PI-EX-SD-21-25
103211_00_en 7
PHOENIX CONTACT GmbH & Co. KG • 32823 Blomberg • Germany
Phone: +49 - 52 35 - 30 0 • Fax: +49 - 52 35 - 34 12 00
www.phoenixcontact.com
9 Safety-Related Applications (SIL 3)
9.1 Installation
Use one of the following base elements:
– PI-EX-TB... basic terminal block
– TT-PI-EX-TB... basic terminal block or
– PI-EX-MB... motherboard
9.2 Response Times
Following a state change at the input, the output enters the
safe state in ≤ 40 ms.
9.3 Operating Mode of the Safety Function
Operating mode according to IEC 61508: "Low demand
mode"
9.4 Failure Behavior and Required Response
1. The safe state is entered in the event of an input
voltage failure.
2. The safe state is reached by removing the device from
the base element.
9.5 Safety Integrity Requirements
Error Rates
– Type A device (according to IEC 61508-2)
– Safety Integrity Level (SIL) 3
PFD
AVG
Values
Since the PFD
AVG
value is 0, it is not necessary to perform
regular Proof Tests; however, this is still recommended
(see Section 9.6).
Failure Limit
The operating mode is based on low demand mode. The
percentage of the device at PFH/PFD for the overall safety
loop is less than 10%.
Figure 5 Safety loop
Conditions
– The failure rates of the components used remain
constant throughout the period of use.
– Propagation of errors by the device in the system is not
taken into consideration.
– The repair time (= replacement) should take eight
hours.
– The failure rates of the external signaling device are
not taken into consideration.
– The average temperature at which the device is to be
used is +40°C. This is based on standard industrial
conditions.
9.6 Proof Test
Even where the PFD
AVG
value is 0, it is still recommended
that you check the function of the valve burner in
conjunction with the entire safety loop.
1. Take appropriate steps to prevent incorrect use.
Prevent other areas of the system from being affected
by the Proof Test
(e.g., set the control system to test mode).
2. When a voltage of between 20 V and 30 V is applied at
the input, check whether a voltage of > 0 can be
measured at the output terminal blocks.
The field device must switch at the same time.
3. Restore the safety circuit to full functionality.
4. Return to normal operation.
10 Appendix
Exida Assessment Summary (3 pages)
λ
SAFE
λ
DANGEROUS
SFF
1
1
SFF = Safe Failure Fraction
DC
S
2
2
DC = Diagnostic coverage (safe or dangerous)
DC
D
2
284 FIT
3
3
FIT = Failure in Time (1 FIT = 1 failure/10
9
h)
0 FIT 100% 0% 0%
T[PROOF] = 1 year 5 years 10 years
PFD
AVG
1
=
1
PFD = Probability of Failure on Demand
0 0 0
Sensor and
switching
amplifier
35%
Processing
15%
Actuator
control
« 10%
Actuator
40%
