The Principles of Leather Manufacture

by H. R. Procter

[185] With regard to fire insurance, I am much indebted to Mr. A. W. Bain, of Leeds for valuable information.

There is, however—thanks to modern science—a method available whereby the great bulk of fires may be checked in their inception; an appliance, automatic in its operation, and of proved efficiency. This appliance is known as the sprinkler. A system of water-pipes is fixed under the ceilings of the building to be protected, to which are attached sprinkling jets at suitable intervals, each of which is closed by a valve held in place by a joint of fusible metal, which gives way if the temperature rises beyond a given point. There are two or three recognised patterns approved by the Fire Offices Committee after patient investigation and practical test. These appliances have now been at work for something like fifteen years in this country. One of the first trades to recognise their utility was that of the cotton-spinner. At one time serious fires in the cotton trade were of frequent occurrence. Now—owing to the efficient fire appliances—while fires may be as frequent in their inception as formerly, they are stopped at such a stage as to prevent any considerable loss. The consequence has been that the cotton-spinner, at one time the owner of a highly-rated risk, and one which few companies cared to insure, is now in the position of having his business eagerly sought after, and large discounts offered him off the charges he was once called upon to pay.

More important still is the consideration to him that his business is not so liable to be interfered with or stopped as the result of fire. There are, it is estimated, at the present moment, no less a proportion than 90 per cent of the cotton-spinners whose premises are protected by sprinkler installations.

Other hazardous risks such as corn-millers’, woollen and worsted manufacturers’, saw-millers’, engineers’, are adopting these appliances freely, and it is a matter of surprise that so very few tanneries or currying shops—so far as I have been able to learn, not more than twelve—have done the same. The consequence is that the loss-ratio in tannery risks still retains its unenviable notoriety: the rates for fire insurance have risen considerably, and as a result the tanners’ profits are correspondingly less. Considering the extent and importance of many of the tannery risks throughout Great Britain, one can only express surprise that these appliances have been so little adopted.

The construction of a new tannery demands serious attention from an insurance standpoint. The boiler-house should be a detached building; the grinding of bark and myrobalans should be conducted in buildings isolated from the general works; in fact no better advice could be given to a tanner, either in the construction of new premises, or the rearrangement and remodelling of old, than to consult an experienced insurance man, whether official or broker, as to the best means of constructing and arranging to secure the most favourable terms.

Another point which should be provided for, and which is often overlooked, is the feasibility of future extension without serious changes of arrangement. It may be taken as a probability of the future, even if it be not already a fact, that small tanneries cannot be made to pay, and that if a business succeeds, its extension will prove desirable; and in an ill-planned yard this may involve either entire reconstruction of a very expensive and inconvenient sort, or the separation of new departments, so as to involve serious increase of carrying. A good arrangement is that of a long front building serving to connect the whole, behind which the various departments are erected at right angles leaving room for extension backwards as required.

As regards the first of these conditions, if the various soaks, limes, bates, and handlers are well arranged, it is hardly necessary to do more than draw the goods from one pit into the next throughout the whole of the process. To, and from the layers, the goods must generally be carried or wheeled. In the sheds, if it be a sole-leather tannery, the butts should first come into turrets or open sheds for the rough drying; then into a room sheltered from draughts to temper for striking. The striking machines or beams should be in an adjoining room, or immediately below; then a small shed-space for drying before rolling; next the roller room; and then the warm stove for drying off. If two of the latter can be provided to be used alternately, it will allow the goods to be aired off without taking down, and they may then be immediately handed or lowered into the warehouse, without fear of over-drying, which is sometimes difficult to avoid where leather must be taken direct out of the hot drying-room. The same principles are easily applied in yards for lighter leathers.

To lessen loss of power in transmission, the engine should be near the centre of the main range of buildings, with perhaps the grinding machinery on one side, and the leather finishing on the other; but this would be rather liable to increase the fire-risk. A very good plan would be to have the engine-house in the centre as suggested, but separated from the buildings on each side by brick gables; and with the boiler-house behind it, and under a separate roof, say of corrugated iron. If it be impossible to have the engine near its work, it is in most cases better to employ a separate high-pressure engine, which may be within a glass partition, and will work all day with scarcely any attention. The loss of power in carrying steam for moderate distances through sufficiently large and well-clothed pipes is much smaller than that of long lines of shafting. The writer has known cases where fully half the indicated power of the engine was consumed in friction of the engine, shafting and belts. High-pressure engines are as a rule to be preferred to condensing for tannery use, since the waste steam can generally be employed for heating, and both the first cost and that of maintenance are smaller. Where much fuel is used, it is quite worth while to have the cylinders indicated occasionally, both running light, and driving the machinery; much information is gained in this way as to the power spent on the various machines, and very frequently large economy is effected by proper adjustment of the valves. To work economically, an engine should be of ample power for all it has to do; and adjusted to its work, not by lowering the pressure of steam, or by checking it at the throttle-valve, but by setting the slide-valves to cut off as early in the stroke as may be. As to how early this is possible, an indicator-diagram will at once give information. If the whole of the waste steam can be used profitably for heating purposes, economy in the working of the engine is of little consequence, but, otherwise, it is very injudicious, for the sake of a little saving in first cost, to put in an old or inferior engine, which has to be dearly paid for in waste of fuel. In the choice of an engine, the advice of an expert engineer is desirable, since many engines which are mechanically well made, are uneconomical through the faults of a rule-of-thumb design. In this respect the English engine-builder is frequently inferior to his better trained continental competitor.

In place of using small steam engines to distribute power, electric driving deserves consideration. For long drives the loss of power is much less than that of shafting, and by concentrating the whole production of the power in one large and well-constructed engine, the cost per horse-power can be much reduced. While large and well-constructed engines may develop 1 horse-power at a cost in coal of 1¹⁄₂ lb. per hour, it is not uncommon to use 12 lb. for the same output. In tanneries, however, the power used bears a much less proportion to total expenses than it does in the textile and many other trades. The first cost of electric driving is somewhat high. Motors of the “armoured” or iron-cased type must be used in all positions where they are subject to wet or dust. It must be borne in mind that an electric motor will not start against a heavy load, as it only develops its full power at a high speed, and if it receive the full pressure of the current before this is attained, its coils will probably be burnt out, unless saved by the melting of its safety-fuse. A similar danger is incurred, if the motor is brought up by overloading while the current is on. It is therefore generally necessary to connect a motor with its work by a belt which is only brought on to the working pulley when its full speed is attained.

In some cases the use of gas-engines is convenient and economical; for though gas from town-supplies is an expensive fuel, the best gas engines give a higher mechanical efficiency than steam-engines, and they work with very little attention.