From which the excellence of Stourbridge and Glenboig bricks is plainly evident in the small percentage of alkalies.

For the following miscellaneous information the author is indebted to the Glenboig Company—

1,000 9 inch x 4 inch x 21 inch =66 cub. ft. 1,000 9 in. × 4 in. x 3 in. x 3 in. = 80 cub. ft.

BUILT WITH FIRECLAY.

1 square yard 9 in. work requires 109 bricks 9 in. × 4 in. × 21 in. and 2 cwts. Ground fireclay, or 92 bricks 9 in. x 4 in. x 3 in. and 1 cwts. ground fireclay. A rod (English) of brick = 114 cub. yds. A rood (Scotch) of brick = 16 cub. yds.

FOR PAVING.

1 yard superficial requires 16 tiles 9 in. x 9 in. 18 tiles 12 in. × 6 in. x 2 in.

32 bricks 9 in. x 4 in. x 3 in. laid flat. 48 bricks 9 in. × 4 in. × 3 in. laid on edge.

One 9 inch x 41 inch × 3 inch = 9 lbs. 17 cub. ft. blocks = 1 ton

334 bricks = 1 load.

1,500 to 2,000 = 1 railway truck. 3,100 to 3,200 9 in. × 43 × 24in. bricks = 1 railway truck (Continental).

6 to 8 tons ground fireclay = 1 railway truck.
8 bags ground clay = 1 ton.
3 casks ground clay = 1 ton.
21 cub. ft. of dry ground fireclay, firmly
packed = 1 ton.

Fireclay suffers no deterioration of quality
from rain.

For shipment it is packed in barrels or bags. The usual shipping size of firebrick is 9 in. × 4 in. x 2 in.

The Glenboig Company make special silica bricks from English chalk flints which weigh 2 tons 12 cwt. per 1000, 9 in. x 4 in. x 24 in. They also make a highly refractory brick from Gartcosh clay, which analyses as below, according to W. Wallace and Jno. Clark, Ph.D., F.C.S., etc.

The proportion of alkalies is thus small and the brick is solid and has small shrinkage from the mould and weighs 131 pounds per cubic foot. The ganister bricks of the Company, which are made from what appears to be a soft sandstone, analyse as below

Where bricks are applied to oil fired furnaces the intense local heat of the oil furnace of course burns the brickwork away in time, or rather melts it on the surface immediately in contact with the flame, causing it to run down and hang in the form of stalactites, but it takes a considerable time to wear through nine inches of brickwork, and the cost of the bricks is more than compensated for in the increased efficiency of the furnace.

It is often the case, says Mr. Page, of Stourbridge, to whom the author is much

x

(a)

indebted, that furnaces and combustion chambers lined with firebrick come to grief through being badly built rather than from the bad quality of the bricks used; at the same time, good work will not make up for bad bricks. The usual type of liquid fuel furnace for kilns is as shown in the annexed illustration (a), the burner being so set that the fuel in vaporized form is more or less concentrated in the centre The consequence is that the intense heat is localized and the brick work

arch at x.

runs down into slag. Various methods have been tried to get over the difficultyone is to cover the grate with broken fire brick, or coke, but this was not altogether

(b)

successful. Another idea is to protect the piers of the arches with bricks piled up

SECTION ON A B

A

ELEVATION

PLAN

8

(c)

loosely in semicircular form with the concave side facing the burner, stacking them

with a space between each one, and crossing the open space with another row of bricks, as shown in plan, Fig. (b), thus distributing the heat over a large area of brick surface.

The bricks would melt after a time, but they could be raked out and a fresh lot put in, and the arches would be saved considerably.

In the case of over-fire arches, Fig. (c), for water tube boilers having a wide span, the best type of brick to use is what is known by the name of the Bullhead or Endwedge, as shown in Fig. (d), or the special bricks of Fig. (f).

In all cases fire bricks should be set with as little jointing material as possible, and for arches the bricks should be specially made to work to the desired radius. Any attempt to use ordinary rectangular bricks is fatal. The pressure becomes con

(g)

centrated on the under side of the arch, as in Fig. (g), and the mass has no rigidity— bricks begin to fall out and the arch is ruined.

The bricks should be set with finely ground fireclay made up with water to the consistency of thick paint. The brick should be dipped in this, and then rubbed into contact with its neighbours.

Fireclay is made up into specially shaped bricks and lumps for different purposes, and bricks and blocks can be made to meet the special requirements in furnace work, but unequally proportioned lumps must be avoided on account of internal stresses, fireclay having its limitations in this respect, as explained above, just as cast iron has. The best plan is to consult a reputable maker. The most usual course is to decide on all other points of construction and make the best job possible on what are generally considered incidentals, such as furnace linings, whereas by taking the limitations of a necessary material into consideration in the first place, much expense and trouble may be saved.

Improperly made bricks and lumps lack homogeneity, and often contain planes of cleavage developed in bricks forced into shape by mechanical pressures. These, being internal, are not seen, but the unequal strains brought on the structure of the brick by heating on one side or end only develop the weakness and cause a block to fly" or break up into several pieces.

66

Good fire bricks should have sharp angles and give a metallic ring on being

rubbed together. They should be kept some time before use in a dry place. Bricks sodden with rain and heated up quickly will tend to burst.

Various substances having been suggested as substitutes for fire brick, it may not be out of place to say something as to the varieties of fireclay goods. The following is the classification generally adopted—

No. IV is a mixture of carbon and clay, the carbon being in a crystallized state as used for arc lamps, etc., or amorphous as graphite, the latter being used for the manufacture of crucibles, etc. Carbon blocks have been suggested, but, apart from the excessive cost, the carbon combines with any free oxygen in the furnace gases and is consumed.

No. II. A mixture containing a greater portion of alumina than pure clay. This also is too costly for general use.

Lime is sometimes used as furnace lining for electrical kilns and will withstand the intense heat of the voltaic arc, but as it retains the property of being hydrated in air, its use is necessarily very limited. This class of fireclay goods is known as basic.

Silicious fireclay goods are composed almost exclusively of silica.

Argillaceous fireclay goods are composed of silica and alumina, and are next in degree of refractoriness to aluminous goods.

It should be borne in mind that the foregoing are each adapted to particular purposes, and the proper admixture of clays for any desired purpose is a matter that only long experience and scientific knowledge can determine, the physical as well as the chemical properties of clay having to be taken into account.

Siloxicon.

The latest refractory material is Siloxicon, a product of the electric furnace consisting of carbon, silicon and oxygen formed at a temperatue of 4,000° to 5,000° F. and therefore very refractory at ordinary temperatures. It is a loosely coherent mass as formed and is ground to pass a 402 sieve. It is an amorphous grey-green compound when cold, becoming light yellow at 300° F. It is insoluble in molten iron, neutral to acid and basic slag, indifferent to all save hydrofluoric acid, and is unattacked by hot alkaline solutions. It is formed into bricks by simple pressure, when damp, and fired. It is neutral to clays and will not oxidise, and appears likely to form a valuable furnace lining where oil fuel is employed.