IS 15562: Design and construction of fuel fired bogie hearth type heat treatment furnaces - Guidelines

2005·1.6 MB·English

by  Bureau of Indian Standards

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IS 15562 (2005): Design and construction of fuel fired
bogie hearth type heat treatment furnaces - Guidelines [MTD
26: Industrical Fuel Fired Furnaces]
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IS 15562:2005
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Indian Standard
DESIGN AND CONSTRUCTION OF FUEL FIRED
BOGIE HEARTH TYPE HEAT TREATMENT
FURNACES — GUIDELINES
lCS 25.180

0 BIS 2005
BUREAU OF INDIAN STANDARDS
MANAK BHAVAN, 9 BAHt4DUR SHAH ZAFAR MARG
NEW DELHI 110002

March 2005 Price Group 5
Industrial Fuel Fired Furnaces Sectional Committee, MTD 26
FOREWORD
This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by the Industrial
Fuel FiredFurnaces Sectional Committee, hadbeenapproved bytheMetallurgical Engineering Division Council.
A bogie hearth or car bottom type furnace is the most widely used batch type furnace for heating and heat
treatment of a variety of metallic and non-metallic products.
Main reasons for selection of bogie hearth furnace are:
a) Capability to handle various sizes and shapes of products.
b) Ease of handling such products.
c) Techno-econom ically found advantageous with respect to both operation and maintenance,
1
d) Double ended version with one additional bogie can ensure operation almost on a continuous basis and 4.
eliminate loss of time due to loading and unloading.
This standard isprepared to cover bogie hearth furnaces needed forheat treatment of cast, forged and fabricated
metallic products under airatmosphere. Suchfurnaces mayalsobedesigned andbuilttooperate under protective
atmosphere, if considered essential, for the heat treatment process.
For the purpose of deciding whether a particular requirement of this standard iscomplied with, the final value,
observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with
IS2: 1960 ‘Rules for rounding off numerical values (revised)’. The number ofsignificant places retained inthe
rounded off value should be the same asthat of the specified value inthis standard.
IS 15562:2005
Indian Standard
DESIGN AND CONSTRUCTION OF FUEL FIRED
BOGIE HEARTH TYPE HEAT TREATMENT
FURNACES — GUIDELINES
1SCOPE IS No. Title
This standard covers requirements for bogie hearth 8849:1991 Glossary ofterms relating tofuel
type heating and heat treatment furnaces. fired industrial furnaces @-st
revision)
2 REFERENCES
3 TERMINOLOGY
The following standards contain provisions which
Forthe purpose ofthis standard, the definitions given
through reference inthistext, constitute provisions of
inIS 8849 shall apply.
this standard. At the time of publication the editions
indicated were valid. All standards are subject to
4 DESIGN CONSIDERATION
revision and parties to agreements based on this
standard are encouraged to investigate the possibility 4.1 Charge Dimension and Unit Weight
of applying the most recent editions of the standards
indicated below : Size,shapeandweight ofindividual charge pieces and
the number of pieces to be chargecVarranged on the
1sNO. Title
hearth per batch load should be decided.
6:1983 Specification for moderate heat
duty fireclay refractories Group 4.2 Handling of Charge Material
‘A‘ ~ourth revision)
Material tobeheattreated maybe loaded orunloaded.
8:1994 High heat duty fireclay either manually or with the help of a mechanized
refractories @fth revision) device. Chargepieces, iflarge, can beplaced directly
210:1993 ~y iron castings — Specitica- on refractory hearth. Small components for heat
t]on ~ourth revision ) treatment are usually charged/arranged in containers/
fixtures.
1030:1998 Carbon steelcastings forgeneral
engineering purposes ~ifth 4.3 Useful Internal Dimensions of the Furnace
revision)
These dimensions are to be decided on the basis of
1875:1992 Carbon steel billets, blooms,
charge dimensions, arrangement of charge pieces on
slabs and bars for forgings ~fth
hearth for uniform heating and the ffee space to be
revision)
provided from circulation of the products of
1977:1996 Low tensile structural steels —
combustion (POC) around the charge before leaving
Specification (third revision)
thefurnace. Typically, the lengthofthehearth should
2042:1972 Insulating bricks @st revision) beat leasttwo times its usetid width.
2062:1999 Steel for general structural
For ease of charge loadinghmloading, height of the
purposes — Specification
bogie hearth (top of the refractory lining) should be
(jifih revision)
900mmto 1000 mmfromshopfloor level. Guideline
3355:1974 Grey iron castings for elevated
data indicating internal dimensions of the furnace
temperatures for non-pressure
based on nature and loading pattern of charge stock
containing parts @st revision)
are I%mishedin Table 1.
4522:1986 Heat resistant alloy steel and
nickel base castings (second 4.4 Operating Temperature
revtiion)
Upto 75Q-800”Coperating temperature, provision for
6911:1992 Stainless steel plate, sheet and re-circulation ofproductsofcombustion (POC)byway
strip (j7rst revision) of selecting appropriate burner system (excess air
8154:1976 Preformed calcium silicate firing/high velocity burner) would be desirable for
insulation (for temperature upto better convective heat transfer. For operating
650 ‘C) (firs? revision) temperature beyond 800”C, radiation being
8183:1993 Bonded mineral wool @rst predominant, suitable combustion equipment should
be selected.
revision)
1
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IS 15562:2005
Table 1 Guideline Data for Internal Dimensions of the Bogie Hearth Furnace
(Clause 4.3)
SI InternalDimension CompactLoadingof ChargeStockLikeWelded
No. ChargeStockon VesselPlacedLoose
Hearth onHearth
(1) (2) (3) (4)
i) Length,m upto15 upto30
ii) Width,m upto4 upto7
iii) Heightm upto4 upto7
iv) Hearthsurfacearq mz upto50 upto160
v) Innervolumeoffurnace,m3 upto 100 upto 1000
vi) Loading/batch,t upto200 upto200
vii) SpecifichearthIoadhg,timz upto4 upto4
For operating temperature limit of maximum 500- IS 1977orIS2062 shouldbeused fortheconstruction i
550°C, indirect heating can be opted along with of tirnace casing. Selection of sizeand placement of
provision ofeffective re-circulation ofPOCbymeans such steel sections are primarily based on the
of suitable fan. dimensions of the furnace and the type of its
construction. Bottom support plate for the fixed
4.5 Rate of Temperature Rise
portion of the fbrnace hearth should be 8 mm thick
Selection of suitable burners, their placement and mild steelplate conforming to IS 1977or IS 2062.
combustion control system should take into account
5.2 Structural for the Bogie
the desired maximum and minimum rate of
temperature rise andalsotherate ofcooling insidethe
Structural for the bogie consist of the base plate,
furnace, if called for, by the heat treatment process.
preferably of 8mm thickness, and arigid framework
withsteelsections conforming to IS 1977or IS2062.
4.6 Connected Heat/Fuel Load in kcal/h
Inordertoprotectthisunder-structure fkomconducted
Requirement ofheatorfuelusageshouldbecalculated heat, it is advisable to maintain an air gap of
based on: approximately 100mmbetween thebaseplate andthe
structuralfiarneworkbyputtingsteelsectionsasinserts.
a) Maximum charge loadhath,
Furnace with total bogie, length not exceeding
b) Operating temperature,
4000 mm base support frame, can be fabricated as
c) Heating rate, one rigid structure mounted on two pairs (four

numbers) of wheel and bearing.
d) Summation of various loss es through inner

lining, leakages through gaps around door/
Wherethetotal lengthofthebogie exceeds4000 mm,
openings andbetween fixedandmovinghearth,
itisrecommendedthatthe~ogiestructuresupportftarne
and
should be fabricated in segments which are bolted/
e) Heat loss through the flue gas leaving the weldedto asinglerigid construction. Each segment is
furnace. . provided with two pairs (four numbers) of wheel
bearing assembly. This will ensure proper alignment
Connected fiel load of the furnace should be about
and uniform loading of bogie under-structure and the
20 percent more than the calculated fitel usage.
wheels on the rails. This will also allow abso~tion
5 CONSTRUCTIONAL FEATURE of shock due to load impact and expansion
of understructure due to variable heat and load
The bogie hearth or car bottom type heat treatment
conditions.
furnace include following two basic arrangements:
a) Fixed or stationary part ofthe furnace, and 5.3 Hearth Support Wheels
b) Moving (bogie hearth orcarbottom) part ofthe Support wheels may be either cast or forged steel
furnace which normally moves over a pair of conforming to IS 1030 or IS 1875 duly annealed,
rail. machined and rim hardened to about 280-320 BHN.
Depending upon the load connection envisaged on
5.1 Furnace Casing
individual wheels, shock/impact during loading/
Mild steel plate of at least 5 mm thickness duly unloading, sizeof wheeVbearing/shaft, etc, should be
reinforced with mild steel sections conforming to selected.
2
IS 15562:2005
54 Rails for Bogie Movement 4-5 t per batch, steel wire rope ties at the front and
back (over a pulley) of the bogie hearth and wound
Sleepers (mild steel channel) conforming to IS 2062
around a winch to be rotated manually can be used,
should be grouted on shop floor (foundation) at
For bogie hearth with larger batch loading capability,
intervals to support a pair of rails to enable bogie
followingcommonly adopted motorized drive/haulage
movement inandout ofthe furnace. Depending upon
mechanism can be recommended.
the load concentration envisaged on individual wheel
and bearing assembly, standard rails of 30-45 kg/m 5.7.1 Rope and Drum Type
size may be selected.
Steelwire rope wound around the rope drum is&iven
5.5 Castings by an electric motor through reduction gear unit,
electromagnetic brake, cutoff limit switches, etc. Two
Castparts being more resistant towear duetoheat are
ends of the steel wire rope would be ties at the front
usedtocoverareasarounddooropenings,sand troughs
and rear (over a pulley) of the moving bogie hearth.
anddipper plates forsealingthegapbetween thefixed
Normally, the haulage speed of such a mechanism is
and moving part of the furnace. Curb angles around
recommended as 3-4 rrdmin.
the periphery ofthe bogie and fixed hearth, which act
as retainer for the refractory lining work, should be 5.7.2 Rack and Pinion Type
made of cast iron or heat resistant cast iron. Selection
Castor fabricated rack would be fitted underneath the
ofthegrade ofcastings tocoverthe above statedareas
bogie structure and is meshed with a cast and heat
of both fixed and moving hearth will depend on the
treated wheel pinion isdriven (rotated) by an electric
operating temperature ofthe furnace andthe extent of
motor, reduction gear unit, electromagnetic brake,
exposure with maximum operating temperature of
cutoff limit switches, etc. Such 8&lve mechanism is
650-700”C, cast iron conforming to grade FG 200 of
suitable for higher haulage speed of up to 10m/min.
IS 210 may be used. Above 700 “C and up to
For high haulage speed, however, suitable control to
1000 “Coperating temperature, heatresistant castiron
achieve acceleration and deceleration during bogie
conforming to IS 3355 may be used.
movement is recommended.
5.6 Door
5.8 Inner Lining of the Furnace
Vertical rise and fall type suspended door, normally
Generally, heat treatment furnace should be lined
counter weighted and operated by a motorized drive
inside with low thermal mass type, that is, less dense
mechanism (small doors canbemanually operated) is
refractory and insulation material to minimize heat
commonly used. For sealing the gap around the door
storage by the inner lining. Actual configuration of
periphery, sand troughs or fibre/asbestos packed
inner lining will be decided on the basis of maximum
mountings can be provided. For large size doors,
operating temperature and the operating practice
clamps, either manually or pneumatically operated,
desired bytheheattreatment shop. For afurnace with
can be provided for better sealing . For small single

800 to 1 000”C maximum operating temperature,
ended bogiehearth fimace, door cou ld beconstructed
typical lining configuration is suggested below as
fixed onto the moving bogie, if otherwise, not found
guideline.
inconvenient.
5.8.1 Burner Blocks
5.6.1 Accessories for Door Support Movement
Can be prefired, dense quality shapes containing
Standard accessories include link or roller chain,
35-58 percent alumina (AIZOJ or shapes made out of
appropriately sized pulleys, sprockets, bearing blocks
suitable quality refractczry castable duly cured for
and shaft in addition to structural for door mast,
attainingrequiredbonding andstrength. Forinstallation
support beam, etc.
of burner blocks, instruction fhmished by the burner
5.6.2 Mechanized Door Drive manufacturer should be followed.
Door operation may be mechanized by means of 5.8.2 Areasaround theburner block canbelined with
electrodrive or hydraulic/pneumatic cylinders with eitherIS8Grade 1quality firebricks orsuitable quality
limit switches, etc, and generally designed for adoor refractory castable.
operating speed of 2 m/min. Door drive mechanism
5.8.3 Fixedportion ofthefbrnacehearth andthe lower
can either be placed on shop floor for ease of
part(approximately 250-300 mmhighfromhearth top)
maintenance oron door mast atanelevated levelwith
of the side wall all around should be lined with IS 8
accessibility for maintenance.
Grade 1fuebricks duly backed by hot and cold face
insulation bricks similar toIS2042 Type 1and Type 2
5.7 Drive/Haulage Mechanizm for Moving Bogie
quality should be used primarily to withstand any
Hearth
possible impact during loadinghmloading of charge
For smaller fimace with maximum hearth loading of material.
3
1S 15562:2005
5.8.4 Side Walls ii) 75 mm thick cold face insulation bricks
conforming to IS 2042 Type 2 quality
Either conventional lining with refractory/insulaltion
bricks or with ceramic fibre blankets could be used. iii) 75 mm micahermiculite base insulation
The thickness of lining should, however, ensure bricks
skin temperature within 45°C above ambient for
iv) 25 mm thick layer of insulating block
Alternative 1,and 35°C for Alternative 2.
S1No. Alternative 2
S1No. Alternative 1
i) 25 mm thick 1 260”C grade 128 kg/cm3
i) 230 mm thick insulating firebricks density ceramic fibre blanket
ii) 115mm thick cold face insulation to IS2042 ii) 50mmthick 1260W grade 96kg/cm3density
Type quality insulation bricks ceramic tibre blanket
iii) 40 mm thick insulating block iii) 50mmthick 1260Y grade64kg/cm3density
ceramic fibre blanket
S1No. Alternative 2
iv) 75 mm thick mineral wool blanket
i) 25 mm thick 1 260”C grade 128 kg/cm3
density ceramic fibre blanket 5.8.6 Bogie Hearth
ii) 50mmthick 1260”Cgrade96kg/cm3 density Curb/retainer blocks for the hearth refractory lining
ceramic tibre blanket all around should be special shape of IS 8 Type 1
quality fwebrick. Depending upon the sizdshape of
iii) 50mm thick 1260”C64gradekg/cm3density charge pieces and method of lotimghmloading, IS 8
ceramic grade blanket quality refiacto~ support blocks orpiers may have to
be provided. As guideline, following typical lining
iv) 75 mm thick mineral wool blanket
configuration canbe suggested:
a) 150mm thick IS 8Type 1quality fwebrick,
5.8.5 Furnace Roof
b) 75 mm thick hot face insulation brick similar
For a furnace having internal width of 2000 mm the to IS 2042 Type 1quality,
arch type roof can be constructed with 230 mm thick
c) 150mmthick coldface insulation brick similar
insulating firebricks backed by 115 mm cold face
to IS 2042 Type 2 quality, and
insulation bricks conforming to IS 2042 Type 2
insulating bricks and 25 mm thick layer of insulating d) 40 mm thick irdating block.
castables.
Tolerance limit for skin temperature measured under
the hearth lining support plate can be 60”C above
5.8.5.1 Suspended type firnace r oof construction
ambient temperature.

Furnace with relatively larger internal width above
5.8.7 Door
4 000 mm, suspended type roof construction is
preferred to ensure higher stability and life of roof Either conventional with fefi’actory/insulating bricks
refractory lining. For furnace having side walls lined or with ceramic fibre blanket can be recommended.
with ceramic fibre blanket (Alternative 2 see 5.8.4)
suspended type roof construction with ceramic tlbre S1No. Altern@ve 1
blanket would beconsidered advantageous. Following
i) 115mm thick insulating fwebricks
alternative lining configuration can be suggested as
guideline. High tolerance in the skin temperature ii) 115 mm thick cold face insulation bricks
measured on furnace roof can be allowed, depending conforming to IS 2042 Type 2 quality or
uponthe design/construction forAlternative 1theskin mica/vermiculite base insulation bricks
temperature shouldbe60”Caboveambienttemperature
iii) 40 mm thick insulating block
whereas for Alternative 2 the same should be within
45°C above ambient temperature. S1No. Alternative 2
i) 25 mm thick 1 260”C grade 128 kglcm3
S1No. Alternative 1
density ceramic fibre blanket
i) 175mm thick special shape bricks of IS 8
ii) 50mmthick 1260”Cgrade 96kg/cm3density
Type 1quality to be suspended at intervals
ceramic fibre blanket
by special shape hanger bricks of same
quality iii) 75 mm thick mineral wool blanket

4
IS 15562:2005
5.8.8 Passage for Escape of the Flue Gases should be used. As a compromise, self-proportioning
oil burners with single air inlet may also be used.
For the escape of flue gases (POC) from the fimace,
either single or multiple flue ports would beprovided 6.2 Gas Burners
inthe inner lining of the fimace. Areas around such
Nozzle mixing gas burners in which combustion air
flueopenings areusually linedwithIS8Type 1quality
and fuel gas arekept separate within the burner itself,
firebricks duly backed with insulation bricks in case
butthenozzle orifices are designed to provide mixing
of conventional refractory lining furnace. For the
of fluids asthey leavethe burner are considered more
escape of flue gases beyond the furnace, either
suitable for heattreatment process. Such burners have
underground passages will be provided or steel
high excess air tiring capacity and high velocity.
encased ducts to be constructed above the mill floor.
These would normally be lined inside with firebricks 6.3 Oil and Gas Combination Burners
conformingto IS 6 quality duly backed by a layer of
insulation bricks and building quality red bricks. Periodic changes inthe supply of fhel aswell asprice
picture may sometime call for changing of fuels.
Chimney/stack would normally be lined inside with Hence, combination burners for fring either fuel oil
firebricks similar to IS 6quality backed by refractory/ or fuel gas are also available for selection.
grog (broken bricks) wherever considered necessary.
6.4 Burner Lighting-Up
6 BURNERS
Every burner should have a pilot ignition and an
For achieving ‘desired rate of temperature rise and
observation port sothatthe‘mainflame canbeseen by
temperature uniformity for heat treatment process,
the operator. The pilot ignition port may be used for
selection of burners for firing fuel oil or gas is
lighting upthe burner manually by ahand held torch.
considered extremely important.
Alternatively, burners canbeprovided with automatic
Heat treatment furnaces generally call for operation
light-up system either by a pilot flame using LPG/
atvarying temperatures throughout the cycle and also
natural gas or spark ignited light oil pilots. Direct
operate often with reduced loading. Hence, fuel electric ignition of burner main flame is also used.
demand will be less during major portion ofthe heat Figure 1 illustrates a typical gas fired pilot flame
treatment cycle. Since the selection of burner ignitionsystemfornozzlemixing gasburners. Forsake
capacity must be based on the fuel requirement at ofoverall safe~, interrupted typepilot should beused.
maximum temperature and loading, the combustion
system must turndown during lower demand. To 7 SUPPLY OF AIR
compensate corresponding lossinburner velocity and
For complete combustion ofeither tiel oil or fuel gas,
thus also the penetration capability of furnace
required volume of air should be provided to the
atmosphere and uniform distribution of heat
burners. In case of oil firing, this total volume of air
throughout theloadbeingheattreate d,finingofburners
would include required volume of air for bath
withexcess airiscommon forheattrea tment fhmaces.
atomization and combustion ofthe fuel oil. In case of
Highvelocity burners with excess airfiring capability
fuel gas fwing, the total air to be supplied is for the
wouId therefore be commonly selected. Excess air
purpose of combustion Qfthe fhel gas. As guideline
firing, will, of course, increase fuel consumption.
for determining the theoretical air requirement for
Burners are selected based on available fuel (oil or complete combustion of fhel oil or fuel gas, ifmaybe
gas), fueIoi1grade, type of fuel gas (also cleanliness mentioned that for every,890kcal heat release 1m3of
and calorific value of gas) and the temperature or air airwould benecessary toensure complete combustion
for combustion. Accordingly, burners can be chosen ofthe fiel.
exclusively for oil tiring, gas firing or combination
7.1 Combustion Air Supply
burner for firing either oil or gas as fuel.
Incaseoflow/medium pressure oilburners andnozzle
Burners with excess air firing capability and high
mixing gasburners, itisnecessary toprovide ablower
velocity burners areconsidered advantageous forheat
motor unit for supplying total quantity of air required
treatment operation. In the event, preheated
for the combustion of fuel oil or fiel gas. Based on
combustion air or fuel gas would be used, burners
thetype offueltobeused(oil orgas)and itspressure
selected should be suitable for the same.
required attheburner, thepressure ratingoftheblower
may vary between 600-1 000 mm W.C. depending
6.1 Oil Burners
upon therecommendation ofthe burner supplier. The
Low medium air pressure oil burners in which overall volumetric capacity of the combustion air
atomizing and combustion air have separate piping blower shouldbe30percent higherthanthetheoretical
and maintain stable flame, even with excessairtiring, air requirement.

5