FIELD OF INVENTION
The present invention generally relates to the expansion joints in a hot blast carrying system of blast furnaces. More particularly, the invention relates to an improved expansion bellow adaptable to hot blast carrying system of blast furnaces. The invention further relates to a process of forming an improved expansion bellow on the hot blast carrying system of blast furnaces. The invention further relates to a process of forming an improved expansion bellow on the hot blast carrying system of blast furnaces.
BACKGROUND OF INVENTION
Expansion joints are necessary in the hot blast carrying system of blast furnaces to take care of the thermal expansion and compaction due to changes in the hot blast temperatures. These expansion joints are installed in different predetermined locations through out the hot blast carrying system. As the system carries hot blast at about 1200°C, the refractory needs to be used in the system with proper expansion allowances mechanisms. A popular mechanism is to provide a calculated gap in the refractory bricks and filling it with high performance insulating resilient material such as ceramic wool. The resilient material expands and get compacted during the operation and takes care of the thermal expansion and compaction of refractory bricks. These expansion allowances are not the integral part of the hot blast system. These allowances

are inserted into the hot blast system as independent expansion joints for easy installation and repair and replacements. Any failure of the expansion joints requires the blast furnace to be brought down for replacement leading to a huge production losses. Hence a reliable expansion joint is essential.
The prior art expansion joint adapted in the blast furnaces uses refractory lining with complicated brick shapes, which are susceptible to fracture owing to the complicated shape and the load factor. Further, the location of the expansion allowances with ceramic wool as provided appears to be on adhock basis without any scientific calculation which allows an easy access for the hot blast to leak from the expansion joint once a crack is formed in the refractory bricks leading to the failure of the expansion joint. Hence a more reliable expansion joint with improved refractory design including stable bricks with accurate positioning of the expansion allowance is needed to reduce the failure in the expansion joints.
The inventors have identified that the basic reasons for the failure of prior art expansion bellow is the leakage of hot blast from inside to the shell due to breakage of bricks which again gives a direct passage for the hot blast through expansion allowance of the backup layers. Once the hot blast reaches the shell the backup castable gets damaged and the shell expands. Eventually due to high temperature and pressure the shell breaks or explodes.

The prior art refractory lining consists of 3 layers for example:
1. a working layer,
2. a backup layer, and
3. an insulation layer
The working layer is the one in contact with the operating medium and is exposed to high temperatures followed by the backup layer to protect the shell. In case the working layer including the backup layer fail, the insulation layer contains the heat inside and contemplates to maintain an acceptable shell temperature.
Figure 1 shows a typical refractory arrangement of earlier design of an Expansion Bellow. The first step of configurating an expansion joint is to suitably position the shaped bricks A,B and C. The second step is to accommodate a thermal expansion Ceramic wool in between the shaped bricks B and C. However, the shaped brick C owing to its irregular shape and load perforce sustain huge stresses which get concentrated at the corners as shown in figure 1. These stresses lead to breakage of the projected portion of the brick C which allows a direct passage of the hot blast to the shell leading to leakage and sometimes explosion of the Expansion Bellow.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an improved expansion bellow adaptable to hot blast carrying system of blast furnaces, which eliminates the disadvantages of prior art.
Another object of the invention is to propose an improved expansion bellow adaptable to hot blast carrying system of blast furnaces, which uses modified-shaped bricks and provides logical positioning of expansion allowances in the brick-lining.
A still another object of the invention is to propose an improved expension bellow adaptable to hot blast carrying system of blast furnaces, which prevents transfer of any stress in the bricks during movement of the refractory owing to provision of a working layer including a back-up layer having multiple independent layers.
A further object of the invention is to propose an improved expansion bellow adaptable to hot blast carrying system of blast furnaces, in which the locations of expansion allowances are provided in a logical and staggered manner.

A still further object of the invention is to propose an improved expansion bellow adaptable to hot blast carrying system of blast furnaces, which is reliable, failsafe and cost-effective.
Another object of the invention is to propose a process for forming an improved expansion bellow on the hot blast carrying system of blast furnaces.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure-1- Shows a typical refractory arrangement for a prior art expansion bellow
Figure 2- Shows a flow-chart illustrating the steps of configurating an improved expansion bellow of the invention.
SUMMARY OF INVENTION:
Accordingly, in a first aspect of the invention, there is provided an improved expansion bellows adaptable to hot blast carrying system of blast furnaces, comprising a first plurality of refractory-lined shaped bricks (A,B) disposed at different locations throughout the hot blast carrying system by maintaining a gap between the each refractory-lined shaped bricks, the gaps being filled with ceramic wool to accommodate thermal expansion of the refractory due to high

temperature sustained by the bricks; a second plurality of refractory-lined irregular shaped bricks (c ) installed on the positions adjoining complicated locations of the internal walls forming the blast furnace, the second plurality of refractory-lined irregular shaped bricks having projected corners constituting weak comers being susceptable to huge stresses concentrating in particular on the weak corners leading to breakage of at least said projected corners, the improvement is the refractory-lined bricks are configured to be of smaller in size and regular in shape; the working layer and the back-up layer each formed with multiple independent layers to eliminate transfer of any stress from one to the other course during movement of the refractory; and expansion allowances are disposed on a logical and staggered basis to prevent breakage of gas through the expansion allowances.
In a second aspect of the invention, there is provided a process of forming an improved expansion bellow on the hot blast carrying system of blast furnaces, the process comprising thermal modeling of the refractory bricks so as to identify the weak areas in the refractory bricks; replacing the existing refractory bricks with simple and regular shaped bricks so as to eliminate the weak area of the refractory brick; forming the working layer into multiple independent layers to facilitate easy movement of the refractory due to thermal expansion or

contraction; forming the back-up layers into multiple independent layers which allows staggered placement of the expansion allowances; and positioning the expansion allowances in a staggered manner so as to eliminate any leakage of hot blast from inside the shell.
The Improved expansion bellow reduces the breakage of the refractory bricks owing to the provisions of refractory bricks of regular shapes. Also the refractory working lining is made into multiple independent layers so as to eliminate transfer of any stresses from one course to other during the movement of the refractory. Such a configuration allows an easy movement of the refractory in the expansion bellow and prevents development of high stresses in the bricks. The locations of the expansion allowance are provided in a logical and staggered way so that there is absolutely no way for gas to leak from the expansion allowances. The back-up layer is also made into multiple layers to facilitate the staggered placement of the expansion allowances.
The refractory arrangement according to the invention is modified. The complicated big brick shapes have been replaced with smaller and simpler brick shapes, as there are no bricks of complicated shapes, so the high stress areas in the bricks have been eliminated. Hence the probability of breakage of bricks is

very low. Also the Main working lining is made into multiple independent layers this improves the easy movement of expansion bellow and reduces the transfer of stresses from one layer to other, Hence prevents unnecessary stress build-up an the expansion allowances have been placed in such a staggered manner to ensure that there should not be any direct passage of hot blast to the shell even after the breaking of the bricks. The back-up lining also been made into multiple layers to accommodate staggered placing of expansion allowances. Hence there will be no leakages of Expansion bellow.
DETAIL DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION:
According to the invention the irregular shaped big size refractory bricks have been replaced with smaller, simpler and regular shaped bricks such that a high expressed process area in the brick as of prior art, are eliminated. The refractory brick now adapted to the expansion bellow eliminate the probability of frequent breakage of bricks. The working layer is made into multiple independent layers which facilitates an easy movement of the expansion bellow and reduces the transfer of stress from one layer to other which interalia prevents building-up

of avoidable stress. Further the expansion allowances according to the invention are provided in a staggered manner such that any direct passage for the hot blast to the shell can be avoided even incase the bricks are broken. Additionally, the backup layer has also been made into multiple layer to accommodate stresses placing of the expansion allowances. Fig. 2 illustrates the method for configurating an improved expansion bellow adaptable to hot blast carrying system of blast furnaces.
The inventive method for forming the expansion bellow comprises the steps of thermal modeling of the refractory bricks so as to identify the weak areas in the refractory bricks; replacing the existing refractory bricks with simple and regular shaped bricks so as to eliminate the weak area of the refractory brick; forming the working layer into multiple independent layers to facilitate easy movement of the refractory due to thermal expansion or contraction; forming the back-up layers into multiple independent layers which allows staggered placement of the expansion allowances; and positioning the expansion allowances in a staggered manner so as to eliminate any leakage of hot blast from inside the shell.

We Claim:
1. An improved expansion bellows adaptable to hot blast carrying system of blast furnaces, comprising:
- a first plurality of refractory-lined shaped bricks (A,B) disposed at different locations throughout the hot blast carrying system by maintaining a gap between the each refractory-lined shaped bricks, the gaps being filled with ceramic wool to accommodate thermal expansion of the refractory due to high temperature sustained by the bricks;
- a second plurality of refractory-lined irregular shaped bricks (c ) installed on the positions adjoining complicated locations of the internal walls forming the blast furnace, the second plurality of refractory-lined irregular shaped bricks having projected corners constituting weak corners being susceptable to huge stresses concentrating in particular on the weak corners leading to breakage of at least said projected corners, the improvement is characterized in that:

- the refractory-lined bricks are configured to be of smaller in size and regular in shape;
- the working layer and the back-up layer each formed with multiple independent layers to eliminate transfer of any stress from one to the other course during movement of the refractory; and
- expansion allowances are disposed on a logical and staggered basis to prevent leakage of gas through the expansion allowances.
2. A process of forming an improved expansion bellow on the hot blast carrying system of blast furnaces, the process comprising thermal modeling of the refractory bricks so as to identify the weak areas in the refractory bricks; replacing the existing refractory bricks with simple and regular shaped bricks so as to eliminate the weak area of the refractory brick; forming the working layer into multiple independent layers to facilitate easy movement of the refractory due to thermal expansion or contraction; forming the back-up layers into multiple independent layers which allows staggered placement of the expansion allowances; and positioning the expansion allowances in a staggered manner so as to eliminate any leakage of hot blast from inside the shell.

3. An improved expansion bellows adaptable to hot blast carrying system of
blast furnaces, as substantially described and illustrated herein with reference to
the accompanying drawings.
4. A process of forming an improved expansion bellow on the hot blast carrying
system of blast furnaces, the process, as substantially described and illustrated
herein with reference to the accompanying drawings.

The invention relates to an improved expansion bellows adaptable to hot blast carrying system of blast furnaces, comprising a first plurality of refractory-lined shaped bricks (A,B) disposed at different locations throughout the hot blast carrying system by maintaining a gap between the each refractory-lined shaped bricks, the gaps being filled with ceramic wool to accommodate thermal expansion of the refractory due to high temperature sustained by the bricks; a second plurality of refractory-lined irregular shaped bricks (c ) installed on the positions adjoining complicated locations of the internal walls forming the blast furnace, the second plurality of refractory-lined irregular shaped bricks having projected corners constituting weak corners being susceptable to huge stresses concentrating in particular on the weak corners leading to breakage of at least said projected corners, the improvement is the refractory-lined bricks are configured to be of smaller in size and regular in shape; the working layer and the back-up layer each formed with multiple independent layers to eliminate transfer of any stress from one to the other course during movement of the refractory; and expansion allowances are disposed on a logical and staggered basis to prevent leakage of gas through the expansion allowances.