THE FLOOR.
The heating of a brick-making floor is one of great import ance, and requires most careful consideration as to its construc tion. How many floors have been laid on most costly systems, only to be removed as unsatisfactory, or have required endless repairs to keep them in order, and in case of steam heating to keep them steam tight. The exhaust steam from the engine may be satisfactorily utilized to heat a very large area. It is the best medium, giving more uniform heat than when the best system of flues is used ; it is much more cleanly, and is cheap. Where, however, " live" steam from the boilers must be used, requiring additional boiler and plant, the saving is not so much as is popularly supposed, and excepting under a strong and undivided management, it is difficult to insure a good supply being maintained during the night.
The following is a good and well-tested system in present use. To prepare the ground take out all old flues, etc., if any, to the depth required, about two feet ; well ram the soil or clay for a foundation perfectly solid and level ; then lay 6 in. to 9 in. bed of concrete, rough towards the bottom and finer towards the face ; and finally finish with a thin layer of good cement or lias lime. If cement is used of a high-class quality, it may be mixed with a proportion of sand to reduce the cost ; but the object of this face is to prevent the steam and hot water perco lating through the concrete, and causing loss of heat, etc. The bed of concrete must be laid with a small fall towards the drain on the side furthest from the steam supply ; the drain will also have a fair amount of fall towards a central well and discharge pipe. There should be provided a steam trap, to check the too ready escape of the steam.
Now, if the size of the quarries to be used for the first course is 24 in. by 24 in. by 2 IZ in. or 3 in. thick, at distances of in. apart, three courses of brickwork must be laid in open chequer work, leaving about six inches clear at the steam supply end. Upon these courses of brickwork the first course of quarries is laid, resting in. each end on the brickwork. On top of these lay a second course of quarries, forming the floor surface, bedded in pure cement. The work must be done with the greatest care to ensure a steam-tight and damp-proof floor when laid, all joints must be grouted with cement until quite full. The top course of quarries must be arranged so that they break joint with the lower course in both directions ; in no case must the joints be allowed to fall upon one another. The top course of quarries need not be more than 2 in. thick ; they must be thick enough, however, to insure their being level and straight, and it will be found necessary to u se two sizes, probably, to ensure a uniform crossing of the joints.
It is of great importance that the floor surface is level and free from hollows at the joints or curved quarries, as it has been found by long experience that a twist given to a brick by being laid on an uneven floor is never totally eliminated by pressing, etc., and still exists in the finished brick. It is therefore advis able, when possible, to have the floor quarries of such a size that a certain number of brick lie on each without crossing the joints ; thus 8 brick can be laid on a 24 in. by 24 in. quarry. The steam supply is distributed evenly by cast-iron pipes, about in. diameter, having holes drilled in them on one side, one of which is central between each of the rows of chequered brickwork. This is supplied with steam from pipes carried overhead from the boilers into the sheds, and then brought down to the floor by a vertical pipe ; 3 in. diameter will be quite large enough for any section, as large as it is de sirable that they should be. Each supply pipe is provided with a valve to regulate the admission of steam, or when neces sary to cut out the section from use.
It is desirable and usual to lay a floor of this description in sections of from thirty to fifty feet in length, each section hav ing its own supply pipe and valve and steam trap at either end, so that if the whole be not required, a portion may be shut off, economizing steam and fuel, and also rendering them easier of repair. This obviates throwing a large part of the floor idle, and allows each section to be graduated in heat as may be re quired, so that too large a quantity of brick are not ready for getting up at once, thus causing waste.
Brick laid on a floor of this class in regular working are ready for taking up in about twelve hours from the time they have been made during the day ; but the more slender the clay and the closer, the longer must be the time allowed for drying. It is often necessary to allow them forty-eight hours in which to stiffen. Another plan, instead of the concrete foundation— cheaper, and having much to recommend it at works where there is only too often a large number of wasted, unsalable brick, but not so efficient in preventing the percolation of water—is to lay a course of brick, fire or old glazed, which must be fairly well burnt, on their edge on the bed of well rammed clay. They must then be carefully grouted with any suitable material, and after the brickwork courses are laid, filled in between with a thin layer of cement. This system is also in very successful use. At all places where a steam floor comes up to the main walls, or divisional walls of buildings, the building must be faced with cement, or the steam and moisture will rise, rotting the brickwork, and making the shed damp and look very unsightly.