Designed and manufactured for the Mammoth Copper Company at Kennet, under the supervision of C. F. Moore, chief engineer. All of the machinery has been designed to meet the most exacting conditions. The evolution of machinery for converting copper has consisted of a progressive series of improvements, due principally to the many practical experiments made by the various operators at different plants throughout the world, and particularly in the United States. By combining the latest ideas that have yielded the best results, and eliminating defects, it has been possible to build a converter which has many advantages over those used a few years ago.
The converter equipment for the Mammoth Copper Company consists of two hydraulically operated stands and eight shells, 96 inches in diameter by 150 inches long.
Referring to the illustration, it will be noted that the shell at the top half has a peculiar shape, which is not found in other converters. The bottom half is 96 inches in diameter, and from the center up to the joint, both sides of the shell are formed in a tangent to a width at the top of about 7 feet. The object of this is to do away with the unnecessary curvature above the center line to permit of a more secure lining being formed.
The parting joint between the bottom half and the top half of the shell is considerably higher than in other designs, the idea being to keep this just as high as possible and away from the extreme action of the molten copper; for it is a fact that in practically all of the barrel converters, with the exception of those at the plants of the Anaconda Copper Mining Company and the Orford Copper Company, this joint is only carried a short distance above the center line; and, since there is here no chance to ram the lining, it is only possible to form the joint with an adobe mixture. The result is that the joint is eaten away very rapidly by the molten matte. In the new type of hydraulically turned converter, built by Allis-Chalmers Company, this vital defect has been overcome by raising the joint between the bottom and top shell.
The bottom section of the shell is made of flange steel plate, which is reinforced longitudinally by four heavy T-rails and rigidly secured at both ends to a solid cast-steel head provided with a riding ring cast integral with and completely encircling the head.
Each head is spherical in shape and reinforced with eight heavy ribs to reduce expansion and contraction resulting from the intense heat. In a great many converters, designed without the ribs, much trouble has been caused and a great deal of expense incurred in fitting relined shells into stands which have the air connections bolted to the heads.
For lifting the shells there is riveted, at the joint on the lower half; a solid cast-steel re-enforcing plate, which has cast integral with it one heavy lug on each plate, making four lifting lugs in all. These reinforcing plates or angles are also arranged for bolting on the top half by three extra heavy bolts on each side.
The pouring top is made of cast steel and is parted on the longitudinal center line, thus making this part in two interchangeable sections, which is an important feature when repairs are considered. In some cases a great many operators are in favor of fitting the top with a short cast-iron pouring nose, which can be removed and thrown away when eaten up by the molten metal, and another substituted, whereas there are others who insist that the separate pouring nose is very objectionable, inasmuch as the additional flanges furnish places for accretions to form. With the top as shown in the illustration, it is only, necessary to rivet a steel plate at the burnt-out portion. The shape of the top of this converter, as well as the bottom, is practically the same as tint of the converters in use at Anaconda, Mont. It is a peculiar shape which gives longer life to the lining.
The wind box is rectangular in shape and consists of a plain casting which lies close to the shell and underneath the riding ring, thus permitting the shells to make a complete revolution and thereby do away with the stop which it has been customary to place on a great many riding rings in order to protect the wind box and prevent the shell from turning too far. With the old stop arrangements it was necessary to be very careful in turning; otherwise an operator might throw the shells off the stands, thus causing a serious accident.
Another feature of the self-contained wind box is that it does away with the long flange and cover which has always been used where the air valves or tuyeres were fitted on the inside of the wind box. It is well known that there is always a great loss of air through the joint in the long cover ordinarily used, because the expansion and contraction and the hard service to which converters are subjected in a very short time ruins the joint.
Individual TuyeresOn each of the Mammoth Copper Company's converters there are sixteen fitted Redpath individual tuyeres, having Dyblie ball valves, and secured to the wind box by swing bolts.
The discharge end of each valve which is at right angles to the inlet, projects several inches inside the shell and through a cast-steel stuffing box secured to the shell. This stuffing box is bored out to suit the projection on the tuyere, and is arranged for holding asbestos packing, to prevent air leaks, while the projection inside the shell is sufficient so that a lining of brick can be fitted securely around it.
Each tuyere is arranged so that the ball valve and its seat are self-contained, and the valve can be quickly taken out and replaced by another. The pipe distance-piece is also independent and easily accessible. Therefore, it will be seen that with this individual arrangement of tuyeres, it is only necessary to disconnect two swing bolts and pull out the tuyere; it is not necessary, when replacing a single defective pipe distance-piece, to disconnect a long and heavy cover and have the great difficulty of trying to make a joint on a long and warped castings.
The opinion of many will probably be that accretions will form between the wind box, tuyeres, and shell, to such an extent that it will not be possible to get at the swing bolts which fasten the tuyeres to the wind box; but this is not the case, because to obviate this there is an angle on top of the wind box, which runs for the full length and is riveted to the shell.
It has been demonstrated that the ball valve is more satisfactory than the roller or flap valve, because the spherical shape of the ball adjusts itself to the valve seat, leaving no chance for grooves to form as a result of the hard usage and constant pounding of the tuyere punching bar.
Air ConnectionOn the air end of each shell, the cast-steel head is arranged to receive the end of the wind box, which is fitted with a ball-joint concave flange, and receives the stationary air nipple of the patented blast connection.
This joint is especially adapted to converters and air joints where it is not possible to bring flanges in line, by reason of the difference in centers of shells, which are bound to become distorted and lose part of their shape after hard usage. This connection consists of a cast-iron T, having the horizontal cylinder fitted with a ball-joint and piston. When the shell is moved into position the lever is pushed forward, and this moves the nipple into the concave flange on the head. The air is then turned on and the pressure upon the piston holds the joint rigidly in place.
This joint is superior to the old method of matching flanges, and has proved to be a great labor-saving device around converter plants.
Hydraulically Operated StandsFor turning the shell each stand built for the Mammoth Copper Company is provided with a pressure cylinder 18 inches in diameter, having a stroke of 7 feet, which is equivalent to turning shells 180 degrees. The piston is fitted with four special metallic packing rings, which are designed to obviate leakage, wear, and the expensive delays due to repairing soft packing.
The upper end of the cylinder is secured to a flange on the bottom of an A frame and at each end are bolted independent heads. The upper head is fitted with a brass neck bushing and a well-proportioned stuffing box. It will therefore be apparent that with this arrangement it is possible to take the piston and rod out through the top, which is a very desirable feature.
The driving stand is a solid cast-iron box section "A" frame with liberal bearing surface at base, which is arranged for securing to foundation with four inch bolts.
The upper portion of this driving frame is designed to receive the turning mechanism, which consists of a cast-steel rack and cast-steel shrouded spur-gear. The rack is connected at the lower end of the piston, and opposite to center line of shaft at the upper end a guide is arranged, with a well proportioned sliding surface. Thus it will be seen that the turning motion is transferred from the piston and rack to the gear.
The gear is keyed to a hollow steel shaft which has fitted to its driving end a universal coupling, arranged so that the shells will rest true on the rollers, and that at the same time the drive will adjust itself to suit the alignment, thus avoiding any undue strains on the driving shaft.
On the head of the shell is a groove, which matches a tongue on the universal drive; the main gear is turned around until the tongue is vertical, when the shell is placed and there is clearance enough on each side of the tongue for keys, which are tapped into place by a light hammer, thus holding the shell rigid to the universal connection.
In some converters this groove on the shell has only sufficient clearance to allow the shell to drop over the tongue, and no-provision is made for using the keys, in which case there is danger of a backlash, due to the clearance and the fact that the piston will have a chance to accelerate before it picks up the shell, the result being a severe shock which is detrimental to the gears.
HousingThere is a sheet-steel housing for each frame, which covers the driving gear to prevent dirt from getting into the operating parts.
Pouring SpoonA very important detail in connection with the pouring of a converter is to obviate spatter or spilling of the copper upon the floor, and to prevent this there is furnished, when requested, a Bennetts pouring spoon, hung on a steel arm on one side of the roller stand, as may be seen from the cut, with the arm so arranged that the spoon can be adjusted to suit the pour of copper from the shell and the position of the molds which rest on the truck directly underneath.
Another important detail, which is not shown in the illustration, is a mold car mover, attached to a slide on the inside of the roller stand next to the frame. This mover is operated by an air or hydraulic cylinder, which in turn transmits its power through a piston rod to a guide with an arm that can be dropped into place on a mold car, thus pushing the car along into the proper position to suit the molds.
The following data in relation to these converters will be of interest:
Weight of shell --19 tons
Weight of lining -- 44 tons
Total -- 63 tons
Cubic feet of concrete in foundation -- 1,200
Capacity of charge -- 40%, matte
First charge (new lining) -- 8.25 tons
Average charge -- 10.00 tons
Maximum charge -- 14 - 16 tons
Air-blast pressure -- 12 - 15 pounds
Assuming six charges per stand per 24 hours, and twenty-six working days per month, the capacity of each 96-inch by 150-inch converter will be about 1,250,000 pounds of copper per month. Of course this will all depend, upon the matte and the conditions under which the converter is operating. In some cases the capacity could be increased 30 per cent, where converting is being done under ideal conditions, whereas in badly arranged plants the above capacity would be high.
C. H. Repath, engineer of the Anaconda Copper Mining Company; F. E. Marcy, of Salt Lake; J. A. Dyblio, and B. H. Bennetts, all deserve special mention for the many features which are incorporated in the hydraulically-operated copper converter described.
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