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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
What are the mountings in front of the Lancashire boiler ?
Pressure gauge and water level indicator
26
What are the mountings provided at the bottom of the Lancashire boiler ?
Blow off cock
27
Where is the fusible plug mounted ?
Top of each main flue tube, just above the grate
28
Why is the efficiency of Lancashire boiler high ?
Because of mountings like economizer, superheater, large heat transfer area
29
Why is the surface area for the burning of coal reduced ?
The furnaces are inside the flue tubes
30
What is another disadvantage of Lancashire boiler ?
Occupies a considerable floor area, requiring extensive brick work
31
Is Babcock and Wilcox boiler a water tube or fire tube boiler ?
It is a water tube boiler
32
How many headers is the main drum of Babcock and Wilcox boiler connected to ?
Two inclined headers
33
What is the function of the inclined headers ?
Easy circulation
34
What are the drum, headers and tubes made up of ?
High quality steel
35
Why ?
To withstand high pressure and temperature
36
Why are the headers provided with holes ?
Cleaning, descaling
37
What does the mud box do ?
Collects sediments which are blown off regularly
38
Where is the furnace of the Babcock and Wilcox boiler kept ?
Below the front header
39
How are the flue gases passed ?
They move back, up and front of the water tubes
40
Why ?
To provide maximum surface area of heat transfer
41
Why is there a damper below the chimney ?
Control flue gas flow rate into boiler
42
How does water enter the header ?
From the drum
43
What happens after the flue gases heat the water ?
The density of water reduces
44
How does water get circulated ?
By thermosyphon action
45
What is thermosyphon ?
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
Where is the superheated steam taken from ?
Main stop valve through superheated header
47
What is the boiler supported by ?
Metallic slings, or wrought iron girders, supported on pillars
48
What is the major advantage of Babcock and Wilcox boiler ?
High steam generation capacity
49
Why can the draft be easily controlled ?
Pressure drop through the boiler of the flue gases is negligible
50
Why does Babcock and Wilcox boiler have high initial cost ?
Considerable planning and management is required
51
What is another disadvantage, stemming from it's big size ?
Most of the components have to be assembled on site
52
What are the three categories of boiler mountings ?
Safety mounting Control mounting Inspection mounting
53
What are safety mounting ?
Safety valve | Fusible plug
54
What are control mounting ?
``` Water level indicators Pressure guage Steam stop valve Blow off cock Feed check valve ```
55
What are inspection mountings ?
Manhole | Mudhole
56
What is the main function of steam stop or junction valve ?
Control flow of steam from boiler to steam pipe
57
What is used to operate the steam stop valve ?
A hand wheel
58
What connects the hand wheel to the valve ?
The spindle
59
What else does the spindle pass through ?
Gland or stuffing box
60
What does the gland or stuffing box do ?
Stop leakages
61
What is the main function of a blow off cock ?
Discharge a portion of water from boiler
62
Why ?
To blow out mud, scale, sediments formed on boiler surface
63
How is the blow off cock used during repairs ?
TO completely empty the boiler
64
Where is the blow off cock generally fitted on boilers ?
Bottom
65
What is a fusible plug ?
A hollow body with a hexagonal flange
66
What is a flange ?
Internal or external rim for strength
67
What is it made up of ?
Gun metal
68
Why does it have a hexagonal flange ?
So that it easily fits into the shell
69
What is the main function of the fusible plug ?
Protect the boiler from damage when water level is low
70
What happens when water level is low ?
The steam causes the fusible plug to melt
71
What happens after it has melted ?
The high pressure steam and water rush through the hole to extinguish the alarm
72
Are there any other benefits of this ?
It gives an audible warning
73
Where is it fitted ?
Over the combustion chamber, above the burning fuel
74
Where are Bourdon pressure gauges mounted ?
On top and in front of the boiler
75
Why ?
So that they are visible to the operator
76
What is the general capacity of a pressure gauge ?
About twice the maximum pressure the boiler is expected to handle
77
How does the Bourdon tube measure pressure ?
It expands in proportion to boiler pressure - atmospheric pressure
78
How are the pressure guages connected to the boiler ?
Through a siphon tube, connected to an elliptical Bourdon tube, and another siphon tube
79
How many water level indicators are provided in a normal boiler ?
Two
80
How are the glass tubes connected to the water and steam levels of the boiler ?
Through metallic tubes which have steam and water cocks
81
Why is there a parallel metallic tube to the glass tube ?
For safety in case of breakages
82
What are some boiler accessories ?
``` Feed pump Economizer Super heater Steam Seperator Air preheater ```
83
What is the difference in between a mounting and an accessory ?
Accessories are not compulsory by law (IBR act), but enhance efficiency

Mechanical Engineering (8 decks)

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