If the machinery is not in use and is not moving, as in (a), the expense of power may be nil, except in so far as the boiler or other source of power may have to be kept in readiness for an immediate demand, when the cost of this must be included, just as in the more wasteful (though often with present plant unavoidable) machinery of class (b). The only way in which the waste in these sections can be avoided is to keep the machinery constantly at work; or, if it is not intended to use it further, to write it off the books. Where the nature of the machine is such that it cannot be continually kept at work (as in the case of a hauling engine or a pump), the times of idleness must be reduced as much as possible or the expenses of this particular part of the plant will be excessive.

If the machinery is not running at full power (class c), it is important to find out the reason for this defect. If the plant is too powerful for the amount of work it has to do, it is a question as to whether more work cannot be given it by a rearrangement of plans; for machinery which is not doing its full work costs nearly as much to run as when fully occupied. Not only so, but most clayworking machinery works more smoothly and satisfactorily when at its proper load than when running light, and the wear and tear is proportionately less. If the cause of waste of power is due to defects in the adjustment of the plant, or to actual defects in construction, it will generally be found that repairs and adjustment will rapidly repay their cost. If it is a question of antiquated plant (as, for instance, an old boiler which the insurance company will not allow to be worked at full pressure), it is often cheaper in the long run to replace it with more modern or, at any rate, more efficient machinery.

It is only when machinery is working at normal speed, with normal output and full time, that it can be regarded as satisfactory ; other conditions involve waste which, however caused, is nevertheless waste, and must be regarded as such without any attempt at 'glossing it over' if economical working is to be secured. The sight of machinery running 'loose' is so common in clayworking, that little or no notice is taken of it; it is considered to be on a level with 'breakages,' 'bad kilns,' etc.—that is, as losses which cannot be avoided. Needless to say, a little study on the part of the manager will rapidly convince him that this is by no means the whole truth. What is true of machinery is equally so of steam used for heating purposes; the amount of this commodity wasted annually in most clayworks is simply astounding.

Waste at the Boiler may usually be checked by a careful watch on the coal-book, or by a small bonus to the fireman if he can reduce the amount of fuel burned and yet keep up the steam. At the presses and mills it may usually be reduced by a system of piecework, accompanied with various encouragements to the men to work as rapidly as possible consistent with good work. This will ensure the full use of the machines when in use, but will not always prevent their running 'loose' unless there is abundant work for the men. A study of the lines of shafting will also indicate whether greater economy cannot be secured by using clutches so as to minimise the amount of idle shafting in motion.

Some machines are so clumsy, and require so much unnecessary power to drive them compared with the work they have to do, that their use involves a continual waste of power. Sometimes this waste cannot be avoided, because two or more classes of goods are made on the same machine; but even then it will often be more economical to obtain a smaller machine for the lighter work, the increased output being utilised in selling the goods at a slightly cheaper rate and still making a greater profit per annum. It is a matter of relative cost.

Waste of Power in Transport is another serious loss in many clayworks, few engines used for this purpose being worked at anything like their greatest efficiency. In most cases it is the result of bad management, by which a succession of small loads at fairly frequent intervals occurs instead of larger ones at longer intervals. The waste here is not only in the power, but also in the labour involved in driving the engine (or ponies), which might, under better arrangement, be employed on other jobs. This does not mean that a cheese-paring policy will be successful, but that in many clayworks a rearrangement of the transport will often result in one man's or lad's labour being available for other work during a considerable portion of the day. This is clearly not a case where generalities will be of use: each works must be considered in the light of its own circumstances and conditions.

Waste Steam is chiefly due to carelessness on the part of the workmen in not turning off cocks when the steam is not required; or in using more steam than is necessary for a particular purpose (this is especially true in drying sheds); or in allowing the machinery to run without working. On this account it is very desirable that the control of all steam-cocks should be in the hands of the foremen only and not in those of the individual workers. Leaks in the piping or in the engine, boiler, or other part of the machinery should be under the responsibility of the

engineer, and some means should be adopted to see that he keeps the plant under his charge in efficient condition. This may readily be done by means of occasional indicator readings of the engines and dynamometer readings of the machines. În fact, it is a good investment to attach some simple form of register to each machine of which the output is not paid for by the piece, in order to ascertain how many hours per day it runs idly or with only partial work.

One of the great advantages of electricity as a source of power is the readiness with which it may be measured, as a simple wattmeter on each machine will register the total power consumed, and a careful study of these records ensures such electrically-driven machinery being worked to the fullest advantage. This information is not so readily obtained for steam-driven plant, but where it can be obtained it almost invariably results in more economical working and reduced running expenses. Unfortunately, so long as steam is so useful and economical a heat-transporter it is hardly likely that electricity will make much headway in many classes of clayworking; but there is little doubt that where heat can be economically obtained from fuel directly, or in those parts of the works where power, but not steam, is required, that electricity will sooner or later be adopted, not only on account of the advantages it possesses as a form of energy, but also from the ease of measurement which enables its exact cost to be so readily obtained. factor of cost is likely to become increasingly important with increasing competition in the future.

This

Waste of Heat is, in some respects, the most serious and most difficult of prevention of any waste in a clayworks. Whether the heat is lost in the form of steam or actual heat from fuel matters little; in either case the money it absorbs per annum is immense.

Waste heat from kilns and furnaces (including boilers and dryer and shed-fires) is a serious matter, yet but little real attention is paid to it. Some aspects of this question have been dealt with in the chapter on 'Firing' (p. 171) and need not be repeated here.

The chief loss is undoubtedly due to unskilled stoking, and to the resultant use of too much or too little air. As a consequence of this either a large amount of heat is wasted in heating air to no purpose, or the combustion of the fuel is incomplete and the full amount of heat is not obtained from it. If only three times the theoretical amount of air is used in firing (a by no means uncommon proportion), not less than 40 per cent. of the fuel used will be wasted in heating this unnecessary excess of air.

The only true control of the stoking which can in any way be regarded as complete, is that which results from a study of the composition of the flue gases (p. 263) and the temperature at which they enter the chimney. For many purposes it is sufficient to determine how much coal is required per gallon of water evaporated per day, as the results of these tests, when the boiler is worked under the best conditions, and to insist on the fireman not using more than (say) 10 per cent. more than this in order to avoid the trouble and expense of testing the flue gases regularly; but for kiln-firing this cannot so readily be done, since, whilst a careful study of the amount of coal consumed by each chamber or kiln is of value, variations in climate, etc., have much more influence on kilns than on boilers, so that a hard and fast rule as to the amount of coal to be consumed in the kilns cannot well be laid down. With sufficient care, however, the amounts can be fixed very closely without any hardship to the firemen.

Faulty construction of the kilns is often a source of loss of heat, as it allows the gases to enter the chimney too soon and at too high a temperature. With a continuous kiln this may be remedied by increasing the number of chambers; but with single kilns it is to a large extent unavoidable, though in some cases by leading the flues through a drying shed the heat may be better utilised. In this case care must be taken not to unduly lessen the draught; if the chimney is too small, the substitution of a fan will often effect an economy. These fans require but little power to run them, and in most cases are cheaper than a chimney of the same capacity.

The utilisation of waste heat from kilns is a matter requiring considerable special knowledge. The flue gases can seldom be turned directly into the shed containing the bricks or other goods, partly because the temperature is too high and partly because of the impurities (notably sulphur compounds) which they contain. As a rule, they are passed into a flue under the floor of the dryer, this floor being frequently made of iron so as to conduct the heat more readily to the bricks or goods, which are then frequently placed on waggons or cars to keep them from actual contact with the hot metal. These cars also serve as a convenient means of transport for the goods through the dryers, which are preferably of a tunnel form (p. 134).

Further particulars regarding the prevention of waste, or of reducing it when it cannot be entirely prevented, will be found in the chapters on 'Tests' and 'Defects,' and under the various operations under which waste may occur.

CHAPTER XIII.

TESTS, ANALYSIS, AND CONTROL.

THE following suggestions for tests, and other means of controlling an economical and efficient production, are intended for the manufacturer and for the practical clay worker and not for the clayworks expert. Detailed descriptions of complex methods which have, of necessity, to be employed in the more accurate testing made by the latter are, therefore, omitted, and the reader is referred to the standard works on the subject when such information is required. For convenience of reference the headings are arranged alphabetically.

A

Anemometer.-An instrument for measuring the volume of air passing through a chimney or flue. It consists of a small wheel with relatively large vanes attached, and is so constructed that the slightest movement of the air sets it in motion. counter is attached in order to register the number of revolutions. This number multiplied by the area of the opening of the flue or chimney through which the air passes gives the number of volumes (cubic feet) of air passing per minute.

Absorption. The power of unglazed clay to absorb water is of great importance for certain purposes, particularly in the brick trade. The test is best carried out by accurately weighing one or more of the articles, immersing them almost, but not quite completely, in water for a short time, and, when partially saturated in this manner with water, to complete the immersion by covering them with the water and allowing them to remain covered for some hours. They are then taken out, their surfaces wiped dry, and the articles re-weighed. The increase in weight gives their absorption capacity. Thus, if a brick weighing 120 ozs. when dry was found to weigh 132 ozs. after immersion and wiping dry, as just described, its absorption capacity would be 13212012, which÷ 120 (the dry weight of the brick) gives 10 per cent. The reason for not immersing the article completely