Ch. 3 - Watertube Boilers

Front 1

Advantages of Watertube Boilers over Firetube Boilers

Back 1

-Available to produce higher temps. and press. than Firetube Boilers

-Can produce much higher horsepower than Firetube Boilers

-Due to smaller volume of water in relation to the boiler hp, can responds more rapidly to steam demand changes

-Operate at higher efficiencies

-Able to burn more types of fuels

-Less likely to experience a boiler explosion than Firetube Boilers

Front 2

Disadvantages of Watertube Boilers

Back 2

-Require extensive setting

-Initial cost much higher

Front 3

Watertube components

Back 3

-Down comer tubes

-Generating tubes

-Screen tubes

-Waterwall tubes

-Superheaters

Front 4

Downcomer tubes

Back 4

large tubes or banks of tubes that supply water from the steam drum to the mud drum and the waterwall header

Front 5

Generating tubes

Back 5

banks of tubes used to convert water into steam

Front 6

Screen tubes

Back 6

banks of tubes that are placed between the radiant area of the furnace and the superheater

Front 7

Waterwall tubes

Back 7

banks of tubes that line the inside of the boiler and transfer heat to the boiler water to produce steam. The use of waterwall tubes allows the boiler to be constructed using less refractory and insulation.

Front 8

Superheaters

Back 8

banks of tubes that receive dry saturated steam and use the heat in the flue gas to raise the temp. of the steam

Front 9

Types of Superheaters

Back 9

-Radiant

-Convection

-Combination

Front 10

Radiant Superheaters

Back 10

superheaters located in the radiant section of the furnace

Front 11

Convection Superheaters

Back 11

superheaters located further back in the combustion gas stream of the boiler

Front 12

Combination Superheaters

Back 12

a superheater in which some of the tubes are in the radiant section and some of the tubes are in the combustion gas stream of the boiler

Front 13

Economizer function and benefit

Back 13

Function-utilizes heat from the exhaust flue gas to preheat the incoming feedwater

Benefits-for every 10Fahrenheit increase in feedwater inlet temp. results in a 1% increase in boiler efficiaency

Front 14

Air Preheater function and benefit

Back 14

Function-recovers heat from flue gas for preheating combustion air before it enters the burner

Benefit-1% efficiency per 40Fahrenheit air temp. rise

Front 15

Types of Watertube Boilers

Back 15

1. Straight tube watertube boiler

2. Bent tube watertube boiler

3. Cast Iron Sectional boiler

4. Flexible watertube boiler

Front 16

Straight tube boilers notes

Back 16

-Steam drum acts as a collection point for steam and water

-Steam drum has sufficient volume for steam to separate from water prior to leaving boiler

-Boiler tubes are pitched (slanted) from front to back to allow for sediment to collect in rear header for blowdown

Front 17

Types of Bent tube boilers

Back 17

-Stirling

-O type watertube boiler

-D type watertube boiler

-A type watertube boiler

Front 18

What is waterwall and its functions?

Back 18

relatively close spaced vertical tubes forming the four walls of the furnace.protect the insulated walls of the furnace; absorb heat from the furnace to increase the units generating capacity; make the furnace airtight (on pressurized furnaces with tangent-welded tubes)

Front 19

"D" Type Watertube boiler

Back 19

Front 20

A _____ drum below the steam drum is used to collect sediment and was blown out from time to time.

Back 20

mud

Front 21

A ____ _____ is constructed of flat plates, referred to as a tube sheet and tube cap sheet.

Back 21

box header

Front 22

Sulfur in the soot then unites with moisture from condensation to produce a ________ ______ .

Back 22

sulfurous acid

Front 23

Welding a flat strip of metal between the waterwall tubes is known as __________ wall construction.

Back 23

membrane

Front 24

_______ consist of relatively close-spaced vertical tubes forming the four walls of the furnace. These tubes help to protect the refractory of the boiler.

Back 24

Waterwall

Front 25

On HRT boilers, the shell is pitched 1 to 2 inches towards the back of the boiler to produce a more effective _______ _______ of the boiler.

Back 25

bottom blowdown

Front 26

______ is the transfer of heat from a liquid flowing over the suface of a body.

Back 26

Convection

Front 27

______ ______ is caused by the difference in density of a liquid due to a difference in temperature.

Back 27

Natural convection

Front 28

Water at it's boiling point is considered _______ liquid.

Back 28

saturated

Front 29

The ratio of the boiler's heat output to it's heat input is _______ ______ .

Back 29

boiler efficiency

Front 30

A power boiler is a steam boiler that operates at pressures greater than ____ psi., or a hot water boiler that operates above ____ or _____ .

Back 30

15

160psi

250 degrees Fahrenheit

Front 31

A supercritical boiler is a boiler that operates in excess of ______ or _______ .

Back 31

3206psia

705 degrees Fahrenheit

Front 32

A boiler horsepower is the evaporation into dry saturated steam of ______ pounds per hour from and at 212 degrees Fahrenheit.

Back 32

34.5

Front 33

______ btu's per hour output is one boiler horsepower.

Back 33

33475

Front 34

The maximum voltage allowable on a control circuit is _____ volts.

Back 34

150

Front 35

A low pressure steam boiler must have an ASME ____ stamp

Back 35

H

Front 36

A high pressure boiler must have an ASME ____ stamp.

Back 36

S