Siemens SIMATIC PCS 7 - Page 387

Characteristic values of redundant automation systems
A.2 Comparison of MTBF for selected configurations
CPU 410 Process Automation/CPU 410 SMART
System Manual, 05/2017, A5E31622160-AC
387
Redundant I/O
MTBF factor
See following
table
Table A-1 MTBF factors of the redundant I/O
Module
MLFB
MTBF factor
CCF = 1%
Digital input modules, distributed
DI 24xDC24V
6ES7 326–1BK02–0AB0
approx. 5
DI 8xNAMUR [EEx ib]
6ES7 326-1RF00-0AB0
approx. 5
DI16xDC24V, Alarm
6ES7 321–7BH01–0AB0
approx. 4
Analog input modules, distributed
AI 6x13Bit
6ES7 336-1HE00-0AB0
approx. 5
AI8x12Bit
6ES7 331-7KF02-0AB0
approx. 5
Digital output modules, distributed
DO 10xDC24V/2A
6ES7 326–2BF01–0AB0
approx. 5
DO8xDC24V/2A
6ES7 322-1BF01-0AA0
approx. 3
DO32xDC24V/0.5A
6ES7 322–1BL00–0AA0
approx. 3
Summary
Several thousand redundant automation systems are in use in different configurations in
manufacturing and process automation. To calculate the MTBF, we assumed an average
configuration.
Based on experience in the field, an assumption of MTBF of 3000 years is 95% reliable.
The system MTBF value calculated is about 230 years for a system configuration with
redundant CPU 410-5H.