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PROCESS CONTROL & INSTRUMENTATION LABORATORY
(BKF4791)
2015/2016 Semester I
Title of Experiment : Gas Pressure Control Using PID Controller (Experiment 6)
Date of Experiment : 8th October 2015
Lecturer Name : Dr. Noorlisa
Group members :
Name ID
1. JOSEPHINE WONG SIAN CHEE KE12056
2.
3.
Group No. : 5
Section : 05
Marks :
1
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FACULTY OF CHEMICAL AND NATURAL RESOURCES ENGINEERING
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Subject Code : BKF4791
Title of Experiment: : Gas Pressure Control Using PID Controller (Experiment 6)
CONTENT
Contents Pages
1.0 Abstract
2.0 Methodology
3.0 Results and Discussion
4.0 Conclusion and Recommendation
5.0 References
6.0 Appendix
2
1.0 ABSTRACT
3
2.0 METHODOLOGY
Experiment 1
Figure 1 Single Capacity Tank Pressure Control Procedure
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PIC91 pressure trend response was compared with the response with different PIC setting and comment in observation column
The process was repeated with different PIC setting
Tank T91 pressure response was observed at PIC91 Process History View.
Pressure Load Disturbances was performed by switching PIC91 contorller to Manual Mode and decrease its MV by 10% for 10 seconds and switched back PIC91 contorller back to auto mode.
The Process History View for PIC91 was called up from its Detail faceplate and the response for the pressure changes in tank T91 was observed and the pressure was waited to reach the set point.
PIC91 Detail faceplate was openned and the first trial PID tunning parameters were inserted as in Table. Then the control loop was set into Auto Mode.
The set point of 15 psig was entered and the output, (MV) was gradually adjust so that the pressure in the tank T91 matches the set point (within ±0.1psig). and the process was left to stabilize.
PIC91 controller was set to PID control and the controller faceplate of PIC91 was called up and the control loop was set to manual mode.
The operator workstation was switch ON and Gas pressure process was selected. Single capacity process was chosen and the bypass valves was checked to make sure B92A and B92 are open
Experiment 2
Figure 2 Multiple Capacity Tank Pressure Control Procedure
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PIC91 pressure trend response was compared with the response with different PIC setting and comment in observation column
The process was repeated with different PIC setting
Tank T92 pressure response was observed at PIC92 Process History View.
Pressure Load Disturbances was performed by switching PIC92 contorller to Manual Mode and decrease its MV by 10% for 10 seconds and switched back PIC92 contorller back to auto mode.
The Process History View for PIC92 was called up from its Detail faceplate and the response for the pressure changes in tank T91 was observed and the pressure was waited to reach the set point.
PIC92 Detail faceplate was openned and the first trial PID tunning parameters were inserted as in Table. Then the control loop was set into Auto Mode.
The set point of 15 psig was entered and the output, (MV) was gradually adjust so that the pressure in the tank T92 matches the set point (within ±0.1psig). and the process was left to stabilize.
PIC92 controller was set to PID control and the controller faceplate of PIC92 was called up and the control loop was set to manual mode.
The operator workstation was switch ON and Gas pressure process was selected. Multiple capacity process was chosen and the bypass valves was checked to make sure B92A and B92 are open
3.0 RESULTS AND DISCUSSIONS3.1 RESULTS
Experiment 6.1: Study single capacity gas pressure control using PID single control loop
Table 3.1: Summary of PID Trial Observations based on Different Values of Gain, Reset and Rate
PID Trial
PIC91A Set point
(Psig)
Gain (100/P)
Reset (I) sec
Rate (D) sec
Observation
I 15 1.7 5.0 0.0 The manipulated output (black line) response was fast and increasing from 60 to 70++ with an
overshoot and the ocssilation damped out over time. This is same to the process output (red line).
When there is a disturbance, it raise back to set point with few osccilation and damped out to set
point in a very short time
II 15 3.5 5.0 0.0 The manipulated output (black line) response was fast and with a very huge amplitude with a range or 55-100. The response did not damped out after 3 ocssilation. The process output (red line) also
showed a similar trend with the manipulated output where it oscillate without damping out to
set point.
III 15 1.7 30.0 0.0 The manipulated output (black line) response start with a small change then with a huge change/
amplitude between 10- 100. The process output (red line) also showed a similar trend osccilating
and did not damped out after few oscillation to set point.
IV 15 1.0 3 0.0 The manipulated output (black line) and process output (red line) showed overshoot and damped out to set point within a short time. There are not
much osccilation and peaks produced.
*The Figures obtained were attached at the appendix
Experiment 6.2: Study multi capacity gas pressure control using PID single control loops
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Table 3.2: Summary of PID Trial Observations based on Different Values of Gain, Reset and
Rate
PID Trial
PIC91A Set point
(psig)
Gain (100/P)
Reset (I) sec
Rate (D) sec
Observation
I 15 0.5 25.0 0.0 The manipulated variable output (black line) and process output (red line)
increased smoothly and process output reach the set point line where gave the
steady state without any oscillation.
II 15 0.9 11.0 0.0 The manipulated output increase remain steady while the process output (red
line) increase smoothly and achieve set point
III 15 3.5 11.0 0.0 The graph is similar to trial II but with steeper increase in manipulated output and process output. Manipulated output
has an overshoot and back to steady state but process output did not show
any overshoot and reach steady state at set point.
IV 15 3.5 5.0 0 The manipulated output has overshoot and oscillate and damped out to steady state while process ouput also showed similar trend which has an overshoot
and oscillate and damped out to set point
.*The Figures obtained is attached at the appendix
3.2 DISCUSSIONS
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1. Based on your observation in both experiment, discuss briefly for each process that was occurred.
Single Capacity Experiment
Comparing Trial 1 and Trial 2 with same Reset (I) and Rate (D) but with different
Controller Gain (P) which is 1.7 and 3.5, an increase in contorller gain has caused the
manipulated output with higher amplitute and higher frequency of oscillation. High
controller gain at 3.5 also cause the process output cannot reach the set point after several
oscillation unlike trial 1. Comparing Trial 1 and Trial 3 with same Gain (P) and Rate (D)
but with different Reset (I) which is 5.0 and 30.0. Higher reset graph has caused the
manipulated output with higher amplitude and higher frequency of oscillation. At higher
reset =30.0, the set point is oscillating and did not damped out. Due to the consideration
of high gain and high reset is not favorable to this process, Trial 4 was tried with lower
Gain (P) and Reset (I) compared to Trial 1. The process output has achieved steady state
at set point faster than Trial 1 but with an overshoot. But the oscillation damped out very
soon compared to Trial 1 too. In conclusion, for this process control will require lower
gain and lower reset.
Multiple Capacity Experiment
Comparing Trial 2 and Trial 3 with same Reset (I) and Rate(D) but with different Gain(P)
which is 0.9 and 3.5, higher Gain (P) resulted in a better response where the process
output acheive steady state at set point faster. Comparing Trial 3 and 4 with same Gain
(P) but with different Reset (I) which is 11s and 5s. Reducing Reset (I) has caused the
process output to response faster however it cause the process output with an overshoot
and oscillate before it damped out to the set point while there are no overshoot in higher
Reset (I) which is 11s. It was concluded that higher Gain (P) for multiple capacity will
have a faster response and reach set point faster. Besides that, reducing Reset (I) time
also improve the speed of the response however, there is a limit the minimum Reset (I)
can go because lower reset in Trial 4 has cause the process output to have an overshoot.
Thus, there is an optimum Gain(P) and Reset(I) for this multiple capacity control system.
2. Which is the best PID setting for each experiment?
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For single capacity, the best trial was trial 1 and trial 4. This is because trial 1 reached set
point at ± 1 psig eventhough it oscillates and damped out and trial 4 has faster response and
reach steady state faster but it has a huge overshoot then only damped out at set point. For
multiple capacity, the best trial was trial 3. This is because the process output acheive steady
state fastest without overshoot and have no oscillation to the set point.
3. Is it possible to use PI controller in both cases? Explain briefly either yes or no.
Yes, we can get a good result without setting rate for both experiments. Trial 1 in single
capacity able to reach steady state at set point after few small amplitude oscillation while Trial 3
in multiple capacity able to reach steady state at set point without overshooting and oscillation in
a very short time.
4.0 CONCLUSION
In conclusion, for single capacity control, reducing Gain (P) and Reset (I) to lower value
will cause the process output to response faster and reach steady state at set point faster.
However if the Reset (I) is too low, it will cause an overshoot but it will damped out very fast
too. PI controller for this process control is adequete.
Secondly, for multiple capacipty control, increase Gain (P) will speed up the process
output but reducing Reset (I) will slower down the process output response. Thus it is considered
to be a better control with higher Gain (P) and lower Reset (I). However, when the Reset (I) is
too low at 5s, the process output will experience an overshoot and ocsillation before damping to
set point at steady state.
5.0 REFRENCES
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Seborg, D. E., Edgar, T. F., Mellichamp, D. A., & Doyle III, F. J. (2011). Process dynamics and control. NJ: John Wiley & Sons, Inc.
6.0 APPENDIX
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Experiment 6.1
Figure 3: Trial 1 ( Gain = 1.7; Reset = 5s; Rate = 0s)
Trial 2
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Trial 3
Trial 4
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Experiment 6.2
Trial 1
Trial 2
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Trial 3
Trial 4
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Rubric for LAB REPORT
Item AssessedUnacceptable
(0)Poor(1)
Average(2)
Good(3)
Score
Abstract
(x 5)
No abstract No highlight of the significant results and/or methodology.
Missing objective and/or conclusion.
Objective Summary of the
methodology Summary of the
results Conclusion
Methodology flowchart
(x 5)
No flowchart Methodology flow is incorrect.
Methodology flow is correct, but not concise.
Methodology flow is correct and concise.
Data Tabulation
(x 3)
No table Tables provided but no captions given OR
Tables provided but captions not in sequence and not mentioned in the text
Tables provided, captions given and numbered in sequence but no units
Tables numbered with the Arabic numerals and have captions in sequence. The units in which results are expressed are given at the top of each column (in parentheses)
Graph
(x 3)
No Graph OR All graphs wrongly
plotted
Graphs provided but no captions given OR
Graphs provided but captions not in sequence and not mentioned in the text
Properly captioned, numbered and graphs mentioned in the text. However, conditions of experiment (P, T) not mentioned in the caption
Properly captioned, numbered and graphs mentioned in the text. Conditions of experiment (P, T) mentioned in the caption
Calculations
(x 5)
Calculations not shown OR
Calculations totally wrong
Skip a few important calculation steps
All calculation steps are clearly written and correct but wrong unit
All calculation steps are clearly written and correct and with correct unit
Results Data sheet with stamp not provided with the report OR
Results given but significant amount not tally with the
Results given but a few not tally with the requirements of
Results shown for all the scopes of experiments
15
Item AssessedUnacceptable
(0)Poor(1)
Average(2)
Good(3)
Score
(x 10) Results not compatible with scopes
requirement/ scopes experiment
Discussion
(x 20)
Only mention the results without meaningful discussion
Attempt to discuss but failed miserably
Elucidation of result but contains some flaws
Elucidation and supported by proper references or logical explanations.
Conclusions
(x 5)
No conclusion sections OR
Conclusions totally not reflecting the scopes
Conclusion missing the important points OR
No recommendation given to improve the experiment.
Conclusions regarding major points are drawn, but many are misstated, indicating a lack of understanding OR
Conclusion is too general. Several recommendations have been given but they are too general and not contributing to the experiment’s improvement.
Important/ significant results are highlighted which also meets the scopes of experiments AND
Several recommendations have been stated.
References
(x 5)
Copy & paste references OR
Ununiformed referencing system OR
80% references from internet OR
Use of Wikipedia
Most of citations in text are not available in list of reference although use same referencing system OR
Internet sources > 60%
A few citations in text are not available in list of reference AND
Use same referencing system
All citations in text are available in list of reference and use the same referencing system AND
All references from reliable resources
Grammar and Spelling
(x 5)
Unreadable and not written in scientific way
Numerous spelling and/or grammar errors. Direct translation using Google Translate.
Occasional spelling and/or grammar errors.
Correct use of words.
Total Assessment Marks (198)
16