FIELD OF THE INVENTION
The Present invention relates to an installation for bull noses of walking beam type re-
heating furnaces involving an external cooling system for the metallic supporting
structure of Bull Noses refractory structure for enhancing life span of Bull Noses. More
particularly, the present invention is directed to an installation providing a cooling system
for the Bull Nose refractory supporting structure (the Bull Nose refractory are hanged
from this structure) which is adapted to forced cool the supporting structure with
compressed air to lower down its ambient temperature to prevent it from deforming,
thus avoiding sudden collapse type failure of Bull Nose in hot zone of Reheating furnaces.
BACKGROUND OF THE INVENTION
Reheating Furnaces in the Plate Mill(PM)/ Hot Strip Mill(HSM) at applicants steel plant are
Walking Beam type slab heating furnaces. The furnace proper at plate mill has been
divided into three heating sections, named as Preheating Zone, Heating Zone & Soaking
Zone & these zones with operating temperatures ranging from about 1000-1400C are
differentiated by the refractory brick lined Bull Noses. There are a total of 6 Bull Noses in
the furnace, which are lined with high alumina bricks hanged by cast stainless steel
hangers (SS - 304). There are total 64 burners in different zones.
In the reheat furnace at HSM also, each zone is differentiated by the refractory brick
lined Bull Noses on the top &. burner tunnel wall / partition wall below the skid level. In
each furnace of Hot Strip Mill, there are also total 6 Bull Noses like Plate Mill, which are
lined with High Alumina bricks hanged by cast stainless steel hangers. In these furnaces
apart from the preheating and soaking zones, there is a Recuperative Zone at charging
end where flue gas from the furnace is extracted and sent to recuperator for waste heat
recovery & then sent to chimney. The operating temperature to which bull nose
refractory of hot zone subjected at the hot face is of 1350 - 1400°C.
In both the cases. Soaking Zone & Heating Zone Bull Noses are made with 60% Alumina
refractory bricks as hot face lining and insulation bricks and Castable at the cold face of
the Bull Noses. Roof is also of same quality of Refractories in both the shops (PM & HSM).

Refractories play a critical role for the total performance and reliable operation of Walking
Beam furnaces which operate under high pressure and operating temperature can vary
low to very high in the various zones of these furnace. Refractories can be the controlling
factor in the success or failure of these furnace and their service life, as well as the safe •
and profitable operation of the plant.
Most of the times these furnaces operate under continuous operating mode and run
throughout the year, before a schedule shutdown for maintenance, scale cleaning or
turnaround. Therefore, the prime objective here is equipment reliability. The shutdown
period is usually short in duration and is planned for mechanical overhaul of gas line,
water line and scale cleaning mainly. The life and durability of refractory lining is not the
determining factor in the frequency and duration of shutdowns.
In spite of its importance, Refractories are in many cases neglected, misunderstood and
abused and the uncared for refractory can cause several problems during regular plant
operations.
The unexpected problems can cause an emergency shutdown or require longer
maintenance time to rectify both damages in the refractory lining of Walking Beam
furnaces as well as mechanical damages to unit equipment. Also, the sudden failure of
the bull nose refractory lining or lining of any other area of the Walking Beam furnace
can pose a significant risk and threat to plant safety. Therefore, it is important to
optimize and to eliminate probable causes of bull nose lining failure in Walking Beam
furnaces.
The performance of any lining in a furnace is considered to be reasonable when similar
service lives are achieved on a regular basis. Pre-mature lining failure may be defined as
one that does not achieve normal or average performance and service life.
The refractory lining and failures in Reheating furnaces are mainly due to thermo-
mechanical stresses, erosion and chemical attack by the duels combustion product. The
most common refractory problems as experienced in these furnaces are :
• Hot spots (Higher casing temperature)

• Excessive cracking
• Spalling of lining (Thermal, mechanical, structural)
• Erosion and thining of lining
• Chemical attack / corrosion from process gases, flue gases etc.
• Mechanical damages
• Causes of refractory wear in Walking Beam type furnaces of Hot mills, (like Hot
Strip Mills, Plate Mill etc.).
Frequent failure of the Bull noses refractory construction in the hot zone Reheating
furnaces of Plate Mill & Hot Strip Mill, both are Walking Beam type furnaces leading to
interruption in production activities of Plate Mill & Hot Strip Mill for more than 7-8 days.
Which includes cooling, heating & actual Refractory jobs. Another problem was
unpredictable performance of bull noses refractory construction in hot zone of Plate Mill &
Hot Strip Mill. Several times it so happened that even all refractory bricks were intact but
entire bull nose construction has fallen suddenly without any indication like hot spot of or
flame shooting out. This has seriously affected the ability of these Walking Beam
Furnaces in both the PM as well as HSM, which means Refractory failure is not main issue
in these break downs metallic support structure is the issue.
In case of Plate Mill, pre-mature failure of Bull Nose # 2 & 3 and sometimes failure of
refractory lined roof at Soaking & Heating Zone. As there is only one furnace in the Plate
Mill any break down specially refractory break down, costs more than 5/6 days, which
includes cooling, heating & actual refractory jobs & another problem was un-predictable
behaviour of Bull Nose # 2 & 3 at Plate Mill and Bull Nose # 3 & 4 at Hot Strip Mill.
Several times it so happened that even all refractory bricks were intact but entire Bull
Nose has fallen suddenly without any indication like hot spot or flame shooting out &
same is applicable to roof area of Soaking Zone & Heating Zone in both the furnaces.
This has affected seriously the availability of the Walking Beam furnaces in both the
shops.
There has been thus a need in the operation and maintenance of reheat furnace in plate
mill/hot strip mill to developing a process of eliminating frequent & pre-mature failure of
refractory lining of bull noses in the hot zone of the Walking Beam type reheating

furnaces of hot mills. There has been a persistent need to identify the cause and
eliminate pre-mature refractory lining failure which costs industries involved in high
temperature processing such as Plate Mill & Hot Strip Mills, $ millions each year resulting
from down time, lost production lining material replacement and installation costs.
OBJECTS OF THE INVENTION
The basic object of the present invention is thus directed to an installation for bull noses
of walking beam type re-heating furnaces providing an external cooling system for the
supporting steel structure for Bull noses refractory mounting in the hot zone of Walking
Beam type Reheating furnaces of Plate Mill & Hot Strip Mill, to avoid bull nose refractory
failure and ensure longer furnace operating life increasing productivity.
A further object of the present invention is directed to an installation for bull noses of
walking beam type re-heating furnaces providing an external cooling system for
supporting steel structure for Bull noses refractory in the walking beam type reheat
furnaces which would restrict the temperature rise of the steel structure when the
furnace is in operation by circulating forced/compressed air for cooling the steel structure
and thus avoiding deformation of structure.
A still further object of the present invention is directed to an installation for bull noses of
walking beam type re-heating furnaces providing said external cooling system for
supporting steel structure for Bull noses refractory in the walking beam type reheat
furnaces wherein the cooling system restricts the temperature rise and deformation of
structure so that premature failure of bull nose refractory lining is eliminated.
A still further object of the present invention is directed to an installation for bull noses of
walking beam type re-heating furnaces providing said external cooling system for
supporting steel structure for Bull noses refractory in the walking beam type reheat
furnaces wherein the system is adapted to ensure availability of the Walking Beam
furnace from capital repair to capital repair of the Plate Mill, which means furnace has to
run at least 12 months without failure and from mid shutdown to mid shutdown in Hot
strip mill which varies from 6 months to 11 months during which furnace is put down for
scale cleaning and refractory maintenance also being done upon inspection.

A still further object of the present invention is directed to an installation for bull noses of
walking beam type re-heating furnaces providing said external cooling system for
supporting steel structure for Bull noses refractory in the walking beam type reheat
furnaces which would avoid sudden collapsing of bull nose construction of hot zone of
Reheating furnace and enable make life of bull noses predictable.
A still further object of the present invention is directed to an installation for bull noses of
walking beam type re-heating furnaces providing said external cooling system for
supporting steel structure for Bull noses refractory in the walking beam type reheat
furnaces which would favour reducing refractory consumption and make reheat furnace
operation more safe and environmental friendly.
SUMMARY OF THE INVENTION
The basic aspect of the present invention is thus directed to an installation for bull noses
of walking beam type re-heating furnaces comprising:
beam/channel holding stainless steel hangers;
said stainless steel hangers adapted to hold refractory brick work construction of
said bull nose;
means adapted to prevent thermal stress failure induced by high transient
temperature.
A further aspect of the present invention is directed to an installation for bull noses
wherein said means adapted to prevent thermal stress failure comprises means adapted
to maintain temperature of said beam/channel at ambient plus 30/40 °C.
A still further aspect of the present invention is directed to an installation for bull noses
wherein said means adapted to maintain temperature of said beam/channel at ambient
plus 30/40 °C comprises a perforated mild steel pipe line along the length of and placed
over the beam / channel holding the stainless steel hangers for the bull nose
construction used to be rested in hanging condition over this mild steel beam;
a compressed air source connected to said perforated pipe for circulating air surrounding
the beam over its length for continuously cooling of the beam throughout the campaign

to thereby restrict the temperature rise avoiding any beam softening and resultant
deformation causing sudden bull nose failure.
A still further aspect of the present invention is directed to an installation for bull noses
wherein said perforated mild steel pipe carrying compressed air for cooling is having 40
to 50 mm outer dia preferably about 40mm dia with 4 to 8 mm preferably about 5mm
dia holes in it to make it perforated.
Yet another aspect of the present invention is directed to an installation for bull noses
adapted to use compressed air as cooling media with a pressure of 1 - 1.5Kg/cm2
continuously blown in said perforated mild steel pipe with flow of air maintained at 80 -
100Nm3/nr.
A still further aspect of the present invention is directed to an installation for bull noses
adapted to maintain the outside temperature of the support metallic beam over which
Bull Nose metallic hangers are suspended, in the range of 75 - 125°C preventing
softening of mild steel beam and thus preventing from sagging down with Refractory
load.
The objects and advantages of the present invention are described hereunder in greater
details with reference to the following accompanying non limiting illustrative drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1: is the schematic illustration of the conventional arrangement of bull nose
hanger bricks laid in support with Stainless Steel-304 (SS 304) hangers resting on mild
steel channel marked as " A"
Figure 2: is the schematic illustration of the external cooling system for steel supporting
structure for bull nose refractory lining according to the present invention erected over
the mild steel beam of the bull nose involving M.S. perforated pipe line for compressed
air marked as 'C .

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURES
The present invention relates to an installation for bull noses of walking beam type re-
heating furnaces involving an external cooling system for supporting steel structure for
Bull noses refractory directed to prevent sudden collapsing of bull nose construction of
hot zone of Reheating furnace and make life of bull noses predictable.
The present work focuses on the structural aspects of bull nose refractory lining in the
Walking Beam type reheating furnaces because most of time any refractory failure occurs
it is immediately assumed that this is either due to refractory material failure or
refractory workmanship failures. The present invention adopted an approach to the
problem of bull nose refractory failure and solved without considering above two reasons
but by preventing supporting structure failure.
Whenever there are some problems in refractory lining, usually it is concluded that either
the refractory material was bad or the installation was poor. However, in reality the
problem are probably due to a combination of multiple factors and may not be solely just
one factor poor installation or inferior quality. To address the problems associated with
Refractories it is necessary to recognize the main factors that are involved and
contributed to refractory related problems. These factors are,
(i) Design of furnace (ii) Design of refractory lining & detail engineering (iii) Selection of
refractory material & specifications (iv) Quality of refractory materials (v) Installation of
lining (vi) Curing, startup & maintenance of lining (vii) Operation practices (viii)
Inspection & maintenance practices (ix) In case of hanging refractory consumption,
design & engineering of mechanical support structure.
The bull nose construction is made with 60% alumina bricks as wear out lining &
insulation bricks and castable as back up lining as shown in the accompanying Figure 1.
These are hanger bricks and are laid in support with Stainless Steel-304 (SS 304)
hangers. These stainless steel hangers are resting on mild steel channel shown as
marked " A" in the Figure 1. The operating temperature to which bull nose refractory of
hot zone is subjected at the hot face is in the range of 1350 - 1400°C.

It has been noticed that many a times pre-mature failure of bull nose refractory
installation of hot zone has occurred during the running operation of Reheating furnaces
of Plate Mill & the Hot Strip Mill. Both are Walking Beam type and without any prior
indication. Due to sudden collapsing of bull nose construction , the furnace production
activity was stalled at least for more than 7/8 days till new construction is made after
cooling. This even so used to happen that the left over thickness is 2/3 of the original
thickness. Upon investigation the principal causes of this type of pre-matured failure of
bull nose construction installation were analysed, and found to be due to fatal thermal
stresses induced by high transient temperature leading to defuse micro cracking in
metallic mild steel beam which caused beam to become soft. The bull nose
construction used to be rested in hanging condition over this mild steel beam. Due to
beam softening, it starts sagging due to the refractory load, leading ultimately to a
collapsing type failure. Therefore to prevent softening of this beam due to high
temperature, continuous cooling of this beam is required, meaning that the temperature
of this beam should not reach beyond 30/40°C above the ambient temperature.
To prevent softening of the mild steel beam a pipe line along the length of the beam was
erected of 40mm dia with 5mm dia holes in it (to make it perforated) and this line along
the length of the beam was erected over the mild steel beam of the bull nose .
Accompanying Figure 2 show the installation of the perforated pipe over the beam
wherein the portion marked yC is the innovative M.S. Perforated pipe line, *A' indicate the
stainless steel hangers holding the refractory brick work construction, 'B' is the M.S.
beam/channel holding the stainless steel hangers, the total innovation has been marked
in Figure 2 as EE. The cooling media adopted is compressed air at a pressure of 1 -
1.5Kg/cm2 . Compressed air at this pressure is continuously blown in this perforated steel
pipe, flow rate of air is maintained in the range of 80 - 100Nm3/nr. This air is
continuously cooling the beam throughout the campaign. Temperature measurements
are taken before installation of the cooling system and found to be avg. 170°C to as high
as 225°C. And after installation of cooling system, temperature of beam is again
measured and found to be in the range of 75 - 125°C, which means reduction by about
100°C. Thus due to the cooling of the beam the softening of this beam is prevented. Now
the sudden collapsing type failures has been eliminated completely and also facilitated
effective utilization of bull nose Refractories in service with increased life and a
predictable life of the bull nose refractory structure.

The external cooling system for steel supporting structure for the bull nose refractory in
walking beam type reheat furnace thus ensure the following beneficial aspects:
1. The innovation has eliminated sudden collapsing of bull nose construction of hot
zone of Reheating furnace.
2. This innovation has improved bull nose life as well improved safety considerations.
3. Improvement in furnace reliability and availability has increased many fold.
4. This innovation has made possible to predict life span of bull noses refractory
construction installation of Reheating furnaces of Plate Mill & Hot Strip Mill and
possible to take corrective measures & shut down decision before break downs
and also possible to take preventive measures. Shut down forecast is also possible
as life has becomes predictive.
5. This innovation has created work friendly environment as hot job has been
eliminated completely.
6. The external cooling system according to the present invention, has been put on
field trial with best performance since the installation and not a single collapsing
type break down / failure took place.
7. Possible to do predictive maintenance of bull nose refractory construction.
8. Improvement in overall economy of refractory maintenance practices.
It is thus possible by way of the present invention to provide an external cooling
system for supporting steel structure for bull nose refractory of the walking beam
type reheat furnaces involving installation of compressed air with perforated pipe
line in first step at the Bull Nose metallic structure span from outside has brought
down the support metallic beam (over which Bull Nose metallic, S.S. 304. Hangers
used to be suspended) outside temperature from 170 - 225°C to as low as 75 -
125°C. This has prevented softening of mild steel beam and thus prevented from
sagging down with Refractory load. Life of Bull Nose due to this has increased many
folds more & above life of Bull Nose also has become predictable & sudden collapse
type break down has been eliminated completely.

We Claim:
1. An installation for bull noses of walking beam type re-heating furnaces
comprising:
beam/channel holding stainless steel hangers;
said stainless steel hangers adapted to hold refractory brick work construction of
said bull nose;
means adapted to prevent thermal stress failure induced by high transient
temperature.
2. An installation for bull noses wherein said means adapted to prevent thermal
stress failure comprises means adapted to maintain temperature of said
beam/channel at ambient plus 30/40 °C.
3. An installation for bull noses as claimed in claim 2 wherein said means adapted to
maintain temperature of said beam/channel at ambient plus 30/40 °C comprises a
perforated mild steel pipe line albng the length of and placed over the beam /
channel holding the stainless steel hangers for the bull nose construction used to
be rested in hanging condition over this mild steel beam;
a compressed air source connected to said perforated pipe for circulating air
surrounding the beam over its length for continuously cooling of the beam
throughout the campaign to thereby restrict the temperature rise avoiding any
beam softening and resultant deformation causing sudden bull nose failure.
4. An installation for bull noses as claimed in claim 3, wherein said perforated mild
steel pipe carrying compressed air for cooling is having 40 to 50 mm outer dia
preferably about 40mm dia with 4 to 8 mm preferably about 5mm dia holes in it to
make it perforated.
5. An installation for bull noses as claimed in anyone of claims 3 to 4 , adapted to use
compressed air as cooling media with a pressure of 1 - 1.5Kg/cm2 continuously
blown in said perforated mild steel pipe with flow of air maintained at 80 -
100Nm3/hr.

6. An installation for bull noses as claimed in anyone of claims 1 to 5 adapted to
maintain the outside temperature of the support metallic beam over which Bull
Nose metallic hangers are suspended, in the range of 75 - 125°C preventing
softening of mild steel beam and thus preventing from sagging down with
Refractory load.

ABSTRACT

The Present invention relates to an installation for bull noses of walking beam type re-
heating furnaces involving an external cooling system for the metallic supporting
structure of Bull Noses refractory structure failure of Bull Noses. More particularly, the
present invention is directed to providing a cooling system for the Bull Nose refractory
supporting structure (the Bull Nose refractory are hanged from this structure) which is
adapted to forced cool the supporting beam structure with compressed air to maintain
temperature of said beam/channel at ambient plus 30/40 °C to prevent it from
deforming, thus avoiding beam softening or sagging under refractory load at elevated
temperature causing sudden collapse type failure of Bull Nose in hot zone of Reheating
furnaces.