VCIOM-05044
Page 18 of 75
DIgITal EPIC-2 TEChnICal Manual
InstallatIon and operatIng InstructIons
6 OPERaTIOn
The DEPIC-2 can operate in three basic
functional characteristics. Even if the DEPIC-2
uses three different modes of operations, it
uses the same hardware and software so the
external look and user interfaces will remain
the same during these different modes of
operation. Please refer to the ordering guide to
select different configurations and features of
the device while ordering. Furthermore, many
features are controlled through software also
so it might be possible to enable those features
later on after the purchase. Please contact
Westlock Controls sales team for more details.
• Valve position transmitter with 4-20 ma
position feedback.
• ESD monitor and basic diagnostics.
• advanced diagnostics with pressure profiling.
Each mode is described in more details in the
following sections.
6.2 Esd MONITOr aNd basIC dIagNOsTICs
For applications in SIS, the DEPIC-2 with ESD
enabled (DEPIC-2 ESD) is a solution to improve
safety in a processing plant; specifically
designed to prevent and mitigate possibly
uncontrollable situations. DEPIC-2 ESD is a SIl
3 compliant valve smart monitor interface that
continuously monitors the ESD valve operation
of the plant and reports any operational
failures. The installation and wiring is still the
same as mentioned in earlier sections.
an emergency shutdown (ESD) valve is a valve
that operates to insure a safe state of a plant
when process conditions become or could
become uncontrollable. hundreds of ESD
valves are part of every petro-chemical and
offshore production plant, as well as part of
pipeline installations. During normal operation,
these valves are energized to stay open or
closed, with the means of a solenoid valve. If
an unsafe situation occurs, the ESD valve is
de-energized to go to its fail-safe position (fail-
closed or fail-open). The solenoid valve vents
the pressure from the spring-return actuator
chamber, to atmosphere. The accumulated
static energy in the actuator spring provides the
necessary force to bring the valve to its closed
position.
Because of its data monitoring capability,
the DEPIC-2 ESD is capable of validating the
health of its integral components. The limited
partial stroke test enables validation of valve,
actuator, and solenoid assembly health without
interfering with the plant process. Periodic
ESD valve testing reduces PFD (Probability of
Failure on Demand) since exercising the valve
reduces the risk of improper operations due to
sticking, and confirms if an impending problem
would prevent the ESD valve to properly
operate.
6.1 ValVE POsITION TraNsMITTEr
In this mode, the DEPIC-2 is used only for valve
position. The field wiring remains the same
as mentioned in the earlier sections. however
the device doesn’t have pressure sensor
manifold in this mode so the air is not tubed
to monitor the pressure and perform other
diagnostics functions. after calibration, the
device basically measures the signal from hall
sensor and coverts the reading into 0% to 100%
position signal after compensation for rotary/
linear conversion. The position reading is then
represented by the 4-20 ma on the loop. The
DEPIC-2 is basically a current sinking device
so the transmitter output is represented on the
same 4-20 ma loop being used to power up the
device. The haRT communication is available
in this configuration so the device can be
operated using other user interfaces discussed
in later sections of the document. In this
mode, the device has some basic information
for diagnostics like valve cycle count, valve
opening/closing time etc. The device doesn’t
monitor the ESD signal in this mode and
doesn’t generate an ESD alarm if there is a
safety demand and the valve moves to fail safe
position.
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