Process model & response of Interacting system

1. 1
Topics & LLOs of IPC class
 Topic:
1. Process model for multi-tank liquid level process system (Interacting
mode of operation)
2. Process response for multi-tank liquid level process system (for
given step input variation for inlet flow rate)
 Lecture Level Outcomes(LLOs):
After completion of this class, students will be able to…
LLO1: develop the process model for multi tank based liquid level
process - With Interacting mode of operation
LLO2: analyze & infer on the plotted process responses of multi-tank
level process system
Course Discussion Topic (CDT) on IPC course

2. 2
Process model for multi-tank liquid level process system
(Cascaded tank based liquid level process system) :
Course Discussion Topic (CDT) on IPC course
Non-interacting mode of operation
Interacting mode of operation

3. 3
Process model for multi-tank liquid level process system (Interacting
mode of operation) :
Course Discussion Topic (CDT) on IPC course
Flow-head equation for tank1:
A1*𝑑ℎ1(t)/𝑑𝑡 = q𝑖 (t) – q1(t)
Where, q1(t)= [h1 (t) – h2(t)] /R1
Flow-head equation for tank2:
A2*𝑑ℎ2(t)/𝑑𝑡 = q1(t) – q2(t)
Where, q2(t)= h2 (t)/R2

4. 4
Course Discussion Topic (CDT) on IPC course
Output level transfer function of multi tank level
process is given by PTF1:
H2(s)/Qi(s) = [R2 / (τp1 τp2 s2+A1R2s+1)]
Where, Process gain: R2 is ‘Kp’;
Process time constants: ‘τp1’ is A1R1 and ‘τp2’ is A2R2
Process model for multi-tank liquid level process system (Interacting
mode of operation) :

5. 5
Course Discussion Topic (CDT) on IPC course
Output flowrate transfer function of multi tank
level process are given by PTF2:
Q2(s)/Qi(s) = [1/ (τp1 τp2 s2+A1R2s+1)]
Where, Process gain: 1 is ‘Kp’;
Process time constants: ‘τp1’ is A1R1 and ‘τp2’ is A2R2
Process model for multi-tank liquid level process system (Interacting
mode of operation) :

6. 6
Reflection spot 1
Course Discussion Topic (CDT) on IPC course
1. Draw the level process system of 4 tank process system with 1st &
2nd tanks in interacting mode of operation and then 3rd & 4th tanks
in non-interacting mode of operation.

7. 7
Reflection spot 1
Course Discussion Topic (CDT) on IPC course
2. Write the level process transfer function for multi-tank level
process with 1st & 2nd tanks operated in interacting mode of
operation and other 3rd & 4th tanks operated in non-interacting
mode of operation.

8. 8
Study of output level & output flow rate response curves of
Interacting type multi-tank liquid level process (for step input
variation) :
Course Discussion Topic (CDT) on IPC course
Output level response

9. 9
Course Discussion Topic (CDT) on IPC course
Outlet flow rate response
Study of output level & output flow rate response curves of
Interacting type multi-tank liquid level process (for step input
variation) :

10. 10
Reflection spot 2
1. Draw output level responses for the single tank and for multi tank
liquid level process system (both in non-interacting & interacting
modes).
Course Discussion Topic (CDT) on IPC course

11. 11
Reflection spot 2
2. Comment on the response speed of process responses for the single
tank and for multi tank liquid level process system (both in non-
interacting & interacting modes).
Course Discussion Topic (CDT) on IPC course

12. 12
Lecture Level Outcomes (LLOs) revisited:
After completion of this class, students will be able to…
LLO1: develop the process model for multi tank based liquid level process - With
Interacting mode of operation
LLO2: analyze & infer on the plotted process responses of multi-tank level process
system
Course Discussion Topic (CDT) on IPC course
For further reading:
Surekha Bhanot, Process Control: Principles and Applications, 6th ed. New Delhi:
Oxford University Press, 2011. (Chapter 2)

13. 13
CDT - LECTURE LEVEL PRACTICE PROBLEMs (LLQs/LLPs) to test the
LLOs
LLP1 (on LLO1 & LLO2):
Course Discussion Topic (CDT) on IPC course
(i) Write the process transfer function for the above liquid level process application. (Consider
tank3 fluid level & tank3 output flow rate as output variables)
(ii) Determine the process parameters.
(iii)Plot the output level & output flow response curves for the given step input across inlet flow
rate and indicate the process parameters on the plotted responses.
(iv) Compare the process responses from dynamic response plots w.r.t. single tank and multi
tank system (non-interacting mode) & multi tank system (interacting mode) and infer on the
speed of response & steady state error characteristics of the process.