Process Control Flashcards by Armin Arboleda

Which of the following term correctly represents transient nature of a process?

A. Steady state
B. Unsteady state
C. Process with dead lag
D. Exponential behavior of process

B. Unsteady state

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Which of the following conservation balancing equations is required for modelling a heater system?

A. Heat and Energy balance
B. Heat and Mass balance
C. Mass and matter balance
D. Heat and Concentration balance

B. Heat and Mass balance

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Which of the following correctly represent the components of a control system?

A. Thermocouple, displacer device, heating coil
B. Measuring element, thermometer, pressure gauge
C. Process, measuring element, controller and final control element
D. Process, measuring element, amplifier and final control element

C. Process, measuring element, controller and final control element

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What variables should we measure in order to monitor the operational performance of a plant?

A. the variables that represent our control objectives
B. Controller output
C. manipulated variable
D. Setpoint

A. the variables that represent our control objectives

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How is the information, taken from the measurements, used to adjust the values of the manipulated variables?

A. control law
B. error
C. desired value
D. measuring device

A. control law

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The input variables can be classified into

A. manipulated variable and disturbances
B. setpoint and desired variables
C. process variables and controlled variables
D. Controller output and Control law

A. manipulated variable and disturbances

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The output variables can be classified into

A. manipulated variable and disturbances
B. setpoint and desired variables
C. measured and unmeasured variables
D. Controller output and Control law

C. measured and unmeasured variables

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Under what circumstances does an open control loop exist?

A. Process variable is not measured
B. Process variable is measured and compared to a setpoint
C. Action is taken with regard to process variable conditions
D. None of the above

A. Process variable is not measured

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Identify which of the following is/are primary element/sensors in process control?

A. Resistance Temperature Detectors
B. Control Valve
C. Converter
D. All the above

A. Resistance Temperature Detectors

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A ____________ is a device that translates a mechanical signal into an electrical signal.

A. Transducer
B. Converter
C. Regulated Power supply
D. PID Controller

A. Transducer

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A _____ is a device that converts a reading from a transducer into a standard signal and transmits that signal to a monitor or controller

A. Transducer
B. Converter
C. Transmitter
D. PID Controlle

C. Transmitter

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Which of the following have the ability to receive input, to perform a mathematical function with the input, and produce an output signal?

A. Actuators
B. Transmitters
C. Transducers
D. Controllers

D. Controllers

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Which of the following is the most common final control element in process control industries?

A. Agitator
B. Pump motor
C. Valve
D. Louver

C. Valve

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______ is a part of final control device that causes a physical change in the final control device when signaled to do so.

A. Controller
B. Pump motor
C. Transmitter
D. Actuator

D. Actuator

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Transfer function is __________

A. The ratio of Laplace transform of the output to Laplace transform of the input with zero initial conditions
B. Process variable
C. Setpoint
D. Controller output

A. The ratio of Laplace transform of the output to Laplace transform of the input with zero initial conditions

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The ________________ process are characterized by:
• Their capacity to store material, energy, or momentum
• The resistance associated with the flow of mass, energy, or momentum in reading the capacity.

A. Higher order
B. Second order
C. First order
D. Zero orde

C. First order

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Non interacting capacities always result in an ___ or ____

A. Under damped, overdamped
B. undamped, overdamped
C. overdamped, critically damped
D. none of the above

C. overdamped, critically damped

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The response of interacting capacities is always _______

A. Undamped
B. Under damped
C. Critically damped
D. Overdamped

D. Overdamped

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The overall response of interacting capacities are more ________ than the noninteracting capacities.

A. Speed
B. Fast
C. Sluggish
D. Quick

C. Sluggish

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When a valve is installed in a process with where the differential pressure (drop) across the valve decreases with increasing flow, the best trim characteristic to choose for the valve would be:

A. Ported
B. Quick-opening
C. Equal percentage
D. Linear

C. Equal percentage

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The main purpose of a control valve positioner is to:

A. Alter the fail-safe status of the valve
B. Improve the precision of the valve
C. Alter the characterization of the valve
D. Increase transmitter accuracy

B. Improve the precision of the valve

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The purpose of valve packing is to:

A. Help reduce cavitation in the valve trim
B. Increase stiction
C. Cushion the valve against harm during shipment
D. Seal process fluid from escaping past the stem

D. Seal process fluid from escaping past the stem

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Cavitation in a control valve is caused by

A. process noise
B. vibration in the piping
C. a laminar flow regime
D. pressure recovery

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D. pressure recovery

The proper “fail safe” status of a valve should always be dictated by:

A. economic savings
B. the configuration of the positioner
C. the controller’s action (direct or reverse)
D. the nature of the process

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D. the nature of the process

Choose the correct option. I: Single seated valves are suitable for small flow rates. II: With double seated valves, the flow can be shut off completely. A. Only statement I is correct B. Only statement II is correct C. Both statements I and II are correct D. Both statements I and II are false

A. Only statement I is correct

A control valve has to control the inlet flow of cooling water to a cooling jacket on an exothermic chemical reactor. We should select A. Air to close valve B. Air to open valve C. Globe valve D. Butterfly Valve

A. Air to close valve

Choose the correct option. P) The gain of a quick opening valve is non-linear. Q) An equal percentage valve is not recommended when the pressure drop across the control valve varies. A. Only P is true B. Only Q is true C. Both P and Q are false D. Both P and Q are true

A. Only P is true

A fluid flows through an equal percentage valve at a rate of 5 m3/h when the valve is 10% open. When the valve opens to 20%, the flow rate increases to 10 m3/h. What is the flow rate in m3/h when the valve opens to 30%? The pressure drop across the valve remains constant. A. 15 B. 20 C. 30 D. 10

B. 20

A fluid flows through a linear valve at a rate of 15 m3/h when the valve is 15% open. When the valve opens to 30%, the flow rate increases to 30 m3/h. What is the flow rate in m3/h when the valve opens to 45%? The pressure drop across the valve remains constant. A. 15 B. 30 C. 45 D. 60

C. 45

What is the main purpose of the control valve positioner? A. Change the valve characteristic B. Improve the precision of the valve C. Minimize cavitation in the valve D. Reduce leakage of process fluid

B. Improve the precision of the valve

The internal elements of a valve are collectively referred to as a valve’s _______ A. guts B. trim C. works D. packings

B. trim

Which one of the following valve parts is NOT usually considered to be a part of the pressure boundary. A. body B. seal rings C. bonnet D. disk

C. bonnet

A control valve is most likely to experience cavitation when the valve is almost fully __________ because of a relatively __________ pressure drop across the valve seat. A. closed; large B. open; large C. open; small D. closed; small

A. closed; large

The primary purpose of a pressure relief valve is to A. maintain system integrity B. reduce system pressure. C. reduce system energy D. maintain system mass.

A. maintain system integrity

This type of control loop measures the disturbance variables to limit the deviation in the output variables by preemptively adjusting the manipulated variable (PHB P8-5). A. Feedback control B. Feedforward control C. Computer control D. Response control

A. Feedback control

The startup and shutdown of a cooling water pump as a response to variations in the temperature of cooling water in a jacketed stirred-tank reactor is a type of _____ event (PHB P8-7). A. Continuous B. Abrupt C. Discrete D. Alternating

C. Discrete

Proportional elements are typically found in transfer functions where the relationship between two variables is characterized as (PHB P8-8). A. Uninterrupted unstable response B. Time-delayed response C. Lagged dynamic response D. Instantaneous dynamic response

D. Instantaneous dynamic response

This type of controller is preferred when slow cycling is acceptable, meaning the equipment can run and shut alternatively to maintain the manipulated variable within an acceptable range (PHB P8-12). A. Continuous Control B. On/Off Control C. Switch Control D. Alternating Control

B. On/Off Control

This type of controller is the most commonly used type in the industry (PHB P8-13). A. On/Off Control B. Proportional Control C. Proportional-plus-Integral Control D. Proportional-plus-Integral-plus-Derivative Control

C. Proportional-plus-Integral Control

The disadvantage of conventional feedback control is the large time lag between the disturbance and the deviation observed in the set point. This can be resolved by using cascade control, which measures the __________ to anticipate a possible deviation in the main variable (PHB P8-19). A. Primary measurement point B. Secondary measurement point C. Set point D. Forecast point

B. Secondary measurement point

Time-delays are typical part of process control systems because of delays in fluid flow effects and dead time in composition analysis, among other reasons. They limit the effectivity of the PID feedback control system. The most common algorithm used in compensating for time-delay is (PHB P8-21). A. Auctioneering B. Override C. Smith predictor D. Adaptive control

C. Smith predictor

This type of control system changes multiple manipulated variables to control one output variable (PHB P8-21). A. MIMO control B. Adaptive control C. Fuzzy logic control D. Split-range control

D. Split-range control

Most industrial facilities require multiple variables to be controlled simultaneously using many manipulated variables. The main variables of concern are typically product quality and product throughput. One way to reduce the number of control schemes is by selecting only the best controller pairings, i.e. which controlled variables have the most impact for each manipulated variable. The most popular method of determining the best controller pairing is called the (PHB P8-23): A. Process interaction minimization B. Decoupling method C. Relative gain array method D. Model predictive control

C. Relative gain array method

What is meant by steady-state optimization (PHB P8-27)? A. Achievement of equilibrium conditions on a transient and oscillating system B. Real-time evaluation of process operating conditions and adjustment of controlled variables to attain business objectives C. Reduction of irrelevant controlled variables to construct an effective dynamic control system D. Adjustment of the process throughput to increase safety and maximize profits

B. Real-time evaluation of process operating conditions and adjustment of controlled variables to attain business objectives

Industrial processes can have tens to hundreds of steps and each step contributes to the final quality of the product. Hence, even a small inaccuracy in each process step can result in large financial losses in the form of waste. This data-driven management philosophy focuses on achieving sustainable and predictable process results by reducing process variations (PHB P8-32). A. Shewhart charts B. Statistical process control C. Six sigma approach D. Lean management

C. Six sigma approach

This type of process plant is capable of producing small quantities of a variety of products, particularly found in food, chemicals, and pharmaceuticals industries (PHB P8-41). A. Specialty plants B. Commodity plants C. Semibatch plants D. Continuous process plants

A. Specialty plants

Batch plants rely on a specific formula that describes the amount of raw material for each batch, and a recipe that describes how the raw materials are to be mixed and processed. In which type of batch process does both the formula and recipe change in every batch (PHB P8-41)? A. Cyclical B. Multigrade C. Flexible batch D. Multirecipe

C. Flexible batch

In process control, valves have various states wherein each state has a separate process function. Which of the following pertains to a temporary state wherein the valve has been commanded to change state, is not yet consistent with the commanded state, and the time to switch between states has not yet expired (PHB P8-42)? A. Open B. Closed C. Transition D. Invalid

C. Transition

An example of this structure found in production facilities is an entire polymerization reactor with the corresponding recirculation pumps, reflux condenser, cooling water pump and jacket, and preheating exchangers (PHB P8-46). A. Item of equipment B. Process unit C. Equipment suite D. Plant

B. Process unit

In which of the following instruments are most likely to indicate discrete measurements (PHB P8-56, T8-7) A. Thermocouple at the top tray of a distillation column B. Level sensor that detects presence of liquid at a specific level C. Industrial sensor that detects excess O2 levels at a furnace effluent D. Venturi meters with a pressure differential that can be translated to flowrate

B. Level sensor that detects presence of liquid at a specific level

The accuracy of an instrument indicates how close to the true values its measurement is. Which of the following is not an expression for accuracy (PHB P8-55)? A. Absolute difference between measured and actual value B. Percentage of the current reading C. Percentage of the span of the measured variable D. Number of times the instrument read the exact actual value to 3 decimal places

D. Number of times the instrument read the exact actual value to 3 decimal places

This type of thermometer takes advantage of the difference in thermal expansion of two metals. Hence, when this composite is heated, its deflection can be translated to a temperature reading (PHB P8-58). A. Thermocouple B. Resistance thermometers C. Pyrometers D. Bimetal thermometers

D. Bimetal thermometers

Manometers are pressure-measuring devices belonging to which of the following classes (PHB P8-59)? A. Electrical methods B. Elastic element methods C. Liquid column methods D. None of the above

C. Liquid column methods

This type of flowmeter takes advantage of the frequency shift observed in sound waves passed through the fluid flow, which is directly proportional to fluid velocity (PHB P8-60). A. Ultrasonic flowmeters B. Magnetic flowmeters C. Coriolis mass flowmeters D. Thermal mass flowmeters

A. Ultrasonic flowmeters

The final control element typically receives signals from the controller and executes an action in the process such as allowing or restricting flow in a pipe, typically using devices called valves. This type of valve utilizes a rotating disk that can limit flow depending on its rotation angle (PHB P8-67, F8-65). A. Ball valve B. Butterfly valve C. Plug valve D. Globe valve

B. Butterfly valve

Process Control Flashcards

(55 cards)