The following text may have been generated by Optical Character Recognition, with varying degrees of accuracy. Reader beware!

VENTILATION AND. REFRIGER- ATION OF AMMUNITION- HOLDS.* BY ADRIEN BOCHET, ; The safety of ammunition holds has always engaged the attention of naval architects, and for many years past meas- utes have been taken for isolating these . holds, 'for protecting them against the various causes which may lead to an acci- dent, and for inundating them in the event of danger. Modern powders, and 'thé considerable develupment in the use of machinery on board ship, have in- creased the risks in a large proportion. Modern powders have excellent ballistic properties, but are also most unstable, and their instability increases very rapid- ly with an increase in temperature. By their gradual alteration they also set free a quantity of inflammable gases which may give rise to, explosive mixtures. The development in engines and boilers, in auxiliary engines, and in the extent of steam pipes laid throughout the ship, has led to a greater heating of the vari- * ous compartments.. The distribution of the armament, and the necessity of pro- viding ammunition holds in proximity to. the guns to be served, have often result- ed in the holds being in locations that are particularly unsuitable from the point ' of view of temperature. Therefore, con- currently with a gradual increase in sen- sibility to heat, which forms one of the characteristics of modern powders, causes tending to augment the temperature of the ammunition have increased in a large proportion also, and numerous attempts have been made with a view to ensure the artificial refrigeration of the holds. Cooling by ventilation alone is a sim- ple and safe means to prevent the ac- cumulation of explosive gases, but is quite insufficient to ensure a decrease in the temperature of the holds when the tem- perature of the air outside reaches 20 de- grees (say 70 degrees Fahr.), and when the causes making for an increase of temperature in the holds. attain a certain importance. "The heating of the air which enters the ship occurs rap:dly on contact with the warm bulkheads, by reason of its low specific heat. A rise of 10 de- grees Cent. has often been noted for courses which appeared as short and di- rect as possible between the upper works of the ship and the fans placed in the holds. Cooling by the means resorted to in refrigeration holds, such as those for the transport of meat, appeared at first to constitute a final solution of the pro- blem. But this failed completely, owing to the very great difference existing be- tween these holds and those for storing ammunition. In the former there is no *Translation of abstract of paper read at the Bordeaux International Congress in Naval Ar- chitecture. TAE Marine REVIEW ventilation, and they remain closed dur- ing the whole passage. They are also maintained at a very low temperature, and one result of this is that the small proportion of moisture contained in the local air on starting gets deposited on the products contained in the refrigerat- ing chamber, and does not injure them in any way. Ammunition holds, on the other hand, require ventilating. Even were one so imprudent as to do away with ventilation completely, or to reduce it in too large a measure, the require- ments of the service would demand the frequent opening of the hold, thus allow- ing every time the outside air to pene- trate into it. Finally, the temperature which it is suitable to maintain in an ammunition hold is much above 0 Cent. (32 degrees Fahr.). One result of this frequent reriewal of the air in an am- munition hold is that the moisture it _contains is condensed on all the surfaces which are maintained at-a lower degree. of temperature than that of the outside air, and the water which cannot be con- gealed, as in the case of a provision hold, _ trickles down the partitions of the holds and. the ammunition. This very grave disadvantage .'can only be avoided by cooling the air entering the ammunition -- hold, so that it is not at a higher tempera- 'ture than that of the contents or of the walls of the hold. - ' The only rational means to cool am- munition holds is to ventilate them with air suitably cooled, and this deduction has received the sanction of actual prac- tice, as it is the only method of cooling which has prevailed so far. It has been applied to 14 French battleships, which carry together 43 ammunition hold cool- ing plants, and to eight Russian battle- ships, which are fitted with 37 similar' plants. It will be fitted also to the ar- mored cruisers Waldeck-Rousseau. and Michelet, now in course of construction. The ammunition holds of these two ships are to be provided with aero-refrigera- tors, in which a circulation of artificially- cooled liquid is maintained constant; the dynamo rooms are to be cooled by a similar installation, but with sea-water circulation. Until recently, the maximum tempera- ture which was thought advisable for am- munition holds was 35 degrees Cent. (95 degrees Fahr.); now, however, this limit has been brought down to 30 degrees Cent. .(86 degrees Fahr.). With the former limit direct cooling by sea-water circulation sufficed, as the temperature of the water taken from a certain depth remained perceptibly lower than 35 de- grees Cent. in all parts of the world. The latter limit, however, can only be reached by having recourse to artificial refrigeration. 49 The refrigerators for cooling the air consist of metallic surfaces, on one side of which the cooling liquid circulates, the air to be cooled circulating on the opposite side. A pump ensures the cir- culation of the liquid, and a fan that of the air. The complete apparatus are built by F. Fouche, 38, Rue des Ecluses St. Martin, Paris, ' The extent to which refrigeration has to be carried depends upon the amount of heat which enters the hold: it is neces- sary, in the first place, to reduce to the lowest possible minimum this amount of heat. The afflux of heat. in the hold is caused by radiation from the warm sides and by conductivity from the metallic pieces they contain, and which are con- nected to the heated sections of the ship. The methods of obaining a ther- mic insulation of the hold are the follow- ing:" Radiation from the warm sides can be reduced by an inside lining made of substances the conductive and emissive properties of which are low, such as cork and asbestos. Another solution is to build a double wall, to obtain an air lin- ing, in which case it is advantageous to ensure in the double wall a circulation of air at the lowest possible temperature. The circulation of a cold liquid inside the double wall will give most satisfac- tory results, provided the liquid be brought sufficiently in contact with all, the metallic pieces that are liable to car- ry heat into the hold by conductivity. It is easy in principle to ensure the thermic insulation of the hold, but in actual practice the application of the vari- ous methods is surrounded with great difficulties, owing to the arrangement of. othe holds, the small space avail- .able, and the necessity , of- prevent- ing. every cause of damage to~ the ammunition. The use of simple insulat- ing inside coverings of a thickness pro- portional to the heating of the walls and -- the available space is evidently the most easy solution of the problem. As this method has hitherto proved of sufficient efficiency, it has alone been developed in actual practice. The use of double walls with air circulation has, however, been successfully combined with the insulation of the sides. The use of a cold liquid screen is sur- rounded by the following difficulties: In order to be efficient, there should be no break or interval in the current. It should reach the whole of the metallic pieces which are liable to cause heat in the hold by conductivity. All risks of inundating the hold in case of leakages hawe to be removed. The cold screen is constituted by a double wall, but it is absolutely im- possible to give the space sufficient di- mensions to allow a men to enter it in order to paint the plates and keep them