Difference between revisions of "PH Loop"

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[PAGE UNDER CONSTRUCTION]
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[[File:Pmc02ph_rig.JPG|500px|right|thumb|The pH control rig]]
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PH control is a difficult problem due to the highly non-linear nature of the system. The steep slope of the titration curve around the pH = 7 point amplifies pH variations for even small base/acid addition variations. The pH control rig in the [[PMC lab]] illustrates that pH control is by no means impossible (albeit on a laboratory scale).
 
PH control is a difficult problem due to the highly non-linear nature of the system. The steep slope of the titration curve around the pH = 7 point amplifies pH variations for even small base/acid addition variations. The pH control rig in the [[PMC lab]] illustrates that pH control is by no means impossible (albeit on a laboratory scale).
  
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C. Steyn, '''Fuzzy Logic Rule-Based Controller Design, Neutralization of Strong Acid with Strong Base'''<br/>
 
C. Steyn, '''Fuzzy Logic Rule-Based Controller Design, Neutralization of Strong Acid with Strong Base'''<br/>
 
[http://ragnarok.up.ac.za/Rigs/02_pH/2007/pH_Control_CWSteyn.pdf Report] | [http://ragnarok.up.ac.za/Rigs/02_pH/2007/ Project files]
 
[http://ragnarok.up.ac.za/Rigs/02_pH/2007/pH_Control_CWSteyn.pdf Report] | [http://ragnarok.up.ac.za/Rigs/02_pH/2007/ Project files]
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=== 2009 (Current) ===
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=== 2009 ===
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A.H. Campher, project to determine methods of obtaining the attainable- and desired output spaces (AOS and DOS) from a process model.<br/>
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A.H. Campher, '''Maintenance, Modelling and Control of the pH-control Rig'''<br/>
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[Report] | [Project files]
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[http://ragnarok.up.ac.za/Rigs/02_pH/2009/CML732_Report_AH_Campher_2009.pdf Report] | [http://ragnarok.up.ac.za/Rigs/02_pH/2009/ Project files]
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=== 2010  ===
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A.B. De Jongh, '''Control of a pH neutralisation system using Gain Scheduling '''<br/>
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[http://ragnarok.up.ac.za/publicftp/lab/Rigs/02_pH/2010/pH/CML732_Report_AB_deJongh_2010.pdf Report] |
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[http://ragnarok.up.ac.za/Rigs/02_pH/2010/ Project files]
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=== 2011 ===
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S.C. Burd, '''Non-Linear Model Predictive Control of a pH Neutralization Process'''<br/>
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[http://ragnarok.up.ac.za/Rigs/02_pH/2011/CML732_SCburd2011.pdf Report] |
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[http://ragnarok.up.ac.za/Rigs/02_pH/2011/ Project files]
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== Documentation ==
 
== Documentation ==
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=== Process Flow diagrams ===
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Large scale renaming of instruments, valves and tanks is being done. This renders all previous rig diagrams obsolete. Only 2009-updated diagrams should henceforth be used.
 
=== Piping & Instrumentation diagrams ===
 
=== Piping & Instrumentation diagrams ===
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[ftp://ragnarok/publicftp/lab/Rigs/02_pH/2011/Diagram/02pH_P&ID_2011.vsd (Visio)] | [ftp://ragnarok/publicftp/lab/Rigs/02_pH/2011/Diagram/02pH_P&ID_2011.pdf .PDF]
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=== Wiring diagrams ===
 
=== Wiring diagrams ===
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[http://ragnarok.up.ac.za/Rigs/02_pH/2010/02pH_WiringDiagram_2010.vsd .VSD (Visio)] | [http://ragnarok.up.ac.za/Rigs/02_pH/2010/02pH_WiringDiagram_2010.pdf .PDF]
  
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== Rig maintenance ==
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=== Connecting the pH rig to the OPTO22 system ===
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=== Pre 2009 ===
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The attachment gives details about operating the pH rig from the Simulink environment and connecting it to the OPTO22
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Maintenance and changes made to the pH rig before 2009 are not explicitly maintained on the wiki. Consult the project documentation of previous years for said changes.
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system.
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=== 2009 ===
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[ftp://ragnarok.up.ac.za/publicftp/lab/Rigs/02_pH/2011/OPTO22.pdf Document]
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'''Wiring/Instrumentation'''<br/>
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Wiring of rig found to be in a state of disrepair. An attempt is made to fix all wiring and restore all electronic equipment to a working condition. Fixed equipment/wiring is listed below:
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* I/P transducer for control valve 2 - re-fitted transducer, reconnected piping and wiring.
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* Control valve 2 - reconnected piping.
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* All the RTDs have been removed from the rig (scavenged?) - in process of replacing them.
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* Control valve 1 seems to be stuck. Apparently the original valve was removed and replaced by current non-working valve. In process of testing valve.
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'''Piping'''<br/>
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== Rig maintenance ==
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Numerous leaks were fixed and connections made where piping has been scavenged off the rig.
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The maintenance of the pH rig is documented [[PH Rig Maintenance|here]].
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'''Structural'''
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* Stands for feed tanks (currently dustbins) were found to not give sufficient support when tanks are full. In process of constructing new feed tank stand.
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* Fitting of stirrers to tanks found to be flimsy - refitting them to more sturdy structures.
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* Rerouted pipe connecting CV001 to FE001 - cut away some of the metal structure to remove strain from pipe.
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Latest revision as of 17:08, 28 November 2011

The pH control rig

PH control is a difficult problem due to the highly non-linear nature of the system. The steep slope of the titration curve around the pH = 7 point amplifies pH variations for even small base/acid addition variations. The pH control rig in the PMC lab illustrates that pH control is by no means impossible (albeit on a laboratory scale).

Current/Previous projects

1999

F.J. Botha, Ondersoek van die Dinamiese Gedrag van Sisteme waar pH Gemeet en Beheer word {Investigation of the Dynamic Behaviour of Systems where pH is Measured and Controlled}
[Hard copy of report available in pH rig folder]

2003

T. Leeuw & G. Mascini, pH Rig 2003 - CPL780 Process Control Laboratory
Report | Project files

2005

A.J. Swanepoel & M. Swanepoel (Botha), Model Based Control Laboratory, pH Control
Report | Project files

2007

C. Steyn, Fuzzy Logic Rule-Based Controller Design, Neutralization of Strong Acid with Strong Base
Report | Project files

2009

A.H. Campher, Maintenance, Modelling and Control of the pH-control Rig
Report | Project files

2010

A.B. De Jongh, Control of a pH neutralisation system using Gain Scheduling
Report | Project files

2011

S.C. Burd, Non-Linear Model Predictive Control of a pH Neutralization Process
Report | Project files

Documentation

Large scale renaming of instruments, valves and tanks is being done. This renders all previous rig diagrams obsolete. Only 2009-updated diagrams should henceforth be used.

Piping & Instrumentation diagrams

(Visio) | .PDF

Wiring diagrams

.VSD (Visio) | .PDF

Connecting the pH rig to the OPTO22 system

The attachment gives details about operating the pH rig from the Simulink environment and connecting it to the OPTO22 system. Document

Rig maintenance

The maintenance of the pH rig is documented here.

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