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Mechanical Engineering > Steam Boilers > Flashcards

Steam Boilers Flashcards

1
Q

Is Lancashire boiler stationary or movable ?

A

Stationary

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2
Q

Where is Lancashire boiler used ?

A

Sugar mills and textile industry

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3
Q

Why should water reserve be high for Lancashire boiler be high ?

A

Large quantity of steam is needed

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4
Q

Is the Lancashire boiler internally or externally fired ?

A

Internally fired

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5
Q

How many passes does it have for flue gases ?

A

3 passes

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6
Q

Why does Lancashire boiler have good steaming quality (allowing for the use of low quality coal) ?

A

Heats water from three sides

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7
Q

What is the shape of the main shell ?

A

Cylindrical

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8
Q

What is the cylindrical shell mounted on ?

A

A brick structure

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9
Q

How many base flue gas lines are there ?

A

One

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10
Q

How many side flue gas lines are there ?

A

Two

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11
Q

How many flue tubes does the main cylindrical shell have ?

A

Two flue tubes

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12
Q

Where are the flue gases generated ?

A

At the grate

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13
Q

How many grates are there ?

A

Each flue tube has one

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14
Q

In what manner is the grate supported by a bridge ?

A

So that ash and coal do not enter the tube

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15
Q

Where do the flue gases go ?

A

End of the tube and then down

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16
Q

What happens to the flue gases when they reach the front of the boiler ?

A

Get divided into two streams and pass through side flues

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17
Q

Where do the flue gases go after travelling through the side tubes ?

A

Expelled to atmosphere through chimney

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18
Q

What should be the water level in the boiler ?

A

Above the main flue tubes

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19
Q

How is the water heated ?

A

By the passage of outgoing flue gases

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20
Q

How is fuel combustion controlled ?

A

Dampers

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21
Q

What do dampers do ?

A

They reduce the flow of air by partial closing of the passage of the chimney

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22
Q

How are the dampers controlled ?

A

By chain and pulley block from outside

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23
Q

Where are superheaters kept, when they are provided ?

A

End of main flue tubes

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24
Q

What the mountings on top of the Lancashire boiler ?

A

Manhole, safety valve, steam collecting pipe

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25
Q

What are the mountings in front of the Lancashire boiler ?

A

Pressure gauge and water level indicator

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26
Q

What are the mountings provided at the bottom of the Lancashire boiler ?

A

Blow off cock

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27
Q

Where is the fusible plug mounted ?

A

Top of each main flue tube, just above the grate

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28
Q

Why is the efficiency of Lancashire boiler high ?

A

Because of mountings like economizer, superheater, large heat transfer area

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29
Q

Why is the surface area for the burning of coal reduced ?

A

The furnaces are inside the flue tubes

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30
Q

What is another disadvantage of Lancashire boiler ?

A

Occupies a considerable floor area, requiring extensive brick work

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31
Q

Is Babcock and Wilcox boiler a water tube or fire tube boiler ?

A

It is a water tube boiler

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32
Q

How many headers is the main drum of Babcock and Wilcox boiler connected to ?

A

Two inclined headers

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33
Q

What is the function of the inclined headers ?

A

Easy circulation

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34
Q

What are the drum, headers and tubes made up of ?

A

High quality steel

35
Q

Why ?

A

To withstand high pressure and temperature

36
Q

Why are the headers provided with holes ?

A

Cleaning, descaling

37
Q

What does the mud box do ?

A

Collects sediments which are blown off regularly

38
Q

Where is the furnace of the Babcock and Wilcox boiler kept ?

A

Below the front header

39
Q

How are the flue gases passed ?

A

They move back, up and front of the water tubes

40
Q

Why ?

A

To provide maximum surface area of heat transfer

41
Q

Why is there a damper below the chimney ?

A

Control flue gas flow rate into boiler

42
Q

How does water enter the header ?

A

From the drum

43
Q

What happens after the flue gases heat the water ?

A

The density of water reduces

44
Q

How does water get circulated ?

A

By thermosyphon action

45
Q

What is thermosyphon ?

A

It is a physical effect and refers to a method of passive heat exchange based on natural convection, which circulates a fluid without the necessity of a mechanical pump.

46
Q

Where is the superheated steam taken from ?

A

Main stop valve through superheated header

47
Q

What is the boiler supported by ?

A

Metallic slings, or wrought iron girders, supported on pillars

48
Q

What is the major advantage of Babcock and Wilcox boiler ?

A

High steam generation capacity

49
Q

Why can the draft be easily controlled ?

A

Pressure drop through the boiler of the flue gases is negligible

50
Q

Why does Babcock and Wilcox boiler have high initial cost ?

A

Considerable planning and management is required

51
Q

What is another disadvantage, stemming from it’s big size ?

A

Most of the components have to be assembled on site

52
Q

What are the three categories of boiler mountings ?

A

Safety mounting
Control mounting
Inspection mounting

53
Q

What are safety mounting ?

A

Safety valve

Fusible plug

54
Q

What are control mounting ?

A 
Water level indicators
Pressure guage
Steam stop valve
Blow off cock
Feed check valve
55
Q

What are inspection mountings ?

A

Manhole

Mudhole

56
Q

What is the main function of steam stop or junction valve ?

A

Control flow of steam from boiler to steam pipe

57
Q

What is used to operate the steam stop valve ?

A

A hand wheel

58
Q

What connects the hand wheel to the valve ?

A

The spindle

59
Q

What else does the spindle pass through ?

A

Gland or stuffing box

60
Q

What does the gland or stuffing box do ?

A

Stop leakages

61
Q

What is the main function of a blow off cock ?

A

Discharge a portion of water from boiler

62
Q

Why ?

A

To blow out mud, scale, sediments formed on boiler surface

63
Q

How is the blow off cock used during repairs ?

A

TO completely empty the boiler

64
Q

Where is the blow off cock generally fitted on boilers ?

A

Bottom

65
Q

What is a fusible plug ?

A

A hollow body with a hexagonal flange

66
Q

What is a flange ?

A

Internal or external rim for strength

67
Q

What is it made up of ?

A

Gun metal

68
Q

Why does it have a hexagonal flange ?

A

So that it easily fits into the shell

69
Q

What is the main function of the fusible plug ?

A

Protect the boiler from damage when water level is low

70
Q

What happens when water level is low ?

A

The steam causes the fusible plug to melt

71
Q

What happens after it has melted ?

A

The high pressure steam and water rush through the hole to extinguish the alarm

72
Q

Are there any other benefits of this ?

A

It gives an audible warning

73
Q

Where is it fitted ?

A

Over the combustion chamber, above the burning fuel

74
Q

Where are Bourdon pressure gauges mounted ?

A

On top and in front of the boiler

75
Q

Why ?

A

So that they are visible to the operator

76
Q

What is the general capacity of a pressure gauge ?

A

About twice the maximum pressure the boiler is expected to handle

77
Q

How does the Bourdon tube measure pressure ?

A

It expands in proportion to boiler pressure - atmospheric pressure

78
Q

How are the pressure guages connected to the boiler ?

A

Through a siphon tube, connected to an elliptical Bourdon tube, and another siphon tube

79
Q

How many water level indicators are provided in a normal boiler ?

A

Two

80
Q

How are the glass tubes connected to the water and steam levels of the boiler ?

A

Through metallic tubes which have steam and water cocks

81
Q

Why is there a parallel metallic tube to the glass tube ?

A

For safety in case of breakages

82
Q

What are some boiler accessories ?

A 
Feed pump
Economizer
Super heater
Steam Seperator
Air preheater
83
Q

What is the difference in between a mounting and an accessory ?

A

Accessories are not compulsory by law (IBR act), but enhance efficiency

Mechanical Engineering (8 decks)

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