This document discusses water level control in tanks using both manual and automatic methods. The manual method uses a sight tube for a human to monitor and adjust water levels, but it is prone to errors. The automatic method uses a float sensor and controller to compare the sensed level to the desired level and actuate a valve without human intervention, improving accuracy. The document also presents mathematical models of liquid level systems and simulations showing how adjusting controller gains impacts performance metrics like settling time and overshoot.

1. TANK WATER LEVEL
CONTROLLER.
SHEKHAR GEHLAUT.
AKANSHA RAUTELA
ADITYA GOEL

2. WATER LEVEL CONTROLER
• Water level controller is used to control the
water level in a tank.
• In many industries like chemical, there is a
restriction on liquid level of a container in such
cases level controller can maintain level of the
liquid at desired value.

3. WATER LEVEL CONTROL.
• There are two methods to control the water level.
i. Manual.
ii. Automatic.

4. i. Manual method.

5. Working of manual method.
• The purpose of this system is to maintain the liquid level
(h) in the tank as close to the desired liquid level H as
possible, even when the output flow rate is varied by
opening the valve.
• In manual method a human controls the liquid level
close to the desired level using a sight tube. Using sight
tube human compares the present level by the desired
level and adjust the valve accordingly.

6. Drawbacks of manual method.
• Error due to human.
• Error due to time wasted in opening and closing of
valves.
• So there is a need of automatic(human less) system to
increase the accuracy.

7. b. Automatic method.

8. Working of automatic method.
• In the automatic method human is replaced by a
controller to increase the accuracy. The liquid
level is sensed by a float and sensed level is then
fed to the controller, controller compares the
sensed level with desired level and error signal is
generated, according to that error signal
actuator controls the output valve.

9. Advantage of automatic method.
• 1- error is reduced by human by a controller.
• 2- automatic method is more reliable as compared to
manual method, it is more stable also.
• 3- it is costly comparatively but accuracy and stability
provided by this method can cover the cost.

10. Laminar v/s Turbulent Flow
• Laminar Flow
• Flow dominated by viscosity
forces is called laminar flow
and is characterized by a
smooth, parallel line motion
of the fluid
• Turbulent Flow
• When inertia forces
dominate, the flow is called
turbulent flow and is
characterized by an
irregular motion of the fluid.

11. Resistance of Liquid-Level Systems
• Consider the flow through a short pipe connecting two
tanks as shown in Figure.
• Where H1 is the height (or level) of first tank, H2 is the
height of second tank, R is the resistance in flow of liquid
and Q is the flow rate.

12. Resistance of Liquid-Level Systems
• The resistance for liquid flow in such a pipe is defined as
the change in the level difference necessary to cause a
unit change inflow rate.

13. Resistance in Laminar Flow
• For laminar flow, the relationship between the steady-state
flow rate and steady state height at the restriction is
given by:
• Where Q = steady-state liquid flow rate in m/s3
• Kl = constant in m/s2
• and H = steady-state height in m.
• The resistance Rl is

14. Capacitance of Liquid-Level Systems
• The capacitance of a tank is defined to be the change in
quantity of stored liquid necessary to cause a unity
change in the height.
• Capacitance (C) is cross sectional area (A) of the tank.

15. Capacitance of Liquid-Level Systems

16. Modelling

17. Modelling
• The rate of change in liquid stored in the tank is equal to
the flow in minus flow out.
• The resistance R may be written as
• Rearranging equation (2)

18. Substitute qo in equation (3)
After simplifying above equation
Taking Laplace transform considering initial conditions to zero

19. The transfer function can be obtained as

20. Modelling
• The liquid level system considered here is analogous to
the electrical and mechanical systems shown below

21. Modelling
• Consider the liquid level system shown in following
Figure. In this system, two tanks interact. Find transfer
function Q2(s)/Q(s).

22. Modelling
• Tank 1 Pipe 1
• Tank 2 Pipe 2

23. Modelling
• Tank 1 Pipe 1
• Tank 2 Pipe 2

24. Taking LT of both equations considering initial conditions to
zero [i.e. h1(0)=h2(0)=0].

25. From Equation (1)
Substitute the expression of H1(s) into Equation (2), we get

26. Using H2(s) = R2Q2 (s) in the above equation

28. SIMULATION AND RESULTS
• RESULT 1—
CONTROLLER GAIN GAIN 2 CONCLUSION
P=50
5
0.0035 Settling time=3
I=300
5
D=0
Overshoot=1
Undershoot=1
Max overshoot=1.2

30. SIMULATION AND RESULTS
• RESULT 2
• — CONTROLLER GAIN GAIN 2 CONCLUSION
P=50
3
0.0035 Settling time=4
I=300
3
D=0
Overshoot=1
Undershoot=1
Max overshoot=1.4

32. SIMULATION AND RESULTS
• RESULT 3—
CONTROLLER GAIN GAIN 2 CONCLUSION
P=50
10
0.0035 Settling time=2
I=300
10
D=0
Overshoot=1
Undershoot=1
Max overshoot=1.1

34. SIMULATION AND RESULTS
• RESULT 4—
CONTROLLER GAIN GAIN 2 CONCLUSION
P=100
5
I=200
5
D=0
0.0035 Settling time=2.5
Overshoot=0
Undershoot=0

36. SIMULATION AND RESULTS
• RESULT 5—
CONTROLLER GAIN GAIN 2 CONCLUSION
P=100
1
0.001
I=200
1
0.002
D=0
0.0035
Settling
time=aprox 0
Overshoot=0
Undershoot=0

38. SIMULATION AND RESULTS
• RESULT 6—
CONTROLLER GAIN GAIN 2 CONCLUSION
P=100
1
0.5 Settling time=3
I=200
1
Overshoot=1
D=0
Undershoot=1