Manufacture of Drain Tile

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Manufacture of Drain Tile at Mason City, Iowa

By W. E. Dornback, Cer., ’11.

The first firm to exploit the clays of Mason City and its immediate vicinity, was that of Nelson and Barr.  Little did these men dream when they installed their crude plant, that in a comparatively small number of years, as an indirect result of their labors, Mason City was to become the greatest drain-tile manufacturing district in the world.  The modern and well equipped plant of the Mason City Brick and Tile Company now occupies the site of Nelson and Barr’s original project.

There are at present eight large brick and tile factories operating in and within a mile of Mason City, and another is in course of construction.  This new plant will be the only one in this locality having a producer-gas fired continuous kiln.  This kiln is of the Youngren type, and is modern in every detail.  Their drying system is also unique for this district, in that the driers are of the Raymond metallic-radiation type, instead of the waste heat type used at the other eight plants.

The names of the eight concerns in operation are:  The American Brick & Tile Co.  (two plants); The Farmers’ Co-operative Brick & Tile Co.; The North Iowa Brick & Tile Co.; The Mason City Brick & Tile Co.; The Mason City Clay Works, and The Mason City Sewer Pipe Co.  The last four of the plants were, until last spring, under the management of the late O. T. Dennison, who, it is claimed, succeeded in building up the largest drain tile business in the United States.  His first plant, the Mason City Brick & Tile Co., was established in 1862, and, since

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this was one of the pioneer plants, it is evident that the growth of the brick and tile industry at Mason City has been phenomenally rapid.

It is safe to say that the discovery of this extensive clay deposit and the building of these eight clay working concerns, have done more than anything else to make Mason City the manufacturing and shipping center of northern Iowa.  Six railroads enter Mason City, giving an excellent outlet for its products in the North, East, South and West.  Drain tile has been shipped as far south as Texas and as far west as the Pacific coast from this place.  This gives one a slight idea of the extent of its sales territory.

The clays used by the above mentioned plants are practically the same for all.  There are a mixture of the so-called Hackberry and Devonian shales in about the proportion of one of the former to five of the latter.  A section in the pit of the American Brick and Tile Company’s new plant shows the following sequence.

4.  Drift (Iowan)…1 to 2 Feet.  3.  Shale, arenaceous and stained a dark yellow, showing indurated ledge of dolomite…2 Feet.  2.  So-called Hackberry shale, clayey…8 to 10 Feet.  1.  Shale, blue in color – Devonian…30 Feet.

A rational analysis of the clay used gave the following results:*  Clay substance…47.08 Per Cent.  Feldspar…6.98 Per Cent.  Quartz…41.45 Per Cent.  Calcium sulphate…4.49 Per Cent.  Total 100.00 Per Cent.  (*  Iowa Geological Survey, Vol. XIV.)

The ultimate analysis gave:  Silica…51.95, Alumina…18.34, Combined water…7.39, Clay and sand…77.68, Iron oxide…7.56, Lime…4.14, Magnesia…3.26, Potash…1.43, Soda…2.69, Total fluxes…19.08, Moisture…0.42, Sulpher trioxide…2.76.  Total 99.94.

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In examining either of the above analyses, it is readily seen that the aggregate of fluxes is rather high, thus accounting for the low fusion point of these clays.  The high carbonate content causes the clay to burn to a salmon red, because of its neutralization of the coloring effect of the iron, and also makes the range of temperature between incipient and complete vitrification very small.  This fact accounts for the failure of Mason City brick and tile to burn to vitrification without distortion or “squatting,” and likewise its inability to stand sufficient firing to take even a commercial salt glaze.

The function of the hackberry shale is to extend the range of temperature between incipient and complete fusion, and to make the ware more refractory.

The new plant of the American Brick & Tile Co. is perhaps as modern and economically arranged as any at Mason City.  It is chosen therefore as typical for the purpose of following through the process of manufacture of, in particular, drain tile.  The plant, buildings, kilns, shipping tracks, etc., were laid out according to plans drawn by Richardson and Lovejoy, ceramic engineers of international repute.  The works are under the management of Mr. C. L. Smith, a man who has had years of practical experience along clay working lines, and who is exerting every possible effort to make his product excelled by none.

The process of manufacture as carried on in this plant is as follows:

The clay pit is at present being worked by hand methods, but the company intends to install a steam shovel in the spring.  From twelve to fifteen men are employed here, throughout the year, digging the clay from the banks and wheeling it to the shed, where it is dumped into a car of about two yards capacity.  This car is hauled by means of a drum and cable up a steep incline of about one hundred yards, to the receiving hopper where it is automatically dumped.  The clay car is loaded, dumped, and returned to the pit, once in every two minutes.

From the hopper the clay is discharged, by its own weight, into a Brewer Co. granulator.  Here the large lumps are separated, by means of the revolving knives, into smaller lumps varying from one-half inch to an inch and one-half in diameter.  From the granulator, the clay drops into a set of disintegrating rolls, where it is reduced to a much smaller size.  One of these corrugated disintegrator rolls runs at 325 R. P. M., and the other at 80 R. P. M.

The clay then drops onto a pair of grinding rolls, both running at 125 R. P. M.  These rolls are both smooth and reduce the clay lumps to suitable size for the pug mill.

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From the smooth rolls, the clay is elevated to the top of the storage bin, where it is either dumped or sent along to the pug mill direct, by means of a 24-inch six-ply conveyor belt, 177 feet long.

When the machines are not running, the clay is sent direct to the storage bin.  This is a room one hundred feet long, fifty feet wide, and about twenty feet high, holding a quantity sufficient to supply the plant, working full blast, for two weeks.  Storage gives the clay an opportunity to “cure,” thereby developing the colloids and making a more plastic and easily worked body.  Under the storeroom floor is a six-ply conveyor belt, 149 feet long, and twenty-four inches wide, which carries the clay from there, as needed, to an elevator which hoists it to the pug mill, where it meets the clay which comes direct from the rolls.

The function of the pug mill is to mix thoroughly the two kinds of clay used, and by the addition of the proper amount of water in the process, to “temper” the clays and make them smooth, plastic, and workable.  The pug mill used here is of the Brewer type, twelve feet in length and having a back gear drive.  It consists essentially of a semi-cylindrical steel trough, in which a series of projecting knives is mounted on a revolving shaft.  The knives, being set spirally around the shaft and each placed at an angle with its plane of revolution, gradually push the clay forward through the mill, at the same time mixing and working it thoroughly.  When the clay has finally been pushed through the mill, it gravitates to the type B, Brewer Auger machine.  The function of this machine is to force the plastic clay, without laminations, and under high pressure, through dies, onto the cutting table, where the tile (bricks or hollow blocks) are cut automatically into proper lengths.  The dies on the auger machine are interchangeable, allowing seven different sizes of tile to be made by this one machine.  These sizes grade between four and twelve inches in diameter.  Ninety tile of the four-inch size can be made per minute.

After the tile have been cut, they are removed from the table by three “off-bearers,” who place them systematically, on double-deck steel drying cars, which are then shoved into the drying tunnels.  There are twelve of these tunnels, one hundred feet long, each carrying two tracks.  The heat for drying is supplied by a twelve-foot fan, which draws the hot waste gases from the kilns, and a ten-foot fan, which forces those gases into the drying tunnel.  The green tile are allowed to remain in the driers until the mechanical water is driven off, then they are pushed onto the transfer tracks and from there are taken to one of the twenty down-draft, periodical kilns, to be “set,” ready for burning.  These kilns are twenty-six feet in diameter, each being supplied with eight fire boxes having sloping grates.  One

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stack built of radial hollow block is used to draw four kilns.  Six new kilns are being installed.  They will be thirty feet in diameter, supplied with ten fire-boxes, and will have the triple draft system under the checkerwork floors.  The stacks for these new kilns will be of radial hollow brick, built in four compartments at the base and having a height of eighty-five feet above grade.  An electric pyrometer system, with a station at the manager’s desk, is to be installed, so that at any time of the day or night, the manager of foreman can determine accurately the temperature in any of the kilns under fire.  The installation of these pyrometers will insure a still more evenly and perfectly burned product.

Within the past few years the demand for larger sized tile than could be made on the auger machine has become so insistent, that the company felt warranted in installing on the third floor of the main factory building, a Taplin-Rice steam sewer pipe press for the manufacture of the larger sizes of straight tile or pipe.

The clay fed to this press is brought up from the pug mill by an elevator and dumped on to the feed belt which supplies the clay cylinder of the press.  The steam-actuated piston now descends on this clay, entraps it, and forces it under considerable pressure through the die.  The clay cylinder is then cut off to the right size and wheeled to the slatted drying floor to dry.  There are two of these floors, one directly below the other, and placed in communication with the track floor by means of a gravity elevator.  The heat used to dry these pipe is that which has radiated from the waste heat driers, which rises through the slatted wooden floors above and evaporates the water from the green tile.  The top drying floor is 208 feet long by 146 feet wide.  The lower is 208 feet by 95 feet.

When sufficiently dried, the pipe are lowered to the track floor and transferred to the kiln being set.  Tile from ten inches up to thirty-six inches in diameter are made by this press.  A fourteen-inch tile when burned must be 14 ½ inches in diameter as it comes from the press, to allow for shrinkage.

When the ware is burned and cooled, it can be either loaded directly on the cars which are switched into the yard on the three spur tracks, or wheeled to the storage yards for future shipment.

The annual output of this one plant is 3,500 carloads of tile and hollow block.  Several of the Mason City plants have also large outputs of hollow clay building block, the Mason City clays making a superior article of this kind.

The value of clay brick, tile and hollow brick sent out of Mason City in 1908 amounted to $723,988.  (The Iowa Engineer, Iowa State College, Ames, Iowa, October 1910, Volume XI, Number 1)