Technical Round Materials-Instrumentation and Control Engineering-Free Download
? Question 1. What Is Instrumentation?
The technology which is used to measured and control the process system of
plant is called instrumentation. It is branch of engineering.
? Question 2. What Is Reynolds Number?
We know with help of reynolds number what type of flow in fluid.
Question 3. Why Do We Use 4-20ma Signal Instead Of 0-10 Ma?
To elevate zero so that we can come to know whether it is dead zero or from
Question 4. What Is The Difference Between Dry Leg And Wet Leg?
Dry leg means in lab. And wet leg means in feild
? Question 5. How Can We Calibrate A Positioner?
A positioner is a device put into a valve to ensure that it is at a correct
position of opening as per the control signal. An I/P converter only sends
the opening/closing request to valve but can not confirm its position.
Positioner senses the valve opening through a position feedback link
connected to valve stem which is its input signal. I/P converter output is
its setpoint input. The difference between these two is the error signal
based on which the positioner positions the valve to correct position to
reduce error to zero. Hence positioner is nothing but a pneumatic feedback
Controlled external supply air to positioner provides power to positioner
to position a valve. Also positioner is used in a valve when valve
operating signal range is different from I/P converter output range.
1. List any four objectives of process control.
Suppressing the influence of external disturbances, Optimizing the
performance, Increasing the productivity, Cost effective.
2. Define process
Any system comprised of dynamic variables usually involved in manufacturing
and production operations. It is defines as a series of operations during
which some materials are placed in more useful state.
3. What is manipulated variable
It is a variable which is altered by the automatic control equipment so as
to change the variable under and make it conform with the desired value.
4. Define Controlled variable
It is the quantity of control system which is directly measured and
5. What do you mean by self regulation?
The output will move from one steady state to another for the sustained
change in input. This means that for change in some input variable the
output variable will rise until it reaches a steady state (inflow =
outflow). It is the tendency of the process to adopt a specific value of
controlled variable for nominal load with no control operations.
Why do we need mathematical modeling of process?
The physical equipment of the chemical process we want to control have not
been constructed. Consequently we cannot experiment to determine how the
process reacts to various inputs and therefore we cannot design the appropr
iate control system. If the process equipment needs to be available for
experimentation the procedure is costly. Therefore we need a simple
description of how the process reacts to various inputs, and this is what
the mathematical models can provide to the control designer.
7. Name different test inputs.
Step, Ramp, Impulse, Sinusoidal, Pulse inputs
8. Name a process giving inverse response
Drum boiler system, in which the flow rate of the cold feed water is
increased by a step the total volume of the boiling water and consequently
the liquid level will decreased for a short period and then it will start
9. Define interacting system and give an example.
Load changes in first process affects the second process and vise versa
when both are connected in series nature is called interacting system. Eg.
Two level tanks are connected in series.
A tank operating at 10ft head, 51pm outflow through a valve and has a
cross section area of 10 sq f calculate the time constant.
11. What is meant by non-self regulation?
A system that grows without limit for a sustained change in input (constant
outflow or outflow independent of inflow condition).
Write any two characteristics of first order process modeling
The smaller the value of time constant the steeper the initial response of
the system. A first order lag proce ss is self regulating the ultimate
value of the response equal to Kp (steady state gain of the process) for a
unit step change in the input.
13. Distinguish between continuous process and batch process.
A process in which the materials or work flows more or less continuously
through a plant apparatus while being treated is termed as continuous
process. The problem of continuous process is due to load changes. (e.g.)
storage vessel control.
A process in which the materials or work are stationary at one physical
location while being treated is termed as batch process. (e.g.) furnace.
14. Explain the function of controller.
The element in a process control loop that evaluated error of the
controlled variable and initiates corrective action by a signal to the
15. What is the purpose of final control element?
Components of a control system (such as valve) is used to directly
regulates the flow of energy or materials to the process. It directly
determines the value of manipulated variable.
16. Define Process control
It is the scheme that describes how much the manipulated variable should
change inorder to bring the controlled variable back to the setpoint.
17. List the two types of process control.
Direct process control
– Controlled variable directly indicates the performance of the process Eg.
Water heater system
InDirect Process control the performance of the process.
– Controlled variable indirectly indicates Eg. Annealing
18. What is Servo operation and Regulatory operation.
If the purpose of the control system is to make the process follow the
changes in setpoint as quick as possible, then it is servo operation.
19. What is mathematical modeling.
Set of equations that characterize the process is termed as Mathematical
20. Define an non-interacting system.
The dynamic behaviour one tank is affected by the other, but the reverse is
not true, then it is non-interacting system. Here the liquid heads are
independent of each other.
21. Define an interacting system.
The dynamic behavior one tank is affected by the other, but the reverse is
also true, then it is non-interacting system. Here the liquid heads are
dependent of each other.
22. Mention two drawbacks of derivative action
(i) The output of controller is zero at constant error condition.
(ii)It will amplify the noise present in the error signal.
23. What are the steps involved to design a best controller?
Define appropriate performance criterion (ISE, IAE, ITATE). Compute the
value of the performance criterion using a P, PI, or PID controller with
the best setting for the adjusted parameters Kp, Ti, Td. Select controller
which give the best value for the performance criterion.
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