2. Performing the PVST using the PVST function of AC.2-SIL:
If standard controls of AC.2-SIL are configured with PVST input, this input can
be used for diagnostics of the safety relevant part of the controls under certain
conditions.
Conditions and required settings:
- Additional non-interacting end position switches for safe and reliable end
position feedback signals are available and wired to the safety PLC.
- A digital input of standards controls (galvanically separated from the other
inputs) is configured to the following value: Execute PVST (949)
- The safety PLC directly controls the PVST or will also receive the control
signal if the PVST input is controlled.
- The PVST is performed with the following operation mode setting: Para-
meter PVST operation mode M0889 = End position test
- The PVST may only be performed from one of the end positions.
-
Parameter PVST operating time M0890 must amount to > 4 seconds.
-
Signals PVST error (953) and PVST abort (954) of the standard controls
are sent via digital outputs (galvanically separated from the other outputs)
of the standard controls to the safety PLC.
PVST is either directly requested at the PVST input of the standard controls by
the safety PLC or the signal for requesting the PVST is also sent to the safety
PLC. While the AC.2 standard controls perform the PVST, the safety PLC
monitors whether
- the actuator was in one of the end positions prior to the PVST (check via
safe end position feedback).
- the actuator left one of the end positions within the set PVST operation
time (check via safe end position feedback).
-
If a fault was signalled via the SIL output contact (SIL module: SIL
fault).
Only if the actuator was in one of the end positions prior to the PVST, has left
this end position during the PVST, the standard controls have neither issued
aPVST error (953) nor a PVST abort (954) signal from standard controls, nor
the SIL module signalled a SIL fault, was the PVST was successfully
completed. If this is not the case the device has to be checked in accordance
with the steps in the <Proof test> chapter.
Performing a PVST includes diagnostics of the safety-related components. This
ensures improved safety figures compared to applications without or with minor
diagnostics.
8.4. Proof test (verification of safe actuator function)
The proof test serves the purpose to verify the safety-related functions of the actuator
and actuator controls.
Proof tests shall reveal dangerous faults which might be undetected until a safety
function is started and consequently result in a potential danger.
Information During execution of the proof test, the safety function is unavailable for a short time.
Depending on both version and configuration, the proof test includes the
following tests:
1. Check Safe ESD safety operation (Safe OPENING/CLOSING).
2. Check SIL fault signal "Actuator monitoring".
3. Check Safe ESD reaction to "Motor protection (thermal fault)" signals.
4. Check Safe ESD reaction to "Limit seating with overload protection" (limit and/or
torque evaluation).
5. Check Safe ESD reaction to "Forced limit seating in end position" (limit evalu-
ation) – for actuators with electromechanical control unit.
6. Check Safe ESD reaction to "Forced limit seating in end position" (limit evalu-
ation) – for actuators with electronic control unit and limit switches.
24
Multi-turn actuators
Tests and maintenance SA 07.2 – SA 16.2/SAR 07.2 – SAR 16.2
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