Tank Gauging Control System Monitoring based
on Innovative DCS
Central University of Finance and Economics, Beijing, China, [email protected]
Amir Firoozshahi, Member, IEEE *, Li Mengyang†
* Islamic Azad University, Damavand branch/ Electronics & Electric Eng. Dept., Tehran, Iran, [email protected]
ABSTRACT- Tank Gauging by DCS (Distributed Control Sys-
tem) is much more than just   automated inventory   manage-
ment, it's about having more control over your fuelling op-
eration, collecting accurate information from your sites with
less   effort   and   allowing   you   to   make   better   decisions   about
your   assets.   The   DCS    is   being   widely   used   in   Power,   Steel
manufacturing,   Oil   and   Gas,   and   Petrochemicals   for   moni-
toring,   advance   process   control,   regulatory   and   sequential
control and various other functions. DCS is operated either
in   single   mode   and   or   it   is   interfaced   with   other   systems
such   as   PLC,   SCADA,   and   Etc   for   enhanced   functionality.
Developing Distributed Control System is a major industrial
concern   since   those   systems   are   more   and   more   complex
and involved in many safety critical application fields. This
paper focuses on an innovative and intelligent DCS for Tank
Gauging    Control    system    that    has    been    designed,    imple-
mented   and   commissioned   in   large   tank   farm   oil   terminal
after case study in international standards. The main scopes
of DCS are described in this paper.
I.            INTRODUCTION
Distributed Control Systems (DCS) are of developing
significance as they are fixed in many safety critical in-
dustrial applications: Oil and Gas, civil aircraft, nuclear
power plant, etc. so a lot of activity in this field has been
dedicated to ensuring and improving HW and SW relia-
bility. Further to SW development, Fault Avoidance has
considered, but Fault Tolerance, an important issue: con-
strained design process, intensive simulation and testing
and even formal methods [1]- [4] are good solution for


this subject. Beside control systems are often distributed
for wholly clear reasons of fault-tolerance, performance,
and sensor/actuator location. Distributed Control Systems
(DCS) are hard to design, debug, test and formally verify.
Those difficulties are closely related to a lack of global
vision of a system when designing it. Most of DCS are
organized as several periodic processes, with nearly the
same   period,   but   without   common   clock,   and   which
communicate by means of shared memory through serial
links or field busses [5]. This class of DCS is quite clear-
ly an important one in the field and thus deserves special
attention.   During   the   last   decade,   the   synchronous   ap-
proach [4] has been successfully and widely used for the
development of   such distributed   control systems.   Based
on clean mathematical principles, one of its salient bene-
fits is its ability to support formal design and formal veri-
fication methods [6]. Halevi and Ray [7] consider a con-
tinuous-time   plant   and   discrete-time   controller   and   ana-
lyze   the   integrated   communication   and   control   system
using a discrete-time approach. Nilsson [8] also analyzes
network control systems in the discrete-time domain. In
Walsh et al. [9], the authors consider a continuous plant
and a continuous controller. The control network, shared
by other nodes, is only inserted between the sensor nodes
and   the   controller.   In   Automatic   Control   of   Deep-Hole
Chrome-Plated System, PC configuration software main-
ly completes the function of data acquisition, history da-
tabase    management,    parameter    setting    of    production
process, simulation display of production scene, warning,
report form and printing [20].
Manual tank dipping is still the most common method
used   today   to   obtain   fuel   levels   for   inventory   manage-
ment   purposes.   At   first   glance   this   may   seem   perfectly
adequate,   so   why   change   to   gauges?   Tank   gauging   is
much   more   than   just automated   inventory management,
it's about having more control over your fuelling opera-
tion, collecting accurate information from your sites with
less   effort   and   allowing   you   to   make   better   decisions


about   your   assets   [10].   In   this   increasingly   competitive
age, it is becoming incrementally more important to do
more with fewer resources. This means fewer inventories
on site, better tanker fleet utilization, less people on site,
more   throughput   per   site   and   less   people   in   the   office
doing more work. Tank gauge automation is instrumental
in meeting these challenges. Accurate information at your
disposal will allow you to plan more effectively and with
less   effort   to   gain   better   results.   Damaging   leaks   and
losses Environmental sensitivity is a growing trend glo-
bally,   increasing   the   awareness   of   both   the   public   and
regulators about the potential dangers of inadequate fuel
management.
This   paper   focuses   on   the   Tank   Management   control
system by three main system: TMS (Tank Management
System),   DCS and VMS   (Valve   Master   Station).   These
systems are connected via Modbus RS485 Network. The
main system is DCS. All of the logic and control philoso-
phy has been done in DCS. The Plant consists of 37 sto-
rage tanks, which some of them are operational and oth-
ers are either under construction or will be constructed in
future.   All   incoming   fluids   normally   enter   into   these
tanks   for   storage   management   and   inventory   purpose,
although by-pass system provides operator of tank farm
to direct the inflows to export jetties, this redirection is
not    concerned    in    normal    operation    because    of    wa-
ter/sludge content of incoming products. Therefore, from
operational   point   of   view   some   tanks   shall   be   so   con-
trolled and managed to contain different crude types un-
der various conditions.
The storage tanks located at 10 different groups. Each
group supports data collection on the computer located in
the main control room. The new and modern tank level
gauging systems incorporate Radar gauges for tanks, with
transmitters   for   temperature   and   pressure.   All   types   of
these gauges offer an upgrade in performance and main-


9-Monitoring of Auto or manual status of valve.
10-Monitoring of Fault on valve & Discrepancy alarm
11-Selecting valve control window by double clicking
on that valve
12-Monitoring of trend by trend bottom.
D.    Tanks Groups Displays
From overview window operator can select each group
window by selecting of that group or in each tank win-
dow he can select group button then he can see the group
window related to that Tank.
In each Group following objects and functions are being
monitored:
•      Monitoring of all Tanks of group
•      Monitoring of Tanks' alarm
•      Monitoring of level status of tank
•      Monitor & Control of valves for each Tank
•      Monitoring products type of Group
E.     Design of Valve Control
Control valves are used mainly within industrial plants
to   control   operating   conditions   such   as   flow,   pressure,
temperature, and liquid level by fully or partially opening
or closing in response to signals received from controllers
that compare a "setpoint" to a "process variable" whose
value is provided by sensors that monitor changes in such
conditions.
The   opening   or   closing   of   control   valves   is   done   by
means of electrical, hydraulic or pneumatic systems. Po-
sitioners are used to control the opening or closing of the
actuator based on Electric, or Pnuematic Signals. These
control signals, more common now are 4-20mA signals
for industry, 0-10V for HVAC systems, & the introduc-
tion of "Smart" systems, HART, Fieldbus Foundation, &
Profibus being the more common protocols.
Proportional-Integral-Derivative (PID) control provides
simplicity, clear functionality, and ease of use. Since the
invention of PID control in 1910 (largely owing to Elmer
Sperry's ship autopilot) and the straightforward Ziegler-
Nichols (Z-N) tuning rule in 1942 [14], the popularity of
PID control has grown tremendously. Today, PID is used
in   more   than 90%   of practical control systems,   ranging
from consumer electronics such as cameras to industrial
processes such as chemical processes [15]-[17].
A   genetic-algorithm-based   PI   controller   for   position
control   of   permanent   magnet   synchronous   motor   intro-
duced. The algorithm is proposed for optimizing the PI
controller gains in the position control. [18]
DCS can send "Open" and "Close" command to each
valve. In page of each tank, operator can see all valves
related to that tank. When operator clicks a valve, control
page of that valve will be open. In that page can see the
name of the valve, function key for opening & closing the
valve, function key for changing mode of the valve from
Auto   and   Manual.   Operator   can   see   the   status   of   Au-
to/Man by a yellow rectangle around AUT/MAN function
key and also status of Hand switch for Open and Close
will be appear around open/close function key as red and
green rectangle.
A.     Condition of Discrepancy:
When operator or any condition caused to send open or
close command to a valve, then after a delay the correct
feedback could not return to the DCS, discrepancy alarm
will be appear. In   this case operator must   acknowledge
this alarm to send other commands to this valve.
B.     Level Switch High High (LSHH) Condition
Each tank has a limit switch which shows HH alarm of
tank. As soon as LSHH of each tank become active both
Input valve of that tank will be close (if those valve have
been in remote mode not local mode). In this case opera-
tor could not open those valves and supervisor must By-
pass LSHH of that tank and then he can open the valves


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