The present invention relates to an improved direct charge transfer (DCT) chute with enhanced life for transferring and segregating hot sinter onto the cooler in a sinter plant. More particularly the invention relates to the improvement of intermediate stone box of the DCT chute to combat the failure of the said box.
BACKGROUND OF THE INVENTION
The function of DCTC of a sinter plant is to transfer and segregate hot sinter onto the cooler. This chute works after sinter machine. A study reveals that the failure of chute is because of chronic failure of intermediate stone box besides few other problems such as excessive scale formation and stress corrosion cracking, buckling of stiffeners, failure of welded joints at very high temperature, dislodging of liners and deformation of chute mother plate.
The chute is a interim conveying medium between two equipment. A chute generally consist of (i) mother plates, (ii) Liner plates & (iii) stone boxes. The liner plates are fixed by various mechanism on the mother plate. The mother plate is basically the shell which gives the shape of the chute. The liner plates fixed on the mother plate are in

the same profile which protects the mother plate from direct exposure of detrimental effects of material.
The disadvantages and problem with prior Art was because of several flaws in the basic assumption with regard to design.
Hence, there was a need to improve the performance of stone box and hence the performance of chute.
OBJECTS OF THE INVENTION
Therefore, it is an object of the invention to propose an improved direct charge transfer (DCT) chute with enhanced life for transferring and segregating hot sinter onto the cooler in a Sinter Plant which is capable of improving stone box which can withstand the load at significantly higher temperature (around 900 degree centigrade).
Another object of the invention is to propose an improved direct charge transfer (DCT) chute with enhanced life for transferring and segregating hot sinter onto the cooler in a Sinter Plant which is able to improve material thrust load onto the toe guard of the intermediate stone box.

A further object of the invention is to propose an improved direct charge transfer (DCT) chute with enhanced life for transferring and segregating hot sinter onto the cooler in a Sinter Plant which can take care of thermal expansion of material.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1: Shows modified and improved DCT chute in sinter Plant according to the
invention.
Fig. 2 : Shows hot sinter being dropped into cooling troughs.
Fig. 3 & Fig. 19 : Shows transverse supports with Box structure in place of I-beam, according to invention.
Fig. 5 : Shows transverse supports made of I-Beam fixed from both ends according
to prior Art.
Fig. 4, Fig. 18 & Fig. 19 : Shows intermediate segment being connected to support with pin joint according to invention.
Fig. 6: Shows Toe guard without any back support as per prior Art.
Fig. 7, Fig. 8 & Fig. 20: Shows additional support for Toe guard in accordance with the invention.
Fig. 9: Shows transverse supports welded at both ends according to prior Art.

Fig. 10; Shows transverse supports with one end of the above supports connection being kept fixed while making the other end free to expand in accordance with the invention.
Fig. 11 & Fig. 21: Shows slotted holes on the stone box support to allow thermal expansion according to the invention.
Fig. 12 & Fig. 13: Shows all critical joints where thermal expansion is required being converted into bolted joints with slotted holes according to the invention.
Fig. 14 : Shows liner fixing according to prior Art.
Fig. 15 : Shows modified and improved lug welding design with linear plate to ensure no gap between liner and mother plate as per invention.
Fig. 16 : Shows welded joints at all slots of a stone box according to prior Art.
Fig. 17 : Shows the ribs of the stone box being welded only at First slot when other two slots are kept free to allow thermal expansion in accordance with the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
The object of the present invention is to combat with the chronic failure of intermediate stone box resulting a very low performance of direct charge transfer (DCT) chute at sinter plant since its commissioning and improve the life of the DCT chute. A

plurality of sinter plant is having the DCTC chute after sinter machine. The said chute transfers and segregates hot sinter onto a cooler.
DISADVANTAGES OF PRIOR ART
There were several flaws in the basic assumptions with regard to design of the chute which are mentioned below.
1. In prior Art, stone box supports were not designed based on chute jamming
condition at temperature around 900 deg. Centigrade. Transverse supports were made of
I Beam (3) and were fixed from both ends (fig.5). Therefore the supports were too weak to withstand the load at significantly higher temperature.
Chute Jamming condition depicts generally the condition when the level of any material inside the chute is above 90% of the total volumetric level. In this case we termed the DCT chute as jammed when the hot sinter level is around 85-90% of total column. High column means higher dead load on the intermediate stone box.
2. Materials, used so far, were not optimally selected vis-a-vis change in behavior with
the increase in working temperature. It was observed that the decline of various physical
properties (strength, high temperature fatigue resistance, toughness etc.) does not follow
a linear relationship.

3. Material thrust load onto the toe guard of the intermediate stone box in the direction of rotation of sinter cooler was not at all considered so far.
4. Adequate allowances for the stone box were not kept vis-a-vis thermal expansion of the material.

5. Chute was not designed considering the peak working temperature of 1000 deg Celsius.
6. Both the ends of the supports were kept fixed.

7. Chute liner fixing arrangement was not appropriate.
8. Material was not appropriate vis-a-vis working temperature (Softening of Steel).

9. Material Thrust Load onto the toe guard of the intermediate stone box, in the direction of rotation of Sinter cooler, was not at all considered so far.
10. Failure of Welded Joints at very high temperature.

FAILUER MODES OBSERVED
1. Multi-axial Bending of Intermediate stone box including the supports.
2. Excessive scale formation and stress corrosion cracking.
3. Buckling of stiffeners.
4. Failure of welding joints at very high temperature.
5. Dislodging of liners.
6. Deformation of chute mother plate.
Solution to the problems and modifications and improvements are carried out as follows:
1. All the existing lateral & longitudinal I beam supports of the top & intermediate
stone box are re-designed to square Box Sections (1) with the web at the center as shown
in Fig. 3, Fig. 4 and Fig. 19 resulting,
i) Superior resistance to Multi-axial bending.
ii) Superior resistance to Torsional Buckling.
2- Pin supports (2) are introduced to protect box supports from direct impact of hot sinter (H). The intermediate segment is connected to support with pin joint shown in fig.3 and Fig.4.

3. New supports (4) are provided at the back of toe guard of intermediate stone box
to take care of the material thrust load as shown in Fig. 7 and Fig. 8.

4. The existing welded end connections for the supports of the stone box are replaced
with high temperature resistant grade of bolted connections (8) having slotted holes (7)
for taking care of thermal expansion as shown in Fig. 12 and Fig. 13.
5. Slotted holes (7) on the stone box support are disposed to allow thermal expansion asshowninfig.il.
6. One end of the stone box supports are kept fixed while making the other end free to expand (6) at high temperature as shown in fig.10.

7. The fixing arrangement of liners are modified to ensure improved reliability ensuring no gap between liner and mother plate as shown in fig.15.
8. The ribs of stone box are welded only at first slot (12) while other two slots (13) are kept free to take thermal loads shown in fig. 17.
9. Material for Stone box and main plate of Chute are selected which is having the
following properties:

a. High temperature heat resistance (resistance to softening)/ High temp corrosion &
oxidation resistance / High temperature fatigue resistance
b. Excellent Creep Rupture Strength/Good weld ability.


253MA is a special alloy steel with high Nickel content. This has a unique property of high creep rupture strength along with high resistance to oxidation at high temperature. This steel enabled us to operate the system at significantly higher temperature with high column load.

WE CLAIM
1. An improved direct charge transfer (DCT) chute with enhanced life for transferring and segregating hot sinter (H) onto the cooler in a sinter plant comprising and
characterized in that;
an improved intermediate stone box having supports of square box section (1) with a web at the centre for improving superior resistance to Multi-axial Bending and to
Torsional buckling;
pin supported (8) box supports for protecting the said box support from direct
impact of hot sinter;
toe guard of intermediate stone box provided with additional supports (4) at the
back of the said guard for combating material thrust load;
supports of the stone box fixed with high temperature resistant graded bolts (8) having slotted holes (7) for taking care of thermal expansion; wherein
one end of the stone box supports are kept fixed while keeping the other end free to expand at high temperature wherein a plurality of ribs of the stone box are welded only at first slot while other two slots are kept free for allowing thermal expansion when the liners are disposed with a fixing arrangement ensuring no gap between the said liner and mother plate wherein the stone box and main plate of chute are made of material which

has high temperature heat resistance, high temperature corrosion and oxidation resistance and high temperature fatigue resistance with excellent creep rupture strength and good weidability.
2. An improved DCT chute as claimed in claim 1, wherein the material of the chute is 253 MA.