58194986 Boiler Construction Ppt

7/31/2019 58194986 Boiler Construction Ppt

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Boiler

Construction

62b - 203


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IntroductionObjectives

Know function, purpose and

location of boiler components

Describe path of a drop of

water/steam through boilerDescribe the flow path of

combustion gases


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Boiler Types

Main propulsion

Supply steam to propulsionturbines and auxiliary equipment

Auxiliary

Supply steam to auxiliary services

only


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600 PSI D Type Lighter and smaller than M type

Both 600 and 1200 psi steam

Superheater protection required during light-off and securing

Uncontrollable superheat

Superheater temperature is directly

proportional to firing rate and steam demand


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Navy Boiler DesignReliability

Flexibility

Wide range of steam loads Rapid changes

Responsive to automatic controls

Relatively compact


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Navy Boiler Design

Efficient operation

5 different heat exchangers

Combustion air Economizer

Furnace

Superheater Desuperheater

Accessability for cleaning and repair


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Boiler Construction

Watersides

Firesides

Casings


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Watersides


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Watersides

Economizer

Steam drum

Water drum

Headers

Downcomers Blowdown piping

Tubes

Generating

Screen

Furnace circuit

Superheater Desuperheater


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Economizer

Multi-pass heat exchanger

Top of boiler at uptake (stack)

Combustion gases pass through


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Economizer

Feedwater in tubes heated

Inlet temp 246 F

Outlet temp 440 F

Vents


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Economizer

2 inch tubes with fins or ringsattached

Attached to the inner casing

Element ends between casings

Check valve between outlet andfeed piping to steam drum


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Steam Drum

Collects steam

Separates moisture

Receives feedwater and distributes

boiler water

Provides a water reservoir


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Steam Drum

Steel cylinder at top of boiler

Four piece construction

Upper half called WRAPPER PLATE

Lower half called TUBE SHEET

Tubes penetrate tube sheet

Disc surfaces welded on each end;manway doors for access


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Steam DrumDrum penetrations

Feed inlet

Saturated steam pipe(outlet)

downcomers & tubes Three safety valve flanges

Surface blow pipe

Two drum level transmitter lines

Two gage glass lines

Drum vents(air cock)

Injection flange(blanked)


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Steam Drum

Baffle plates / apron plates

Attachment framing supports drum

internals

Separate steam/water mixture from

feedwater in the drum

Direct steam mixture to moisture

separators


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Steam Drum Moisture separators

Primary separators

Cyclone separators impart swirling motion to

steam/waterHeavy water flung to sides and back down

Secondary separators

Chevron separators / corrugated scrubbers

change direction of steam rapidly

Moisture hits scrubber & drains down


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Steam Drum

Dry pipe / dry box

Collects steam as it exits scrubbers

Collected steam comes into contact with

safety valves and vents

Directs steam to saturated outlet piping


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Steam Drum Internal feed pipe

Pipe runs length of drum with holes at equal

intervals

Distributes incoming feedwater evenly

Surface blow pipe

Pipe runs length of drum with holes at equal

intervals

Removes contaminates from water surface


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Steam Drum

Receives water from economizer

Distributed through internal feedpipe


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Steam Drum

Water flows to ends & into

downcomers

To water drum and headers


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Downcomers

Large diameter piping (4- 8)

Send water from steam drum to

water drum/ headers


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Downcomers

Located between inner and outer

casings

Path for cool, dense water to flow

down


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Water Drum

Receives water from the steam drum

Distributes water to the generating

tubes

Collects sludge and solid matter

Has bottom blow connections toremove sludge


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Water Drum

Upper half is TUBE SHEET

Bottom half is WRAPPERPLATE

Drum heads welded with one

manway for access


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Headers

Similar purpose, but smaller than

water drum

Distribute water to side wall, rear

wall, and screen tubes


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Headers

Handhole plugs for access

Bottom blow connections to remove

sludge


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Boiler Tubes

Generating tubes (1" diameter)

Connect water and steam drumMost numerous tubes in boiler

Generate the majority of steamSonic baffles


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Boiler Tubes Furnace circuit tubes (1. 5 -2")

Connect rear wall & side wall headers to steamdrum

Protect furnace refractory Generate some steam

Water screen tubes

Connect water and steam drum Protect s/h tubes from direct radiant heat


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SuperheaterReceives all steam from steam drum

Raises steam temp above saturation

Vertically or horizontallyconfigured

Multi-pass heat exchanger

Two headers support tubes

Backfill valves


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Superheater

Tubes (1.5" dia) connected to

headers at each end

Tubes bent in u shape


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Superheater

Headers have handhole plugs

Steam flow required to protect s/h

from heat during start up &

shutdown


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Desuperheater

Heat exchanger in either water drum or

steam drum

Reduces superheated temperature forlower energy applications (auxiliaries)

Reduces material cost and QA

requirements

Multi-pass tube loop


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Desuperheater

Must verify desuperheater inlet

valve locked open prior to

operating or hydrostatic test of

boiler

If valve is shut, pressure differentialwill crush the desuperheater


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Blowdown Piping

Surface blow - steam drum Control water chemistry

Surface blow while steaming boiler

Bottom blow - water drum andheaders Removes sludge

Only when boiler secured


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Firesides


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Furnace

Steel inner casing

Space for combustion

225 cubic ft of air to 1 lb of fuel Lined with refractory

Insulates inner casing from high temperature(3000o F)

Directs gases over the tubes

Protect headers from flame and radiant heat


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Refractory Types Firebrick

Inner furnace wall

Fire/temp resistant to 3000 F

1/10 insulation cap. Of insulating block Insulating brick

Insulate to 2500 F

Cannot withstand flame

Intermediate insulation


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Refractory Insulating block

Insulate to 1500o F

Cannot withstand flame; Good insulator

1" layer next to inner casing Silicon baffle tiles

High strength heat conductor

Between screen tubes

Directs gas flow through the superheater


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Refractory

Refractory mortar

Seals joints; Cushions against stress

Two types (both air dry)Class 1: dry - for firebrick & tile

Class 2: ready mixed - for insulating brick

Burner tile

Shaped to fit specific burner

Protect burner assembly/casing


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Refractory Anchors

Anchor bolts

Secure firebrick and burner tile

Bolt clips welded to inner casing

Anchor clips

Hold insulating brick to inner casing

Anchor strips

Hold castable in place


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Refractory Installation

Depot level work

S/f repair only

Anchor bolts a must

Paint metal surfaces

Expansion joints 1/4" Styrofoam between every 4th rowof brick; Then burn away


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Refractory Life

Aging factors

Rapid temperature changesShock and vibration

Boiler panting


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Fuel Oil Burners

Atomizer assemblies

Burner barrel

SSD

Air registers

Bladed cone Diffuser


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Soot Blowers

Location

Fixed elementsRotary elements


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Casings


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Boiler Casings Two steel casings

Inner casing holds furnace/tubes

Outer casing holds accessories

Space between is combustion air path Advantages

Reduces heat loss

Preheats combustion air

Reduces fireroom temperatures


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Boiler Casings

Inner casing leaks Lower furnace temp- combustion/fuel

increase

Thermal stress in refractory

Forced draft blowers speed up Fuel inefficient


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Boiler Casings

Outer casing leaks

Increase fireroom temperature

Combustion gases may enterfireroom

Forced draft blowers speed upFuel inefficient


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Boiler Casings

Steam smothering system

Boiler air casing fires

Fuel on furnace deck


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Combustion Air Path

Intake plenum

Forced draft blower supply

Inner and outer casing

Air register

Gas path

Exit through economizer and out stack


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Monitoring Exhaust Gases

Periscope

Smoke indicators / stack gasanalyzers


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Boiler Foundations

Fixed saddles or feet

One end of drums & headersBolted fast to hull girder


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Boiler Foundations

Sliding feet

Other end of drums & headers

Oblong bolt holes for movementLubrication points for grease

AO 177 feet do not require lube

Movement indicator attached

Should move 1/4" to 1/2" cold to hot


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Boiler Foundations

Frozen sliding foot

do not steam boilersoak with a solvent to free

last resort-jack boiler up


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Summary

Watersides

FiresidesCasings

58194986 Boiler Construction Ppt

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