Transcript INSTRUMENTATION FOR P&ID’s

INSTRUMENTATION
FOR
P&ID’s
But first....
 Design pressures...
It’s best to group equipment and give it all
the same maximum op. pressure
What groups would you create?
What would the max op. pressure be?
Ground rules for additional
equipment
 Send non-useful gases (Gas_purge 200 kg/hr, Lights
51 kg/hr) for combustion in the syngas htr (it’s a
fired heater)
 Send Fusil_oil (19 kg/hr) to waste treatment plant or
to the syngas htr (need tank & pump)
 - implications?
Ground rules for additional
equipment
Storage Tanks
 Provide an ‘off spec’ tank for the Product sized for 12
hours of hold-up at normal rates
 In addition, provide at least 2 tanks for the Product
 Provide an 8 hour storage tank for the Recovr_water
 Storage Tanks can have L/D = 1 (or less)
 Show product storage tanks sending material to
“existing truck and railcar loading”
 Show Recovr_water storage tank sending water to
“waste treatment” plant - recycle issues?
Ground rules for additional
equipment
Pumps
 Put a pump on the “acetone column” bottoms
product so we can run it at as low a pressure as
possible (at simulation stated pressures) to ensure
we remove all lights etc.
 don’t put a pump on “degasser” bottoms (let’s
increase the pressure accordingly)
 what are the trade-off’s?
 Provide a pump on the “off spec” storage tank to
recirc material back to the Acetone column feed.
 This will help us during start-up or upsets
Ground rules for additional
equipment
?
hrs
?
hrs
12
hrs
8 hrs
Now Back to our regularly
scheduled show...
Instrumentation Cookbook
Instrumentation
 Why Are We Doing This
ESTIMATOR - To Size The Pumps We Need
To Include “Inline” Instrumentation
Provide A Basic Understanding Of Controls
Nomenclature and Their Application
FE
PI
Instrumentation Cookbook
Instrumentation
 Objective:
To Produce A Viable Control Scheme in a
way that uses and improves our
understanding of the simulation and gives
us essential information to size the pumps
To have some examples of controls that
could be applied to our process
To understand why these control schemes were
selected so that you can form your own
judgement
Instrumentation Cookbook
Control Loop
 A Simple Feedback Control Loop
Set Point Often not shown
Measured
Variable (temp,
pressure, flow...)
FE
FIT
Controller
Manipulated
Variable
FIC
FV
Controllers
Initiating or
Measured Variable
Analysis
Burner, Combustion
Users Choice
Users Choice
Voltage
Flow Rate
Flow Quantity
Flow Ratio
Users Choice
Hand
Current (Electrical)
Power
Time
Level
Users Choice
First
Letter
A
B
C
D
E
F
FQ
FF
G
H
I
J
K
L
M
Recording Indicating blind
ARC
AIC
AC
BRC
BIC
BC
Readout Devices
Switches and Alarm Devices
Self
Actuated
Control
Valves
Recording Indicating High
Low
Comb
AR
AI
ASH
ASL
ASHL
BR
BI
BSH
BSL
BSHL
Transmitters
Recording Indicating Blind
ART
AIT
AT
BRT
BIT
BT
Instrumentation Naming
ERC
FRC
FQRC
FFRC
EIC
FIC
FQIC
FFIC
IRC
JRC
KRC
LRC
HIC
IIC
JIC
KIC
LIC
EC
FC
FCV FICV
FFC
ER
FR
FQR
FFR
EI
FI
FQI
FFI
ESH
FSH
FQSH
FFSH
ESL
FSL
FQSL
FFSL
HR
IR
JR
KR
LR
HI
II
JI
KI
LI
ISH
JSH
KSH
LSH
ISL
JSL
KSL
LSL
ESHL
FSHL
 Instrument Society Of America (ISA)
Initiating or
Measured Variable
Analysis
Burner, Combustion
Users Choice
Users Choice
Voltage
Flow Rate
Flow Quantity
Flow Ratio
Users Choice
Hand
Current (Electrical)
Power
Time
First
Letter
A
B
C
D
E
F
FQ
FF
G
H
I
J
K
HC
KC
LC
KCV
LCV
Solenoids,
Relays,
Computing Primary
Devices
Element
AY
AE
BY
BE
EY
FY
FQY
HY
IY
JY
KY
EE
FE
FQE
FE
Well Of
Test Point Probe
AP
AW
BW
FP
Viewing
Device,
Glass
HS
ISHL
JSHL
KSHL
LSHL
Safety
Device
BG
FG
IE
JE
KE
ISA Typical Letter Combinations.xls
ERT
FRT
EIT
FIT
FQIT
ET
FT
FQT
HRT
IRT
JRT
KRT
LRT
HIT
IIT
JIT
KIT
LIT
HT
IT
JT
KT
LT
Final
Element
AV
BV
EZ
FV
FQV
FFV
HV
IZ
JV
KV
Instrumentation Cookbook
P&ID’s - Symbology
 Equipment Symbology
 Instrumentation Symbology
 See the document “P&ID Symbols and
Photos.DOC”
Instrumentation Cookbook
P&ID’s - Symbology
LIC
Located in DCS
(process control
computer)
Software Signal
LT
Physically
located
‘in field’
Physical wire
“hardwired”
Instrumentation Cookbook
The “Control Valve”
Actuator driven by
Compressed
Air
Valve
Elec Signal
To valve
(4-20 mA
DC signal)
Instrumentation Cookbook
Typical Controls
 Level
 Flow
 Pressure
 Temperature
 Composition
Instrumentation Cookbook
Level Control
 Purpose
Prevent the tank from overfilling / running
dry
LT
LIC
LV
Instrumentation Cookbook
Level Control
 Purpose
Hold a liquid “Seal”
LT
LIC
No Gas!
LV
Instrumentation Cookbook
Level Control
 Purpose
Prevent pump from running dry and thus
being destroyed
LT
LIC
LV
Note: - valve always on disch to prevent flashing on pump suction
- pump may also require a minimum flow bypass
Control Systems
Aside - Speed
 Measured Variable can be slow to measure
(I.e. the composition using an analyser) or
fast (pressure)
 The Manipulated Variable can be slow too
(I.e. adjusting the hot water tap in your
shower)
 The level in a tank can take hours to change
(slow)
Control Systems
Aside - Speed
 Slow Things
 Say > few seconds
 Reducing Pressure
by Opening a valve
on a large gas filled
tank
 Measure Composition
(analysers)
 Change Level In
Large Tank
 Fast Things
 Less than a second
 Measure Pressure
 Measure Flow (Diff
Press)
 Measure Temp (?)
But…. It’s all RELATIVE !!
Instrumentation Cookbook
Flow Control
 Purpose: Ensure steady material flow rate
Smooth feed to columns
Set Production rate
 Fast to Measure
 Flow Changes usually require a control valve
to change it’s position which can take
seconds.
 Vapour systems have a ‘capacitance’ that
need to be overcome before the flow changes
are experienced everywhere in the system
Instrumentation Cookbook
Flow Control
FT
FIC
FE
M
FT
FIC
I
FE
FV
SIC
Variable Speed Drive
Mount FE upstream in vapour systems to minimize pressure/density
effects
Instrumentation Cookbook
- Ratio Flow Control
SP
FIC
FT
FE
FRIC
FV
FIC
SP
FT
FE
SP
 Set one flow
rate
 Other flow is
proportionally
controlled to
first flow
 Ensure correct
mixture / recipes
FV
Instrumentation Cookbook
Pressure Control
 Similar to Level (control of material inventory)
 Very fast for incompressible fluids
 Hard to say for compressible fluids, depends
on system volume but probably slow
Instrumentation Cookbook
Pressure Control
 Control Upstream | Control Downstream
PIC
PIC
PT
PT
PV
Need to control vessel pressure
PV
Need to downstream (header or
process) pressure
Instrumentation Cookbook
Pressure Control
 Condensable Gas
PIC
PV
PT
Need to control vessel pressure
Fast or slow?
Instrumentation Cookbook
Pressure Control
 Liquid Pressure Control
PIC
PT
PV
Control pump discharge pressure - not very useful
Instrumentation Cookbook
Pressure Control
 Liquid Pressure Control
PIC
FIC
PT
FT
PV
Control pump discharge pressure - ensure
constant feed pressure to FV
FE
FV
Instrumentation Cookbook
Temperature Control
 Normally control the ‘flow’ of one fluid to
change the temperature of another
 In Reality it’s an LMTD change that affects
the exchanger duty
 Q = U A Tln
Instrumentation Cookbook
Temperature Control
 Liquid / Liquid - control on cooling media
C/w
Instrumentation Cookbook
Temperature Control
 Liquid / Liquid - control on process
C/w
Instrumentation Cookbook
Temperature Control
 Steam Pressure Control
T
Increase Stm
Pressure
Instrumentation Cookbook
Temperature Control
 Condensate Level Control
Reduce flooded
Area
Instrumentation Cookbook
Cascade Control
 Example - Driving to Montreal
You’re driving / steering the car
Someone else is telling you which roads to
drive on and when to turn
Instrumentation Cookbook
Cascade Control
 One Control Loop Determines Setpoint of a
Second Loop
FT
FE
High Speed
P
M
I
Low Speed
Flow
SIC
SP
Variable Speed Drive
FIC
SP
-Using the
flow through
the pump to
control the
rotational
speed of the
pump
Instrumentation Cookbook
Cascade Control
PIC
FIC
FT
FE
FV
PT
 Common Around Distillation
Columns Where There Are
Slow Loops
Instrumentation Cookbook
Controller Interaction
 Many Controllers Interact but some
configurations Interfere with each other
 I.e.
the control of reflux flow interacts with the
column bottom level control
but two flow controllers on the same pipe
will interfere with each other (they duel for
control of the flow)
Instrumentation Cookbook
Controller Interaction
 Duelling Control ?
LT
LIC
FIC
LV
FT
FE
Instrumentation Cookbook
Controller Interaction
 Duelling Control ?
LIC
LT
FIC
FT
FE
LV
Instrumentation Cookbook
Controller Interaction
 Duelling Control ?
SP= 75 psig
PIC
SP= 35 psig
PIC
PT
100 psig
Compressed
Air
PV
PT
PV
User 1
User 2
User 3
User 1
User 2
User 3
P&ID Cookbook
-By Equipment
P&ID Cookbook
- Pumps
PI
PI
PRV
HS
I
HS
M
Pump - Min Flow Bypass
RO
PI
LT
PI
LIC
LV
HS
I
HS
M
Reflux Tanks
Set@
Vent to Safe Locn
PI
From Condenser
From Pump
HLL = 4’-6”
NLL = 3’-6”
LLL = 2’-0”
LLLL = 2’-0”
TI
LSLL
I
LIT
LAHL
LIC
TO
LV
LALL
Pump
S/D
To Pump
Compressors - Centrifugal
 For our purposes treat controls as a black box
 But... Provide an input control signal (cascade)
 Remember cooling water req’d (lube system...)
CWS
Control
From ?
CWR
SIC
M
By Vendor
By Owner
Columns
Composition control
Pressure control
Put a control
scheme to
ensure
Feed rate is
constant or is
slowly
changing
Level control
Level control
Composition
control
Treat the
top and bottom
independently
of each other
Columns Bottoms
 Put level control on bottoms outflow
when
 outflow rate > 10 x boil up rate
 Put level control on Steam control
 boilup rate > 10 x outflow rate
 otherwise either scheme okay
FIC
FT
HHLL
5 bar
Stm
LIT
HLL
NLL
LLL
LLLL
T
TE
LAHL
LIC
TIC
Low
P Cond
TE
Columns - Overhead
TIC
PIC
PT
CWS
FV
CWR
FIC
Set@
PV
PI
RO
FT
HLL = 4’-6”
NLL = 3’-6”
LLL = 2’-0”
LLLL = 2’-0”
TI
LSLL
I
LIT
LAHL
LIC
PI
PI
LALL
Pump
S/D
LV
HS
I
HS
M
Instrumentation Cookbook
Column Control
 If a flow rate dominates use it to control the
level
 Column Overhead Control - Scheme 1
when the draw rate is 10 x > reflux rate
Manipulate Distillate draw rate to control Reflux
level
Manipulate reflux rate to control Column
Composition
Instrumentation Cookbook
Column Control
 Column Overhead Control - Scheme 2
when the reflux rate is 10 x > draw rate
Manipulate Distillate draw rate to Manipulate
Column Composition
Manipulate reflux rate to control control Reflux
Drum level
Instrumentation Cookbook
Tanks - Storage
PRV
Temperature
Control
May Be
Required
-does material
freeze / boil?
LAHH
LSHH
LY
LSHH
TI
s
I
LI
LSLL
LAHL
LIT
LV
I
M
Workshop
Hand this in at the end of class...
 Draw the level control that should go on a
storage tank
 Provide a different control scheme for the
reactor / condenser / flasher P&ID
 draw it
 explain how your scheme works and responds to
upsets
 explain the pros/cons of your scheme
 using a BFD, including the syngas process,
show how pressure control can be done
END
Instrumentation Cookbook
Tanks - Process Surge
PSV
Consider
Pressure
Control
LT
LIC
LV
Heat Exchangers - Condenser
Vent to Safe Locn
TV
TIC
TV on condenser outlet
to prevent c/w flashing
inside condenser during
turndown
CWS
TAHL
TE