Specifications

40 PHOENIX CONTACT
S
1
S
2
F
1
F
2
F
1
F
2
P
1
P
2
P
1
P
2
P
1
P
2
P
1
P
2
b
c
d
e
a
PL
PL ≤ PL
r
Bro_Safety_Info_DE_Rev01.indd 36-37Bro_Safety_Info_DE_Rev01.indd 36-37
EN ISO 13849-1: 2006
Safety-related parts of control systems (SRP/CS)
START
Determining limit values of the machine
Risk identification
Risk estimate
Risk assessment
Is the machine
safe?
END
Risk reduction
Yes
No
Risk analysis
Risk
assessment
In order to identify dangers and implement
preventive measures, EN ISO 12100-1
recommends an iterative process:
1. Determining the physical and time-related
limits of a machine
2. Identifying dangers and estimating risks
3. Estimating the risk for each identified danger
4. Risk assessment
Risk assessment
and reduction
Risk assessment
and structure of
the safety function
Validation
Determining the required performance level (PL)
a)
S = Severity of injury
S
1
= Mild, reversible injury
S
2
= Severe, irreversible injury to one or
more persons or death
F = Frequency and/or duration
of the danger
F
1
= Seldom to frequent, short duration
F
2
= Frequent to permanent, long
duration
P = Possibilities for avoiding
the danger
P
1
= Possible under certain conditions
P
2
= Hardly possible
Low risk
High risk
DC
CCF
MTTF
d
b) Design of the control system architecture and determining the
capacity attained
The PL of SRP/CS is determined by estimating the following parameters:
• Category (given as a defined structure)
• MTTFd (mean duration up to a dangerous failure)
• Diagnostic coverage degree (DC) from a table
• CCF (failure following a common cause) as a point system according to various
criteria
The attained PL is recorded using a table and must be equal to or greater than the
required PL.
Functional saf
A redu
De
a) D
Ef
D
or
Permanen
finge
Revers
treatment
R
Determi
b)
attained
Architecture
(SRP/C
The implementation of safety-related control system
functions must be checked. Validation proves that the safety function
fulfills
docum
EN_DE_Safety_Rev.01.fm Seite 16 Freitag, 30. Mai 2008 1:22 13
Textfarbe Schmuck 45,0° 240,0 LPI