REPLACEMENT

OF T H E A N N U L A R

AIR CONDUIT

FOR HOT

BLAST

(UDC 669.162.222: 004.67) A.

V.

Volodarskii,

N. I .

Samokhin,

and

L. I.

Kamenskikh

Translated from Metallurg, No. 4, pp. 8-9, April, 1965

Replacement of the tuyere apparatus and the annular air conduit for hot blast during major overhaul of the b l a s t - f u r n a c e is, as a rule, accomplished at the same t i m e as other repair jobs and determines the duration of the standstill of the furnace for repair. Installation and adjustment of the annular pipe r e l a t i v e to the furnace axis and obtaining the same length of all nozzles of the tuyere apparatus are especially labor consuming. Until 1964 the following arrangement of the work was adopted in the Zhdanov special construction-assembly of the annular air conduit for hot blast in accordance with the plan and specifications was carried out on a separate platform near the furnace. Here with the help of a form the conical branch pipes were cut. Four d i a m e t r i c a l l y o p posite t u y e r e units were then assembled, and the c o a x i a l i t y of their mountings and fastening with respect to the furnace axis was checked. After halting the furnace and c o m p l e t i n g the disassembly work the annular air conduit was installed on special cantilever brackets welded to the support columns of the hearth (Fig. 1), and the mounting to the furnace axis was checked (dimension "a"). The job of replacing the annular pipe was conducted simultaneously with other repair jobs: r e m o v a l of charge and brick rubble from the shaft, assembly of the casing and coolers, and etc. Therefore, the fastening of the annular pipe required halting other jobs; this extended the total duration of the repair work. Due to periodic heating and cooling and nonuniform distribution of loads from thrust of the masonry and l o a d ing of the superstructure of the furnace, during use the casing of the tuyere zone is deformed, and in a plane perpendicular to the furnace axis an ellipse is formed whose diameters differ from 80 to 120 ram. To achieve the same length of the nozzles during assembly of the tuyere apparatus, the c o n i c a l branch pipes installed during the test assembly and bound to the furnace axis must be cut off from the pipe and displaced an amount equal to the difference between the planned and actual diameters in the plane of the tuyere apparatus. In 1964 a new method of assembly of the tuyere apparatus was used during a major overhaul of second category at a blast-furnace of the plant "Azovstal' ". On a separate platform, test assembly of the casing of the annular pipe for hot blast is conducted whereby a l l p l a n n e d dimensions are met. Then in prepared openings are i n stalled the conical branch pipes in such a manner that they extend from the pipe by 120-150 m m , and they are temporarily fastened. Flanges were first mounted on the conical branch pipes.

Fig, 1, Installation of the annular pipe in the planned position: 1) annularpipe; 2) support cantilever brackets; 3, 4) tackles.

The pipe, with the exception of the sites where the conical branch pipes fit and the assembly joints, was then lined with brick. The volume of the preliminary lining amounted to about 65% of the total volume.

191

~

; .--200

I

'&70 2

2

3

Fig. 2. Sealing the assembly joint of the annular pipe: 1) collar-cover plate; 2) annular pipe; I-IV) axes of the annular air conduit, the assembly joint, and the branch pipe respectively.

Axis'i, Ft~e ---ular~lg",,,,

][ ~,~. ~

Fig. 4. Fastening of the conical branch pipe to the annular pipe: i) annular pipe; 2) inner shell-apron; 3) outer shell-apron; 4) conical branch i~ipe; I) axis of the annular pipe; II) axis of the branch pipe.

/

-

L2 722 A x i s o f the l o w e r f l a n g e of t h e bell

/ A x i s or the a i r t u y e r e t

Fig. 3. Installation of the support platform: 1) tuyere elbow-bell; 2) 16-ram sheet: 3) support platform.

g

:

All these jobs took 14 days and were completed before the blast-furnace was halted for repair. After disassembly of the old air conduit for hot blast and the tuyere apparatus, special cantilever support brackets were installed on the furnace. The annular pipe was mounted in individual reinforced units of 8-18 tons. The entire pipe consisted of seven assembly units. The method used precludes the necessity of binding the pipes to the furnace axis. The annular pipe along the perimeter is installed at the same distance (planned dimension) from the line of flexure of the casing between the tuyere zone and the bosh. With such installation the formation of large gaps between sections of the annular pipe is possible, which precludes the possibility of butt welding (Fig. 1, dimension b). Such joints are assembled with special collars which are lap-welded to both sides of the section (Fig. 2).

Special support platforms are mounted on the casing of the hearth for assembly of the bell units of the tuyere apparatus below the annular pipe at the same time that the cantilever support brackets are installed (Fig. 3). The support platforms are installed above each tuyere flange. On the platforms there is a sheet with bored holes 36 m m in diameter which coincide exactly with the holes of the lower flange of the bell of the tuyere apparatus. The sheet is installed precisely as marked with the help of a theodolite, and fixes the following positions: a) the top of the sheet should correspond to the planned position of the bottom of the flange of the bell of the tuyere apparatus; b) the holes in the sheet should be disposed such that the bell be located exactly in the axis of the tuyere apparatus; c) the distance from the flange of the tuyere zone to the vertical axis of the flange of the bell should be as planned. After final installation and checking the sheet is welded to the cantilever bracket, on it are installed the belts of the tuyere apparatus which have already been lined, and these are fastened with bolts. After this the conical branch pipe of the annular pipe is freed from its temporary fastenings, and the flanges of the bell and the conical branch pipe are coupled with bolts.

192

If, when the flanges of the conical branch pipe and the bell are coupled, the branch pipe rests on the casing of the annular pipe, it is then not possible to join the flanges; the annular pipe is then cut off, and the branch pipe is displaced until the holes coincide exactly. Gaps formed between the body of the annular pipe and the conical branch pipe are covered with special aprons inside and outside the pipe (Fig. 4); these are welded around the perimeter, and then refractory lining of the annular pipe proceeds, After welding the aprons the temporary platform under the belt is removed, and the ball sockets, elbows, and nozzles are installed. The method of assembly described reduces labor consumption and shortens the standstill of the furnace during major overhaul. All jobs were completed within 15 days and 8 h (instead of 22 days),

193