Bosch Rexroth 4WRPD - 2.7.4 MTTFd, DC, CCF

Safety instructions 17/48
RE 29391-B/05.2021; 4WRPD(H), 4WRPQ(H), 4WRPF(H), 4WRLD, 4WRLF, 4WRLQ, 5WRPF10, 5WRPQ10, Bosch Rexroth AG
2.7.4 MTTF
d
, DC, CCF
For valves on Multi-Ethernet basis, MTFF
d
valves can be calculated according to the
information specified in the table using the following formula:
Table 6: Information for calculation of the MTTF
d
value
For the MTTFd values given, the restrictions apply that are described in RE 08012
(see “Exceptions/limitations“ regarding “Admissible spool designs; maximum
longitudinal spool acceleration” in the chapter “Proportional directional valves” on
page 5).
The DC depends on the system and on the use of a safety PLC (see chapter 2.2
“Intended use“).
By using the valves as intended, a CCF of at least 65 points can be reached.
=
+ +
1
1 1 1
dTotalMTTF
MTTF
dHydraulic part MTTFdSwitch-off path
MTTFdMains adaptor
MTTF
d
values
Type of
actuation
Valve type Hydraulic
components
Switch-off path SELV/PELV power
supply unit
MTTF
d
value
Valve and
switch-off path
electronics
(w/out power
supply unit)
Example of total
MTTF
d
value
(for power supply
unit with MTTF
d
value of 1 million h)
Direct
operated
valves
4WRPFH
4WRPDH
4WRPQH
4WRPF...EA/EB
5WRPF10
5WRPQ10
(single-solenoid
valves)
150 years 1000 years
MTTF
d
value depending
on power supply unit
manufacturer
(MTTF
d
= approx. 2 x
MTBF)
e.g. MTBF = 500000 h
 MTTF
d
value =
approx. 1 million h (114
years)
130 years 0
4WRPD
4WRPF
4WRPQ
(double-solenoid
valves)
150 years 1000 years
(only one switch-off
path regarded as
safety-relevant)
130 years 60
Pilot operated
valves
4WRLD
4WRLF, 4WRLQ
75 years 1000 years 69 years 43