Recent questions tagged chemical-instrumentation-process-control

Description : Explain in detail principle, construction and working of Radiation Pyrometer with neat sketch.

Last Answer : Radiation pyrometer Principle: According to Stefan Boltzmann's law, the intensity of radiant energy emitted by a hot target varies as the fourth power of its absolute temperature. ... is calibrated in terms of target temperature by using either a voltmeter or Wheatstone bridge circuit.

Description : Describe construction and working of Dead Weight Tester used in pressure calibration.

Last Answer : Dead weight tester:  Construction: It consists of a very accurately machined, bored and finished piston which is inserted into a close-fitting cylinder. The cross sectional areas of ... within the cylinder when the fluid gauge pressure equals the dead weight divided by the piston area.  

Description : Compare Servo and Regulatory process used in process control.

Last Answer : Comparison of Servo & Regulatory process:

Description : Explain differential pressure measurement method as indirect method for level measurement.

Last Answer : Differential pressure measurement as indirect method for level measurement:  Closed vessel: Differential pressure (DP) transmitters used for liquid level application measure hydrostatic pressure head. In a closed ... side of the DP and the low pressure side is vented to atmosphere.  

Description : State the working principle of variable area flow meter

Last Answer : Principle of Piston type variable area flow meter: In piston type flow meters, the size of flow restriction is adjusted by an amount necessary to keep the pressure differential constant when the flow rate changes and the amount of adjustment required is proportional to flow rate.

Description : Describe construction and working of Resistance Temperature Detector (RTD).

Last Answer : RTD:  Construction and working: Resistance thermometer bulbs consist of a coil of fine wire wound or in a frame of insulating material. The resistance wire itself must be homogeneous in order to ... surrounding it. Thus RTD is used to measure temperature in terms of change in resistance.

Description : Explain the working of valve actuators used in control valve.

Last Answer : Working of spring diaphragm actuator: Actuator is the portion of the valve that responds to the applied signal and results in the movement of the stem due to which the flow rate of fluid changes. ... input signal. The diaphragm is made of neoprene or any other synthetic elastic element.

Description : Describe open loop and closed loop system.

Last Answer : Open loop and closed loop system: Open system: When the input is independent of the output, the system is called open- loop system. The control action is based on only some ... system is called closed- loop control system. The output is continuously measured and fed to the input. 

Description : State the working principle of Bellows pressure gauge with neat sketch.

Last Answer : Bellows pressure gauge: Diagram: Principle: Bellows element is the elastic element which gets deflected at the free end when pressure is applied through fixed end. This free end deflection can be taken as the measure of pressure inside it.

Description : List different electrical temperature sensors. Explain any one of them.

Last Answer : Different electrical temperature sensors: 1. RTD 2. Thermistors 3. Thermocouples Thermocouple: Explanation: If two dissimilar metals are joined together so as to form a closed ... difference in temperature between the two junctions and on the characteristics of the two metals.

Description : Explain Static Error and Dynamic Error in measurement systems.

Last Answer : Definition of static error and dynamic error  Static error: It is the difference between the true value of a quantity not changing with time and the value indicated by the instrument  Dynamic ... changing with time and the value indicated by the instrument if no static error is assumed.

Description : Explain the capacitance type level measurement method with neat diagram.

Last Answer : Capacitance level indicator  Explanation: It consists of two conductors separated from each other by dielectric material between them. There is an insulated capacitance probe fixed near and parallel to ... , the dielectric constant changes due to which capacitance changes. Thus any change.

Description : Describe Turbine flow meter with neat sketch.

Last Answer : Turbine flow meter: Diagram Description: It consists of a multibladed wheel mounted in a pipe along an axis parallel to the direction of fluid flow in the pipe. The flow of liquid past the ... each blade on the turbine wheel moves past it and these pulses are measured by a pulse counter. 

Description : Write the names of different types of control valves.

Last Answer : Types of control valve: 1. Based on number of plugs: Control valves can be classified as single seated valve and double seated valve 2. Based on action: Control valves operated through pneumatic actuators ... Valve 4. Butterfly valve 5. Rotary valve 6. Ball valve 7. Sliding cylinder valve

Description : Enlist the names of different controllers

Last Answer : Controllers 1.On-Off or Two position controller 2. Proportional (P)controller 3. Integral (I)controller 4. Derivative (D) controller 5. PD controller 6. PI controller 7. PID controller

Description : Define : (i) Speed of Response (ii) Time Lag.

Last Answer : Definition (i) Speed of response: It is the rapidity with which an instrument responds to changes in the measured quantity.  (ii) Time lag: It is the period during which the instrument does not respond to a change in the value of the variable.

Description : State the principle of ultrasonic flow meter

Last Answer : Principle of ultrasonic flow meter: In ultrasonic flow meters, the measurement of flow rate is determined by the variation in parameters of ultrasonic oscillations. Time Difference Type ultrasonic flow meters ... transverse a pipe section, both with and against the flow of liquid within the pipe.

Description : Give the names of any four pressure gauges used for pressure measurement.

Last Answer : Pressure gauges used for pressure measurement : Bellows pressure gauge, diaphragm pressure gauge, strain gauge, Force balance pressure gauge (Dead weight pressure gauge) and Bourdon tube pressure gauge.

Description : List any four temperature measuring devices.

Last Answer : Temperature measuring devices : RTD, thermocouple, thermistor, thermometer, bimetallic thermometer, radiation pyrometer, optical pyrometer

Description : Define : (i) Sensitivity (ii) Repeatability  

Last Answer : Definition:  (i) Sensitivity: It is the smallest change in the value of the measured variable to which an instrument responds.  (ii) Repeatability: It is the closeness of agreement ... same value of input under the same operating conditions, approaching the measurement from the same direction.

Description : Explain solenoid valve with construction and working of it.

Last Answer : Solenoid valve  Construction: A solenoid valve consists of an electromagnetic coil and a valve. The electromagnetic coil actuates an armature or a valve stem in a magnetic field to control ... on-off switching option in the system and are actuated by electric signals from remote locations. 

Description : Explain with block diagram the working of programmable logic control system. (PLC).

Last Answer : Programmable logic controller:  Block diagram: OR Explanation: PLCs are industrially hardened microcomputers that perform discrete or continuous control functions in a variety ... provides an interface between the PLC and user during program development, start-up and trouble shooting

Description : State the function of valve actuator and valve positioner. 

Last Answer : Function of Valve actuator: It is that portion of the valve that responds to the applied signal and results in the movement of the stem due to which the flow rate of fluid changes. ... to the control signal. Valve positioner improves the speed of response and reduces the hysteresis effect. 

Description : State the factors to be considered for control valve selection.

Last Answer : Factors to be considered for control valve selection: The basic steps in control valve selection are 1. The first step in control valve selection involves collecting all relevant data and completing the ... force or friction. A hand wheel is needed if manual operation of the valve is expected.

Description : Explains DCS architecture with the help of a block diagram.

Last Answer : DCS architecture: Block diagram: Explanation: In DCS equipment is separated in functional area and is installed in different work areas of a process plant. The plant operator ... has flexibility of implementation of sequential control and integration among the various types of control. 

Description : Explain the working and principle of electromagnetic flow meter with neat diagram.

Last Answer : Electromagnetic flow meter:  Principle: Electromagnetic flow meter works on the principle of Faraday's law of electromagnetic induction which states that when a current carrying conductor moves through stationary ... of fluid changes causing the induced emf to change. Diagram:

Description : Explain with neat diagram working of Mc Leod gauge used for vacuum measurement.

Last Answer : Mc Leod gauge:  Working: To operate the gauge, the piston is first withdrawn, causing the level of mercury in the lower part of the gauge to fall below the level of the junction between the two tubes. ... the fluid.  The expression for calculating the unknown pressure is Diagram: 

Description : List the classification of temperature measuring instruments with one example each.

Last Answer : Classification of temperature measuring instruments with one eg 

Description : Explain the working and principle of LVDT.

Last Answer : LVDT: Principle: The differential voltage of two secondary windings of a transformer is varied by positioning the iron core through an externally applied force. Working  When the pressure ... upon the position of the core which in turn depends upon the pressure fed inside the bellows.

Description : State the advantages and disadvantages of Bourdon type pressure gauge.

Last Answer : Bourdon tube: Advantages: 1) Low cost 2) Simple construction 3) Wide pressure range 4) High accuracy in relation with low cost Disadvantages: 1) Low spring gradient 2) Susceptible to shock and vibration 3) Susceptible to hysteresis

Description : Explain the working and principle of bi-metallic thermometer.

Last Answer : Bimetallic thermometer:  Principle: When heated different solids expand differently depending on their coefficient of thermal expansion. Working: Bimetallic strip consists of two strips of metal such as ... bimetallic strip is utilized to deflect a pointer over a calibrated scale.

Description : Define dead zone of instrument and explain the reasons of dead zone.

Last Answer : Definition of dead zone: It is the largest range of values of a measured variable to which the instrument does not respond. It is the largest change of input quantity for which there is ... highly stressed material. Intentionally dead zone is provided to increase the life span of the instrument.

Description : Difference between open loop and closed loop control system

Last Answer : Difference between open loop and closed loop control system : Sr No. Open loop control system Closed loop control system  1 Feedback doesn't exists Feedback exists 2 ... and hence costly 9 Highly affected by nonlinearities Reduced effect of non-linearity

Description : Draw a neat sketch of Ultrasonic flowmeter. 

Last Answer : Diagram of ultrasonic flow meter (Time Difference Type ):

Description : Explain the working and principle of thermal flow meter.

Last Answer : Thermal flow meter: Principle: Working : It consists of an electric immersion heater for the heating of flowing fluid. Two thermocouples (or resistance thermometers) T1 and T2 are placed at each side ... values of Q, T1 and T2 the flow rate W of liquid is determined from the equation

Description : Explain with principle the instrument for air purge method of level measurement.

Last Answer : Air purge method for of level measurement:  Principle: When liquid is held in a tank, then it exerts equal pressure on the walls of the tank. Such a pressure is due to the weight ... the hydrostatic pressure. The gauge then measures the air pressure needed to overcome the pressure of the liquid.

Description : Explain the working and principle of dead weight tester.

Last Answer : Dead weight tester:  Principle: It works on the principle that the downward force of the weight on the top of the piston is balanced by the pressure exerted by the fluid beneath the piston  ... within the cylinder when the fluid gauge pressure equals the dead weight divided by the piston area.

Description : List four temperature scales and state its icepoint and boiling point of water on each scale.

Last Answer : Temperature scales with ice point and boiling point of water :

Description : Explain the construction of Rotameter.

Last Answer : Construction of rotameter: It consists of a tapered glass tube mounted vertically with smaller end on the lower side. A float is installed in the tube after the meter is mounted in ... the pipeline by means of flanges or threads along with the inlet and outlet piping supported in bracket.

Description : Write different types of controllers used in control system.

Last Answer : Types of controllers:  1.On-Off or Two position controller 2. Proportional (P)controller 3. Integral (I)controller 4. Derivative (D) controller 5. PD controller 6. PI controller 7. PID controller

Description : Write the names of any four flow meters used for flow measurement.

Last Answer : Flow meters used for flow measurement : Rotating vane meter, ultrasonic flow meter, Piston type flow meter, thermal flow meter, electromagnetic flow meter.

Description : Give the names of different electrical temperature measuring devices.

Last Answer : Electrical temperature measuring devices: RTD, thermocouple, thermistor

Description : Enlist the names of different pressure measuring instruments.

Last Answer : Pressure measuring instruments: LVDT, bellows pressure gauge, diaphragm pressure gauge, strain gauge, Force balance pressure gauge (Dead weight pressure gauge) Bourdon tube pressure gauge, Mc Leod gauge etc.

Description : Write the names of different temperature measuring instruments.

Last Answer : Temperature measuring instruments: RTD, thermocouple, thermistor, mercury in-glass thermometer, bimetallic thermometer, radiation pyrometer, optical pyrometer

Description : Define - (i) Drift (ii) Sensitivity

Last Answer : Definition (i)Drift: Drift is the gradual shift in the indication or record of the instrument over an extended period of time during which the true value of the variable does not change (ii) ... : It is the smallest change in the value of the measured variable to which an instrument responds.

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