R5311106-process Control Instrumentation

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Code No: R5311106

III B.Tech I Semester(R05) Supplementary Examinations, May 2009 PROCESS CONTROL INSTRUMENTATION (Common to Electronics & Instrumentation Engineering and Instrumentation & Control Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. In a jacketed tank, the temperature of process stream θ1 is preheated to a temperature θ2 by means of steam with temperature θs through the jacket. Assume that the capacity of the tank wall is negligible and that the temperature inside the jacket is uniform. (a) Derive the transfer function of this system to study the temperature response if the rate of flow of process stream is constant. (b) Make correction in the transfer function if the rate of flow of the process stream is also a variable. Also discuss about the time constants for a high flow rate and a low flow rate. [8+8] 2. (a) Give one example for Interacting first order elements in series. (b) Write the differential equation for this combination and determine the transfer function. [3+10+3] (c) Comment on the transfer function. 3. (a) Explain the principle of different types of discontinuous controller modes with examples. Mention them applications. (b) Distinguish between multi position controller mode and floating control mode with neat sketches. [10+6] 4. (a) Explain in detail, the realization of proportional-integral action with the aid of bellows, flappernozzle etc. (b) Draw a three mode electronic controller and derive the expression for the output voltage. [8+8] 5. Illustrate with relevant graphs the following methods of optimum settings from the plant response. (a) Damped oscillation method. (b) Reaction - curve method.

[16]

6. (a) Give the principle of the control valve and give its O/P equation. (b) A pressure difference of 1.5 psi occurs across a constriction in a 4 cm diameter pipe. The constriction constant is 0.008 w3 /s/(kPa)1/2 . Find i. the flow rate in m3 /sec. ii. flow velocity in m/sec. [8+8] 7. A heating furnace requires a control valve passing 10gpm preheated light fuel oil (SP.gr. = 0.8) at full load and only 2 gpm at the smallest heating load. The source pressure constant at 50psi gage, but there is 10psi drop in the oil pre heater and 20 psi drop at the furnace burner nozzles. Remaining pressure drop occurs only at control valve when it is fully opened. (a) Find out control valve size required for the above application. (b) Find out required rangeability of the valve (c) Find out characteristic coefficient (α).

[6+4+6]

8. (a) What is the fundamental characteristics of cascade control. (b) Explain the basic principles of cascade control with one industrial application. [8+8] ?????

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Code No: R5311106

III B.Tech I Semester(R05) Supplementary Examinations, May 2009 PROCESS CONTROL INSTRUMENTATION (Common to Electronics & Instrumentation Engineering and Instrumentation & Control Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. A Cylindrical tank with an area of 20 ft2 and a height of 10 ft has a normal liquid depth of 6ft. The flow to the tank is 10±1 cubic ft/min, and the liquid is discharged through a control valve to a process at atmospheric pressure. ( 1 ft = 0.305 metre) Calculate the time constant if the tank is (a) Open to the atmosphere (b) Closed, with a constant pressure of 10 psig above the liquid. (c) Closed, with a fixed amount of air sealed above the liquid. The initial pressure is 10 psig. [16] 2. (a) Differentiate between a “Servo operation” and “Regulator operation”. (b) Give a typical example for servo operation and explain. (c) Explain the regulator operation with an example.

[4+6+6]

3. (a) Discuss the effects of an integral controller on the closed loop response of first order process. (b) With neat sketches, explain the principle of derivative control action. Summarize its characteristics. [8+8] 4. (a) Explain in detail, the realization of proportional-integral action with the aid of bellows, flapper-nozzle etc. (b) Draw a three mode electronic controller and derive the expression for the output voltage. [8+8] 5. (a) What is meant by process tuning and list the various methods of tuning of PID parameters. (b) Discuss process reaction method for control loop tuning. [8+8] 6. (a) Explain the principle of operation of a stepping motor and give its sole as an actuator. (b) A hydraulic system uses pistons of diameter 2cm and 40cm. What force on the small piston will raise a 500 kg mass. [10+6] 7. A heating furnace requires a control valve passing 10gpm preheated light fuel oil (SP.gr. = 0.8) at full load and only 2 gpm at the smallest heating load. The source pressure constant at 50psi gage, but there is 10psi drop in the oil pre heater and 20 psi drop at the furnace burner nozzles. Remaining pressure drop occurs only at control valve when it is fully opened. (a) Find out control valve size required for the above application. (b) Find out required rangeability of the valve (c) Find out characteristic coefficient (α).

[6+4+6]

8. (a) Explain the process of controlling reflux in distillation column. (b) Explain the control of indirect bottom product in a distillation column. [8+8] ?????

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Code No: R5311106

III B.Tech I Semester(R05) Supplementary Examinations, May 2009 PROCESS CONTROL INSTRUMENTATION (Common to Electronics & Instrumentation Engineering and Instrumentation & Control Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Derive the process differential equations and the transfer function for the following two capacity level process as shown in the figure1.

Figure 1: (b) This level process is an interacting system – say “TRUE” or “ FALSE”. Support your answer with valid reasons. (c) Define the system time constants of the above process. [9+4+3] 2. (a) Differentiate between a non-interacting system and an interacting system. (b) Give one example each for non-interacting system and interacting system. (c) Derive the transfer functions for the above two systems and discuss how they differ.

[3+2+11]

3. (a) Explain with neat sketches, the characteristics of two position and three position controller modes. (b) What is cycling? Suggest a suitable modification to overcome cycling. [6+10] 4. (a) Explain in detail with a neat sketch, the working principle of a pneumatic PID controller. Write a note on various time constants involved. (b) Outline the design steps involved in the implementation of an electronic PD controller and explain. [8+8] 5. (a) Explain the following terms as applicable to system evaluation with necessary graphs. i. Stability ii. measure of quality . (b) Discuss the quarter - amplitude criterion to evaluate the response.

[8+8]

6. (a) A 4-20mA control signal is loaded by a 100-Ω resistor and must produce a 20-40 volt motor drive signal. Find an equation relating the input current to the output voltage. (b) Explain with an example the need of signal conditioning system in the final control operation. [8+8] 7. Write short notes on. (a) Sliding stem Valves (b) Rotating shaft Valves.

[8+8]

8. (a) What is the fundamental characteristics of cascade control. (b) Explain the basic principles of cascade control with one industrial application. [8+8] ?????

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Code No: R5311106

III B.Tech I Semester(R05) Supplementary Examinations, May 2009 PROCESS CONTROL INSTRUMENTATION (Common to Electronics & Instrumentation Engineering and Instrumentation & Control Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ????? 1. (a) Mercury thermometer is a first order system - Say “True” or “False”. (b) Prove your answer by deriving the transfer function of this system. (c) How will this system behave with a linearly varying input? Explain the dynamics. 2. (a) Differentiate between a non-interacting system and an interacting system. (b) Give one example each for non-interacting system and interacting system. (c) Derive the transfer functions for the above two systems and discuss how they differ.

[2+6+8]

[3+2+11]

3. (a) what is meant by differential gap and how it is related to the performance of the final control element? (b) Define proportional band. Explain the relation between proportional gain, proportional band and offset error. (c) With a neat sketch explain the integral controller mode action. Summarize the characteristics. [5+5+6] 4. (a) With a neat sketch, explain the realization of electronic single speed floating controller. How the floating rate can be adjusted in such a controller? (b) State the kind of control action realized in the following circuit figure1. Also determine the input-output relationship. [10+6]

Figure 1: 5. (a) Explain the following terms as applicable to system evaluation with necessary graphs. i. Stability ii. measure of quality . (b) Discuss the quarter - amplitude criterion to evaluate the response.

[8+8]

6. (a) Draw the block diagram of the final control operation and explain each block with examples. (b) A magnetic amplifier requires a 5-10 Volt i/p signal from 4-20mA control signal Design a signal conversion system to provide this relationship. (Assume the values of suitable components). (c) What is an actuator and what is its role in the final control operation of a process control system.[6+6+4] 7. A heating furnace requires a control valve passing 10gpm preheated light fuel oil (SP.gr. = 0.8) at full load and only 2 gpm at the smallest heating load. The source pressure constant at 50psi gage, but there is 10psi drop in the oil pre heater and 20 psi drop at the furnace burner nozzles. Remaining pressure drop occurs only at control valve when it is fully opened. (a) Find out control valve size required for the above application. (b) Find out required rangeability of the valve (c) Find out characteristic coefficient (α). 8. Write short notes on (a) Material balance in a distillation column (b) Quality control (top and bottom product) in a distillation column (c) Quantity control (top and bottom product) in a distillation column. ?????

[6+4+6]

[5+6+5]