Title of Invention

AN IMPROVED DEVICE FOR HEAT INSULATION OF LADLE COVER AND A METHOD OF CONSTRUCTING THE SAME

Abstract

An improved device for heat insulation of ladle cover , characterised in that the device comprises multiple layers of strips of ceramic fibre blanket wrapped tightly around the outer peripheral surface of four concentric metallic rings (r1 to r4) of increasing diameter and held in position with respect to said rings by means of twentyfour metallic rods (R1 to R24) inserted into the said rings and the layers of ceramic fibre strips wrapped around the rings to form a dish-like body which is kept suspended with its horizontal plane parallel to the inner surface of the ladle cover by means of twenty hangers (H1 to H20) each having its one end fixed to the inner surface of the lader cover and other end to the junction of a rod and ring laid in the said dish-like body formed. A method of constructing the improved device is also disclosed. Reference: Figures 1, 2a, 2b, 2c, 2d and 2e of the accompanying drawings.

Full Text

The present invention relates to an improved device for heat insulation of ladle cover and a method of constructing the same. The invention relates more particularly to an improved heat insulating device for ladle cover, in which strips of ceramic fibre blanket are wrapped in the form of coils around the outer peripheral surface of a number of concentric rings of increasing diameter made of stainless steel strips and held in position thereon by a number of stainless steel rods introduced radially into the rings as well as the layers of ceramic fibre blanket strips wrapped around the rings and the dish-shaped body thus formed is kept suspended with its plane Parallel to the horizontal inner surface of the ladle cover by means of a number of stainless steel hangers and the method followed for constructing the said device. In the steel manufacturing process, ladles, used for transportation/treatment of molten metal, are required to be preheated by means of burners and maintained at a high temperature of around 1OOO°C by heat insulation of the ladle cover before tapping molten metal into the ladles, with a view to preventing formation of skulls, damage of the refractory linings and loss of molten metal temperature in the ladles and extending the working life of the ladle covers. The existing device for heat insulating the ladle covers comprises fixing in two layers a ceramic fibre blanket of thickness 25 mm with the direction of fibres in the two layers perpendicular to each other, by means of stainless steel studs and washers of AISI 310 grade which are not kept covered up by the ceramic fibre blanket, and are therefore corroded by oxidation by the high temperature environment inside the ladles, resulting in the failure of the insulation device within a relatively short period i.e. 6 to 9 months with consequent increase in the down time of the ladles and cost of maintenance of the insulation device. The object of the present invention is to provide an improved device for heat insulating ladle covers, having an expected longer working life of around three years. Thus the invention provides an improved device for heat insulation of ladle covers, characterised in that the device comprises multiple layers of strips of ceramic fibre blanket wrapped tightly around the outer peripheral surface of four concentric metallic rings of increasing diameter and held in position with respect to said rings by means of twentyfour metallic rods inserted into the said rings and the layers of ceramic fibre strips v/rapped around the rings to form a dish-like body which is kept suspended with its horizontal plane parallel to the inner surface of the ladle cover by means of twenty hangers each having its one end fixed to the inner surface of the lader cover and other end to the junction of a rod and ring laid in the said dish-like body formed. The invention provides also a method of constracting the improved device comprising the following steps in sequence :- (i) 200 mm wide and 50 mm thick strips are cut from ceramic fibre blanket of type HTZ, density 128 kg/m3 and composition by weight % : Al2O3 - 33 to 36, SiO2 - 44 to 48, ZrO2 - 16 to 18, TiO2 - 0.3 and Fe2O3 - 0.1; (ii) the strips ar*r wrapped manually first round the outer peripheral surface of innermost ring in multiple layers tightly upto a radial thickness of 600 mm; (iii) the next outer ring is then fitted around the outer peripheral surface of the outermost layer of the ceramic fibre strips wrapped around ring and pressed by means of a fixture made from a 50 mm wide metallic strip fitted around the outer peripheral surface of ring to reduce the radial thickness of ceramic fibre strips wrapped around ring from 600 mm to 500 mm; (iv) eight rods are then inserted into matching holes in ring and next into matching holes of inner rings, and in four hangers; (v) the free ends of ring are joined by a screw through the matching holes therein and the free ends of hangers are fixed to the inner surface of ladle cover by welding; (vi) eight rods and ring are removed and ceramic fibre strips are wrapped manually around the outer peripheral surface of ring tightly upto a radial thickness of 600 mm; (vii) ring is again fitted around the outer peripheral surface of the outermost layer of the ceramic fibre strips wrapped around ring in the same manner as in steps (iii) to (vi), followed for fixing ring; (viii) outer ends of eight rods are fixed at the matching holes in ring and the rods are fixed next into matching holes of inner rings, and in four hangers by eight cotter pins respectively through hole in each rod, and the free ends of hangers are fixed to the inner surface of the ladle cover by welding; (ix) wrapping of ceramic fibre strips, fixing of ring, sixteen rods, eight hangers and twenty cotter pins are performed in the same manner as in steps (ii) to (viii). The invention is described fully and particularly in an unrestricted manner with reference to the accompanying drawings, in which - Figure 1 is a schematic bottom view of the existing device for heat insulating ladle covers; Figure 2a is the schematic bottom view of the improved device for heat insulating ladle covers; Figure 2b is the vertical section at A-A in Fig. 2a; Figure 2c is the vertical section of a rod; Figure 2d is an enlarged view of hanger and ring at area A in Fig. 2b; and Figure 2e is an enlarged view of portion B in Fig. 2a where the two free ends of a ring are joined by a serew. Referring to Fig. 1 the existing device for heat insulating the inner surface of a ladle cover comprises two layers of 25 mm thick ceramic fibre blanket with the fibres in the two layers being directed perpendicular to each other, and fixed tightly to the inner surface of the ladle cover by means of stainless steel studs (1) of AISI 310 grade which are welded to the ladle cover at their one end at a separation of 150 mm from the adjacent ones and stainless steel washers of the same grade. The outer ends of the studs and the washers are left exposed to the hot environment inside the ladle and so get corroded in a relatively short period of 6 to 9 months of use of the ladle causing displacement of the ceramic fibre blanket layers in the downward direction and making the device ineffective• Referring to Fig. 2a, the improved device for heat insulating ladle covers comprises concentric rings (r1 to r4); radially introduced rods (R1 to R24); hangers (H1 to H20); and cotter pins (PI to P24). Referring to Figs. 2b to 2d, each metallic hanger (H) having the upper end welded to the inner surface of ladle cover (2) is typically of length 150 mm, with a hole (3) of diameter 1A mm at a distance of 100 mm from the upper end thereof; each ring (r) is made of metallic strip of width 150 mm with a hole (A) of diameter 14 mm matching with hole (3) of diameter 14 mm of the hangerj each metallic rod (R) is of length 1050 mm with a pointed end (5), head end (6) and a cotter pin hole (7) of diameter 6 mm. Referring to Fig. 2e, the two free ends (8 and 9) of each ring (r) are joined together by a screw through matching holes (10 and 11) of diameter 5 mm positioned at a distance of 20 mm from each of the two free ends thereof. The method of constructing the improved device comprises the following steps in sequence :- (i) 200 mm wide and 50 mm thick strips of ceramic fibre blanket of type HTZ, density 128 kg/m3 and composition by weight % Al2O3, - 33 to 36, SiO2 - 44 to 48, ZrO2 - 16 to 18, TiO2 - 0.3 and Fe2O3 - 0.1 are PrePared; (ii) the strips are wrapped round the outer peripheral surface of ring (r1) in multiple layers tightly upto a radial thickness of 600 mm; (iii) ring (r2) is fitted around the outer peripheral surface of the outermost layer of the ceramic fibre strips wrapped around ring (r1) and tightened by means of a fixture made from a 50 mm wide metallic strip fitted around the outer peripheral surface of ring (r2) to reduce the radial thickness of ceramic fibre strips wrapped around ring (ri) from 600 mm to 500 mm; (iv) rods (R17, R18, R19, R20, R21, R22, R23, R24) are inserted into matching holes in rings {ri, r2, r3) and hangers (H1, H2, H3, HA); (v) the free ends of ring (r2) are joined by a screw through the matching holes (10, 11) therein and the free ends of hanger ladle cover (2) by welding; (vi) rods (R17, R18, R19, R20, R21, R22, R23, R2A) and ring (r3) are removed and ceramic fibre strips are wrapped around the outer peripheral surface of ring (r2) upto a radial thickness of 600 mm tightly; (vii) ring (r3) is fitted around the outer peripheral surface of the outermost layer of the ceramic fibre strips wrapped around ring (r2) in the same manner as in steps (iii) to (vi) followed for fixing ring (r2); (viii) outer ends of rods (R17, R18, R19, R20, R21, R22, R23, R2A) are fixed at the matching holes in ring (r3) by cotter pins (P17, P18, P19, P20, P21, P22, P23, P24) respectively through hole (7) in each rod,and the free ends of hangers (H5, H6, H7, H8, H9, H10, H11, H12) are fixed to the inner surface of the ladle cover by welding; (ix) wrapping of ceramic fibre strips, fixing of ring (rA), rods (R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16), hangers (H13, H14, H15, H16, H17, H18, H19, H20) and cotter pins (PI, P2, P3, PA, P5, P6, P7, fB, P9, P10, P11, P12, P13, P1A, P15, P16) are performed in the same manner as in steps (ii) to (viii). The rings, rods, hangers and cotter pins used in the construction of the improved device for heat insulation of the ladle cover are each made of stainless steel of Grade 304, and kept covered up completely with the ceramic fibre strips to prevent their corrosion by oxidation in hot environment inside the ladle. The expected working life of the improved device is around 3 years i.e. A to 6 times longer than that of the existing device for heat insulation of ladle cover, making the modified device cost effective because of reduced down time of ladles and cost of replacement of the heat insulation device at relatively short intervals of 6 to 9 months. We Claim :- 1. An improved device for heat insulation of ladle covers, characterised in that the device comprises multiple layers of strips of ceramic fibre blanket wrapped tightly around the outer peripheral surface of four concentric metallic rings (r1 to r4) of increasing diameter and held in position with respect to said rings by means 6f twenty four metallic rods (R1 to R24) inserted into the said rings and the layers of ceramic fibre strips wrapped around the rings to form a dish-like body which is kept suspended with its horizontal plane parallel to the inner surface of the ladle cover by means of twenty hangers (H1 to H20) each having its one end fixed to the inner surface of the lader cover and other end to the junction of a rod and ring laid in the said dish-like body formed. 2. The device as claimed in claim 1, wherein the rings, rods and hangers are each made of stainless steel of grade 304. 3. The device as claimed in claim 1, wherein the strips of ceramic fibre blanket are each 200 mm wide and 50 mm thick. 4. The device as claimed in claim 3» wherein the ceramic fibre blanket is of type HTZ, density 128 kg/ar and composition by weight % : Al2O3 - 33 to 36, SiO2 - 44 to 48, ZrO2 - 16 to 18, TiO2 - 0,3 and Fe2O3 - 0.1, 5. The device as claimed in claim 1, wherein each hanger is of length 150 ram and is provided with a hole of diameter 14 mm at distance of 100 mm from its end which is attzched to the inner surface of the ladle cover. 6. The device as claimed in claim 1, wherein each ring is made of stainless steel strip of width 150 mm in the vertical plane thereof. 7. The device as claimed in claim 1, wherein each rod is made of length 1050 mm having one end pointed and other end plugged with a cotter pin hole of diameter 6 mm near the head end. 8. The device as claimed in claim 6, wherein each ring is provided with a hole of diameter 5 mm at a distance of 20 mm from each of its two free ends. 9. A method of constructing the device as claimed in any preceding claim, comprising the following steps in sequence:- (i) 200 mm wide and 50 mm thick strips are cut from ceramic fibre blanket of type HTZ, density 128 kg/m3 and composition by weight % : A12O3 - 33 to 36, SiO2 - 44 to 48, ZrO2 - 16 to 18, TiO2 - 0.3 and Fe2O3 - 0.1; (ii) the strips are wrapped manually first round the outer peripheral surface of innermost ring (ri) in multiple layers tightly upto a radial thickness of 600 mm; (iii) the next outer ring (r2) is then fitted around the outer peripheral surface of the outermost layer of the ceramic fibre strips wrapped around ring (r1) and pressed by means of a fixture made from a 50 mm wide metallic strip fitted around the outer peripheral surface of ring (r2) to reduce the radial thickness of ceramic fibre strips wrapped around ring (r1) from 600 mm to 500 mm; (iv) eight rods (R17, R18, R19, R20, R21, R22, R23, R24) are then inserted into matching holes in ring (r3) and next into matching holes of inner rings (r2, ri), and in four hangers (H1, H2, H3, H4); (v) the free ends of ring (r2) are joined by a screw through the matching holes (10, 11) therein and the free ends of hangers (Hi, H2, H3, H4) are fixed to the inner surface of ladle cover (2) by welding; (vi) eight rods (R17, R18, R19, R20, R21, R22, R23, R24) and ring (r3) are removed and ceramic fibre strips are wrapped manually around the outer peripheral surface of ring (r2) tightly upto a radial thickness of 600 mm; (vii) ring (r3) is again fitted around the outer peripheral surface of the outermost layer of the ceramic fibre strips wrapped around ring (r2) in the same manner as in steps (iii) to (vi), followed for fixing ring (r2); (viii) outer ends of eight rods (R17, R18, R19, R20, R21, R22, R23, R24) are fixed at the matching holes in ring (r3) and the rods are fixed next into matching holes of inner rings (r2, ri), and in four hangers (H1, H2, H3, H4) by eight cotter pins (P17, P18, P19, P20, P21, P22, P23, P24) respectively through hole (7) in each rod, and the free ends of hangers (H5, H6, H7, H8, H9, H10, H11, H12) are fixed to the inner surface of the ladle cover by welding; (ix) wrapping of ceramic fibre strips, fixing of ring (r4), sixteen rods (R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16), eight hangers (H13, H14, H15, H16, H17, H18, H19, H20) and twenty cotter pins (P1, P2, P3, P4, P5, P6, P7, P8, P9, P10, P11, P12, P13, P14, P15, P16, P17, P18, P19, P20) are performed in the same manner as in steps (ii) to (viii). 10. An improved device for heat insulation of ladle covers, substantially as herein described and illustrated in Figs. 2a to 2e. 11. A method of constructing an improved device for heat insulation of ladle covers, substantially as herein described. An improved device for heat insulation of ladle cover , characterised in that the device comprises multiple layers of strips of ceramic fibre blanket wrapped tightly around the outer peripheral surface of four concentric metallic rings (r1 to r4) of increasing diameter and held in position with respect to said rings by means of twentyfour metallic rods (R1 to R24) inserted into the said rings and the layers of ceramic fibre strips wrapped around the rings to form a dish-like body which is kept suspended with its horizontal plane parallel to the inner surface of the ladle cover by means of twenty hangers (H1 to H20) each having its one end fixed to the inner surface of the lader cover and other end to the junction of a rod and ring laid in the said dish-like body formed. A method of constructing the improved device is also disclosed. Reference: Figures 1, 2a, 2b, 2c, 2d and 2e of the accompanying drawings.

Documents:

1027-cal-1998-granted-abstract.pdf

1027-cal-1998-granted-assignment.pdf

1027-cal-1998-granted-claims.pdf

1027-cal-1998-granted-correspondence.pdf

1027-cal-1998-granted-description (complete).pdf

1027-cal-1998-granted-drawings.pdf

1027-cal-1998-granted-examination report.pdf

1027-cal-1998-granted-form 1.pdf

1027-cal-1998-granted-form 2.pdf

1027-cal-1998-granted-form 3.pdf

1027-cal-1998-granted-form 6.pdf

1027-cal-1998-granted-pa.pdf

1027-cal-1998-granted-reply to examination report.pdf

1027-cal-1998-granted-specification.pdf