VCIOM-05044
Page 19 of 75
DIgITal EPIC-2 TEChnICal Manual
InstallatIon and operatIng InstructIons
• The ESD device performs as a smart solenoid
to pneumatically activate an On/OFF valve.
• It is primarily used for Safety Instrumented
Systems (SIS) that require field devices to
be certified for safety related applications
according to IEC-61508.
• It is certified by EXIDa for usage to a SIl3
safety integrity level.
• Interacts with a SIS logic solver.
• Works with existing 24 VDC as a 4-20 ma
output signal (position transmitter), 2 wire
installations with superimposed haRT
communications.
• Monitors SIS voltage to solenoid as a control
signal to determine a set-point for 0% or
100% in conjunction with a discrete 0-24 VDC
signal as the safety trip trigger.
• Communicates haRT over existing wires
(4-20 ma).
• generates an alarm during ESD condition
to notify the user.
In addition, DEPIC-2 ESD is a PST controller
that mounts on a pneumatically actuated
valve assembly. Its role is to position an
emergency shutdown valve to 0% or 100%
with a Probability of Failure on Demand
(PFD) in accordance with IEC-61508 for SIl3
application (SIl = Safety Integrity level).
It replaces solenoid valves, typically utilized
to actuate a spring-return or double-acting
actuator, while providing extensive online valve
diagnostics. The PST function offered in this
mode has limited functionality as it doesn’t
use the pressure sensor data during the PST.
In this mode, the PST is basically a time based
test, where it monitors the valve moves to the
pre-configured travel limit and returns to its
fully energized position. It can still generate an
alarm if the PST fails. however more advanced
PST and other tests like SOVT and FST are not
available in this mode of operation.
6.3 adVaNCEd dIagNOsTICs wITH
PrEssurE PrOfIlINg
In this mode, the DEPIC-2 has the pressure
sensor manifold and the air is tubed to the
manifold to monitor the actuator and/or
supply pressure. The DEPIC-2 can collect
signature information on any Full-Stroke
or Partial-Stoke movement of a valve if
configured to do so (Signatures Enabled
and Pressure Sensors used). It also offers a
pressure based diagnostic test SOVT (Solenoid
Operated Valve Test), where it monitors the
change in the actuator pressure to make sure
the spool valve of the solenoid is working.
a Signature is a collection of sensor readings
(position and pressure) read periodically
during valve movement. The Full-Stroke and
PST Signatures consist of both a Baseline
and Maintenance Signatures. The Baseline is
obtained shortly after commissioning of a valve
in process and is used as a reference of normal
operating performance. The Maintenance
Signature is collected anytime the valve moves
after the Baseline is collected and is used to
compare with the Baseline to aid in detecting
degradation in valve/actuator performance
over time which can be used to predict possible
failures before they occur. This feature can be
very important in safety applications.
The following 2 figures show examples of
Full-Stroke Signatures as they might appear
displayed on a haRT host using the haRT DD.
FIguRE 15
Closing full stroke signature
FIguRE 16
Opening full-stroke signature
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