Appendix
5.3.3
Categories according to EN 954-1
5.3.3.1
Control categories (paragraph 6 and following)
If an error occurs, the standard EN 954-1 classifies the performance of the safety-related parts of
a control into 5 categories: B, 1, 2, 3, 4. These categories are used as a reference for the selection
of the relevant control category:
•
The selected category depends on the machine and the extent to which the control units are
used for the protective measures.
•
The selection of the category for the individual safety-related parts of the control mainly
depends on the following factors:
–
the risk reduction reached through the safety function to which this part contributes,
–
the probability that an error occurs in this part,
–
the risk resulting from the occurrence of errors in this part,
–
the possibilities of preventing the occurrence of errors in this part,
–
the technologies used.
5.3.3.2
Notes for selection
B
C a t e g o r y
1
2
3
4
S t a r t i n g p o i n t f o r r i s k
a s s e s s m e n t o f t h e s a f e t y -
r e l a t e d p a r t s o f t h e c o n t r o l
s y s t e m s e e E N 9 5 4 - 1 P a r t 4 . 3
S 1
S 2
F 1
F 2
P 1
P 2
P 1
P 2
P r e f e r r e d c a t e g o r i e s f o r p o i n t s o f r e f e r e n c e
P o s s i b l e c a t e g o r i e s r e q u i r i n g a d d i t i o n a l m e a s u r e s
M e a s u r e s t h a t c a n b e e x t e n d e d d e p e n d i n g o n t h e r i s k i n v o l v e d
S
Degree of injury
S1
S2
small injury (usually reversible)
serious injury (usually irreversible)
F
Frequency and/or time of the exposure to danger
F1
F2
rarely to frequently and/or short time of exposure
frequently to permanently and/or long time of exposure
P
Possibility of avoiding the exposure to danger
P1
P2
possible under certain conditions
hardly possible
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