CHAPTER XXVII.
CONSTRUCTION AND MAINTENANCE OF TANNERIES.
As few architects have specially studied the construction of tanneries, and in most cases much of the arrangement depends on the knowledge of the tanner himself, a short chapter on the subject will not be out of place.
In the selection of a site, a clay or loamy soil is to be preferred to a gravelly or sandy one, as lessening the liability to leakage, and waste of liquor. Perhaps, however, the first consideration of all is the possibility of drainage and disposal of effluent waste liquors and washing waters, since it is now rarely possible to run these, without previous treatment, into a river or stream. Some information is given in [Chapter XXVIII.] on the methods of partial purification which are available to the tanner, but these are always costly and troublesome, and the possibility of running direct into a sewerage system, or a tidal river is of great advantage. Under the Public Health Act, authorities are bound to receive manufacturing effluents into their sewers if the latter are of sufficient capacity, and the effluents not such as either to damage the sewers, or interfere with the processes of purification adopted by the authority. This act is in many districts practically superseded by special legislation, but tanners’ effluents are generally received into sewers if freed from solid matter. When mixed with other sewage, they do not interfere with irrigation or bacterial treatment. In selecting a site within a sewered district, regard must be had to the possibility of causing a nuisance to the neighbourhood by foul smells. Really injurious smells should not be caused by a properly conducted tannery, but it is difficult to avoid odour, and a single badly disposed neighbour may cause infinite trouble and expense.
Another important consideration is the water supply, since for the large quantities used in a tannery, town water is generally very expensive. With regard to quality and impurities of water information may be found in [Chapter X.]; but, as a general rule, the softer and purer the supply the better. It is also of great advantage when the source is at such a level that the water can flow into the tan-yard, or at least into the beam-house, without pumping. Filtration too, when needed, is much facilitated by a sufficient head of water.
Commercial facilities, such as nearness to markets and sources of supply of raw materials, and the availability of rail and water carriage are of an importance at least equal to the points already considered, but hardly come within the scope of this work.
The site chosen, the next question is the arrangement of the buildings. It is very doubtful, where ground is not inordinately expensive, whether it is wise to erect drying-sheds over the pits. In case of fire, very serious damage is done to liquor and leather by the heat and burning timber. If the turret form of drier be decided on, strong foundations are required, and the ground-floor or basement is occupied with heating apparatus; if fan-drying, no lofty buildings are needed, and the drying rooms are conveniently placed over the finishing and currying shops; and, on the other hand, the tan-house may be easily and cheaply covered with slated roofs, with nearly vertical sections of glass, to the north if possible, like a weaving-shed, through which sufficient light for convenient work and cleanliness is admitted. The direct rays of the sun should be avoided, but in the writer’s opinion the balance of advantage is largely in favour of a liberal supply of light. Iron roofs are unsuitable, since the moisture condenses on, and rusts them; and particles of oxide fall into the liquors, and cause iron-stains.
Good ventilation along the ridge of the roof should be provided, wherever there is any steam or hot liquor used; or the condensed moisture soon leads to decay.
In arranging the general plan of the buildings, much depends on local circumstances; but as far as possible, they must be so arranged that the hides and leather work straight forward from one department to another with as little wheeling or carrying as possible; that the buildings where power is used be near to the engine so as to avoid long transmissions, which are very wasteful of power; and that the different buildings be so isolated as to diminish the risk of the whole being destroyed in case of fire.
A chapter on the construction and maintenance of tanneries and leather works would be incomplete if it did not refer to the very important question of Fire Insurance.[185] To an extent this may be regarded as a fixed charge against any business, very much in the same way as local and imperial rates. It is not, however, to be lost sight of, that to some considerable extent the amount of insurance premium is regulated by the insured himself. If a man conducts his business in unsuitable and badly constructed buildings; if attention is not paid to some of the elementary hazards connected with a fire outbreak; he must not blame the insurance companies for the demand of what he considers an excessive premium. If this faulty construction and imperfect equipment of buildings pertain to any considerable extent throughout a given trade where the process is more or less hazardous, it is futile to appeal to insurance companies, which, after all, are merely commercial and not charitable institutions, for a reduction in the rates. The only standard to guide the company is the loss-ratio, and given a high loss-ratio, there must be a corresponding premium paid.