2TLC172245M0201, rev. B
13
www.abb.com/jokabsafety
2013-04-22
Minimum safety distance
When using interlocking guards without guard locking to safeguard a hazard zone, the minimum allowed safety
distance between the guarded opening and the hazardous machine must be calculated. In order to ensure that the
hazardous machine motion will be stopped before it can be reached, the minimum safety distance is calculated
according to EN ISO 13855 (“Positioning of safeguards with respect to the approach speeds of parts of the human
body”).
The minimum safety distance is calculated according to the formula:
S = (K x T) + C
Where
S
= minimum safety distance (mm)
K
= approach speed of a human body; 1600 mm/s
T
= the total time from opening of the guard until the hazardous machine movement has stopped, i.e. including
control system reaction times and other delays (s)
C
= a safety distance taken from Table 4 or Table 5 of EN ISO 13857:2008, if it is possible to push fingers or a
hand through the opening towards the hazard before a stop signal is generated
NB: In some cases, T might be reduced by the opening time of the guard until the opening size permits access of
the relevant parts of the body. Refer to EN ISO 13855 for further details and EN ISO 13857 for specified values.
