Sunway Lab Manual 2014

CHEMICAL ENGINEERING

LABORATORY MANUAL

CHE 3162 Process Control

For Year 2014

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CHE3162 Process Control Laboratory

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Laboratory Safety Guidelines

Extracted from Engineering – Laboratory Safety Handbook [1]

General and Personal Safety Reminders

1. Acts of carelessness are prohibited.

2. Do not carry out any unauthorized experiments, tasks or job, and only perform the given experiments, tasks or job

according to directions.

3. Never work in a laboratory alone or at least without another person within easy call.

4. Smoking is not allowed in any area within the campus.

5. Wear safety glasses or face shields when working with hazardous materials and/or equipment.

6. Wear gloves when using any hazardous or toxic agent. They should be removed before leaving the lab, using

telephones, opening refrigerators, or entering common areas.

7. Clothing: When handling dangerous substances, wear gloves, laboratory coats, and safety shield or glasses. Shorts

and sandals should not be worn in the lab. Safety shoes are required when working near heavy machineries.

8. Wash hands before leaving the lab and before eating.

9. Consumption of food or beverages in the laboratory is forbidden. Food may not be stored in lab refrigerators.

10. Tie back medium length and long hair when working near flames or entangling equipment.

11. Do not use any equipment unless you are trained and approved as a user.

12. Pregnant women should take special care with exposure to certain chemicals, which can be harmful to fetal

development. Consult the Material Safety Data Sheet, Supervisor, or contact your Physician.

13. All accidents, no matter how minor, should be reported to the School/Staff member supervising the laboratory or, if

unavailable, call 46333 from internal phone or 03-55146333.

14. Know the location of all safety equipment (e.g. eyewash, fire extinguisher, fire blanket, safety showers, and spill kit)

and how to use them.

15. Incident and Hazard Report Forms are also available through University’s OH&S Committee. Submitted reports will

help alert Committee to hazards on campus or unsafe work practices, and determine the frequency of accidents

and/or injuries.

16. Keep aisles clear.

17. Maintain unobstructed access to all exits, fire extinguishers, electrical panels, emergency showers, and eyewashes.

18. Do not use corridors for storage or work areas.

19. If leaving a lab unattended, turn off all ignition sources and lock the doors.

20. Do not store heavy items above table height. Any overhead storage of supplies on top of cabinets should be limited

to lightweight items only. Also, remember that a 36" diameter area around all fire sprinkler heads must be kept clear

at all times.

21. Be careful when lifting heavy objects. Seek assistance, lift comfortably, avoid unnecessary bending, twisting,

reaching out, and excessive weights, lift gradually and maintain good physical shape.


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Disciplines and Attitudes

1. The laboratories are meant for conducting your experimental work, not for other non-academic activities. You will

be asked to leave the lab immediately and serious action may be taken if you are found misusing or not adhering to

the lab rules and regulations.

2. Never indulge in reckless behavior in the laboratory.

3. Never adopt a casual attitude in the laboratory and always be conscious of potential hazards.

4. Never run in the laboratory or corridors.

5. Do not sit on workbenches.

6. Tidy up your workplace after each use.

Good Practice

1. Take care to ensure that electrical leads are not weakened by pulling in and out, and the plugs, sockets, etc, are in a

serviceable condition.

2. Report all incidents or near misses to your supervisor or respective technical staff immediately.

3. Keep benches clean and free from apparatus that is not being used.

4. Clean working areas and return back equipment after use.

5. Wear a Lab Coat, apron and gloves when handling the chemicals solution at Chemical Engineering Lab.

Fire and Explosion emergency

Do’s during outbreak of fire

Do raise the alarm immediately by:

BREAKING the nearest fire alarm glass

Call emergency ext. 46333 or 03-55146333

Informing nearest Technical Officer/Staff member

Do alert others in the vicinity

Do keep calm and cool

Do walk briskly to the fire escape doors

Do walk briskly down to the escape routes (staircase) to the Assembly Area

Do crawl on the floor if and when there is a thick smoke

Do assemble at allocated area at Assembly Area

Do report to Floor/Zone Marshal of any injured persons, or persons assumed to be left in the building

Do give priority to old, disabled and pregnant ladies.

Do’s during explosion

Do immediately take cover under tables, desks, or under objects which will give protection against falling glass and

debris

After the initial effects of the explosion have subsided, call emergency ext. 46333 or 03-55146333


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Do’s before outbreak of fire or explosion

Do familiarize yourself with the escape route (through staircase, never use the lift)

Do familiarize yourself with Assembly Area (Monash University Open Field)

Do keep your important personal items in a safe place for easy retrieval during emergency

Do familiarize yourself with fire escape doors (refer floor plan layout)

Accident & Medical Attention

Do’s in the event of accident and medical emergency

Do call ext. 46333 or 03-55146333

Give your name; describe the nature and severity of the medical problem and the location of the victim. Do not hang

up unless released by the person on the other line.

Keep the victim still and comfortable until help arrives.

If it’s a non-emergency case

Inform the nearest Technical Officer/ Staff member

Basic First Aid Procedures and Response

If chemicals are splashed into the eyes:

Notify the nearest Technical Officer/ Staff member

Quickly proceed to eyewash station.

Wash eyes copiously with water for 10 to 15 minutes. Ensure that the eyes are held open while washing

Wash skin areas that come into contact with chemicals, irrespective of the concentration of the substance

In case of serious cut:

Notify the nearest Technical Officer / Staff member

Stop blood flow using direct pressure with a clean towel.

Elevate the injury to reduce blood flow

Level 5: Engineering Laboratories Floor Plan

Chemical Engineering Lab & Research Lab

Exit Exit


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Liquid Flow Control

1.0 Introduction

Most processes require control to maintain the quality of the product(s) of the process as well as ensuring safety

of operation. In chemical processing, the systems involved are usually so complex and/or hazardous that this

control needs to be implemented by means of an automatic control system rather than relying on manual control.

The simplest forms of both automatic and manual control rely on adjusting a “manipulated variable” (MV) in

order to compensate for observed undesired variations of the process variable (PV) or output. Implementation

requires only the minimum knowledge of the system dynamics — i.e. does the process output increase or decrease

in response to an increase of the manipulated variable?

Fundamentals of process control system in industries comprise of process, measurements, controller and control

element. When all these components are interlinked and information can be passed around the loop, a closed loop

control exists. Currently, the Proportional-Integral-Derivative (PID) algorithm is the most common control

algorithm used in industry. Often, PID is used to control processes such as heating and cooling systems, fluid flow

monitoring, flow control and temperature control. In PID control, you must specify a process variable and a set

point. The process variable is the system parameter that needs to be controlled such as temperature, pressure and

flow rate while the set point (SP) is the desired value of the controlled parameter. A PID controller determines a

controller output value, such as the heater power or valve position and applies the controller output value to the

system, which in turn drives the process variable towards the set point value.

The process control unit (LS-33 139 Basic Flow Control Unit) is used in this laboratory experiment to control the

water flow rate in the system. A pump delivers water from a storage tank through a piping system. The flow rate

will be measured by the flow sensor and the value will be fed back to the control valve to regulate the incoming

flow rate.

This experiment is designed for students to demonstrate on the basic control principles and theory of industrial

process control system. The unit used in these experiments is a scaled down process model of a common

industrial process. The students will be required to conduct experiments on closed loop (i) Proporational

Controller, (ii) Proportional-Integral Controller, (iii) Proportional-Derivative Controller, (iv) Proportional-

Intergral-Derivative Controller and Step Test Closed Loop Tuning.


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1.1 Objective

To demonstrate the basic flow control process.

To study the responses from different PID settings in the closed loop flow control.

To demonstrate the step test closed loop tuning method in the flow control process.

1.2 Pre-Lab preparation

Review related sections in lecture:

Transfer functions and control loop block diagrams (lectures 3-6)

PID feedback control loops (lecture 10 & 11)

Proportional only- control loop responses (including offset) to setpoint changes and disturbances

(lecture 12)

Zeigler-Nichols tuning using ultimate frequency ωu and ultimate gain Kcu (lecture 13)

Complete Pre-lab Questions in Appendix II

Warning: Ensure appropriate safety attire and PPE are used/worn to laboratory session (i.e. lab coat, covered

shoes, long pants, safety glasses, long hair must be tied back), else you will not be permitted to perform the lab.


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1.3 Unit Assembly

Figure 1. LS-33 139 Basic Flow Control Unit


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2.0 Equipment Start-up

*Check and ensure whether all the piping and fittings are well connected. Please avoid the electronic instruments

from getting wet*

a) Place the LS-33 139 Basic Flow Control Unit on a level table.

b) Connect the communication cable from the RS-485 port to the computer.

c) Switch ON the computer.

d) Start the LS-33 139 Basic Flow Control DAQ software on the desktop.

e) Fill the tank until the water level reached approximately 3/4 of the tank.

f) Switch ON the main power supply and the apparatus power supply (in front of the control panel).

3.0 Experimental Procedures

3.1 Closed Loop Flow Control

3.1.1 Proportional Controller

*The following steps will be performed through the DAQ software on the computer*

a) Set the flow rate to a desired value within the range of 0.5LPM to 7LPM in the DAQ software. Initial set

point is set to 4LPM.

b) Set the KP = 1, KI = 0 and KD = 0.

c) Press the “Run/Execute” button to start the software.

d) To record the data, click on the “Logging Started” button.

e) Record the time you started the experiment (to allow easy traceability of the results later).

f) Switch ON the submersible water pump.

g) Allow the system to run for few minutes and observe the response of the system from the graph.

h) Click on the “Data Analysis” button to access all recorded data and the response graph.

i) Repeat the experiment with equal increment in the Proportional Gain Kp (ie: 4, 6, 8, 10, 12, 14 etc) and

observe the system response to varying Proportional Controller.

j) Record the time at which each Kp value is changed (to trace back the respective results later).

k) Increase the proportional gain until the response oscillates or to a point where the error between the set value

and current value is unable to be reduced. Record the data and graph.

l) The data and response graph can be exported to Excel by clicking ‘‘Export to Excel’’.

m) Switch OFF the water pump before pressing the STOP button at the end of the experiment.

n) Discuss the effect of different Proportional Gain on the system response.

3.1.2 Proportional-Integral Controller


a) Set the flow rate to a desired value within range of 0.5LPM to 7LPM.


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b) Set the proportional gain to the critical gain (KP = 5), and set KI = 0.01.


d) To record the data, click on the “Logging Started” button.

e) Record the time you started the experiment.

f) Switch ON the submersible water pump.

g) Allow the system response to stabilize. Record the data and ‘Print Scrn’ the generated response graph.

h) Switch OFF the submersible water pump and wait for the flow output to drop till 0LPM.

i) Vary the Integral Gain (ie: KI = 0.001, 0.05, 1 and 10) and repeat Steps (f) to (h).

j) Record the time at which each KI is changed (to trace back the respective results later).

k) Observe the system response to Proportional-Integral controller and comment.

3.1.3 Proportional-Derivative Controller


a) Set the desired set value within 0.5LPM to 7LPM.

b) Set the proportional gain to the critical gain, KI = 0, and KD = 0.01.

c) Run the program and observe the response

d) Allow the system response to stabilize. Record the data and ‘Print Scrn’ the generated response graph.

e) Switch OFF the submersible water pump and wait for the flow output to drop till 0LPM.

f) Repeat the experiment with increasing derivative gain (ie 0.02, 0.2, 2, etc).

g) Record the data and save the graph generated by each trial.

h) Observe and compare the system response curve of different combination of proportional and

derivative gain.

3.1.4 Proportional-Integral-Derivative Controller


a) By concluding the findings from the previous few experiments, retune the controller by adjusting Kp, Ki, Kd.

b) Repeat the experiment with different PID values in order to achieve the best system response.

c) Compare the system response curve of PID controller tuned with the system response curve obtained from

previous experiment.

3.2 Step Test Closed Loop Tuning Method


a) Set the flow rate to desired value within range 0.5LPM to 7LPM in the DAQ software. Initial set point is set

to 4LPM.

b) Set the Kp, Ki, Kd, value from the previous experiment.



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d) Switch ON the submersible water pump and wait till the system stabilize.

e) Click on the “Open Loop” Button. Adjust the sliding bar to maximum (100%).

f) At the same time, click on the “Logging Started” Button and now all the data will be recorded.

g) Let the water flow for 20 seconds or until the system stabilizes.

h) After that, adjust the sliding bar to 90%.

i) Repeat step (g) to step (h) with decreasing valve opening (decrement of 10%) until it is fully closed.

j) Click on the “Logging Started” button again to stop recording the data.

k) Click on the “Data Analysis” Button to view and analysis the recorded data.

l) From the recorded data, choose two different valve opening percentage which gives the smoothest flow.

m) Go back to the “Main Panel”, and again click on the “Open Loop” Button.

n) At the same time, click on the “Logging Started” Button to record the data.

o) Slide the bar to the chosen valve opening percentage, start with the higher opening.

p) After that let the water flow for 20 seconds and follow by the other valve opening percentage

value.

q) Repeat step (j) and (k) to analyse the recorded data.

r) Follow the calculation step provided to calculate the P, I and D value for Closed Loop control.

Calculation Step:

1) Process Gain, Kp - describes how far the Process Variable (PV) moves in response to a change in controller

output (CO).

PV = Flow Rate (LPM)

CO = Valve Opening Percentage (%)

2) Time Constant, Tp - describes how fast the PV moves in response to a change in the CO.

The Tp computed in five steps:

a) Determine ΔPV, the total change in PV from final steady state minus initial steady state.

b) Determine the value of the PV (LPM) that is 63% of the way toward the total ΔPV change, or

“initial steady state + 0.63 (ΔPV)”.

c) Note the time (min) when the PV passes through the “initial steady state + 0.63 (ΔPV)” value (refer to

response graph).

d) Determine the time (min) when the “PV starts a first clear response” to the step change in the CO from

the graph.

e) The passage of time from step (d) minus step (c) is the process time constant, TP.


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3) Dead Time, Ѳp - is the time delay that passes from when a CO action is made and the measured PV shows its

first clear response to that action.

The Tp computed in three steps:

a) Locate the time when the “PV starts a first clear response” to the step change in the CO. It has already

been identified when computing Tp above.

b) Locate the point in time when the CO was stepped from its original value to its new value.

c) Dead time, Ѳp is the difference in time of step (a) minus step (b) in minutes.

4) Substitute Kp, Tp and Ѳp into Table 1 below to calculate the P, I and D value for Closed Loop control.

*Tc is the larger of (0.1TP) or (0.8Ѳp)*

Kc Ti Td

PI

-

Ideal PID

Table 1

4.0 Equipment Shut Down

a) Switch OFF the water pump before pressing the STOP button at the end of the experiment

b) Exit the DAQ software.

c) Switch off control panel power and shut down the computer.

d) Retain the water for the following experiment session.

e) Transfer the ‘.jpg’ files saved on the desktop to USB drive.

f) Turn off power to PC and control unit.

5.0 Report Requirements

Each group will need to submit a group long report for this laboratory. This lab report is worth 5%.

Refer Appendix I for the report and assessment details.

Due date: The report should be submitted to the CHE3162 assignment box one week after the completion

of experiment i.e. the lab session is performed on Monday, the report is due by 5pm on next week’s

Wednesday. The standard late penalty of 10% per day overdue applies.


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6.0 References

[1] “Laboratory Safety Handbook”, March 2010. [Online]. Available:

http://www.eng.monash.edu.my/images/stories/engineering-at-

monash/laboratory20safety20handbook.pdf [Accessed: July 16, 2012].

[2] “User manual for “LS-33 139 Basic Flow Control Unit”, Lotus Scientific (M) Sdn Bhd.

http://www.eng.monash.edu.my/images/stories/engineering-at-monash/laboratory20safety20handbook.pdf

http://www.eng.monash.edu.my/images/stories/engineering-at-monash/laboratory20safety20handbook.pdf


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APPENDIX I

CHE3162 Process Control: Assessment and Report Discussion

Assessment

The assessment for the subject will be as follows:

A closed-book 5 question quiz will be conducted within the first 15 minutes of the laboratory session.

Questions in the quiz are specific to the laboratory assignment and will cover the basics of the process.

Quiz questions are similar to those in Appendix II.

(Marked by demonstrators - 10 marks)

Assessment of the group attendance and ability to follow the procedures


Assessment of a 15-page long group report


Report Content Mark Allocation

Summary 5

Introduction 5

Aim 2

Experimental Apparatus and Procedure 10

Results and Analysis 15

Discussion and Conclusion 35

Overall Report Presentation (i.e. figures, tables, references, nomenclature) 8

Writing Style (i.e. grammar, spelling) 5

Total 85

The results of the laboratory experiment should provide insight into the impact of proportional control and

proportional-integral control on the process studied (i.e. level control). The requirements for long reports and

marking criteria are posted on Blackboard under “Labs”.

Report Discussion

Your report should:

Present the data from the process rig and comment.

Define proportional gain, integral gain and derivative gain.

Discuss the effect of proportional gain applied on the proportional-only control system. Relate the effect

to response of the system (e.g. rise time, overshoot percentage, settling time and steady state error).

Discuss the effect of integral gain applied on the proportional-integral control system. Relate the effect to

response of the system (e.g. rise time, overshoot percentage, settling time and steady state error).

Discuss the effect of derivative gain applied on the proportional-derivative control system. Relate the

effect to response of the system (e.g. rise time, overshoot percentage, settling time and steady state error).


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Discuss the system response curve of PID controller tuned and compare it with the system response

curved obtained from proportional controller, proportional-integral controller, and proportional-derivative

controller.

Discuss whether the step test closed loop tuning method is suitable for all types of process control.


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APPENDIX II

CHE3162 Process Control: Pre-Laboratory Questions

** Clear and concise answer is sufficed. This is will be a 15-min, 5-Questions quiz. **

1. Define Manipulated Variable, Setpoint and Process Value.

2. What is feedback control loop?

3. What is the advantage of applying feedback control loop?

4. What is proportional control?

5. What is integral control?

6. What is derivative control?

7. What is the main difference between proportional control and integral control?

8. What is the advantage and disadvantage of using Proportional-Integral (PI) control?

9. List two examples of the common application for PI control.

10. What is the purpose of loop tuning?

11. Give two examples of loop tuning methods.

12. Why is it necessary, during the experiment, to wait for the system to reach steady state prior to data taking?

13. What is steady state error and how can this error be eliminated?

14. What issue will arise if integral time is too short?

15. Illustrate the benefit of PID control with a given example of its application.

Documents

Sunway Lab Manual 2014