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

4

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

5

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

6

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

7

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?

8

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

9

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

10

Experiment 6.1

Figure 3: Trial 1 ( Gain = 1.7; Reset = 5s; Rate = 0s)

Trial 2

11

Trial 3

Trial 4

12

Experiment 6.2

Trial 1

Trial 2

13

Trial 3

Trial 4

14

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