Installation manual
PSC1-C-10 Installation manual V2.6
Page 158 of 173
Version: 57E
12.3.5
Hardware specification
In the hardware specification, the complete system layout and in particular the components used here
are to be described with their specific characteristic data. The hardware specification is used as the
basis for determining the safety level achieved based on the architecture and the characteristic data of
all devices involved in a safety function.
In addition, the design measures for protection against systematic and common cause failures are to
be stated in the hardware specification.
12.3.5.1
Selection of SRP/CS and equipment
The SRP/CS (safety related parts of control system) are to be selected appropriately for achieving the
safety level required for each safety function. The components are to be marked with the safety-
related function in a complete overview of the system and assigned to the individual safety functions.
The safety-related characteristic data are to be determined for these components.
The characteristic data include the following values:
MTTF
d
= mean time to dangerous failure
DC
avg
= average diagnostic coverage
CCF = common cause failure
On a SRP/CS, the software and systematic failures are also to be considered.
In principle, an analysis is to be undertaken on the SRP/CS involved in a safety function according to
the scheme sensor / PES / actuator.
Sensor
PES
Aktuator
