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INST 262 > Control Valve Terminology (Process Control) > Flashcards

Control Valve Terminology (Process Control) Flashcards

1
Q

A device that is mounted on the actuator to complement the actuator’s function and makes it a complete operating unit. Examples include positioners, supply pressure regulators, solenoids, and limit switches

A

Accessory

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2
Q

A pneumatic, hydraulic, or electrically powered device that supplies force and motion to open or close a valve.

A

Actuator

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3
Q

The general name given to a form of dead band that results from a temporary discontinuity between the input and output of a device when the input of the device changes direction. Slack, or looseness of a mechanical connection is a typical example

A

Backlash

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4
Q

The rate of flow through a valve under stated conditions

A

Capacity

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5
Q

The interconnection of process control components such that information regarding the process variable is continuously fed back to the controller set point to provide continuous, automatic corrections to the process variable

A

Closed Loop

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6
Q

A device that operates automatically by use of some established algorithm to regulate a controlled variable. The controller input receives information about the status of the process variable and then provides an appropriate output signal to the final control element

A

Controller

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7
Q

The range of valve travel over which a control valve can maintain the installed valve gain between the normalized values of 0.5 and 2.0

A

Control Range

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8
Q

Includes all components normally mounted on the valve: the valve body assembly, actuator, positioner, air sets, transducers, limit switches, etc

A

Control Valve Assembly

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9
Q

The range through which an input signal can be varied, upon reversal of direction, without initiating an observable change in the output signal

A

Dead Band

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10
Q

The time interval (Td) in which no response of the system is detected following a small (usually 0.25% - 5%) step input. It is measured from the time the step input is initiated to the first detectable response of the system being tested

A

Dead Time

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11
Q

A valve trim element used to modulate the flow rate with either linear or rotary motion. Can also be referred to as a valve plug or closure member

A

Disk

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12
Q

An inherent flow characteristic that, for equal increments of rated travel, will ideally give equal percentage changes of the flow coefficient (Cv)

A

Equal Percentage Characteristic

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13
Q

The device that implements the control strategy determined by the output of the controller

A

Final Control Element

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14
Q

A force that tends to oppose the relative motion between two surfaces that are in contact with each other

A

Friction

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15
Q

In its most general sense, it is the ratio of the magnitude of the output change of a given system or device to the magnitude of the input change that caused the output change

A

Gain

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16
Q

The maximum difference in output value for any single input value during a calibration cycle, excluding errors due to dead band

A

Hysteresis

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17
Q

The relationship between the flow coefficient and the closure member (disk) travel
as it is moved from the closed position to rated travel with constant pressure drop across the valve

A

Inherent Characteristic

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18
Q

The magnitude ratio of the change in flow through the valve to the change in valve travel under conditions of constant pressure drop

A

Inherent Valve Gain

19
Q

The relationship between the flow rate and the closure member (disk) travel as it is moved from the closed position to rated travel as the pressure drop across the valve is influenced by the varying process conditions

A

Installed Characteristic

20
Q

The magnitude ratio of the change in flow through the valve to the change in valve travel under actual process conditions.

A

Installed Valve Gain

21
Q

Shorthand for current-to-pressure transducer

A

I/P

22
Q

The closeness to which a curve relating to two variables approximates a straight line

A

Linearity

23
Q

An inherent flow characteristic that can be represented by a straight line on a rectangular plot of flow coefficient (Cv) versus rated travel. Therefore equal increments of travel provide equal increments of flow coefficient, Cv

A

Linear Characteristic

24
Q

The combined gain of all the components in the loop when viewed in series around the loop

A

Loop Gain

25
Q

This is typically accomplished by placing the controller in the manual operating position

A

Manual Control

26
Q

The condition where the interconnection of process control components is interrupted such that information from the process variable is no longer fed back to the controller set point so that corrections to the process variable are no longer provided

A

Open Loop

27
Q

A part of the valve assembly used to seal against leakage around the valve disk or stem.

A

Packing

28
Q

A position controller (servomechanism) that is mechanically connected to a moving part of a final control element or its actuator and that automatically adjusts its output to
the actuator to maintain a desired position in proportion to the input signal

A

Positioner

29
Q

All the combined elements in the control loop, except the controller. Typically includes the control valve assembly, the pressure vessel or heat exchanger that is being controlled, as well as sensors, pumps, and transmitters

A

Process

30
Q

The ratio of the change in the controlled process variable to a corresponding change in the output of the controller

A

Process Gain

31
Q

An inherent flow characteristic in which a maximum flow coefficient is achieved with minimal closure member travel

A

Quick Opening Characteristic

32
Q

A device that acts as a power amplifier. It takes an electrical, pneumatic, or mechanical input signal and produces an output of a large volume flow of air or hydraulic fluid to the actuator. It can be an internal component of the positioner or a separate valve accessory

A

Relay

33
Q

The minimum possible change in input required to produce a detectable change in the output when no reversal of the input takes place.

A

Resolution

34
Q

Usually measured by a parameter that includes both dead time and time constant

A

Response Time

35
Q

A device that senses the value of the process variable and provides a corresponding output signal to a transmitter. It can be an integral part of the transmitter, or it may be a separate component.

A

Sensor

36
Q

A reference value representing the desired value of the process variable being controlled

A

Set Point

37
Q

Stick/slip and this are colloquial terms that are sometimes used to describe static friction which is a major cause of dead band in a valve assembly

A

Stiction

38
Q

A device that senses the value of the process variable and transmits a corresponding output signal to the controller for comparison with the set point.

A

Transmitter

39
Q

The movement of the closure member from the closed position to an intermediate or rated full open position

A

Travel

40
Q

A pointer and scale used to externally show the position of the closure member typically with units of opening percent of travel or degrees of rotation.

A

Travel Indicator

41
Q

The internal components of a valve that modulate the flow of the controlled fluid

A

Trim

42
Q

A systematic procedure designed to ensure the correct valve capacity for a set of specified process conditions

A

Valve Sizing

43
Q

A stand-alone relay that boosts, or amplifies, the volume of air supplied to the actuator

A

Volume Booster

INST 262 (5 decks)

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