boiler tubes. waterwall header steam drum (wrapper sheet) economizer tubes screen tubes superheater...

Boiler Tubes

Waterwall Header

Steam Drum (Wrapper Sheet)

Economizer Tubes

Screen TubesSuperheater Tubes

Water Drum

Downcomer

Generating Tubes

Tube Sheet

Air in

Waterwall Tube

Classification of TubesClassification of Tubes

Generating TubesGenerating Tubes Screen TubesScreen Tubes DowncomersDowncomers Superheater TubesSuperheater Tubes Water Wall Tubes (Roof Tubes and Floor Tubes)Water Wall Tubes (Roof Tubes and Floor Tubes) Support TubesSupport Tubes RisersRisers Circulating TubesCirculating Tubes

Boiler TubesBoiler Tubes

Tubes Required for One BoilerTubes Required for One BoilerTube TypeTube Type NumberNumber O.D.O.D. Wall ThicknessWall Thickness

Screen tubes – Two RowsScreen tubes – Two Rows 30 each30 each 2.0”2.0” 0.165”0.165”

Generating Tubes – 19 RowsGenerating Tubes – 19 Rows 60 each60 each 1.25”1.25” 0.120”0.120”

Refactory Retainer Waterwall TubesRefactory Retainer Waterwall Tubes 2828 2.0”2.0” 0.165”0.165”

Rear Waterwall TubesRear Waterwall Tubes 4545 2.0”2.0” 0.165”0.165”

Side Waterwall FeedersSide Waterwall Feeders 1919 2.0”2.0” 0.165”0.165”

Rear Waterwall FeedersRear Waterwall Feeders 1919 2.0”2.0” 0.165”0.165”

Rear Waterwall RisersRear Waterwall Risers 2929 2.0”2.0” 0.165”0.165”


Tubes Required for One BoilerTubes Required for One BoilerTube TypeTube Type NumberNumber O.D.O.D. Wall ThicknessWall Thickness

DowncomersDowncomers 88 4.0”4.0” 0.203”0.203”

Superheater SupportSuperheater Support 22 3.0”3.0” 0.203”0.203”

Superheater – 1Superheater – 1stst Pass Pass 5454 1.25”1.25” 0.120”0.120”

Superheater – 2Superheater – 2ndnd Pass Pass 5151 1.25”1.25” 0.120”0.120”

Superheater – 3Superheater – 3rdrd Pass Pass 5151 1.25”1.25” 0.120”0.120”

Superheater – 4Superheater – 4thth Pass Pass 4545 1.25”1.25” 0.120”0.120”

Superheater – 5Superheater – 5thth Pass Pass 4242 1.25”1.25” 0.120”0.120”

Economizer ElementsEconomizer Elements 7272 2.0”2.0” 0.165”0.165”

Generating TubesGenerating Tubes

Generating tubes make up the main tube Generating tubes make up the main tube bank of the boiler. They generate steam bank of the boiler. They generate steam from the water within. These tubes are from the water within. These tubes are generally small in diameter in order that generally small in diameter in order that the boiler will have a high evaporation rate the boiler will have a high evaporation rate and a fast response.and a fast response.

Screen TubesScreen Tubes

Screen tubes are large diameter water Screen tubes are large diameter water tubes placed between the fires and the tubes placed between the fires and the main generating tube bank, or between main generating tube bank, or between the fires and the superheater tubes. They the fires and the superheater tubes. They protect these smaller tubes from the protect these smaller tubes from the intense radiant heat.intense radiant heat.

Usually consist of 2 to 4 rows of tubesUsually consist of 2 to 4 rows of tubes

DowncomersDowncomers

Downcomers supply the lower water Downcomers supply the lower water drums and waterwall headers with water drums and waterwall headers with water from the steam and water drum.from the steam and water drum.

Downcomers are the largest diameter Downcomers are the largest diameter tubes in the boiler.tubes in the boiler.

Downcomer are located away from the Downcomer are located away from the boiler heat source, possibly behind the boiler heat source, possibly behind the generating tubes, between the inner and generating tubes, between the inner and outer boiler casing or outside the boiler.outer boiler casing or outside the boiler.

DowncomersDowncomers

The design capacity of the downcomers The design capacity of the downcomers depends on:depends on: The total capacity on the generating The total capacity on the generating

tubes in weight of water evaporated per tubes in weight of water evaporated per hourhour

The desired circulation characteristics of The desired circulation characteristics of the boilerthe boiler

Water Wall TubesWater Wall Tubes

Water wall tubes are tubes installed along Water wall tubes are tubes installed along the walls, floor and roof of the furnace and the walls, floor and roof of the furnace and either freely exposed, partially covered, or either freely exposed, partially covered, or completely embedded in the refractory of completely embedded in the refractory of the boiler.the boiler.

Water is supplied to the water wall tubes Water is supplied to the water wall tubes from the steam and water drum by from the steam and water drum by downcomers and headers.downcomers and headers.


Steam generated in the water wall tubes is Steam generated in the water wall tubes is returned to the steam and water drum by returned to the steam and water drum by means of water wall headers and risers or means of water wall headers and risers or may be returned to the rear header in the may be returned to the rear header in the straight tube boiler.straight tube boiler.


Advantages of Water Wall Tubes are:Advantages of Water Wall Tubes are: Water wall tubes protect the refractory of the Water wall tubes protect the refractory of the

boilerboiler The absorption of large amounts of heat from The absorption of large amounts of heat from

the furnace which permits higher combustion the furnace which permits higher combustion ratesrates

They increase the steam generating capacity They increase the steam generating capacity of the boilerof the boiler


The reduction of maintenance of the The reduction of maintenance of the refractory by maintaining lower brickwork refractory by maintaining lower brickwork temperature.temperature.

The equalization of furnace temperatureThe equalization of furnace temperature


Types of water wall tubesTypes of water wall tubes Bare tubes fully exposed in the furnaceBare tubes fully exposed in the furnace Partially studded and partially covered Partially studded and partially covered

with refractory (Plastic Chrome Ore)with refractory (Plastic Chrome Ore) Fully studded and completely covered Fully studded and completely covered

with refractory.with refractory.


The reason for the studding is to serve as The reason for the studding is to serve as an anchor for the refractory and to an anchor for the refractory and to absorb heat from the refractory and absorb heat from the refractory and transfer it by conduction in the tubestransfer it by conduction in the tubes

Support TubesSupport Tubes

Support tubes are large diameter, thick Support tubes are large diameter, thick walled water tubes used in vertical tube walled water tubes used in vertical tube boilers for support of the upper steam and boilers for support of the upper steam and water drum. water drum.

The support tubes may have hangers The support tubes may have hangers attached along their length for the purpose attached along their length for the purpose of giving support to the superheater tubesof giving support to the superheater tubes

RisersRisers

Risers are large diameter tubes that return Risers are large diameter tubes that return the steam and water mixture from the the steam and water mixture from the waterwalls back to the steam and water waterwalls back to the steam and water drum.drum.

A closed circuit comprising the steam and A closed circuit comprising the steam and water drum, the downcomers, the water water drum, the downcomers, the water wall tubes, water wall headers and risers wall tubes, water wall headers and risers is thus formedis thus formed

Circulating TubesCirculating Tubes

Circulating tubes are large diameter found Circulating tubes are large diameter found in straight sectional header boilers in straight sectional header boilers connecting the rear sectional headers with connecting the rear sectional headers with the steam and water drum.the steam and water drum.

Their purpose is to return steam and water Their purpose is to return steam and water mixture that collects in the rear headers mixture that collects in the rear headers back to the steam and water drumback to the steam and water drum


What is the difference between a tube and What is the difference between a tube and pipe?pipe?


Boiler tubes are designated by their Boiler tubes are designated by their outside diameteroutside diameter

Wall thickness is determined by boiler Wall thickness is determined by boiler pressure they will be subjected topressure they will be subjected to

Boiler tube size will determine how quickly Boiler tube size will determine how quickly boiler can respond to change of load boiler can respond to change of load demands (surface area vs. volume)demands (surface area vs. volume)


Boiler tubes are secured to the tube Boiler tubes are secured to the tube sheets by rolling or weldingsheets by rolling or welding

Leaking tubes are plugged or replacedLeaking tubes are plugged or replaced

Boiler TubesBoiler Tubes The wall thickness is usually designated The wall thickness is usually designated

by BWG – Birmingham Wire Gauge.by BWG – Birmingham Wire Gauge. Tube are made out of seamless steel or Tube are made out of seamless steel or

seamless high temperature steel alloys seamless high temperature steel alloys depending on the location in the boiler.depending on the location in the boiler.


Boiler tube size will determine how quickly Boiler tube size will determine how quickly boiler can respond to change of load boiler can respond to change of load demands (surface area vs. volume)demands (surface area vs. volume)

The tubes are long enough to allow the The tubes are long enough to allow the tube to extend a minimum of ¼” and not tube to extend a minimum of ¼” and not more than ½” beyond the end of the tube more than ½” beyond the end of the tube sheet.sheet.

Pipe (1/8” to 12”) is designated by its Pipe (1/8” to 12”) is designated by its nominal diameter.nominal diameter.

Boiler Tube SizeBoiler Tube Size The size of the tubes have a large bearing The size of the tubes have a large bearing

on the operating characteristics of the on the operating characteristics of the boiler.boiler.

As the size of the tube used in As the size of the tube used in construction of the boiler is reduced the construction of the boiler is reduced the ratio of heating surface are per unit ratio of heating surface are per unit volume of water becomes larger.volume of water becomes larger.

Since more small sized tubes can be Since more small sized tubes can be placed in the same space, more heating placed in the same space, more heating surface is obtainedsurface is obtained

Boiler Tube SizeBoiler Tube Size

Greater heating surface areas per unit Greater heating surface areas per unit volume of water and more tubes result in volume of water and more tubes result in higher evaporation rates.higher evaporation rates.

High evaporation rates result in a boiler High evaporation rates result in a boiler with a fast response to changes in load.with a fast response to changes in load.


Calculate the surface area and volume of Calculate the surface area and volume of Boiler tube which is 4 inches in diameter Boiler tube which is 4 inches in diameter and 1 inch long.and 1 inch long.


Surface area equals tube circumference X Surface area equals tube circumference X tube length.tube length.

Area = Area = ΠΠD*LD*L Area = 3.14*4*1Area = 3.14*4*1 Area = 12.5664 inArea = 12.5664 in22


Volume equals cross section area times Volume equals cross section area times length.length.

Volume = (Volume = (ΠΠ/4)*D/4)*D22*L*L Volume = .7854 * (4*4) * 1Volume = .7854 * (4*4) * 1 Volume = 12.5664 inVolume = 12.5664 in33


Ratio of surface area to volume containedRatio of surface area to volume contained Surface Area/VolumeSurface Area/Volume Surface Area/Volume = 12.5664/12.5664Surface Area/Volume = 12.5664/12.5664 Surface Area/Volume = 1 to 1 ratioSurface Area/Volume = 1 to 1 ratio


Calculate the surface area and volume of Calculate the surface area and volume of Boiler tube which is 2 inches in diameter Boiler tube which is 2 inches in diameter and 1 inch long.and 1 inch long.


Surface area equals tube circumference X Surface area equals tube circumference X tube length.tube length.

Area = Area = ΠΠD*LD*L Area = 3.14*2*1Area = 3.14*2*1 Area = 6.2832 inArea = 6.2832 in22


Volume equals cross section area times Volume equals cross section area times length.length.

Volume = (Volume = (ΠΠ/4)*D/4)*D22*L*L Volume = .7854 * (2*2) * 1Volume = .7854 * (2*2) * 1 Volume = 3.1416 inVolume = 3.1416 in33


Ratio of surface area to volume containedRatio of surface area to volume contained Surface Area/VolumeSurface Area/Volume Surface Area/Volume = 6.2832/3.1416Surface Area/Volume = 6.2832/3.1416 Surface Area/Volume = 2 to 1 ratioSurface Area/Volume = 2 to 1 ratio


The 2” tube has twice the surface area to The 2” tube has twice the surface area to volume then the 4” tube.volume then the 4” tube.

So the 2” tube will have a evaporation rate So the 2” tube will have a evaporation rate twice that of the 4” tube.twice that of the 4” tube.


Calculate the velocity of the water thru the Calculate the velocity of the water thru the same 2” and 4 inch tubes for a 600 psia same 2” and 4 inch tubes for a 600 psia boiler.boiler.

ṁ = ṁ = ρρVAVA ṁ = Mass Flow (lbs/hr)ṁ = Mass Flow (lbs/hr) ρρ = Density (lbs/ft = Density (lbs/ft33)) V = Velocity (ft/sec)V = Velocity (ft/sec) A = Area (ftA = Area (ft22))


ṁ = ṁ = ρρVAVA ṁ = VA/ṁ = VA/ννspec spec ννspecspec = Specific = Specific

VolumeVolume ṁ = 60,000 lbs/hrṁ = 60,000 lbs/hr From Steam Tables From Steam Tables ννff = =


ννf f = 0.02013 ft= 0.02013 ft33/lbm/lbm

Area of the 2” tube isArea of the 2” tube is


ννf f = 0.02013 ft= 0.02013 ft33/lbm/lbm

Area of the 2” tube is Area of the 2” tube is A = A = ΠΠDD22/4/4 A = 3.14*((2/12)A = 3.14*((2/12)22)/4)/4 A = 0.0216 ftA = 0.0216 ft22


ṁ = VA/ṁ = VA/ννff

60,000 lbs/hr = V * 0.0216 ft60,000 lbs/hr = V * 0.0216 ft2 2 / / 0.02013 ft0.02013 ft33/lbm/lbm


Velocity = 15.53 ft/secVelocity = 15.53 ft/sec


Calculate the velocity of the water thru the Calculate the velocity of the water thru the 4 inch tube for a 600 psia boiler.4 inch tube for a 600 psia boiler.

ṁ = ṁ = ρρVAVA A = A = ΠΠDD22/4/4 A = 3.14*((4/12)A = 3.14*((4/12)22)/4)/4 A = 0.087 ftA = 0.087 ft22


ṁ = VA/ṁ = VA/ννff

60,000 lbs/hr = V * 0.087 ft60,000 lbs/hr = V * 0.087 ft2 2 / / 0.02013 ft0.02013 ft33/lbm/lbm


Velocity = 3.85 ft/secVelocity = 3.85 ft/sec


Boiler Tubes are secured to the drums or Boiler Tubes are secured to the drums or headers by rolling or welding.headers by rolling or welding.


The drum or header which the tube is The drum or header which the tube is going to rolled must be clean a free of any going to rolled must be clean a free of any chemicals, dirt or any other solids.chemicals, dirt or any other solids.

The holes must clean and be as perfectly The holes must clean and be as perfectly circular as possible.circular as possible.

The ends of the tubes should extend The ends of the tubes should extend beyond the drum or header by ¼ to 3/8 beyond the drum or header by ¼ to 3/8 inches.inches.


The tubes are usually held in place by The tubes are usually held in place by collars on either end of the tubes on the collars on either end of the tubes on the outside of the drums or headersoutside of the drums or headers


Once the tube is securely held in place Once the tube is securely held in place and expanding or rolling tool is place and expanding or rolling tool is place inside the tube and expands diameter of inside the tube and expands diameter of tube against the metal of the drum or tube against the metal of the drum or header.header.

When the tube is expanded and is secured When the tube is expanded and is secured the portion of the tube which is extending the portion of the tube which is extending out in the drum or header is them flared or out in the drum or header is them flared or “belled” with a belling tube.“belled” with a belling tube.


This aids in reducing fluid friction as water This aids in reducing fluid friction as water enters or leaves the tubes.enters or leaves the tubes.

When all the tubes have been rolled the When all the tubes have been rolled the boiler is closed and filled with water.boiler is closed and filled with water.

The water pressure is pumped up to 1.5 The water pressure is pumped up to 1.5 times the design pressure (Mean times the design pressure (Mean Allowable Working Pressure – MAWP).Allowable Working Pressure – MAWP).

If any tubes leak the are then rerolled and If any tubes leak the are then rerolled and retested.retested.


Tubes the are secured in the boiler by Tubes the are secured in the boiler by welding must be done by a certified welder welding must be done by a certified welder with a certified welding procedure which with a certified welding procedure which must be approved by the U.S.C.G. and the must be approved by the U.S.C.G. and the American Bureau of Shipping (ABS).American Bureau of Shipping (ABS).

After all the tubes have been welded in After all the tubes have been welded in place the boiler will require a 1.5 times place the boiler will require a 1.5 times MAWP hydro test.MAWP hydro test.


The Coast Guard or ABS my require that The Coast Guard or ABS my require that some or all the welds be X-Rayed.some or all the welds be X-Rayed.

If there are any leaks, the weld will have to If there are any leaks, the weld will have to be ground out and then rewelded.be ground out and then rewelded.

The boiler will have to be retested.The boiler will have to be retested. If you have to do any welding repairs on If you have to do any welding repairs on

the boiler, you are required to notify the the boiler, you are required to notify the Coast Guard at your first port of call.Coast Guard at your first port of call.

Leaking Boiler TubesLeaking Boiler Tubes

If it is determined that you have a leaking If it is determined that you have a leaking boiler tube and the boiler tube can not be boiler tube and the boiler tube can not be replaced. The boiler tube will have to replaced. The boiler tube will have to plugged.plugged.

You will have to determine which tube is You will have to determine which tube is leaking.leaking.

This is usually done by filling the boiler This is usually done by filling the boiler with water and pressurizing it.with water and pressurizing it.


Once you have determined which boiler Once you have determined which boiler tube is leaking you have to gain access to tube is leaking you have to gain access to it on the waterside of the boiler.it on the waterside of the boiler.

The tube is then plugged at both ends with The tube is then plugged at both ends with metal plugs that are part of the spare parts metal plugs that are part of the spare parts for the boiler.for the boiler.

You must ensure that the tube you are You must ensure that the tube you are plugging has a hole in it.plugging has a hole in it.


If you do not hole the tube its is possible If you do not hole the tube its is possible that the air in the tube will expand while that the air in the tube will expand while the boiler is being brought up to pressure the boiler is being brought up to pressure and blow out the plugs.and blow out the plugs.

boiler tubes. waterwall header steam drum (wrapper sheet) economizer tubes screen tubes superheater...

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