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Danica’s Steamfitter III Review > Controls Part A > Flashcards

Controls Part A Flashcards

1
Q

What are the four principal interests of instrumentation control variables?

A
  1. Temperature
  2. Pressure.
  3. Liquid level.
  4. Rate of flow.
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2
Q

What is a manipulated variable?

A

The manipulated variable is the quantity or condition that is regulated by the automatic control system in such a manner that it causes the desired change in the controlled variable.

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3
Q

What is a controlled variable?

A

The controlled variable is the quantity or condition that is measured and controlled. It exists in the controlled medium.

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4
Q

Of temperature, pressure, liquid level, and rate of flow, which are measured directly or indirectly (inferentially)?

A

Temperature – indirectly or inferentially
Pressure -directly
Liquid level – directly
Rate of flow – directly

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5
Q

Temperature is the indication of _____________ activity.

A

Molecular

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6
Q

Methods for the control of a variable can be divided into two broad categories. What are they?

A

Manual control and automatic control.

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7
Q

control of a single variable ordinarily involving an operator, a measuring means, and a final control element is which method of control? Manual or automatic?

A

Manual

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8
Q

When the primary element (thermostat) is located outside of the room it is controlling the heat for, is this an example of an open loop or a closed loop control system?

A

Open loop

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9
Q

When the primary element (thermostat) is located inside of the room it is controlling the heat for, is this an example of an open loop or a closed loop control system?

A

Closed loop

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10
Q

A cascade controller will have a minor loop and a main loop. Which loop reacts faster to changes of the process?

A

The minor loop

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11
Q

All automatic control systems must have a control system, A measuring means and a controlling means. Therefore, there are two basic parts, common to all automatic control systems. they are the controller and the controlled system. What is the controlled system?

A

The process which you’re trying to manipulate.

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12
Q

What are the two purposes of a controlling device?

A

To measure and control the variable.

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13
Q

What is the primary elements purpose?

A

The primary element is the portion of the measuring means that first utilizes or transform energy from the controlled medium to produce an effect in response to the change in the value of the controlled variable.

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14
Q

A __________, located between the primary element and controlling means, is used to convert the value of the process, variable into a proportional signal, and transmit the signal over, fairly long distances to the controller in a controller room.

A

Transmitter

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15
Q

Define “controlling means”?

A

The controlling means consists of those elements of a controller that are involved in producing an action that establishes a desired value in the controlled variable.

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16
Q

What is the final control element?

A

The portion of the controlling means that directly changes the value of the manipulated variable.

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17
Q

Thermometers and pressure gauges are examples of which?
1. Gauges
2. Recorders
3. Indicators
4. Final control elements

A
  1. Indicators
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18
Q

What is the purpose of an auxiliary device?

A

Auxiliary devices such as relays and switches are control modules that are generally placed between the controller and the final control element. These devices modify the controller signal and some manner before the signal reaches the final control device.

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19
Q

What are the three Primary heating equipment and controls?

A

Low pressure steam boilers
Low temperature hot water boilers
Direct fire air handlers

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20
Q

Which type of control system typically includes a bellows, and a bulb connected by a length of tubing, filled with a fluid the source of energy, as well as the sensing element and control device are contained within a single instrument?

A

Self-actuated control system

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21
Q

What is an electro mechanical control system?

A

A control system powered by line or low-voltage and controls the system by starting and stopping the flow of current.

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22
Q

Which type of control system uses compressed air as a source of energy?

A

Pneumatic control system (typically 15 to 25 psi)

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23
Q

The controlled system is made up of all of the equipment in which the controlled variable exists. This includes all of the automatic control equipment, true or false?

A

False.

24
Q

An example of a direct means of measurement is using a pressure gauge to calculate the height of liquid and a vessel, true or false?

A

False.

25
Q

An example of a primary element is the float and a low water cut off that senses, the height of the boiler water and a steam boiler, true or false?

A

True

26
Q

A closed loop system gives feedback on the isolated controlled area back to the controller, true or false?

A

True

27
Q

In a cascade system, there’s generally a major interloop, and a minor outer loop, true or false?

A

False. It’s a main loop and a minor loop.

28
Q

A three-way diverting valve has two, inlets and one outlet. True or false?

A

False. One inlet and two outlets.

29
Q

What is the difference between a three-way mixing valve and a three-way diverter valve?

A

A three-way mixing valve has two inlets and a common outlet and a three-way diverting valve has two outlets, and a common inlet.

30
Q

The two types of operations when multiple controlled devices are being used are parallel operation, and __________ operation?

A

Sequence

31
Q

In parallel operation two or more valves will open and close together. What do the valves do in sequential operation?

A

Operate in sequence according to their spring range.

32
Q

What is a pneumatic operator?

A

A pressure actuated device.

33
Q

What are the two types of pneumatic operators?

A

Valves and dampers

34
Q

If I normally open valve is receiving, no pressure or signal, would it be open or closed?

A

Open

35
Q

On a reverse acting controller when the temperature decreases the pressure on the output signal does what?

A

Increases

36
Q

On a __________ acting controller, when the temperature increases, the pressure on the output, signal increases.

A

Direct

37
Q

The type of controller that can continually exhaust branch line control air is a _________ type.

A

Bleed

38
Q

When moving a dial on a thermostat to 21°C, you are adjusting the _____ point.

A

Set

39
Q

When control air is exhausted from the branch line only while reducing the branch line pressure, is this a bleed or non-bleed type control element?

A

 non-bleed

40
Q

When considering the type of change in branchline pressure, a controller may be classified as either of two modes, which are?

A

Proportional- When the pressure is changed, gradually, in response to a change in the condition
two position (positive acting)- where the valve only has on and off operation of the control device

41
Q

What is the difference between a single pressure device and a two pressure device?

A

Single pressure devices are a pressure of 15 psi and two pressure devices using main, which can be set as high as 30 and adjusted.

42
Q

Relays can be classified as two position or switching. this type of relay will switch from one control signal to another. What does PE and EP stand for?

A

Pneumatic electric, which relays pneumatic signals to electric signals.
Electric pneumatic, which converts electric signals to pneumatic signals

43
Q

Control valve accessories include positive positioners, and volume boosters. What are they?

A

Positive position is a relay designed to provide close regulation of valve position under varying conditions of load or friction.
A volume booster is normally used in a final control element to increase stroking speed

44
Q

The piece of equipment that is usually placed just ahead of the return air dampers in the central air handler and is wired in series with the fan circuit to shut off the fan if the return air temperature rises above, the setpoint is called what?

A

Fire stat

45
Q

A freeze-stat uses what element that stretches across the face of the coil, causing fans to shut down if the temperature drops on the outlet side of the preheat coil?

A

The averaging element

46
Q

An auxiliary device is usually found between the controller and the final element, true or false?

A

True

47
Q

An electric pneumatic relay converts a pneumatic signal into an electric signal, true or false?

A

False

48
Q

A bias start relay is used to sequence overlapping spring ranges on the final element. True or false?

A

True

49
Q

A positive positioner is used in a control valve operator to increase the stroking speed, true or false?

A

False

50
Q

One of the primary importance of instrumentation:
1. PH factor.
2. Humidity.
3. Pressure
4. Density

A
  1. Pressure.
51
Q

A device that will give a direct measurement is a:
1. Gauge glass.
2. Thermometer.

A
  1. Gauge glass
52
Q

An example of a type is indicator is a:
1. Transducer
2. Bimetal strip
3. Blind transmitter.

A
  1. Bimetal strip.
53
Q

Using a direct acting controller in a normally closed valve as the temperature rises the normally closed valve will open or close?

A

Open

54
Q

What is the max pressure setting on an instrument air main?

A

25 Psi.

55
Q

The type of controller that exhausts from the branch line only while reducing the branch line pressure is:
A. Bleed type.
B. Non-bleed type.

A

B. Non-bleed type.

56
Q

Two position controllers are also called what?

A

Positive acting

57
Q

A volume booster is used on a:
A. Final element.
B. Primary element.
C. Transmitter.

A

A. Final element.

Danica’s Steamfitter III Review (12 decks)

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