Controllers -Controller is a device that takes a decision in order to maintain the steady state of the system on the basis of error signal. Controllers are the need of the controls system To supress the effect of external disturbance in order to maintain the steady state To maintain the stability of the system. To optimize the process in order to increase the profits. Error signals are input to the controller. Controller takes decision in the form of decision signal as ideal valve opening and hence corresponding air pressure is given in the form pneumatic signal. Error = hsp -h = Setpoint variable (Controlled variable) – Measured variable. Decision signal is in terms of pneumatic signal to the valve. 1.Liquid level control – Proportional action Controller (P action)   2.Gas pressure control - Proportional action Controller (P action)   3.Vapor pressure control – For fast response PI controller , for slow response PID controller.   4. Flow Conrol-Proportional Integral Controller (PI action)   5. Temperature control – Proportional integral derivative controller (PID action)   6. Composition control – Proportional integral derivative controller (PID action) In this Seminar report I mentioned all types of controllers that used in chemical industries for various purpose. Controllers are need of control system to control different types of process and operation in the plant so it is difficult to choose controllers because it reduces effort and gives safety to the plant so in this seminar report i study important examples in which controllers are used. I also mentioned introduction of control loop because its helps us to understand the behavior of controller in process.

1. Dr. BABASAHEB AMBEDKAR TECHNOLOGICAL UNIVERSITY
Lonere, Mangaon, 402104
2021-2022
MINI PROJECT -
Use of different types of controllers in chemical industry.
SUBMITTED BY - KETAN PRASHANT KULKARNI
PRN-1930331507009
UNDER GUIDANCE OF – PROF Y.S.MAHAJAN

2. INTRODUCTION
• Controllers -Controller is a device that takes a decision in order to maintain the steady state of the
system on the basis of error signal.
• Controllers are the need of the controls system
• To supress the effect of external disturbance in order to maintain the steady state
• To maintain the stability of the system.
• To optimize the process in order to increase the profits.
• Error signals are input to the controller.
• Controller takes decision in the form of decision signal as ideal valve opening and hence
corresponding air pressure is given in the form pneumatic signal.
• Error = hsp -h = Setpoint variable (Controlled variable) – Measured variable.
• Decision signal is in terms of pneumatic signal to the valve.

3. Input and output variables
• Input variables :
• The variables that can change the output
variable/controlled variables .
• It is a variable which we give to the system to
change the output
• They are of two types : -
• Manipulated variable
• The variables whose values can be adjusted by
any human operator or by any controller.
• Disturbance variable
• The variables whose values cannot be adjusted
by any human operator or by any controller.
• Output variables :
• The Variables that we want to control is
known as output variable or controlled
variable
• They are of two types
• Measured output variable
• The output variable that can be
measured cheapily , effectively and
accurately.
• Unmeasured output variable
• The output variable that can not be
measured cheapily , effectively and
accurately.

4. Proportional Action controller
• Proportional control is a form of feedback control. It is the simplest form
of continuous control that can be used in a closed-looped system.
• c(s) = Kc.e(S),
• P action does not change the nature of the signal. If the input signal is
step then output signal will also be step.
• P-action is a zero order system.
• If we add P-action with a 1st order process then the overall order of the
system will be first order.
• P-action always works on the basis of present error.
• Disadvantage :
• For a very small change in the error signal.P-action does not work well and
unable to work because of which that error value persist in the system and
we will never be able to achieve the orginal steady state .
• Proportional Band (PB)
• Range of the error signal required to
move the valve from fully open to fully
closed condition.
• Kc∝ (1/ PB)
• As controllers gain increases , offset
decreases, so if Kc increased then the
range of proportional band will
decrease or error signal range will
decrease.
• Every P action can’t be on-off action
for that short time solution is that by
increasing value Kc then value of error
signal range will decrease.

5. Integral and Derivative action controller
• Integral control is a second form of feedback
control. It is often used because it is able to
remove any deviations that may exist.
• I action controller always works on the basis
of past error.
• I action completely reduces offset to zero
• I action controllers affect the system by
responding to accumulated past error.
D-control correlates the controller output to the
derivative of the error.
D action controller always works on the basis of
future error.
D-control is a form of feed forward control. D-
control anticipates the process conditions by
analyzing the change in error

6. Proportional integral action controller
• PI control is a form of feedback control. It provides a faster response time than I-only control due to the
addition of the proportional action.
• PI action is of 1st order and that’s why they are slower than P-action.
• PI Action changes the nature of the input signals. If error signal is step then PI action changes the
nature to ramp.
• In P-action along with I action together produces response even for very small change in error signal
and this response is able to move the valve which in turn reduces the offset to zero
• Disadvantage-
• In the case of PI Action, we use to store the error signal magnitude in the storage device But like every
storage device, this one also get full after some time and that's why need a reset. That is why PI action
also known as Reset Action Controller.
• Because of reset, controller's setting also got erased. That is why tuning is required. In In tuning, we
calculate the value of controller's parameter and set them along with many other settings. This tuning
process can be manual or even automatic these days.

7. Proportional Derivative action controller
• PD-control is combination of feedforward and feedback control, because it operates on both the
current process conditions and predicted process conditions.
• In PD-control, the control output is a linear combination of the error signal and its derivative.
• The Main problem of P action is Offset and that Can be eliminated by I Action. But if we use D-
Action along with P-Action then it may become more faster but the problem of offset will remain
as it is D-Action does not eliminate offset.
• That is why PD Action is not in use in chemical engineering practices.

8. Proportional Integral derivative controller
• PID action exhibits 1st order dynamics.
• PID action just like the PI action are slower than P-action but in some cases it can be fast
• Proportional-integral-derivative control is a combination of all three types of control methods.
• PID-control is most commonly used because it combines the advantages of each type of control. This
includes a quicker response time because of the P control, along with the decreased/zero offset from the
combined derivative and integral controllers.
• This offset was removed by additionally using the I-control. The addition of D-control greatly increases the
controller's response when used in combination because it predicts disturbances to the system by measuring
the change in error
• In PID controller past , present and future errors and disturbances are solved.
• PID action just like the PI action changes the nature of the input signal. Means step change in error signal
results in ramp change in the response.
• Offset in this case of PID action is zero just like the PI action because of the presence of I action in both the
actions

9. Drawbacks of PID controller
Derivative Windup
• Because of the use of derivative control, PID control cannot be used in processes where there is a lot
of noise, since the noise would interfere with the predictive, feedforward aspect.
• Thus a bounded and stable response becomes unstable and unbounded response .It caused by D –
action so it is known as derivative windup
• Just like the PI Action , PID action also known as Reset action and tuning is required after the reset.

10. Examples in which controllers are used
1.Liquid level control – Proportional action Controller (P action)
2.Gas pressure control - Proportional action Controller (P action)
3.Vapor pressure control –
For fast response PI controller , for slow response PID controller.
4. Flow Conrol-Proportional Integral Controller (PI action)
5. Temperature control – Proportional integral derivative controller (PID action)
6. Composition control – Proportional integral derivative controller (PID action)
•

11. Conclusion
• In this Seminar report I mentioned all types of controllers that used in
chemical industries for various purpose.
• Controllers are need of control system to control different types of process
and operation in the plant so it is difficult to choose controllers because it
reduces effort and gives safety to the plant so in this seminar report i study
important examples in which controllers are used.
• I also mentioned introduction of control loop because its helps us to
understand the behavior of controller in process.