Process Instrumentation Diagram Student Copy · Process & Instrumentation Diagram (P&ID) Purpose 1....
Transcript of Process Instrumentation Diagram Student Copy · Process & Instrumentation Diagram (P&ID) Purpose 1....
Process & Instrumentation Diagram (P&ID)
Purpose
1. To indicate the instruments or control devices attached to the process.
2. To indicate the control system architecture associated with the process.
How it is done?
Standard symbols and notations representing instruments or control devices are placed to the
pipings and vessels. Standard symbols and notations are available from ISA-5.1(1984) standard.
Methodology?
Process piping and sub-piping
A thick straight line represent main process piping
A thin straight line represent process sub-piping either
to instruments or by-pass process line.
PG
© Abdul Aziz Ishak, Universiti Teknologi MARA Malaysia (2011) 1
Naming rule
1 2 3 4
Measurement Device Device / Condition Condition
P
T
L
F
A
Pressure
Temperature
Level
Flow
Analysis
C
T
R
I
A
S
G
Controller
Transmitter
Recorder
Indicator
Alarm
Switch / Safety
Gauge
C
T
R
H
L
V
Controller
Transmitter
Recorder
High
Low
Valve
H
L
High
Low
Complete guide on P&ID symbols & notations are available from ISA 5.1 (R1984)
Examples
No such
devices yet.
� �
PC
PIC
LG
FR
TAL
TALL
TAHL
Pressure Controller
Pressure Indicating Controller
Level Gauge
Flow Recorder
Temperature Alarm Low
Temperature Alarm Low Low
Temperature Alarm High Low
PCC
PTC
PTR
PIR
TRR
TRA
TAV
Complete guide on P&ID symbols & notations are available from ISA 5.1 (R1984)
© Abdul Aziz Ishak, Universiti Teknologi MARA Malaysia (2011) 2
Instruments / control devices:
A circle representing locally
mounted instrument
A circle with horizontal line
representing control room
panel mounted instrument.
A circle with horizontal line
inside a square representing
its function in DCS.
Symbols
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Follow the standard published by the Instrument Society of America (ISA)
Instrument Line (Signal) Symbols
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Final control elements
Control
valves =
Manual
valve= Not darkened � Always openOR
Manual
valve= Darkened � Always closedOR
NC
Solenoid
valve=
NCNO
NO � Normally open
NC � Normally closed
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Current to pneumatic
transducerI/P
Devices (hardware) SymbolsDevice names
Pressure relief valve /
Pressure safety valvePSV PRV
Notations
I/P
Thyristor TY TY
Inverter VY VY
© Abdul Aziz Ishak, Universiti Teknologi MARA Malaysia (2011) 6
PG
Examples
= Pressure Gauge
PIC= Pressure Indicating Controller
FT = Flow Transmitter
TT
TE
= Temperature Transmitter
= Temperature Element (RTD/TC)
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Can you read the following P&ID?
TT
product
Fuel
�
��
� Main process line
� Process instrument piping
� Temperature transmitter
� Temperature controller
� Flow controller
� Current to pnuematic transducer
Feed
TC�
FT
FCI/P TC SP
� �
�
��
�
�
�
Control valve
� Electrical signal
� Pneumatic signal
ASD
1112� Temperature controller DCS function
11 Automatic shut down PLC unit
12 Solenoid valve
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Controller
Final
Control
Element
Process
Sensor
SP,
Set point
PV,
Controlled
Variable
PV,
Controlled Variable
© Abdul Aziz Ishak, Universiti Teknologi MARA Malaysia (2011)
What is feedback control?
Outcome of an action is fed back to
the controller for corrective action.
Merit?
Simple design. Easy to tune (for linear, fast & short dead time
processes: flow, level & pressure).
Demerits?
Slow recovery for slow process upon load disturbance or change in
set point (such as temperature control). A process with long dead
time may exhibit oscillatory process response and with longer
settling time.
9
Controller
2
Final
Control
Element
Process 2SP,
Set point
PV,
Controlled
Variable
Process 1Controller
1
Sensor
2
PV,
Controlled Variable
© Abdul Aziz Ishak, Universiti Teknologi MARA Malaysia (2011)
Sensor
1
PV,
Controlled Variable
2
What is cascade control?
The inner loop controller obtains its set point
from the outer loop controller.
The purpose is to eliminate the effect of
disturbances.
Merit?
Faster recovery time as compared to SISO feedback
control.
Demerits?
Controllability will be worst than SISO if both
controllers were not properly tuned.
10
Feedforward
Controller
Final
Control
Element
SP,
Set point
PV,
Controlled
Variable
Feedback
Controller
Disturbance
Sensor
Process
D,
Disturbance
© Abdul Aziz Ishak, Universiti Teknologi MARA Malaysia (2011)
Sensor
PV,
Controlled Variable
What is feed forward control?
A method of control based on process
model: mass and energy balances.
Purpose
To compensate disturbances (D) before they
affect the controlled variable (PV).
Demerit
a) Fail to work if any of the sensor broke
down.
b) Poor process controllability due to
inaccurate process model.
11
TT
I/P
Steam in
Steam out
TC
Heated
product out
Product
in
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Steam outin
12
TT
I/P
FT
FC
Steam in
Steam out
TC
Heated
product out
Product
in
© Abdul Aziz Ishak, Universiti Teknologi MARA Malaysia (2011)
Steam outin
13
TT
Σ X
L/L
I/P
FT
FC
FTTT
Steam in
Steam out
TC
Product
in
Heated
product out
© Abdul Aziz Ishak, Universiti Teknologi MARA Malaysia (2011)
Steam outin
14
X I/P
FT
FC
FT
Steam in
Steam out
Product
in
Heated
product out
© Abdul Aziz Ishak, Universiti Teknologi MARA Malaysia (2011)
Steam outin
15
Using correct P&ID symbols, draw the following
instruments to the reboiler as shown in figure
below.
(i) Steam pressure gauge
(ii) Reboiler vapor pressure gauge
(iii) Steam temperature gauge
(iv) Vessel over pressure relief valve
(v) Steam over pressure relief valve
(vi) Liquid level gauge at overflow
compartment
Reboiler vapor
Steam
compartment
(vii) Liquid level gauge at liquid boiling
compartment
(viii) Temperature gauge at liquid boiling
compartment.
Condensate
Bottom product
Tower bottoms
Install appropriate control systems for the
following tasks:
(i) Liquid level control at over flow
compartment
(ii) Reboiler vapor pressure control
(iii) Liquid temperature control
(iv) Reboiler vapor pressure alarm high
(v) Liquid temperature alarm high
(vi) Low and high level liquid alarm at
liquid over flow compartment
Reboiler vapor
Steam
liquid over flow compartment
(vii) Low liquid level alarm at boiling liquid
compartment
(viii) Steam flow cut upon low liquid level.
Condensate
Bottom product
Tower bottoms