1. INSTRUMENTATION FOR P&ID’s

2. 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?

3. 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?

4. 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?

5. 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

6. Ground rules for additional equipment?
hrs ?
hrs 12
hrs
8 hrs

7. Now Back to our regularly scheduled show...

8. 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 PI FE

9. 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

10. Instrumentation Cookbook Control Loop
A Simple Feedback Control Loop
Set Point
Often not shown
Measured
Variable (temp,
pressure, flow...)
Controller
Manipulated
Variable FE
FIT
FIC FV

11. Instrumentation Naming
Instrument Society Of America (ISA)
ISA Typical Letter Combinations.xls

12. Instrumentation Cookbook P&ID’s - Symbology
Equipment Symbology
Instrumentation Symbology
See the document “P&ID Symbols and Photos.DOC”

13. Instrumentation Cookbook P&ID’s - Symbology
Located in DCS
(process control
computer)
LIC
Software Signal
Physically
located
‘in field’ LT
Physical wire
“hardwired”

14. Instrumentation Cookbook The “Control Valve”
Actuator - driven by Compressed Air
Elec Signal
To valve
(4-20 mA
DC signal)
Valve

15. Instrumentation Cookbook Typical Controls
Level
Flow
Pressure
Temperature
Composition

16. Instrumentation Cookbook Level Control
Purpose
Prevent the tank from overfilling / running dry LT
LIC LV

17. Instrumentation Cookbook Level Control
Purpose
Hold a liquid “Seal” LT
LIC
No Gas! LV

18. 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

19. 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)

20. 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 !!

21. 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

22. Instrumentation Cookbook Flow ControlFT
FIC FE
FIC M FT I FV
SIC FE
Variable Speed Drive
Mount FE upstream in vapour systems to minimize pressure/density effects

23. Instrumentation Cookbook - Ratio Flow ControlSP
FIC
Set one flow rate
Other flow is proportionally controlled to first flow
Ensure correct mixture / recipes FT
FRIC SP FV FE
FIC SP FT FV FE

24. 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

25. Instrumentation Cookbook Pressure Control
Control Upstream | Control Downstream
PIC
PIC PT PT PV PV
Need to downstream (header or process) pressure
Need to control vessel pressure

26. Instrumentation Cookbook Pressure Control
Condensable Gas
PIC PV PT
Need to control vessel pressure
Fast or slow?

27. Instrumentation Cookbook Pressure Control
Liquid Pressure Control
PIC PT PV
Control pump discharge pressure - not very useful

28. Instrumentation Cookbook Pressure Control
Liquid Pressure Control
PIC
FIC PT
Pressure control on pump provides a steady pressure to the flow control valve
Essentially the pump flow is fixed through this scheme.
By making the pressure at the inlet of the FV constant the flow control will be
better (more linear).
Show pump curve dropping as flow increases. FT PV
Control pump discharge pressure - ensure constant feed pressure to FV FV FE

29. 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
Increase in hot flow rate in second box

30. Instrumentation Cookbook Temperature Control
Liquid / Liquid - control on cooling media
Bottom box shows decrease in hot stream flow rate and corresponding
- decrease in LMTD to reduce overall duty of exchanger
- increase in c/w outlet to reduce LMTD
-decrease in cooling water flow
C/w

31. Instrumentation Cookbook Temperature Control
Liquid / Liquid - control on process
C/w

32. Instrumentation Cookbook Temperature Control
Steam Pressure Control T
Increase Stm
Pressure

33. Instrumentation Cookbook Temperature Control
Condensate Level Control
Reduce flooded
Area

34. 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

35. Instrumentation Cookbook Cascade Control
One Control Loop Determines Setpoint of a Second Loop FT
-Using the flow through the pump to control the rotational speed of the pump FE
FIC M SP
Flow DP
High Speed
Low Speed I
SIC SP
Variable Speed Drive

36. Instrumentation Cookbook Cascade Control
PIC
FIC FT FE FV PT
Common Around Distillation Columns Where There Are Slow Loops

37. 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)

38. Instrumentation Cookbook Controller Interaction
Duelling Control ? LT
LIC
FIC LV FT FE

39. Instrumentation Cookbook Controller Interaction
Duelling Control ?
LIC LT
FIC FT FE LV

40. Instrumentation Cookbook Controller Interaction
Duelling Control ?
SP= 75 psig
SP= 35 psig
PIC
PIC PT PT
100 psig
Compressed
Air
User 2
User 3
User 1 PV PV

41. P&ID Cookbook -By Equipment

42. P&ID Cookbook - Pumps
PRV M I HS PI

43. Pump - Min Flow Bypass RO PI LT PI
LIC LV HS I M HS

44. Reflux Tanks Set@ From Condenser TO LV I To Pump PI TI LIT
Vent to Safe Locn PI
From Condenser
From Pump
LAHL
HLL = 4’-6” TI TO LV
LIC
NLL = 3’-6”
LIT
LLL = 2’-0”
LLLL = 2’-0”
LSLL I
LALL
Pump
S/D
To Pump

45. 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
CWR
Control
From ?
SIC M
By Vendor
By Owner

46. Columns Level control Pressure control Put a control scheme to ensure
Treat the
top and bottom independently of each other
Pressure control
Level control
Composition control
Put a control scheme to ensure
Feed rate is constant or is slowly changing

47. Columns - Bottoms FT LIT TE FIC LIC TIC
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
Columns - Bottoms
FIC FT
HHLL
5 bar
Stm
HLL
LIT
NLL
Cascade temperature to steam flow
LLL
LLLL
Low
P Cond T TE
LAHL
LIC
TIC

48. Columns - Overhead FV FT TE
TIC
FIC
CWS
CWR PV PT
PIC RO

49. 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

50. 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

51. Instrumentation Cookbook Tanks - Storage
PRV
Temperature Control
May Be Required
-does material freeze / boil?
LAHH
LSHH I LY TI
LSHH s LI
LSLL
LAHL
LIT I M LV

52. Workshop Draw the level control that should go on a storage tank
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

53. END

54. Instrumentation Cookbook Tanks - Process Surge
PSV
Consider Pressure Control LT
LIC LV

55. Heat Exchangers - Condenser
Vent to Safe Locn TV
TIC
CWS
TV on condenser outlet to prevent c/w flashing inside condenser during turndown
TAHL TE