Table of Contents
Advertisement
S5-115U Manual
14.1.3 Failure Distribution
Despite the extensive measures described above, one must still reckon with the occurence of
failures. Experience has shown that, in installations with programmable controllers, failures can
be distributed approximately as follows:
Enhancement of
availability by
programmed
diagnostic functions
Failures
Figure 14-2. Distribution of Failure Occurrences in Installations Incorporating Programmable
Controllers
Meaning of error distribution:
•
Only a small number (approx. 5 %) of failures occur inside the electronic control system. These
can be broken down as follows:
-
CPU failures (about 10 %, i.e. only 0.5 % of all failures);
these failures are evenly divided among the processor, memory, bus system and power
supply.
-
I/O module failures (about 90%, i.e. only 4.5 % of all failures)
•
The highest number of all failures (about 95 %) occur in the sensors, actuators, drives, cabling
etc.
EWA 4NEB 811 6130-02b
Reliability, Availability and Safety of Electronic Control Equipment
Central
functions
10 %
Internal
failures
90 %
5 %
Input/Out-
put modules
95 %
External
failures
Control
Plant
system
Processor
Memory
each
25 %
Bus
system
Power
supply
Central
unit
14-3
Advertisement
Table of Contents
