FIELD OF THE INVENTION
The present invention relates to a system for removing hearth scale from reheating
furnaces and, in particular, to a system for removing hearth scale from walking
beam type reheating furnaces in operating conditions. Importantly, the system of
the invention which would enable removing hearth scale from the said walking beam
type reheating furnaces in operating conditions would enable achieving higher
campaigning life of furnace and avoid the need for frequent downing of the furnace
which adversely affected the refractory life and also lead to production loss. The
method of scrap removal using the system ofnthe invention is simple to carry out
and cost effective and is directed to favour wide scale application and use of the
same for removal of hearth scale ,in particular, from the walking beam type
reheating furnaces.
BACKGROUND ART
It is known that walking beam type reheating furnaces are conventionally used to
heat up steel slabs, blooms, billets in batches or in continuous for hot rolling. The
scale formed during such heating process peels off and falls on the hearth. In fact,
when the charge reaches in semi plastic range and is lifted by the walking beam it
sagged. The scale formed at the bottom surface cracks and falls on the hearth
exposing fresh steel surface for further scaling. This vicious cycle leads to heavy
deposition of scale in the center of soaking zone. The scale deposition rate in the
middle of the soaking zone is nearly four times higher than the other parts of the
furnace. It causes a very short campaign life of furnaces, as the only way to remove
the scale is to stop and cool the furnaces. Such process usually takes about one
week of stoppage of furnace leading to production loss. The deposition patterns
usually depend upon the skid pattern, discharge temperature and holding pattern
etc.
It would be dearly apparent from the above that the problem of scale deposition is
common in all varieties of walking beam type of reheating furnaces. Therefore, while
the scale deposition is common, the manner of its removal' as discussed above has
been difficult and more importantly necessitated the downing of the furnaces. Thus
while on one hand the removal of the scale was essential to improve the life of the

furnace, on the other hand such removal of scale necessitated the downing of the
furnace for usually about one week leading to production loss. Accordingly, removing
hearth scale from walking beam type reheating furnaces has been difficult, complex
and more importantly associated with production loss.
OBJECT OF THE INVENTION
It is thus the basic object of the present invention to provide a system for removal
of hearth scale from walking beam type of reheating furnaces which would enable
removal of the hearth scale from the furnaces in operating condition without
requiring the stoppages of furnaces leading to huge production loss.
Another object of the present invention is directed to the provision of a system and
method of hearth scale removal from walking beam type reheating furnaces in
operating conditions which would achieve higher campaign life of the furnace and
avoid conditions adversely affecting refractory life and also the production loss.
Another object of the present invention is directed to the provision of a system and
method for removal of hearth scale from walking beam type reheating furnaces
which would be simple and user friendly and at the same time would be cost
effective for ready and wide scale application / use for removing hearth scale from
walking beam type reheating furnaces.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a
system for removal of scale from walking beam furnaces adapted for use also
while in operation of the furnace comprising:
a scrapper carrying slab means having hinged scrapper means ; —
said hinged scrapper adapted such that the scrapper means can be rotated by 270°
with respect to said hinge to hang downwards when said scrapper carrying slab is
pushed inside the furnace;

a locking slab means adapted to lock the scrappers in its downward hanging
position inside the furnace ;
means to move the said scrapper carrying slab with said scrapper extending
downwards into the furnace for scale scrapping and thus maintained, along with
said locking slab, from the charging end towards the discharge end along the scale
deposit area of the furnace to thereby remove the scale from the hearth.
Preferably, the above system includes means preferably crane means for lifting of
the scrapper carrying slab with the scrappers on top and placing in front of a pusher
unit to facilitate the disposition of the scrapper inside the furnace for the scrapping
operation.
Also the system for removal of scale from walking beam furnaces comprises
means for centering and rotating the scrappers by 180° such as to rest on the roller
table such that the slab when pustied in such" disposition in the furnace the
scrappers hang downwards inside the furnace.
The width and weight of said locking slab(2) is selected such that the scrappers(6)
do not get displaced while taking the load of scale and adapted to be charged such
that the said scrapper(6) means are locked in its downwards hanged disposition
inside the furnace to facilitate scale removal.
Moreover, the said scrappers are adapted to favour the lowering of the scale level
by its length and dispose in the scale hopper.
The system is adapted such that the said scrapper carrying slab can be cooled after
discharge from the furnace and the scrappers adapted to be placed on the slab top
and kept insulated after removing from the roller table for subsequent operation.
The scrapper means used in the above system can comprise sets of scrappers at
selective distances each having two billets are welded on the available full length of
the scrapper carrying slab with said required flexibility of 270° movement.

Importantly, the scrappers are adapted such that it can rotate 270° around the

hinge. Also, the scrappers are anchored and insulated to resist the heat and to
retain the strength at furnace temperature such as after one hour of tripping.
Preferably, the scrappers are adapted based on the clearance of skid from the
charging and discharging wall, from upper and lower screen wall, if any, from the
burner tunnel such the walls and scrappers do not get damaged.
Importantly, the system of the invention can comprise one or more scrappers
secured to the scrapper carrying slab means selectively provided based on the
location to be cleaned along the width of the furnace, the width of the scrappers
selectively provided based on the gap to be cleaned between the skids with due
consideration of positioning errors ,if any , during charging.
The length of the scrappers are selectively provided based on the balance there
between the clearance allowed by the furnace design, strength of the scrapper
material, temperature at the time of cleaning, handling facilities and the area to be
cleaned. In accordance with an aspect the system can comprise two or more sets of
scrappers charged one behind the other with the scrapper length in increasing order
upto the last locking slab.
The above disclose system of the invention thus basically involves the provision of
slab with hinged scrappers selectively adapted keeping charging / discharging wall
gaps, skid distribution and scale deposition patterns in view.
Sets of scrappers and preferably two sets of scrappers, each having two billets are
welded on the available full lengthof the scrapper carrying slab having required
flexibility of 270° movement.
It is possible to lift the slab and scrapper arrangement by suitable means to be
placed on roller table in front of the pushers. After proper centering the slab is
charged into the furnace keeping the hooks in hanging position. The scrappers are
thus adapted to be rotated and placed over the slab.

The scrappers are usually made of temperature resistant material and the scrappers
and hinge are adapted based on the clearance of skids from the charging and
discharging upper walls, from upper and lower screen wall if any, from the burner
tunnel such the walls and scrappers do not get damaged.
Advantageously, the system of the invention the apparatus can have one or more
scrappers attached to the slab depending upon the location to be cleaned along with
the width of the reheating furnace. Width of the scrapper usually depend upon the
gap to be cleaned between the skids with due consideration of positioning errors, if
any, at the time of charging. The length of the scrapper are selectively provided by
making balance among the clearance allowed by the furnace design, strength of the
scrapper material, temperature at the time to cleaning, handling facilities and the
area to be cleaned.
The basic feature as discussed about can be used in any type of walking beam
furnaces for variety of charged type.
Importantly, in case of higher degree of accumulation of scale two or more set of
scrappers can be charged, one behind the other with the scrapper length in
increasing order and in last locking slab also being provided.
In accordance with another aspect of the present invention there is thus provided for
a method for removal of scale from walking beam furnaces also while in operation
using the system as disclosed above.
In accordance with a preferred aspect the method for removal of scale from
walking beam furnaces also while in operation using the system comprises:
emptying the furnace and cutting -off the gas supply to thereby reduce the
furnace temperature;
providing the scrappers carrying slab with scrappers resting on top in front of
pusher /charging machine using a crane means;
centering the scrappers ,lifting and rotating the same to rest on the roller
table;

pushing the slab inside the furnace and taking forward by operating the beam
until the scrapper fall vertically downwards;
charging the locking slab to thereby lock the scrappers there between the
slabs;
moving the pair of slabs in the scale accumulated area and talcing forward in
continuous observation;
carrying and dumping in hoppers scale equal to the hanging length of the
scrappers.
Following the above method once the slab reaches the discharge end it is taken out
by extracting machine and cooled with water; followed by rotating the scrappers
and placing over the slab manually or with crane; and after insulation keeping the
scrappers ready for further use.
As mentioned above in the method of scale removal using the system , the number
of scrappers and its arrangement are selected based on the degree of accumulation
to be removed.
The invention therefore provides for the system and method for hearth scale
removal involving the hinge scrappers which is directed to favour simple and
effective scale removal without necessitating without downing the furnace.
The details of the invention its object and advantages are explained hereunder in
greater detail in relation to non-limiting accompanying figures of the system as
discussed hereunder:
BRIEF DESCRIPTION OF THE ACCOM PANYING FIGURES
Figure 1 is a top plan view of the system for hearth scale removal in accordance
with the present invention disposed in relation to a walking beam type reheating
furnace;

Figure 2 is an illustration explaining the scrapper disposition inside the furnace
following the manner of operation of the scrapper based scale removal system in
accordance with the present invention.
Reference is first invited to Figure 1 which illustrates the manner of disposition of
the scrapper assembly in accordance with the invention on the reheating furnace for
the required scale removal. As shown in said figure the system basically involves a
first slab (1) comprising the scrapper carrying slab is provided on which the scrapper
system is secured such as by welding. A second slab (2) comprises the locking slab
which is adapted to lock the scrapper assembly when the scale load is encountered.
The hinge (3) is Provided to hold the scraper assembly and facilitate its 270°
rotation. The fixed (4) and moving (5) skids comprise basic features of any walking
beam furnace provided to cause the movement of siab/charge from charging to the
discharging end. The scrapper assembly (6) constitute the main body which
performs the cleaning, of the hearth seale.
Reference is further invited to accompanying Figure 2 which further illustrates the
disposition of the scrappers inside the furnace for scale removal from the hinged
means with respect to the scrapper carrying slab for the removal of the scale. As
apparent from the said figure two sets of scrappers, each having two billets of
diameters of about 100mm. and length 1000 mm. are welded on the available full
length slab having flexibility of 270° movement. The slab and scrapper arrangement
are adapted to be lifted by crane and placed on the roller table in front of pushers.
After proper centering the slab is charged into the furnace keeping the hooks in
hanging position. It is possible that the hook is required to be charged after 45 to 60
days of furnace operation while the scale level of hearth is about to come in the level
of moving skid. During shut down of the mill furnace is made empty. As soon as the
last charge is discharged, the furnace, is tripped and the slab (l) with scrapper is
charged. A wider slab locking slab (2) is charged just behind the slab (1) for locking
of the scrapper. The beam is operated in discharge priority. A means such as a hook
means can be provided to carry the scale in its range and dump into hoppers and
troughs from where it can be removed easily.

Thus for use of the system for scale removal of the invention, the furnace is made
empty and gas supply cut-off to lower the temperature. Thereafter the system
involving the scrapper means with the scrapper resting on the top of slab (1) is
placed in front of pusher /charging machine via a crane. After centering scrappers
are lifted and rotated to rest on roller table. Now slab is pushed inside the furnace
and taken forward by operating the beam. Once the scrapper falls vertically
downwards, beam is stopped and the wider locking slab (2) is charged immediately
locking the scrappers .The pair of slabs are moved in the scale accumulated area
and taken forward in continuous observation. Scale equal to the hanging length of
scrappers is carried and dumped in the hoppers .Once slab reaches the discharge
end it is taken out by extracting machine and cooled with water. The scrappers are
rotated and placed over the slab manually or with crane. After reinsulation the
scrappers are kept for further use.
When scrapper comes in contact with scale it has the lifting tendencies due to the
load applied by the same. The locking slab width and weight ensure the effective
utilization of scrappers. A light weight slab will slip or lift easily causing free
movement of scrappers once counter load is applied by the scale.
Importantly, the system as above can have one or more scrappers attached to the
slab depending upon the location to be cleaned along with the width of the reheating
furnace. Width of the scrapper usually depend upon the gap to be cleaned between
the skids with due consideration of positioning errors, if any, at the time of charging.
The length of the scrapper are selectively provided by making balance among the
clearance allowed by the furnace design, strength of the scrapper material,
temperature at the time to cleaning, handling facilities and the area to be cleaned.
Advantageously, in case of higher degree of accumulation of scale, two or more sets
of scrappers are charged one behind the others with the scrapper length with
increasing order and a last locking slab is provided.
It is thus possible by way of the present invention to provide for a system for
removal of hearth scale from walking beam type of reheating furnaces which would
enable removal of the hearth scale from the furnaces in operating condition without
requiring the stoppages of furnaces leading to huge production loss. Importantly,

the invention is directed to also achieve higher campaign life of the furnace and
avoid conditions adversely affecting refractory life and also the production loss. The
system and method for removal of hearth scale from walking beam type reheating
furnaces is simple and user friendly and at the same time would be cost effective
for ready and wide scale application / use for removing hearth scale from walking
beam type reheating furnaces.

WE CLAIM:
1. A system for removal of scale from walking beam furnaces adapted for use also
while in operation of the furnace comprising:
a scrapper(6) carrying slab(l) means having hinged(3) scrapper means ;
said hinged(3) scrapper adapted such that the scrapper(6) means can be rotated by
270° with respect to said hinge to hang downwards when said scrapper carrying slab
is pushed inside the furnace;
a locking slab(2) means adapted to lock the scrappers in its downward hanging
position inside the furnace ;
means to move the said scrapper carrying slab(l) with said scrapper(6) extending
downwards into the furnace for scale scrapping and thus maintained, along with said
locking slab(2), from the charging end towards the discharge end along the scale
deposit area of the furnace whereby scales equal to the hanging length of scrappers(6)
are carried and dumped in the hoppers, to thereby remove the scale from the hearth.
2. A system for removal of scale from walking beam furnaces as claimed in claim 1
comprising crane means for lifting of the scrapper carrying slab(l) with the
scrappers(6) on top and placing in front of a pusher unit.
3. A system for removal of scale from walking beam furnaces as claimed in anyone of
claims 1 or 2 comprising means for centering and rotating the scrappers by 180° such
as to rest on the roller table such that the slab when pushed in such disposition in the
furnace the scrappers hang downwards inside the furnace.
4. A system for removal of scale from walking beam furnaces as claimed in anyone of
claims 1 to 3 wherein the width and weight of said locking slab(2) is selected such that
the scrappers(6) do not get displaced while taking the load of scale and adapted to be
charged such that the said scrapper(6) means are locked in its downwards hanged
disposition inside the furnace to facilitate scale removal.

5. A system for removal of scale from walking beam furnaces as claimed in anyone of
claims 1 to 4 wherein said scrappers(6) are adapted to favour the lowering of the scale
level by its length and dispose in the scale hopper.
6. A system for removal of scale from walking beam furnaces as claimed in anyone of
claims 1 to 5 wherein said scrapper carrying slab(l) is adapted for cooling after
discharge from the furnace and the scrappers(6) adapted to be placed on the slab top
and kept insulated after removing from the roller table for subsequent operation.
7. A system for removal of scale from walking beam furnaces as claimed in anyone of
claims 1 to 6 comprising sets of scrappers each having two billets which are welded on
the available full length of the scrapper carrying slab with said required flexibility of
270° movement.
8. A system for removal of scale from walking beam furnaces as claimed in anyone of
claims 1 to 7 wherein the scrappers are adapted such that it can rotate 270° around the
hinge.
9. A system for removal of scale from walking beam furnaces as claimed in anyone of
claims 1 to 8 wherein the scrappers are anchored and insulated to resist the heat and to
retain the strength at furnace temperature such as after one hour of tripping.

10. A system for removal of scale from walking beam furnaces as claimed in anyone of
claims 1 to 9 wherein the scrappers and hinge are adapted based on the clearance of
skids from the charging and discharging upper walls, from upper and lower screen wall
if any, from the burner tunnel such the walls and scrappers do not get damaged.
11. A system for removal of scale from walking beam furnaces as claimed in anyone of
claims 1 to 10 comprising one or more scrappers secured to the scrapper carrying slab
means selectively provided based on the location to be cleaned along the width of the
furnace, the width of the scrappers selectively provided based on the gap to be cleaned
between the skids with due consideration of positioning errors, if any, during charging.

12. A system for removal of scale from walking beam furnaces as claimed in anyone of
claims 1 to 11 wherein the length of the scrappers is selectively provided based on the
balance there between the clearance allowed by the furnace design, strength of the
scrapper material, temperature at the time of cleaning, handling facilities and the area
to be cleaned.
13. A system for removal of scale from walking beam furnaces as claimed in anyone of
claims 1 to 12 comprising two or more sets of scrappers charged one behind the other
with the scrapper length in increasing order upto the last locking slab.
14. A method for removal of scale from walking beam furnaces also while in operation
using the system as claimed in anyone of claims 1 to 13.
15. A method as claimed in claim 14 comprising :
emptying the furnace and cutting -off the gas supply to thereby reduce the
furnace temperature;
providing the scrappers carrying slab with scrappers resting on top in front of
pusher /charging machine using a crane means;
centering the scrappers ,lifting and rotating the same to rest on the roller table;
pushing the slab inside the furnace and taking forward by operating the beam
until the scrapper fall vertically downwards;
charging the locking slab to thereby lock the scrappers there between the slabs;
moving the pair of slabs in the scale accumulated area and taking forward in
continuous observation;
carrying and dumping in hoppers scale equal to the hanging length of the
scrappers.

16. A method as claimed in claim 15 wherein once the slab reaches the discharge end it
is taken out by extracting machine and cooled with water; followed by rotating the
scrappers and placing over the slab manually or with crane; and after insulation
keeping the scrappers ready for further use.
17. A method as claimed in anyone of claims 15 or 16 wherein the number of scrappers
and its arrangement is selected based on the degree of accumulation to be removed.
18. A system for removal of scale from walking beam furnaces adapted for use also
while in operation of the furnace and a method of scale removal using such system
substantially as herein described and illustrated with reference to the accompanying
figures.

A system for removing hearth scale from reheating furnaces and, in particular, to a
system for removing hearth scale from walking beam type reheating furnaces in
operating conditions. The system basically includes a scrapper carrying slab (1) a
locking slab (2) a hinge means (3) supporting a scrapper assembly (6). The system
would enable removing hearth scale from the said walking beam type reheating
furnaces in operating conditions to achieve higher campaigning life of furnace and
avoid the need for frequent downing of the furnace which adversely affected the
refractory life and also lead to production loss. The method of scrap removal using
the system of the invention is simple to carry out and cost effective and is directed
to favour wide scale application and use of the same for removal of hearth scale ,in
particular, from the walking beam type reheating furnaces.