WBUT Question Papers EC Process Control Engineering B Tech 7th Sem 2011-12

WBUT Question Papers EC

Process Control Engineering B Tech 7th Sem 2011-12

Time Allotted : 3 Hours

Full Marks : 70

The figures in the margin indicate full mftrks.

Candidates are required to give their answers in their own words

as far as practicable.


p ( Multiple Choice Type Questions )

1. Choose the correct alternatives for any ten of the following :

i)  The function of reset action in a process controller is to

a) reduce rise time

– b) reduce steady state error

c)             reduce oscillation in the response

d) increase overall gain.

ii)               The basic limitation of P action controller only is

a) Very slow error correction

. b) High overshoot

. ■ * . &

c)              Non-zero offset

d)             Instability of process.


iii)         For 100% error to the proportional controller, its o/p is 50%. The PB is

a) 200%                                 b) 100%

c) 50%                                   d) 150%.

iv)         C-C controller tuning technique is used for

a) Open loop system b) Closed loop system

c) Both of these                     d) None of these.

v)           If Kp and Td denote the proportional gain and the

derivative time constant respectively of a PD controller then the rate time xd is denoted by

a) Kp/Td                                b) Td/Kp

c) Kp Td                                  d) 1/KpT.

vi)         The type of isolator generally used in I/O module of PLC is

a) electrical                           b) electronics

c) magnetic                           d) optical.

vii)       The proportional sensititivity is maximum in a) P controller b) I controller

c) PD controller                     d) PID controller.

viii)     PLC supports

a) C programming                 b) Java programming

c) Ladder programming d) VB programming.

ix)       Which type of networking connectivity is generally supported by DCS ?

a) LAN                                   b) MAN

c) WAN                                  d) None of these.

x)         An example of an Industrial Control System is a) PLC      b) DCS

c) PLC & DCS                        d) None of these.

xi)       DDC is a type of which control scheme ?

a)  Analog control        b) multi variable


ratio control d) feed forward control.

GROUP -B ( Short Answer Type Questions )

Answer any three of the following.            3×5= 15

  1. What is reset action ? Prove that P.B = 100/Kc , where
  2. symbols have their usual meaning.                                    1 + 4
  1. Explain the ON-OFF controller characteristics without differential gap and with differential gap. Write their advantage and disadvantage. 3 + 2
  2. What is pneumatic controller ? Describe with proper diagram the function of pneumatic relay in a pneumatic controller1 + 4
  1. What do you mean by “Process Reaction Curve” ? How is it obtained for a particular process ? How the time constant of a first order process can be determined from the process reaction curve ?   1 + 1+3
  2. What is gateway connectivity in DCS ? Describe the generic gateway in DCS.                                                                                   1+4

7337 3                                           [ Turn over

GROUP -C ( Long Answer Type Questions )

Answer any three of the following. 3 x 15 = 45

  1. What is process resistance and process capacitance ? Discuss pneumatic P-I and P-D controller with a schematic diagram. Explain an electronic PD controller and derive its control equation from its circuit diagram.                                                               2 + 8 + 5
  2. What do you mean by tuning of controller ? What are the
  3. basic criteria of tuning of controller ? Explain the open loop

tuning technique of Cohen-Coon. What are the basic criteria of Ziegler-Nichols tuning method ? What is 1 /4 decay ratio ?


  1. What is PLC ? What are the advantages of PLC control system ? What are different data files available in PLC ? What is the function of 1/O module in a PLC ? Describe the basic functional blocks of a PLC with suitable diagram.


  1. What is the necessity of control valve sizing ? What are the
  2. factors that should be known for selecting a valve ? A control
  3. valve regulates the liquid flow of a tank. The water level is
  4. controlled in the tank at a 50 feet by regulating the outflow.

The measured inflow varies from 0 to 140 gallons per minute. Calculate Cv for the valve. What is valve cavitation ? What

are the conditions to avoid cavitation ? 2 + 3 + 5 + 2 + 3

  1. Write short notes on any three of the following :              3×5

a)           Pneumatic actuator.

b)           DDC.

c)           PID controller.

d)           DCS.                     ’ •

e)           Boiler drum level control.                                   .

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