8.
Tests and maintenance
Test and maintenance tasks may only be performed by authorised personnel who
have been trained on functional safety.
Test and maintenance equipment has to be calibrated.
Information
Any test/maintenance must be recorded in a test/maintenance report.
Impact of testing/maintenance on relevant devices, equipment or other work must
be evaluated.
8.1.
Safety equipment: check
All safety functions within a safety equipment must be checked for perfect functionality
and safety at appropriate intervals. The intervals for safety equipment checks are to
be defined by the plant operator.
The plant operator has to establish a safety schedule for the entire safety lifecycle
of the SIS. It should include the strategy for achieving safety as well as different
activities during the safety lifecycle.
8.2.
Internal actuator monitoring with control via standard actuator controls
The device, consisting of actuator with actuator controls and integral SIL module has
an internal actuator monitoring. By controlling standard controls/actuator via standard
operation commands, internal actuator monitoring is automatically performed. Internal
actuator monitoring identifies most of the safety-related actuator components. If a
fault occurs, the fault would be signalled via the output contact of the SIL module
(
SIL failure
).
To ensure the safety figures of the Safe ESD safety function, the device has to be
controlled at least once per month via the standard controls, including output contact
assessment of the SIL module (
SIL failure
). If it cannot be ensured that the
device is controlled by the standard controls at least once per month, a <Partial Valve
Stroke Test (PVST)> has to be performed instead.
The control signal and the pertaining operation of the actuator have to be present
for at least 4 seconds. If control signal and pertaining operation of the actuator are
present for at least 4 seconds without signalling a fault via the SIL output contact
(SIL module:
SIL failure
), the test was successful. Otherwise, the device has
to be checked in accordance with the steps in the <Proof test: execute> chapter.
Other intervals can be selected for automated actuator monitoring.
The following should be observed In this case:
●
The PFD values and all other safety figures affected by the diagnostic interval
have to be recalculated. The respective values (refer to chapter 9.2.) are not
valid.
●
Automated diagnostics should be performed at least 10 times more often than
the proof test.
●
Automated diagnostics should be performed at least 10 times more often than
the demand rate of safety function.
8.3.
Partial Valve Stroke Test (PVST): execute
— Option —
There are two options for performing the PVST.
27
Part-turn actuators
with AC 01.2-SIL/ACExC 01.2-SIL
Tests and maintenance