Transcript logic system - Itering Languages

KHABAROVSK REFINERY
HYDROPROCESSING PROJECT
ARU / SWS – CONTROL SYSTEM and ESD
TRAINING COURSE
APRIL 29th – MAY 3rd 2013, MADRID, SPAIN
CONTROL SYSTEM
The purpose of this section is to give a general
explanation of how the control system works.
Process variables, that determine a good operation of
the Unit, play a different role depending upon the
type of operation.
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MAIN CONTROL LOOPS OF AMINE
REGENERATOR AND SOUR WATER STRIPPER
SECTIONS
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2.
3.
4.
5.
6.
RICH AMINE FLASH DRUM PRESSURE
REGENERATOR REFLUX DRUM PRESSURE
STEAM FLOWRATE TO STRIPPER REBOILER
SOUR WATER STRIPPER PRESSURE
SOUR WATER STRIPPER TEMPERATURE
SOUR WATER FEED SURGE DRUM PRESSURE
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RICH AMINE FLASH DRUM PRESSURE
With the purpose to avoid amine degradation caused by the oxidation of the
DEA solution coming into contact with air, inert gas blanketing facilities are
provided.
The pressure in the drum is controlled by the pressure controller PIC-1001
acting on two control valves: vent gas valve PV-1001A and inert gas valve
PV-1001B.
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RICH AMINE FLASH DRUM PRESSURE
Split range valves
Some control loops have two control valves controlled by one controller.
A plot shows the valve position versus controller output.
Provide 5% deadband to prevent simultaneous pressuring and venting.
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REGENERATOR REFLUX DRUM PRESSURE
The pressure in the drum is controlled by the pressure controller PIC-1005
acting on two control valves:
PV-1005A located on the line that leads acid gas to SRU Section and
PV-1005B located on the line to acid flare.
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REGENERATOR REFLUX DRUM PRESSURE
Split range valves
Provide 5% deadband to prevent system malfunction.
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STEAM FLOWRATE TO STRIPPER REBOILER
The higher is the flowrate of sour water fed to the stripper, the higher the
saturated steam flowrate to the Reboiler must be.
The steam flow rate to the Stripper Reboiler is controlled on the basis of the
measured flow of the spur water solution entering the Stripper column.
The flowrate of SW to the column is
regulated by the flow controller FIC
located on the discharge line of
Stripper Feed Pump, that acts on the
flow valve FV located on the column
feed stream and that receives a signal
from the level controller LIC located
on Sour Water Feed Surge Drum.
The stripping steam is generated in the
Stripper Reboiler by means of LP
Steam, whose flow is controlled by
the flow controller FIC-2019 acting on
FV on the LP Steam line. The FIC2019 set point is resetted by the
signal coming from FIC-2002.
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SOUR WATER STRIPPER PRESSURE
The overhead pressure in the
column is controlled
by the
pressure controller PIC-2002 acting
on two control valves:
PV-2002A located on the line that
leads acid gas to SRU Section and
PV-2002B located on the line to
acid flare.
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SOUR WATER STRIPPER PRESSURE
Split range valves
Provide 5% deadband to prevent system malfunction.
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SOUR WATER STRIPPER TEMPERATURE
The overhead pressure in the
stripper sets the stripped water
temperature in the stripper
bottom at the right value, so as
to obtain a good performance.
The overhead temperature in
the Stripper is controlled by
TIC-2007, which resets the flow
controller FIC-2007 acting on
the flow valve FV-2007 on the
delivery line of the Stripper
Pumparound Pump.
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SOUR WATER STRIPPER TEMPERATURE
Split range valves
Provide 5% deadband to prevent system malfunction.
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SOUR WATER FEED SURGE DRUM
PRESSURE
The pressure in the drum is controlled by the pressure controller PIC-2001
acting on two control valves:
PV-2001A located on the inert gas line and
PV-2001B located on the line to acid flare.
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SOUR WATER FEED SURGE DRUM
PRESSURE
Split range valves
Provide 5% deadband to prevent simultaneous pressuring and discharging.
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LOGIC SYSTEM
What is the LOGIC SYSTEM?
A Logic System is an integrated highly automated safety facility, able to
perform several actions:
Handling all the start-up and shut-down phases of the Plant;
Isolate the whole plant, one unit of the plant from the other, or just a
section of one unit;
Interact with the DCS system;
Keep always the Plant under safe conditions.
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LOGIC SYSTEM
HOW DOES IT WORK?
The working principle of a Logic System is:
INPUT:
Upset signal from the Plant
OUTPUT: One or more actions performed automatically on valves,
equipment, …
MAIN FUNCTIONS OF A LOGIC SYSTEM
Shut-Down Procedure
Start-Up Procedure
Avoid Upset conditions during normal operation that could damage the
personnel or the equipment
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LOGIC SYSTEM
MAIN FEATURES OF LOGIC SYSTEM
All the logics are handled by a central hardware called PLC (programmable
logic control)
Input/output signals of PLC are usually electrical, not digital.
PLC input signals: output signals from instrumentation installed in the plant.
PLC output signals: input signals for SD, ESD, control valves.
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LOGIC SYSTEM – START UP
When starting-up a section of a plant, the logic system
shall strictly follow a well determined procedure.
This procedure is tied to verify the necessary conditions,
in order to guarantee the safety of the operation.
These conditions are called PERMISSIVES.
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PERMISSIVE DURING START-UP
HOW IS A START-UP PERFORMED?
Start-up is guided and monitored by well competent operators and
specialist engineers.
Start-up must be performed both from field and control room.
The operators in control room shall monitor the start-up via
graphic pages.
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PERMISSIVE DURING START-UP
On the graphic pages, the whole plant is graphically represented:
-
Equipment
Instruments
SD, ESD, control valves
Control loops
Alarms and SD causes
Furthermore, in the graphic pages the operator can check if all the logic
conditions necessary for the start-up are met.
If some of the required permissives are not met, the logic system doesn’t give its
permission to start-up.
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CAUSE & EFFECT DIAGRAM
The protective system (ESD) shall be based on the input (causes) and
the output (effects) as shown in the Cause & Effect Chart
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ARU SECTION – ESD SYSTEM
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SWS SECTION – ESD SYSTEM
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Rome
Viale Castello della Magliana 75
00148 - Italy
Ph. +39 06 602161
Fax +39 06 65793002
[email protected] – www.tecnimontkt.it
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THANK YOU FOR THE ATTENTION