Title of Invention

COOLING SYSTEM FOR CONTINUOUS ANNEALING FURNACES

Abstract Cooling system for continuous annealing furnaces for producing annealed strips. The system comprises a plurality of sets of fans (2) and motors(3) provided atleast one of the walls (4) of the cooling chamber of the said continuous annealing furnace, said fans (2) projecting inside the cooling chamber and the corresponding motors (3) outside the said chamber, each said fan (2) and corresponding motor (3) being connected by a bearing shaft(5) passing through the said wall (4) and heat shields provided between the said fans and motors characterized in that the heat shield is comprised of ceramic fibre sheet (1). The system is also applicable in any cooling operation and can be very well utilized for any furnace or similar application.
Full Text COOLING SYSTEM FOR CONTINUOUS ANNEALING FURNACES
Field of the invention
The present invention relates to a coupling system for continuous annealing furnaces for producing annealed strips. The cooling system of the present invention has favourable effects in the process of annealing and results in improved quality of annealed strip. The system is also applicable in any cooling operation and can be very well utilized for any furnace or similar application.
Background of the invention
In manufacture of metal or alloy, especially steel, the strips are finally rolled in tandem mill after manufacture. These strips before annealing poses little or no cold working properties due to grain elongation and distortion of the crystalline lattice pattern during manufacture. This high degree of deformation is restored to a microstructure equilibrium allowing recrystallisation of these grains by heat treating at below the lower critical temperature known as annealing. Annealing process is carried out in batch furnaces or in continuous annealing lines. The draw ability of the strip of the continuous annealed material is better than box annealed material if annealing is carried out at higher temperature-ranges.
Continuous annealing lines primarily comprise arrangements for cleaning of strips and annealing furnace. Annealing furnaces comprise different zones or chambers like heating, holding, slow cooling and fast cooling.
In the fast cooling chamber there are large number of cooling fans for cooling of the strips before they come out of the protective atmosphere of the furnace The fans are suitably arranged in the chamber walls and are so fitted such that the blades are inside the chamber and the corresponding motors are outside. In order to protect the motor and bearings from the elevated temperatures of the chamber, a heat shield is built

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between the blades and the motor. Such conventional heat shields utilize running water to absorb the heat generated inside the chamber so that the motor does not heat up. Such water shields comprise an annular space having water inlets and outlets. Water enters the annular space through the inlet, absorbs heat and hot water flows out through the outlet. Such water shields are quite common and have diverse applications in the industry.
The aforesaid system has some inherent drawbacks especially in cases when the cooling chamber has an atmosphere of protective gases. A typical atmosphere in the cooling chamber of an annealing furnace is 95% Nitrogen and 5% Hydrogen. The atmosphere does not allow any oxidation of the high temperature strips inside the cooling chamber. However, in cases of water leakage, even as little as a few drops can destroy the protective atmosphere and lead to unwanted oxidation of the strips. The water leaking out of the water-flow space vapourizes easily in the elevated temperature of the cooling chamber and leads to formation of oxidising atmosphere inside the chamber, thus destroying the protective atmosphere. This leads to surface deterioration of the strips.
In addition to this, the industrial water used in such cooling purposes forms scales and depositions inside the annular space or pipelines through which the water flows into and out of the annular space. Such deposits cause decrease in the flow of cooling water and may lead to complete blockage if proper maintenance is not carried out in time. Maintenance of pipelines would mean closing down a portion of the system during the cleaning operation. Deposition/scaling can be avoided by prior purification of cooling water but the use of purified water is uneconomical. Moreover, one often finds steam at the outlet pipe and drain which are in the proximity or in contact with the motor. This steam comes in contact with the motor, reduces its insulation and eventually results in motor burning. Subsequently, the cooling system becomes nonfunctional.

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In conventional systems, the cooling water-flow annular space is integral with the fan and motor. The absence or non-functioning of a single fan and motor would mean stopping the water flow in atleast a part of the system. In most situations the cooling water flows through a series of annular spaces and fans and disassembling one fan and motor would mean shutting down the complete series and in turn shutting down the complete furnace. Similarly, an operation of assembling of a fan would mean the shutdown of the furnace. This leads to increased down time and subsequent decrease in productivity. Even if few of the fans are non-functional, all the fans in series have to be stopped resulting in decrease in the line speed of the continuous annealing furnace.
US 6069652 teaches a furnace video camera apparatus from monitoring industrial processes for viewing the interior of the heated chamber. The patent teaches ceramic heat shield tube telescopically surrounding and spaced from at least a portion of the camera. Importantly, in US 6069652 heat prevention is effected by use of the ceramic tubes. Furthermore, in US 6069652 cooling fluid is used.
Thus there is a need for an improved cooling system which will effect fast and effective cooling of the hot strips in the fast cooling chamber and will not have the drawbacks of the conventional cooling systems.
Objects of the invention
The object of the invention is to provide a cooling system in a continuous annealing furnace that is efficient and improves the quality of annealed strips produced in the said furnace.
Another object of the invention is to provide a cooling system that is fast and leads to increased productivity of annealed strips.
Another object of the present invention is to provide a cooling system that does not have the inherent drawbacks associated with the use of water for shielding of heat between the motor and the hot chamber.
Another object of the present invention is to provide a cooling system which requires very less down time for repair and maintenance.

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A further object of the present invention is to provide a cooling system that ensures long life of the fan motors.
Yet further object of the present invention is to provide a cooling system which helps in maintaining the protective atmosphere in fast cooling chambers in annealing furnaces.
The applicants have now surprisingly found that the aforesaid objects can be achieved by the use of suitable insulating materials in place of the annular water-flow spaces, the insulating material preferably being ceramic fibres.- The applicants have further found that unlike US 6069652 providing heat shields between fans and motors in the form of ceramic sheet/blanket provides fast and effective cooling and at the same time eliminates use of any liquid cooling arrangement.
Summary of the invention
Thus according to the present invention there is provided a cooling system for continuous annealing furnace for producing annealed strips comprising:
a plurality of sets of fans and motors provided at atleast one of the walls of the cooling chamber of the said continuous annealing furnace, said fans projecting inside the cooling chamber and the corresponding motors outside the said chamber, each said fan and corresponding motor being connected by a bearing shaft passing through the said wall; and
heat shields provided between the said fans and motors characterized in that the heat shield is comprised of ceramic fibre sheet.
Detailed description
The present invention describes a completely new approach for protection of the motor and bearings of the cooling components/fans. The system comprises a plurality of sets of fans and motors provided at atleast one of the walls of the cooling chamber of the continuous annealing furnace. In each of the sets the fan projects inside the cooling chamber and the corresponding motor outside the chamber. The fan and the motor is

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connected by a bearing shaft passing through the wall of the cooling chamber. Heat shields are provided between the fans and motors. These heat shields are made of ceramic fibre and form portions of the said wall in the regions around the said bearing shaft substantially covering the area of the fans. The heat shields are circular in shape covering the area of the fans. They may also be of different shapes but must substantially cover the area of the fans to adequately protect the motor from the heat generated inside the cooling chamber. The chamber has a number of fans depending on the size of the chamber, the amount of cooling required and the production speed.
Any grade of ceramic fibre can be used in the heat shield of the present invention. Preferably, grades of ceramic fibre for applications wherein the temperature is around 1260°C and 1400°C are proposed. However, since the temperature of cooling chamber remains much lower than either of the aforesaid temperatures, any grade of ceramic fibre can be used.
Ceramic fibres are classified as per their chemical analysis. One is alumina silica based and the other is alumina zirconium based: Either of the two can be used on the present application.
The present invention effectively removes the drawbacks associated with the prior art cooling systems. As the present invention does not use running water, the problems associated vaporization of water thereby destroying the protective atmosphere of the cooling chamber is avoided. The present system does not involve any inlet and outlet for running water and saves installation cost on pipelines and water pumps. Furthermore, problems like scaling and deposition inside pipelines and damage of fan motors due to emergence of steam from pipelines in proximity is non-existence. The present system also requires less down time during any installation/maintenance as the ceramic fibre heat shields can be made integral with the wall of the cooling chamber and removal of the heat shield and/or shutting down of the furnace is not required during any fan motor failure or general maintenance operation.

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In addition to removing the drawbacks of prior art systems, the present invention also results in high productivity of annealed steel. Furnace productivity depends on many factors out of which fast cooling is one factor. Since the present system ensures that the fans do not break down and that all the fans work simultaneously with longer life, high cooling and productivity of line speed is achieved.
Description of preferred embodiments
The invention will now be described with reference to non-limiting embodiments shown in the figures of the drawings, in which
Figure 1 shows a typical continuous annealing furnace.
Figure 2 shows a typical arrangement of fans in the cooling chamber of a continuous annealing furnace.
Figure 3 shows typical fan and motor with heat shield using water.
Figure 4 shows a fan and motor with heat shield using ceramic fibre,
Figure 5 shows a detailed view of a portion of the heat shield of figure 4.
Figure 1 shows a typical continuous annealing furnace. The furnace comprises different zones or chambers like heating chamber (1), holding chamber (2), slow cooling chamber (3) and fast cooling chamber (4). All the chambers have fop covers (5) and bottom covers (6). The heating chamber (1) has an entry side (7) through which the continuous metal/steel strip is made to enter the furnace and into the heating chamber by the help of rollers. At the entry pint there is a pair of seal rolfers (8) for preventing the ingress of air in the furnace,. A continuous strip is made to pass through the chambers the last being the fast cooling chamber which comprises cooling fans {9} After cooiing the strip exits the furnace through the exit side (10).

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Figure 2 shows the arrangement of fans in the fast cooling chamber of a typical continuous annealing furnace. Fans 1 to 63 are arranged as shown in the figure.
Figure 3 shows a conventional fan-motor set with heat shield using water. The annular space (1) for the flow of water is provided between the fan (2) and motor (3) and forms a portion of the wall (4) of the fast cooling chamber. A bearing shaft (5) connects the fan with'the motor and passes through the annular space. The space (1) is provided with a water inlet (6) and water outlet (7) through which running water enters and exits the annular space respectively. The outlet is also provided with a funnel (8) for collecting water flowing out of the space.
Figure 4 shows a fan and motor set with ceramic fibre heat shield in accordance with the present invention. A ceramic fibre sheet (1) is provided between the fan (2) and motor (3). The sheet (1) forms a portion of the wall (4) of the fast cooling chamber. A bearing shaft (5) connects the fan with the motor and passes through the wall. The ceramic fibre sheet (1) is annular in shape and forms an annular portion of the wall around the bearing shaft. The size of the sheet (1) is such that it covers the area projected by the fan (2) perpendicularly on the wall.
Figure 5 shows a detailed view of a portion of the heat shield of the present invention and illustrates the easy installation of ceramic fibre into a conventional system using water. In such a system as illustrated in Figure 3, the water inlet (6), water outlet (7) and the funnel (8) are removed. Thereafter, referring to Figure (5), the back plate (1) of the annular space is removed carefully without damaging the circular ring (2). A ceramic fibre sheet (3) of the same size as the inner surface of the annular space is inserted into the space which was for water. The back plate (1) is finally rewelded with the circular ring (2). Thus, the new system can be easily and effectively installed into the conventional systems.

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WE CLAIM
1. A cooling system for continuous annealing furnace for producing annealed strips comprising :
A plurality of sets of fans (2) and motors (3) provided at atleast one of the walls (4) of the cooling chamber of the said continuous annealing furnace, said fans projecting inside the cooling chamber and the corresponding mo9tors outside the said chamber, each said fan and corresponding motor being connected by a bearing shaft (5) passing through the said wall; and
heat shields provided between the said fans (2) and motors (3) characterized in that the heat shield is comprised of ceramic fibre sheet (1).
2. A cooling system as claimed in claim 1 wherein said heat shields form portions of the said wall in the regions around the said bearing shaft and substantially covering the area of the said fans.
3. A cooling system as claimed in claim 1 wherein the said heat shields are substantially circular in shape.
4. A cooling system as claimed in claim 1 wherein the said ceramic fibre is selected from grades of ceramic fibre for applications wherein the temperature is around 1260°C and 1400°C.


Dated this 27th day of January 2003
Cooling system for continuous annealing furnaces for producing annealed strips. The system comprises a plurality of sets of fans (2) and motors(3) provided atleast one of the walls (4) of the cooling chamber of the said continuous annealing furnace, said fans (2) projecting inside the cooling chamber and the corresponding motors (3) outside the said chamber, each said fan (2) and corresponding motor (3) being connected by a bearing shaft(5) passing through the said wall (4) and heat shields provided between the said fans and motors characterized in that the heat shield is comprised of ceramic fibre sheet (1). The system is also applicable in any cooling operation and can be very well utilized for any furnace or similar application.

Documents:

00033-kol-2003-abstract.pdf

00033-kol-2003-claims.pdf

00033-kol-2003-correspondence.pdf

00033-kol-2003-description(complete).pdf

00033-kol-2003-drawings.pdf

00033-kol-2003-form-1.pdf

00033-kol-2003-form-18.pdf

00033-kol-2003-form-2.pdf

00033-kol-2003-form-3.pdf

00033-kol-2003-p.a.pdf

33-kol-2003-granted-abstract.pdf

33-kol-2003-granted-acceptance publication.pdf

33-kol-2003-granted-claims.pdf

33-kol-2003-granted-description (complete).pdf

33-kol-2003-granted-drawings.pdf

33-kol-2003-granted-examination report.pdf

33-kol-2003-granted-form 1.pdf

33-kol-2003-granted-form 18.pdf

33-kol-2003-granted-form 2.pdf

33-kol-2003-granted-form 3.pdf

33-kol-2003-granted-letter patent.pdf

33-kol-2003-granted-pa.pdf

33-kol-2003-granted-specification.pdf


Patent Number 194958
Indian Patent Application Number 33/KOL/2003
PG Journal Number 30/2009
Publication Date 24-Jul-2009
Grant Date 09-Sep-2005
Date of Filing 27-Jan-2003
Name of Patentee STEEL AUTHORITY OF INDIA LIMITED
Applicant Address RESEARCH & DEVELOPMENT CENTRE FOR IRON & STEEL, DORANDA, RANCHI
Inventors:
# Inventor's Name Inventor's Address
1 SAHU ASIM KUMAR RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL, STEEL AUTHORITY OF INDIA LTD., DORANDA, RANCHI-834002
2 MARIK APURBA KUMAR RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL, STEEL AUTHORITY OF INDIA LTD., DORANDA, RANCHI-834002
3 DUTTA TAPAS KANTI RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL, STEEL AUTHORITY OF INDIA LTD., DORANDA, RANCHI-834002
4 PANDEY KEDAR NATH RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL, STEEL AUTHORITY OF INDIA LTD., DORANDA, RANCHI-834002
5 GANTI MAHAPATRUNI DAKSHINA MURTY RESEARCH AND DEVELOPMENT CENTRE FOR IRON AND STEEL, STEEL AUTHORITY OF INDIA LTD., DORANDA, RANCHI-834002
PCT International Classification Number C03C 10/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA