Pe - A2 - Unit 12 - High Pressure Boiler Design

Front 1

Electric boilers are not usually used in _______ heating systems, but are sometimes found in smaller ones. (often used in hospitals, schools and hotels)

Back 1

larger

Front 2

Electric boilers are also used in facilities where large amounts of electricity are available at low ______.

Back 2

cost

Front 3

What are the two general designs of electric boilers?

Back 3

• Electrode type

• Immersion heater type

Front 4

A ___________ type boiler operates at voltages up to 16,000 volts and at the power ratings up to 30,000 kilowatts.

Back 4

electrode

Front 5

In all types of ___________ type boilers, power is supplied to the terminals which are connected to the electrode adapters which pass through insulators to the outside of the shell.

Back 5

electrode

Front 6

Pure water (does or does not) conduct electricity.

Back 6

does not

Front 7

Boiler water is given the proper salinity by the addition of ________.

Back 7

salt

Front 8

In all electrode boilers, the amount of current passing through the water is directly proportional to the length of the ___________ submerged in the water.

Back 8

electrodes

Front 9

Electrode type boilers are completely self-__________.

Back 9

regulating

Front 10

In electrode type boilers, a high pressure limit switch is (required or not required).

Back 10

not required, because at no-load, the pressure will increase enough to force the water out of the generating chamber. The boiler does not need a low-water cutoff either, since the current flow will stop when the level drops below the electrode.

Front 11

In an electrode type boiler, the water supply to the regulating chamber is controlled by a ________ valve which regulates the supply from the feed water pump.

Back 11

float

Front 12

The ___________ boiler is manufactured as a packaged unit.

Back 12

electrode

Front 13

The ___________ heater boiler differs from the electrode boiler in that no electric current travels through the water. Instead, the electric current flows through a heating _________ which is entirely submerged beneath the boiler water level.

Back 13

immersion, element

Front 14

Control of the __________ heater boiler is accomplished by turning on and off the power supply to on, two or more elements as required.

Back 14

immersion

Front 15

The package boiler concept is also used for some immersion heater types. These packaged units may include: controls, feed pumps and condensate tank all within one _______.

Back 15

cabinet

Front 16

The immersion heaters are arranged in the boiler so that they are easily accessible for maintenance or ___________.

Back 16

replacement

Front 17

Advantages of electric boilers:

• very compact

• no fuel storage space required

• quickly & easily installed

• 98% of the energy delivered is absorbed as heat in the boiler

• produce no pollution

• are silent in operation

Back 17

Disadvantages of electric boilers:

• usually high comparative cost of the electricity required

• most designs are limited in pressure to about 21,000 kPa due to the effect of high temperature on the electrodes or elements

Front 18

The immersion heater type boiler capacity can be as high as __________ kW

Back 18

1,500 kW

Front 19

The amount of steam produced by an electrode type boiler depends on the _________ of water in the basket.

Back 19

level

Front 20

Control of the immersion heater boiler is done by turning on and off the __________ of heating elements.

Back 20

number

Front 21

An advantage of an electric boiler is that it has a ________ efficiency of energy transfer form the electricity to the boiler water.

Back 21

high

Front 22

Most electric boilers are limited in pressure to about 2100 kPa due to the effect of high temperature on the ____________ or electrodes.

Back 22

elements

Front 23

The immersion heater boiler has its elements arranged as groups of elements ____________ in the water space.

Back 23

submerged

Front 24

Electric boilers have energy conversion efficiencies close to ________%.

Back 24

100%

Front 25

Control of the immersion heater boiler is done by turning on and off the ________ supply to one or more elements as required.

Back 25

power

Front 26

An immersion electric boiler capacity can be as high as: ______ kW

Back 26

1,500 kW (and for pressures up to 2100 kPa)

Front 27

Electrode type boilers operate at voltages up to ___________ volts.

Back 27

16,000 volts (and power ratings up to 30,000 kilowatts)

Front 28

A steam boiler is basically a closed container, __________ filled with water which is evaporated into team under pressure by the application of heat.

Back 28

partially

Front 29

A ______ _________ boiler is also a closed container, but is completely filled with water. Although it is called a boiler, the water in it does not boil, since no steam is produced.

Back 29

hot water

Front 30

Provincial legislation defines a boiler as a pressure vessel in which a gas or _________ can be generated under pressure, or in which a liquid can be put under pressure, by the direct application of a __________ source.

Back 30

vapour, heat

Front 31

Boilers are typically automated for easier operation but they still require ___________ supervision and maintenance to achieve uninterrupted, efficient and safe operation.

Back 31

regular

Front 32

The satisfactory operation of a biker depends to a great extent on the knowledge that the boiler ________ has of the proper operational and maintenance procedures.

Back 32

operator

Front 33

Read definitions on pages 51-3 to 51-7

Back 33

General boiler terms

Front 34

The earliest steam boiler consisted of a single closed container or shell, partially filled with water and enclosed in a ________ setting which formed a furnace under the shell.

Back 34

brick

Front 35

The part of the boiler through which the heat is transferred from the combustion gases to the boiler water is called the __________ ___________.

Back 35

heating surface

Front 36

A boiler which has its furnace is located outside the shell would be classified as an externally _________ boiler.

Back 36

fired (this boiler design was very inefficient because the heating surface was small and the time the hot gases were in contact with the heating surface was short. Most of the heat went out the chimney instead of being absorbed by the water.

Front 37

Advances in boiler designs have been made through the years. The _______ improved considerably

Back 37

efficiency

The following changes were made:

• the addition of chimney or stacks

• the shell or drum was lengthened

• switch to internally fired method

• increase of heating surface (fire tubes)

Front 38

A boiler _________ is the travel of the combustion gases once along the length of the boiler.

Back 38

pass

Front 39

There are two ways of maximizing the interaction between boiler water and combustion gases. You can pass hot gases through tubes running through the liquid (which are called _______ tubes) or they could pass the water through tubes surrounded by the hot combustion gases(these are called ______ tubes).

Back 39

fire, water

Front 40

The chief aim in modern boiler design is the production of a boiler that will be safe and ____________ in operation and economical in _______ consumption.

Back 40

efficient, fuel

Front 41

The 10 commandments:

1. must have large heating surface

2. all parts exposed to fire must be covered by water

3. must have a thorough circulation of water to prevent overheating

4. must be properly insulated

5. steam space must be large

6. must be readily accessible for inspection

7. must incorporate proper workmanship, simple construction

8. must have strong construction

9. must have proper allowance for expansion and contraction of parts

10. must be furnished with the approved fittings such as gauges and safety valves

Back 41

The boiler should be designed to absurd the maximum amount of heat, at the same time, provide maximum safety and reliability in operation. Design should also feature compactness to keep down building costs.

Front 42

Some boilers have been developed which uses fluids other than _______ as the heat transfer medium.

Back 42

heat

Front 43

High pressure, temperature, and capacity boilers are used for producing __________ power.

Back 43

electrical

Front 44

__________ flooding boilers are used to inject large amounts of heat energy into geological formations.

Back 44

Thermo

Front 45

A steam boiler should be compact in design in order to reduce ________ _________.

Back 45

building costs

Front 46

Power boilers usually require ____ blowdown valves.

Back 46

2

Front 47

High-pressure boilers operate at pressures above _______ kPa

Back 47

103 kPa

Front 48

The low water cut-off is a device fitted to the boiler to shut the _______ valve off if the water level becomes too low.

Back 48

fuel

Front 49

A low pressure steam boiler is one which operates:

a) at 103 kPa

b) above 103 kPa

c) below 103 kPa

d) at or below 103 kPa

Back 49

d) at or below 103 kPa

Front 50

The wind box of a boiler is the ductwork surrounding the __________ on the outside of the boiler into which the air for the burners is introduced.

Back 50

burners

Front 51

An example of a boiler fitting would be a:

a) temperature controller

b) sootblower

c) drum

Back 51

a) temperature controller

Front 52

Boiler structural strength must be at least equal to the various ________ requirements.

Back 52

code

Front 53

A pressure gauge is sometimes called a steam gauge.

A steam gauge indicates the _________ pressure of the boiler.

Back 53

internal

Front 54

On older boilers the brickwork, which tended to surround the furnace was termed the ________ of the boiler.

Back 54

setting

Front 55

The Haycock boiler was used around the year ________.

Back 55

1720

Front 56

An induced draft fan handles flue ________ from the combustion process.

Back 56

gases

Front 57

An early boiler having a longitudinal shell or drum had as its heating surface only the _______ part of the shell

Back 57

lower

Front 58

A boiler component which surrounds the burner of most boilers is the ___________.

Back 58

windbox

Front 59

A device which usually uses air or steam to do its job is the ____________.

Back 59

sootblower

Front 60

A major disadvantage of a firebox boiler is that the ___________ and inspection can be difficult.

Back 60

cleaning

Front 61

For what use was the wetback Scotch boiler primarily designed for? ( ___________ service)

Back 61

marine service

Front 62

What boiler type is built ready for installation? ( _________ boiler)

Back 62

packaged

Front 63

A hot water heating boiler may not exceed __________ kPa operating, nor a water temperature of 121˚C

Back 63

1103 kPa

Front 64

The number of tube ________ are increased to augment the heat transfer capability in a fire tube boiler.

Back 64

passes

Front 65

The firebox boiler is a ______ pass fire tube boiler.

Back 65

two

Front 66

A component used to increase the volume of the steam space in a locomotive boiler was the: (steam _________)

Back 66

steam dome

Front 67

With regard to a steam boiler, the lettering "HRT" means:

Back 67

horizontal return tubular

Front 68

In a packaged firetube boiler the flue gas velocity within the unit is maintained by varying the firetube ___________ area

Back 68

cross-sectional

Front 69

The wetback Scotch boiler was designed primarily for _________ service.

Back 69

marine

Front 70

A ____________ is a water-filled section which surrounds the firebox in locomotive boilers.

Back 70

water leg

Front 71

When the hot combustion gases travel through boiler tubes which are surrounded by the boiler water, the boiler is called a:

Back 71

firetube boiler

Front 72

The water leg was introduced with the ______________ boiler.

Back 72

locomotive

Front 73

A firetube boiler is one which has water on the ___________ of the tubes and the hot gas on the __________ of the tubes.

Back 73

outside, inside

Front 74

A major disadvantage of a firebox is _________ and inspection can be difficult.

Back 74

cleaning

Front 75

A device used to prevent the carry-over of moisture with the steam of an HRT boiler is the _______ pipe.

Back 75

dry

Front 76

The fire line in a fire tube boiler will be the __________ part of the heating surface.

Back 76

highest

Front 77

High pressure _____________ can be of various straight or bent configurations.

Back 77

watertubes

Front 78

The bent tube boiler design allows the tubes to be attached radially on the outside of the ___________.

Back 78

drum

Front 79

Since furnace pressure is often positive in a packaged water tube boiler, to prevent flue gas leakage a ________ casing forms a seal for the furnace.

Back 79

steel

Front 80

In general, the advantages a D-type water tube boiler has over an O-type boiler is that _________ heating surface is available to radiant heat.

Back 80

more

Front 81

The low-pressure water tube and tubular boilers tend to have a _________ initial cost.

Back 81

higher

Front 82

A copper tube tubular boiler can be ________ or oil.

Back 82

gas

Front 83

Large steam generators are usually of the ___________ tube type.

Back 83

water

Front 84

Air heaters in a boiler __________ the temperature of the flue gases going to the stack.

Back 84

reduce

Front 85

A steam generator economiser is usually located between the air preheater and the primary ___________.

Back 85

superheater

Front 86

A package tubular steam boiler often has a steel sheeting in front of the waterfall tube due to the ___________ action of the flame.

Back 86

erosive

Front 87

A cross drum straight tube boiler could have ____________ inclined tubes than a longitudinal drum unit.

Back 87

more

Front 88

The combustion chamber of a serpentine watertube boiler is located ________ the tube.

Back 88

below

Front 89

In a longitudinal straight tube boiler the downcomer feeds ____________ water to a ___________ header.

Back 89

cooler, rear

Front 90

__________ tube watertube boilers make more efficient use of the furnace.

Back 90

Bent

Front 91

The purpose of a superheater is to ____________ the temperature of the _____________.

Back 91

increase, steam

Front 92

In order to keep sale concentrations within safe limits the packaged tubular steam boiler utilizes an automatic __________.

Back 92

blowdown

Front 93

The bent tube boiler design allows the tubes to be attacked radially on the outside of the _________ or __________.

Back 93

shell, drum

Front 94

A disadvantage of the watertube or tubular boiler is water _____________ monitoring.

Back 94

treatment

Front 95

An initial problem with the tubular boiler being used as a steam unit was _____________ ______________ forming scale on the tube.

Back 95

dissolved impurities

Front 96

A problem with a D-type watertube packaged boiler is excessive _____________.

Back 96

vibration

Front 97

Large steam generating units are usually built so that high, pressure, high temperature, and dry steam can be generated in order that large steam __________ can be used to drive electrical _______________.

Back 97

turbines, generators

Front 98

Watertube boilers are better suited to higher pressures than fire tube boilers, because they: (select all that apply)

a) incorporate a bent tube design

b) are larger than fire tube boilers

c) do not have flat surfaces subjected to pressure

d) usually have smaller diameter tubes

e) have smaller diameter drums

Back 98

a) incorporate a bent tube design

b) are larger than fire tube boilers

c) do not have flat surfaces subjected to pressure

d) usually have smaller diameter tubes

e) have smaller diameter drums

Front 99

The common thickness of shells and drums ranges from ________ mm, to ___________ mm.

Back 99

6mm - 250mm

Front 100

Single-welded butt joints have the filler metal applied on __________ side.

Back 100

one

Front 101

Tubes for high pressure service are usually constructed by piercing and ____________.

Back 101

rolling

Front 102

The sections of tube that are welded directly to a boiler drum or header, and to which the main tubes are then welded, are called tube _______.

Back 102

stubs

Front 103

Stays (are or are not) normally required in water tube boilers?

Back 103

they are not, because the surfaces are built to withstand the internal pressures. The ends are rounded unlike fire-tube boilers which have flat ends.

Front 104

In early boilers, furnace walls were constructed of brick. Today this method has been replace by the use of _________ to form the furnace walls.

Back 104

tubes

Front 105

A Morison furnace is found in ___________ boilers.

Back 105

firetube

Front 106

A boiler nozzle attachment is used for connecting a _________ or fitting.

Back 106

valve

Front 107

Boiler stays are used to support __________ surfaces in a boiler.

Back 107

flat

Front 108

A non-destructive test on a boiler is an ___________ test.

Back 108

x-ray or ultrasound

Front 109

Tubes for high pressure service are usually roll and ___________ construction.

Back 109

pierce

Front 110

Boilers supported from the top are free to expand _____________.

Back 110

vertically

Front 111

With regard to welding, heat treatment will __________ stresses in the material due to welding.

Back 111

relieve

Front 112

In welding terminology, the first bead laid in a welding job is referred to as the __________.

Back 112

root

Front 113

Internal furnaces are contained within the ________ of the boiler.

Back 113

shell

Front 114

Manholes are provided for ___________ purposes.

Back 114

inspection

Front 115

Firetube boilers have their tubes fixed into flat steel plates, otherwise knows as heads or _________ sheets.

Back 115

tube

Front 116

In firetube boilers, longitudinal or ___________ stays are often used to support the area of the tube sheets below the tubes.

Back 116

through

Front 117

A Morison type furnace is of the ________-tube variety.

Back 117

fire