Siemens SIMATIC S7-400H System Manual page 445

Table A-1 MTBF factors of the redundant I/Os
Module
Digital input modules, distributed
DI 24xDC24V
DI 8xNAMUR [EEx ib]
DI16xDC24V, Alarm
Analog input modules, distributed
AI 6x13Bit
AI8x12Bit
Digital output modules, distributed
DO 10xDC24V/2A
DO8xDC24V/2A
DO32xDC24V/0.5A
Summary
There are now several thousand applications of redundant automation systems in the field,
in various configurations. To calculate the MTBF, we assumed an average configuration.
Based on experience in the field, an assumption of MTBF of 3000 hours is 95% reliable.
The system MTBF value calculated is about 230 years for a system configuration with
redundant CPU 417-5H.
S7-400H
System Manual, 03/2012, A5E00267695-11
Characteristic values of redundant automation systems
A.2 Comparison of MTBF for selected configurations
MLFB
6ES7 326–1BK00–0AB0
6ES7 326–1RF00–0AB0
6ES7 321–7BH00–0AB0
6ES7 336–1HE00–0AB0
6ES7 331–7KF02–0AB0
6ES7 326–2BF00–0AB0
6ES7 322–1BF01–0AA0
6ES7 322–1BL00–0AA0
MTBF factor
CCF = 1%
approx. 5
approx. 5
approx. 4
approx. 5
approx. 5
approx. 5
approx. 3
approx. 3
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