Valve
VOFC-LT-M32C-...
Festo AG & Co. KG
Postfach
73726 Esslingen
Germany
+49 711 347-0
www.festo.com
Operating instructions
8063751
1607NH
[8063752]
Original: de
Valve VOFC-LT-M32C
English
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1
About this document
This document describes the use of the above-mentioned product. It contains
additional information for the use of the product in safety-oriented systems (safety
handbook in accordance with IEC 61508).
1.1 Applicable documents
– Certification documents
– VOFC assembly instructions
All available documents for the product
www.festo.com/pk.
1.2 Target group
The documented is targeted towards persons who assemble and operate the
product. It is additionally targeted towards individuals who are entrusted with
the planning and application of the product in a safety-related system.
1.3 Specified standards
Version status
IEC 61508-1:2010
IEC 61508-4:2010
IEC 61508-2:2010
IEC 61511:2016
Fig. 1
2
Safety
– Only use the product in original status without unauthorised modifications.
– Only use the product if it is in perfect technical condition.
– Observe product labelling.
– Use media only in accordance with specifications (
Section 10).
– Product must be regularly checked by a qualified person and the check must be
documented (
Section 9.1)
Return to Festo
– In the event of malfunctions or failure, replace the product and let Festo know
about the failure. Return defective products to Festo.
– Before returning, please contact the technical consultant from Festo in order to
clarify the conditions of the return.
3
Use for intended purpose
The VOFC-LT-M32C valves are indirectly actuated, electromechanical control
valves. They comprise a basic valve from the VOFC-LT-M32C series in combination
with a solenoid coil from the VACC-S13 series.
Depending on the application, the valves are supplied with internal or external
pilot air (
Section 6). The valves are suitable for controlling pneumatic actuators.
4
Further information
– Accessories (
www.festo.com/catalogue)
– Documents and documentation (
www.festo.com/sp)
5
Information on functional safety
5.1 Attainable safety rating
The product is suitable for use as an element in a safety-related system in accord-
ance with IEC 61511.
– In low-demand mode up to SIL 2.
– In high-demand mode up to SIL 1.
Taking into account the necessary minimum hardware fault tolerance of HFT = 1,
the product can also be used up to SIL 3 with a redundant design of the entire
system.
Note
The suitability for certain applications can only be determined in connection with
the assessment of further components of the subsystem.
5.2 Safety function
The safety function comprises the safe venting of a control unit connected to
port 2. The safety function is triggered by switching off the power supply at the
solenoid coil.
As long as the voltage remains switched off at the solenoid coil, the connection
between ports 2 and 3 is released. This switching position represents the safe
status.
5.3 Operating conditions
– General instructions on safe operation
Section 2.
– Periodic tests (performance test)
Section 9.
– Ambient conditions and additional technical specifications
Section 10.
5.4 Limitations of application
The service life is not limited if the operating conditions are complied with.
– Maximum admissible interval for a complete performance test: 7 years.
5.5 Characteristic values
Safety standards (in accordance with IEC 61508)
Value
Probability of Dangerous Failure on Demand
(Probability of Dangerous Failure on Demand)
PFD
spec
2.41 · 10
-4
Assumed Test Interval (Assumed Test Interval)
T
i
1 a
Confidence Level (Confidence Level)
1-
á
95 %
Safe Failure Fraction (Safe Failure Fraction)
SFF
75 %
Hardware Fault Tolerance (Hardware Fault Tolerance)
HFT
0
Diagnostic Coverage (Diagnostic Coverage)
DC
0
Type of Sub System (Type of Sub System)
Type A
Mode of Operation (Mode of Operation)
Low demand and
high demand
Degree of coverage of dangerous errors through
the re-test (Proof Test Coverage).
PTC
99 %
Mode of Operation (Assumed Demands per Year)
n
op
1 / a
Total Failure Rate (Total Failure Rate)
ë
S
+
ë
D
1.10 · 10
-7
/ h
Failure rate for dangerous errors detected (Lambda
Dangerous Detected)
ë
DD
0
Failure rate for dangerous errors not detected (Lambda
Dangerous Undetected)
ë
DU
2.75 · 10
-8
/ h
Failure rate for safe errors (Lambda Safe)
ë
S
8.25 · 10
-8
/ h
Mean Time Between Failure (Mean Time Between Failure)
MTBF
1,037 a
Mean Time Between Dangerous Failure (Mean Time
between Dangerous Failure)
MTBF
D
4,149 a
Average Probability of Failure on Demand (Average
Probability of Failure on Demand)
PFD
avg
(T
I
= 1 a)
1.21 · 10
-4
PFD
avg
(T
I
= 2 a)
2.42 · 10
-4
PFD
avg
(T
I
= 5 a)
6.05 · 10
-4
PFD
avg
(T
I
= 7 a)
8.47 · 10
-4
Probability of dangerous failure per hour (Probability of
dangerous failure per hour)
PFH
2.75 · 10
-8
Fig. 2
6
Function
The VOFC-LT-M32Cvalves are 3/2-way valves with internal pilot air supply. If the
operating pressure is less than 2 bar, an external pilot air supply with > 2 bar must
be connected.
When the system is de-energized, the armature is pressed onto the nozzle by
a spring. Thus, the internal pilot air line leading to the membrane is closed.
