carpet is laid on a step or raised platform above floor level, the general formula for carpets applies, but the minimum distance of 750 mm may be reduced by 0.4H, where H is the height of the carpet above the floor:
S=(1600 x T) + 1200
Two-handed control
If access to the hazardous area is protected by another safety device (such as a light curtain), the two-hand control may be positioned at a minimum distance S of 100 mm from the hazard.
Otherwise, the distance between the pushbuttons and the hazardous area shall be calculated using the following formula:
S=(1600 x T) + 250
Fixed Touchpad
If access to the danger zone is protected by another safety device, the fixed proximity switch may be positioned at a minimum distance of 100 mm.
Otherwise, the distance between the button and the dangerous area will be calculated according to the formula:
S=(1600 x T) + 1800
