CLIAMS:1. A basic oxygen furnace converter for steel-making, said basic oxygen furnace converter comprising:
a vessel with refractory lining connected to at least one trunnion;
a tilting drive for tilting said vessel;
plurality of bracket(s) positioned on said vessel;
wherein said brackets are connected to said vessel through welding the centre block of said bracket(s) with said trunnion using a tie rod therefore preventing elongation of said vessel during high temperature, thereby increasing the reliability and prolonging period of vessel replacement.
2. The basic oxygen furnace converter as claimed in claim 1, wherein said trunnion supports said vessel on a shaft of an electric motor, thereby said converter rotate about its horizontal axis on trunnions.
3. The basic oxygen furnace converter as claimed in claim 1, wherein said trunnion is supported through said bracket(s). ,TagSPECI:TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to basic oxygen furnace (BOF) Converters for steel making. More particularly, the present invention provides an improved suspension bracket (s) of Basic oxygen furnace (BOF) Converters for increasing the reliability and thereby prolonging the period of vessel replacement.

BACKGROUND AND THE PRIOR ART
Presently, two numbers of 66 Ton LD Converters are running in SMS-I named as Converter # P & Q, producing about 0.4Mt of Steel per annum. These converters were installed & commissioned in 1966. The basic features of the converters are given below,
The Basic Features of the Converter
a) Capacity : 66 Tons.
b) Types : Eccentric mouth.
c) Specific volume : 0.63 M3/Ton
d) Suspension type : Bolted brackets with water cooled trunion. (6 numbers of Big bracket and 2 numbers of small bracket).
e) These converters are first generation converters with eccentric mouth.
Originally, Tar bonded dolomite bricks were used in these converters, which was giving lining life of 100-150. Subsequently, the lining was changed to Magnesia carbon bricks from Tar bonded dolomite bricks in the year 1996, to enhance the lining life. This change gradually improved the lining life and thereby the techno economics of converter. The lining life of converters since year 2004 is given in table 1.
However, the thermal conductivity of Magnetia carbon brick being higher, the shell temperature went up to as high as 400 Deg Cent. This temperature resulted in elongation of the converter shell. The phenomenon of elongation took place due to creep & it occurs over a period of 2 to 3 years of time.
The elongation of vessel goes as high as 80 to 90 mm & there by the brackets from the trunion gets detached (Drawing No. CDB/R-54481 is shown in fig 2). Therefore, while tilting the converter, there was heavy jerk and it was giving knock/impact to the main bearing as well as the tilting drive.
In July 2006, there was major breakdown for 10 days in the tilting drive of Converter # Q, due to bull gear bearing (Inner & Outer bearing race) failure. This break down primarily occurred due to heavy jerk as explained above. This converter was last replaced in 1996. Due to elongation of the vessel, the suspension brackets got detached.
Almost on daily basis converter remained down due to failure of brackets and temporary vertical stiffeners were welded regularly. Due to repetitive break downs, the converter down time went as high as 64 hours during the period July to November 2006. The down time was only because of bracket failure. Accordingly, the equipment availability drastically came down. It was a major area of concern because of the unreliability of Converter.
It was observed that the original 8 nos of brackets, which are of cast design and bolted to the converter are also getting inclined due to elongation of fixing bolts over a period of time, along with the elongation of vessel itself which is explained earlier.
There are 8nos of brackets in total which are bolted to the converter and the trunnion is supported through the brackets. Out of 8 brackets, 6 brackets are called big brackets and 2 are called small brackets. 2Nos. each big bracket is fixed on the drive side, non drive side and slag side. 2 nos of small brackets are fixed on tap side. The bolted brackets are fixed into the Converter shell through counter sunk bolt. The counter shunk head of the bolt is inside the shell of the Converter and the nuts are fixed from outside the Converter. Once the Converter shell elongates and the bracket is detached from the trunion, there is heavy impact which comes on the bracket and same times the bolts also get sheared, there by the bracket becomes unstable.
US3391919 disclosed a mounting for a converter from a trunnion ring in which the trunnion ring supports the converter vessel by a plurality of rods depending from the top of the trunnion ring, secured to the vessel below the trunnion ring, and having universal freedom, for example, by reason of ball and socket connection to the trunnion ring at the top. The load is applied centrally to the trunnion ring cross-section.
Since there was a repetitive breakdown due to such failure, the innovation of fabricated bracket is thought of and is designed with tie rod which is shown in figure 2. The fabricated bracket is replaced in position one by one by removing the old bolted brackets.
OBJECTS OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.
Another object of the present invention is to provide an improved suspension bracket (s) of basic oxygen furnace (BOF) converters.
Another object of the present invention is to provide a fabricated bracket for increasing the reliability and thereby prolonging the period of vessel replacement.
Another object of the present invention is to provide a tie rod for preventing elongation of the converter shell, thereby providing stable bracket.
These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.
The present invention provides suspension bracket (s) of welded design for basic oxygen furnace (BOF) converters.
According to an aspect of the present invention, there is provided a basic oxygen furnace converter for steel-making, said basic oxygen furnace converter comprising:
a vessel with refractory lining connected to at least one trunnion;
a tilting drive for tilting said vessel;
plurality of bracket(s) positioned on said vessel;
wherein said brackets are connected to said vessel through welding the centre block of said bracket(s) with said trunnion using a tie rod therefore preventing elongation of said vessel during high temperature, thereby increasing the reliability and prolonging period of vessel replacement.
Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
Figure 1 illustrates the old design bolted bracket shown in blue circle
Figure 2 illustrates the fabricated bracket in knockdown condition after welding to the converter, constituting fabricated bracket.
Figure.3 illustrates the bottom bracket shown is of old bolted design. Top bracket shown is of fabricated design after replacement in converter # 5.
Figure.4 illustrates the both top & bottom fabricated bracket with tie rod connection in converter # 4.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.
Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.
Accordingly, present invention provides an improved suspension bracket (s) of Basic oxygen furnace (BOF) Converters for increasing the reliability and thereby prolonging the period of vessel replacement.
Since fabricated brackets are of welded design, it could be welded to the outer shell of Converter very easily, without any affect on refractory, which is inside. The center block of the brackets as shown in the figure 2 is flushed with the groove of the trunion and complete welding of the bracket is done to the converter shell. The top & bottom bracket is connected with 80 x 1900 mm bolt as per figure 2 for tie rods. This tie rod prevented further elongation of Converter shell, thereby the bracket and trunion became stable.
Therefore, during the preparedness of vessel replacement the Converter could be used gainfully without any down time. To make the Converter stable the fabricated brackets IS replaced one by one in Converter#P and making the Converter stable. Presently 6 out of 8 brackets are replaced with fabricated design.
Presently the Converter is running safely without any breakdown due to bracket failure by using the fabricated brackets.
Usefulness of the present invention:
A) Technical:
· Break down due to failure of bracket after 4 to 5 years of running of Converter is eliminated, thereby increasing the Converter availability. Detail of which is shown in the economic usefulness.
· Break down of tilting drive and main bearing is eliminated, due to elimination of jerk during tilting of Converters.
· Production loss due to down time for failure of brackets is eliminated.
· Higher lining life is possible because of stability and reliability of Converters. Shown in table 1 given below:

TABLE 1
CONVERTER#P CONVERTER#Q
Sl. Conv. Start date after relining Lining Life Sl. Conv. Start date after relining Lining Life
1 04/04/04 1050 1 05/02/04 730
2 10/09/04 1126 2 11/06/04 858
3 17/02/05 1003 3 23/11/04 1034
4 14/08/05 1314 4 20/05/05 1042
5 09/02/06 1604 5 27/11/05 1219
6 25/08/06 1828 6 07/05/06 1248
7 02/04/07 2012 7 31/10/06 1516
8 12/12/07 2109 8 20/05/07 1069
9 10/08/08 2070 9 05/10/07 1567
10 28/04/09 2350 10 19/06/08 1447
11 18/01/10 1690 11 19/12/08 1426
12 09/08/10 1690 12 01/07/09 957
13 07/04/11 2031 13 08/11/09 1746
14 22/11/11 1535 14 15/05/10 1792
15 24/04/2012 1296 15 02/07/11 1647
16 16/01/2013 1884 16 12/02/12 1490
17 17 11/10/12 1843

· Prior to the innovation, there was a spalling affect of the refractory with slag splashing coating, which was falling down due to heavy jerk of the Converter. This was resulting in reduction in lining life.
· Repair of brackets of Converter was possible because it is of fabricated / welded design, which is done from outside the vessel.
· The vessel is stable by using fabricated design brackets.
B) Economic.
· The total Mechanical down time from 2005-06 to 2012-13 has been given below.

Financial year Mechanical delay in BOF Converters/year. Time saved in Hrs. after innovation/modification.
2006-07 179 Hrs 20 Mts. --
2007-08 127 Hrs 25 Mts. 52
2008-09 122 Hrs 22 Mts. 57
2009-10 113 Hrs 13 Mts. 66
2010-11 106 Hrs 35 Mts. 73
2011-12 99 Hrs. 30 Mts. 80
2012-13 98 Hrs. 50 Mts. 81
Total = 409 Hrs

· As mentioned that there was a delay of 64 hrs., exclusively for Converter bracket failure in addition to other delays in Fin-Yr. 2006-07, totaling 179 Hrs 20 Mts as indicated above. Subsequently it is seen from the above table there has been a gradual reduction in delay which was possible by introducing the fabricated bracket in the BOF Converters.
· Considering from 2007-08 till 2012-13, reduction in total delay is 409 Hrs. in 6 (Six) years which is coming about 68 Hrs saving in delay due to bracket failure, per annum.
· Considering the average cost of Steel as Rs 30,036/-, the heat Size of SMS-I as 66 Tons and thereby, there is a saving of 81 blows in 68 hrs (Tap to tap time 50 Mts.) per Annum. Hence, the cost saving for 81 blows shall be ( 30,086x66 x 81) = 16,05,72,456.00. Therefore, the direct cost saving due to innovation is Rs 16,05,72,456.00 ( Rupees Sixteen crores, Five lakhs, Seventy Two thousand & Four hundred fifty six only)
C) Impact in Industry.
· There has been a very positive impact on the industry due to the above innovation, since; lot of resource and man hours was getting lost due to failure of brackets, before the innovation was done. Therefore, the moral of the employees have also gone up.
· This modification can be implemented in any of the old Converters where ever there is a bolted design of suspension bracket of the Converter.