SECTION OF CHEMICAL PROCESS

MALAYSIAN INTITUTE OF CHEMICAL & BIOENGINEERING TECHNOLOGY

PROCESS CONTROL LABORATORY

LABORATORY INSTRUCTION SHEETS

COURSE CODE
EXPERIMENT NO. EXPERIMENT 3

EXPERIMENT TITLE Gas Temperature Control Plant

DATE
GROUP NO.
LECTURER/INSTRUCTOR/TUT 1)
OR 2)
DATE OF REPORT
SUBMISSION
ATTENDANCE/PARTICIPATION/DISIPLI
/5%
NE:
INTRODUCTION: /5%

PROCEDURE: /5%

RESULTS& CALCULATIONS /15%

ANALYSIS /15%
DISTRIBUTION OF MARKS
FOR LABORATORY REPORT: DISCUSSIONS: /20%
ADDITIONAL QUESTIONS /15%
CONCLUSION /10%

SUGGESTIONS& RECOMENDATIONS /5%

REFERENCES: /5%

TOTAL: /100%

EXAMINER COMMENTS: RECEIVED DATE AND STAMP:

 CAMPUS : UniKL MICET EDITION: 1
LABORATORY: SECTION of 1
REVISION NO:
PROCESS TECHNOLOGY
29 SEPT
EXPERIMENT:GAS EFFECTIVE DATE:
2014
TEMPERATURE PROCESS
AMENDMENT
CONTROL
DATE:

STUDENT CODE OF ETHICS

SECTION OF CHEMICAL PROCESS TECHNOLOGY

MALAYSIAN INSTITUTE OF CHEMICAL & BIO

ENGINEERING TECHNOLOGY

I hereby declare that I have prepared this report with my own efforts. I also admit to

not accept or provide any assistance in preparing this report and anything that is in

it is true.

1) Group Leader: ………………………………………….. (Signature)

Name : __________________________________
Matrix No. : __________________________________

2) Group Member 1: ………………………………………. (Signature)

Name : __________________________________
Matrix No : __________________________________

3) Group Member 2:……………………………………….. (Signature)

Name :__________________________________
Matrix No. : __________________________________

4) Group Member 2:……………………………………….. (Signature)

Name :__________________________________
Matrix No. : __________________________________

Experiment 3: Gas Temperature Process Control

 CAMPUS : UniKL MICET EDITION: 1
LABORATORY: SECTION of 1
REVISION NO:
PROCESS TECHNOLOGY
29 SEPT
EXPERIMENT:GAS EFFECTIVE DATE:
2014
TEMPERATURE PROCESS
AMENDMENT
CONTROL
DATE:

OBJECTIVE

• To control the Air-Heater process using PID controller.

• To tune the PID controller by Ziegler-Nichols open-loop method.
• To control the Air-Heater process using ON-OFF controller.

LEARNING OUTCOME
• To identify the important components of the air temperature control system and
to mark them in the P&I Diagram
• To carry out the start-up procedures systematically.
• To determine the values of the parameters for a first order plus dead time transfer
function model of a thermal process.

1. I NT RO DUCT IO N

This model uses air to simulate a gas or vapor phase temperature process. The
temperature process is a multicapacity lag/dead time process with no noise. It uses a
transistor to adjust the heat flow to the heater. The air flow rate is measured using a
rotameter. A selective control technique is employed here that automatically select
only a less heat demanding output to manipulate only one final control element (the
transistor/heater). This system requires a high gain PID controller.

2. EXPERIMENTAL EQUIPMENT

The equipment used here is the air temperature process control training system, Model
AT922 (Figure 1 1 .1).

2.1 AIR TEMPERATURE PROCESS, MODEL AT922

The process plant consists of forced convective annulus electric air heater to heat
the incoming process air from an external compressor air supply system. The
process air is connected to a pressure regulator (AR90) and flows into the heater
and then to the process vent VT or to another air process control training system.
By varying the air flow rate at the discharge manual valve downstream of the
rotameter F190, the air flow load changes through the heater can be implemented

The purpose of the PID control is to maintain the air temperature (TE91 /TIT91) at the
heater exit, at the operator setpoint without burning out the heater.

Experiment 3: Gas Temperature Process Control

 CAMPUS : UniKL MICET EDITION: 1
LABORATORY: SECTION of 1
REVISION NO:
PROCESS TECHNOLOGY
29 SEPT
EXPERIMENT:GAS EFFECTIVE DATE:
2014
TEMPERATURE PROCESS
AMENDMENT
CONTROL
DATE:

3. EXPERIMENTAL PROCEDURE

3.1 IDENTIFICATION OF MAJOR COMPONENTS IN THE PLANT

Go around the experimental set-up, identify the following components and mark them in
the P&I Diagram (Figure 11.2).

• AR90: The pressure regulator at the process inlet

• FS90: The Flow Switch that will cut-off the heater power when very low air is
detected
• MV90A: Manual valve at the process inlet
• PRV90 : Relief valve to prevent excessive pressure from AR90 TCY90
Transistor,
installed inside the cubicle, below the control panel
• TE91: Resistance Temperature Detector (RTD), measures the temperature of the
hot air at the exit of the heater
• TIT91: Temperature Indicating Transmitter for TE91
• TE92: Type K thermocouple element, reads the temperature of the heater
element.
• TIT92: Temperature Indicating Transmitter for TE92
• TR91: Recorder
• TIC90: ON/OFF Temperature Controller. Prevents heater burnt -out
• TIC91: PID Temperature Controller — Loop 1
• TIC92: PID Temperature Controller — Loop 2
• FI90: Variable area flow meter to measure the flow rate of air through the heater.
• VT: Process Vent
• HV90: Heater bypass

Experiment 3: Gas Temperature Process Control

 CAMPUS : UniKL MICET EDITION: 1
LABORATORY: SECTION of 1
REVISION NO:
PROCESS TECHNOLOGY
29 SEPT
EXPERIMENT:GAS EFFECTIVE DATE:
2014
TEMPERATURE PROCESS
AMENDMENT
CONTROL
DATE:

3.2 START-UP PROCEDURES

The start-up procedure given below must be carefully followed before starting any
experiment.

I) Switch the PANEL, SCADAIDDC selector at the front of the cubicle to the
"PANEL, SCADA" position.
2) The heat er should be switched OFF.
3) Switch on the main power supply. The main switch is at the front of the
cubicle.
All panel instruments will lit up.
4) If any "ANNUNCIATOR" gets activated, press the "ACKNOWLEDGE"
button to silence the buzzer.
5) Open the swing front cover of the recorder TR91 and press the 'RCD' push
button to STOP its chart drive, if it is running.
6) Make sure the compressor is running and the compressed air is available at the
process air regulator AR90.
7) Shut the manual valve MV90A and set AR90 to a pressure of 45 prig (as
indicated by AR90).
8) Make sure the heater bypass valve HV90 is shut.
9) Open the vent valve VT fully to discharge the air to the atmosphere. Make
sure the manual valve MV90B is completely shut.
10) The following shoul d be veri fied:
• Annunciator FAL90 is activated and should be acknowledged — Reason
: No air flow yet because MV90A is shut.
• The pressure gauge PG90 read atmospheric. If it reads more, then check
and open VT.
• The variable area flow meter FI90 shows no air flow.
• Check TE92/TIT92 is not rising because the heater is still OFF.

11) Manually open fully the inlet valve MV90A so that the air flow rate at FI90
reads about 45 Nm 3/Hr. Do not alter the air pressure previously set at AR90.
12) Check now the pressure gauge PG90 reads slightly above atmospheric.
13) Start record by push the 'RCD' button to switch ON the recorder chart drive.
The chart drive is preset to 500mm/Hr.
14) Press 'RCD' to stop the recorder.

Experiment 3: Gas Temperature Process Control

 CAMPUS : UniKL MICET EDITION: 1
LABORATORY: SECTION of 1
REVISION NO:
PROCESS TECHNOLOGY
29 SEPT
EXPERIMENT:GAS EFFECTIVE DATE:
2014
TEMPERATURE PROCESS
AMENDMENT
CONTROL
DATE:

3.3 PROCEDURE
I. To determine the parameters of the transfer function G1 relating the air temperature to
the electrical power input.

1) Set the air flow rate: Open and adjust MV90A so that FI90 reads about 45
Nm3/Hr. The maximum airflow has now been set.
2) Press the 'RCD' push button in TR91. Wait for the response of the RED pen
(TE91 /TIT91) and GREEN pen (TE92/TIT92) to be almost steady..
3) Note the average air flow rate at the variable area flow meter FI90.
4) With TIC91 in MANUAL (M) mode, adjust its MV = 30%.
5) Switch ON the heater and mark on the recorder chart paper besides the RED and
GREEN pen, the instant the Heater is switched ON.
6) Record the responses till the temperatures become steady.

II. To determine the parameters of the transfer function G2 relating the air
temperature to the air flow rate (disturbance or load variable).

7) Make sure the system is under steady state conditions initially.

8) Disturb the airflow rate for a short while by closing partially and opening the
vent VT or by opening and closing the bypass valve HV90.
9) Simultaneously mark on the chart paper the instant the air flow is disturbed.
Also record the % of change in the air flow rate.
10) Record the response till the temperatures becomes steady.
11) Switch OFF the heater and stop the recorder.
12) Examine the responses at the chart paper.
13) Draw the steepest tangent for each of the temperature response trajectories to
intersect the baseline to define the dead time (DT). Using a ruler, measure the
distance in mm between the point of intersection and the instant when the heater
was switched ON .

The dead time in time units is given by

Dead Time = Distance in mm x 3600 sec

Record chart speed, 500 mm/Hr Hr

Experiment 3: Gas Temperature Process Control

 CAMPUS : UniKL MICET EDITION: 1
LABORATORY: SECTION of 1
REVISION NO:
PROCESS TECHNOLOGY
29 SEPT
EXPERIMENT:GAS EFFECTIVE DATE:
2014
TEMPERATURE PROCESS
AMENDMENT
CONTROL
DATE:

14) The slope of the steepest tangent gives the Response Rate (RR).
15) The process gain K is equal to the maximum change in the air temperature at
the exit divided by the % change in the manipulated variable.
16) The time constant of the process, T, is equal to the response rate divided by the
maximum change in the air temperature at the exit.

3.4 CONTROL OF AIR HEATER PROCESS USING PID CONTROLLER

1) C heck t he vent VT i s ful l y open ed.

2) The process air supply and flow rate should remain as previously set in
Section 3.3.
3) Set a set point (SV) at 60 oC for Trial I PID and 80 oC for Trial II PID.
TIC 91 is still in Manual (M) mode.
4) Set SSW (at the PID2 page) to '1' so that only TIC91 is used. This step makes
the PID 2, Loop 2 disabled.
5) Access the PID values in controller TIC91/TIC92 and set the following trial
values.
Trial 1 PID Value
PB 1 :10% TI: 100sec TD: 25 sec SV: 60OC
Trial II PID Value
PB2 :10% TI: 22 sec TD: 5 sec SV: 80OC

6) Transfer TIC91 to Auto (A) mode. Make sure the heater is ON.
7) Observe patiently the control response of both the heater surface
temperature (TE90/TIC90, recorder Green pen) and the heated air
temperature (TE91/TIC91, recorder Red pen). Write the set point and PID
values on the recorder chart paper beside its response.
8) In particular, note that the heated air temperature overshoots the set-point even
when the heater surface temperature has started decreasing.

Experiment 3: Gas Temperature Process Control

 CAMPUS : UniKL MICET EDITION: 1
LABORATORY: SECTION of 1
REVISION NO:
PROCESS TECHNOLOGY
29 SEPT
EXPERIMENT:GAS EFFECTIVE DATE:
2014
TEMPERATURE PROCESS
AMENDMENT
CONTROL
DATE:

9) Apply the experiment with the following disturbances.

LOAD DISTURBANCE: Switch the controller to Manual (M) mode
and step increase the control output (MV) by about 20%. Quickly switch
TIC91 back to Auto(A) mode.
SETPOINT CHANGE : Step-increase the temperature set point at
TIC91 so that it is about 10 oC above the air temperature.
At each load change, the control is being disturbed and TIC91, with its preset
PID values will try to restore control to its set-point.
10) Switch off the heater but let the air flows to cool down the heater to room
temperature before shutdown the machine

4. RESULTS
1. Using the step response data, determine the parameters of the First order with
Delay model.
2. Report should contain the block diagram representation of the process.
3. Process Reaction Curve and calculation of Ziegler-Nichols Optimum settings.
4. System responses to step change in set point and load.
5. The ON-OFF sequence for a given High Alarm Limit, PH2.
6. The value of the dead band of the ON-OFF controller and its effect on the
frequency of oscillation.

Experiment 3: Gas Temperature Process Control

 CAMPUS : UniKL MICET EDITION: 1
LABORATORY: SECTION of 1
REVISION NO:
PROCESS TECHNOLOGY
29 SEPT
EXPERIMENT:GAS EFFECTIVE DATE:
2014
TEMPERATURE PROCESS
AMENDMENT
CONTROL
DATE:

P&I Diagram of Air Temperature Process Control System

Experiment 3: Gas Temperature Process Control