Unit 9: Plant Instrumentation & Controls

Question 1

Open Loop Control Systems

Answer 1

Is a control system with no automatic systems in place. Any changes made to address errors are done manually.

Question 2

Closed Loop Control Systems

Answer 2

Are automatic control systems. They respond to changes in process conditions and can be made to change to any condition set.

Question 3

Process

Answer 3

defined as an operation that uses energy to produce a change in a material or an energy conversion.

Question 4

Set Point

Answer 4

is the desired value of process variable

Question 5

Process Variable

Answer 5

Is the current status of a process that is being controlled.

Question 6

Error

Answer 6

Difference between the measured variable and the set point

Question 7

Transmitter

Answer 7

Converts a sensing elements measurement into a signal that can be transmitted a distance to the controller.

Question 8

Pneumatic Instruments

Answer 8

use variations in compressed air to transmit information and can range from 20-100 kPa

Question 9

Transducer

Answer 9

Is a device that converts one form of energy into another form of energy.

Question 10

Manometers

Answer 10

A very accurate device for measuring low pressure levels. Inclined manometers are used for even smaller pressures.

Question 11

What component protects pressure sensing elements against such conditions as high temperature, cyclic pressures, vibrations, and corrosion?

Answer 11

Siphons (pigtails) pipe that maintains a water seal through is pig tail shape/curves

Question 12

Float Cage

Answer 12

A float measuring device used when it is not practical to have the measuring device inside of the vessel to measure level.

Question 13

Modulating Controller

Answer 13

Can create an infinite amount of output control levels

Question 14

Two-Position Controllers

Answer 14

Simply can output an on or off signal to respond to an error.

Question 15

Multi-Position Controllers

Answer 15

Are similar to two-position controllers but add a few extra positions in-between on and off. Such as low-medium-high.

Question 16

Damper

Answer 16

Is a device that controls the flow of air through ducts or wall openings

Question 17

Damper Operators

Answer 17

Used to adjust the damper position and adjust the air flow intake.

Question 18

Actuators

Answer 18

Moves a valve steam which varies the size of the valve opening. Essentially receives a signal from a controller which can actuate the valve and control flow.

Question 19

PLC

Answer 19

Programmable Logic Controllers

Question 20

Switches

Answer 20

Interrupt or divert electrical power and can be manually or automatically controlled.

Question 21

Thernostats

Answer 21

is an electrical control that is used to maintain the temperature of a heated space or substance at a desired set point.

Question 22

Bi-Metal Thermostat

Answer 22

Is a metal strip that reacts to changes in temperature. As the metal experiences the temperature change it bends either to open or close an electrical switch.

Question 23

Aquastat

Answer 23

Is a thermostat that is used to sense and control the temperature of liquids.

Question 24

Relay

Answer 24

is a device that controls large amounts of energy with small amounts of energy.

Question 25

What are Programmable Logic Controllers generally used for?

Answer 25

They are generally used to control a sequence of events