The great expense and anxiety due to fires in coal sheds makes the advisability of submerged storage for coal very important. At Key West and Dry Tortugas, Fla., 35,000 tons of coal have been stored in four large steel coal sheds—two at each place— with about 6000 tons in four old wooden coal sheds. The coal in these four steel sheds has been stored at depths varying from twenty to thirty-five feet, and this pressure has necessarily generated fires in the coal.
At Key West there was one cargo of 2600 tons of coal, received last September, which contained a very large amount of crude sulphur. This ship, Evelyn, had been engaged in the sulphur trade last summer previous to taking this cargo of coal.
Fires broke out in this coal about a week after the coal had been stored in the shed; and these fires, instead of coming from the bottom of the coal pile where the pressure was greatest, were found to be in the upper strata of the coal in the shed. It was necessary to remove the Evelyn's entire cargo in the process of fighting the fires. In this removal large lumps of sulphur were found, and it is estimated there must have been ten to fifty tons of crude sulphur in that cargo.
To fight these fires a long patent drive-point nozzle was used, and at one time seven streams of salt water were being pumped into this shed and men were employed day and night to fight the fire. The Evelyn's cargo had to be entirely removed from that shed. It was placed in lighters and on the pier, and has gradually been expended, while the sulphur has probably all been consumed.
Fires in other parts of this coal, and in other sheds, have also broken out from time to time, and these have been extinguished largely by the use of a patent drive-point nozzle. This nozzle is arranged to couple with an elbow having a large anvil head that can be hammered, and it is fitted with a valve. The rest of the nozzle is a pipe in sections of about six feet long, so that it can be lengthened up to thirty feet. At the lower extremity of this nozzle there is a drive point, which is simply a cone inserted at the bottom to give a sharp point. A shoulder in the pipe prevents the point from being driven up. The point, however, drops out when the pipe is withdrawn from the pile, and this point is lost. The object of the point is to facilitate driving the nozzle into the coal without choking the pipe with coal. The hammer head at the coupling of the hose affords an anvil which can be hammered to drive the point into the coal, and the nozzle then penetrates and permits the water to be applied to the fire.
In trying to put out a fire by means of a stream of water, the water flows around on top outside, and does not reach the seat of the fire, as a rule.
It seems that the pressure of the weight of the coal causes gases to be evolved, especially in little pockets where lumps of coal bridge over air spaces. The air in these small pockets causes combustion of the gas there, and fine coal around is probably fused to form an arched furnace. As this proceeds the coal is coked and the furnace gradually enlarges. Smoke and gas escape through crevices in the coal and form the only indication of the existence of such pockets of fire in the mass of the coal.
Such a mass of coal is a bad conductor of heat, and temperatures by thermometers in temperature tubes give no indications of the site of a fire.
In these coal sheds there are a great many temperature tubes and ventilating pipes, and thermometers placed therein give the temperature in those pipes. These temperatures are taken constantly, but they give no indication of a fire or of any great heat except right there in those pipes.
We have had fires five feet away from one of these pipes, and there was no evidence given by these temperature tubes whatever that there was any abnormal heat in the coal pile.
All these temperature tubes and ventilating pipes are rather expensive fittings, and of no use, but rather a source of danger, in that they contribute to form these pockets of combustion in the coal. When coal is placed in the shed the big lumps fall down to the sides, and these big lumps bridge over air spaces, where the pockets of combustion have always been found. These temperature tubes and ventilating pipes also provide places where lumps of coal bridge air spaces and form pockets of combustion, and it is only when a fire develops close alongside one of these ventilating pipes that the temperature there shows fire. These ventilating pipes also afford an escape for the gases which are pressed out of the coal.
These gases constitute the chief and only value of coal, in that they furnish the heat units, and their escape from the coal represents a loss of so many heat units from that coal.
Therefore, the use of these ventilating pipes is not only dangerous, but should they not cause a fire to be generated, they deprive the coal of its value in heat units. These ventilating pipes are also very expensive and should all be removed. They do not give access to the fire to extinguish it, but only promote combustion. When a fire is generated, smoke will find exit and indicate that there is a fire. This smoke, however, does not always appear directly over the seat of the fire, but finds its exit in a devious path, at times as much as ten or twelve feet to one side of the fire.
Upon such evidence of fire the patent drive-point nozzle has been used and water has extinguished it. It is frequently necessary to use three or four such nozzles, though in this soft bituminous coal the drive point feature has not been found of much use—simply using the pipe suffices. By using four or five such long pipes in a space within ten square feet of the point where the smoke appeared, the seat of fire has generally been reached, and water has invariably extinguished the fire.
There is no doubt that water will always extinguish a fire, provided the water can be applied at the site in sufficient quantities. The old idea that water caused spontaneous combustion has been thoroughly exploded. Chemical decomposition might be caused by fresh water, in that fresh water will dissolve some vegetable matter, and those chemical solutions thus formed may contribute somewhat to the formation of solutions that would cause fire. But this cannot be true of water in contact with coal. Salt water Will not dissolve coal and liberate the gases that would develop heat. There is no possibility of spontaneous combustion from water, whether in minutes quantities or by flooding.
Water will extinguish coal fires, and coal kept in water cannot burn until the water is removed.
If the coal is kept under water, it is evident there will be no combustion of the coal.
The British Admiralty experiments with the submerged storage of coal have not been concluded; but indications here at Key West point out very clearly that it will be of great advantage to have coal stored under salt water.
There is no reliable data of a scientific character to demonstrate that fact, from the experience here at Key West. Coal that dropped from the coal sheds into the sea water around the coal sheds has been removed and consumed in the boilers of the distilling plant. It is not known how long that coal had been submerged under salt water, and the only point positively ascertained was that the coal did seem to burn better in the boilers of the distilling plant than similar coal which had not been submerged. This was only the opinion of the firemen at the boilers. There were no accurate measurements taken as to the combustion of this coal, the heat units evolved, the products of combustion, and comparative value; but it was evident that this coal, after having been submerged for at least a year, was as good as the coal which had recently been brought here. No deleterious effect was observed upon the boilers by the use of this coal which had been a long time submerged in sea water.
The coal in the coal sheds has been saturated with water, especially that in the same shed with the Evelyn's cargo, and from all that can be ascertained, this coal has not been in any way injured by having been saturated with salt water. The Evelyn's cargo, which contained a good deal of sulphur, and consequently, after the fires, had a good deal of coke, has been consumed, and the rest of this coal that is here now will be watched to see if it has suffered by having been saturated with salt water.
Fires generate here in the tropics from coal every winter. The coal which is in the old wooden coal sheds at Key West, stored nine feet high, has recently been on fire, and it was necessary to employ the patent nozzle, which extinguished it. This coal is all kept under roof, in order that the escape of gases may be prevented.
It is claimed that if a ton of fine bituminous coal be spread out on a concrete pavement and exposed in open air in this climate for one year, it will lose all its calorific properties. The gases are simply free to evaporate from the coal, and when the coal has lost all its gas it will have lost all its heat units and be simply coke.
In a coal pile, the top surface of the coal in this climate becomes practically burned out. The gas from the upper layer has been free to exude or evaporate by the action of the sun and the atmosphere, and it is only because the upper layers of coal cover the mass that the mass retains any of its heat units.
From this it is evident that if covered by salt water the gases cannot escape from the upper layers. All the gases will be practically retained in the mass of coal. There is no loss of heat units while stored under water.
The salt water storage will obviate all loss of coal due to dust. The fine coal dust will not be blown away, and it is a very conservative estimate that at least fifty to one hundred tons of coal have been lost in the shape of dust in handling the fifteen thousand tons of coal in one year at Key West Naval Station.
During the past six months I have been making a careful study of this subject, and I have recommended that the steel coal sheds shall be converted into concrete water-tight cisterns, having the same coal hoisting machinery as at present, but merely lined with concrete walls, with sloping sides, and inverted pyramidal bottom, fitted with drain-pipes at the bottom to drain off the water when necessary, and also to have means to flood it with water. Such a water-tight concrete cistern would store the coal, and should have no dangerous ventilating pipes or other aids to combustion. By having an inverted pyramidal floor the grab buckets can be used to remove all the coal without hand labor to load skip buckets.
The advantages of such a water-tight concrete coal shed are as follows:
(a) The submerged storage of coal therein will hermetically seal the gases in that coal.
(b) Small pockets of combustion cannot be formed with that coal under water.
(c) The gases cannot be evolved from the coal under water.
(d) The pressure upon the particles of coal at different depths will not be so great. The pressure at the bottom will not develop heat, because the pressure in a reservoir of water fifty feet deep does not generate any heat at the bottom of that reservoir by the weight of the superincumbent mass of water.
(e) Fires in the coal stored under water are impossible.
(f) The expense of fighting fires during the past ten months at Key West would more than defray the cost of converting that shed into a concrete water-tight cistern as proposed.
(g) The evolution of gases in the sheds at present has a very deleterious effect upon the steel work and makes it necessary to paint these sheds much more frequently than iron and steel structures are otherwise required to be painted.
(h) Such submerged storage will obviate the loss of coal by fire.
(i) Coal so stored will be delivered damp, and there will be no loss of coal dust carried away by the wind.
(j) In such a concrete water-tight cistern the wet coal will not come in contact with any steel work, and there will be no corrosive action upon steel work by. the salt water not in contact.
(k) In fighting fires at present, streams of salt water are poured in upon the fires, and this salt water has a very deleterious effect upon the steel framework of the shed, which would not be the case when no fires are generated.
(l) Coal delivered to ships from such a concrete water-tight cistern would be damp. It could easily be arranged that shortly before delivery—one or two days, perhaps—the water could be drawn off from the upper part of the coal shed to deliver the coal without water, when the coal would simply be damp, and not dusty.
The foregoing advantages of submerged salt water storage appear to me to be incontestable, and the disadvantages are merely supposed deleterious effects of salt water and difficulty in drying coal that has been long saturated with salt water.
It is claimed the wet coal will injure the bunkers of ships, but the Navy Department has recently authorized wet coal to be delivered to ships, and therefore this objection cannot be sustained. Coal is just as wet from water used in extinguishing fires as it would be if kept constantly submerged under salt water, and the objection of having wet coal in the bunkers can be ignored. The very slight corrosive action of damp coal in the bunkers of the ship is of no importance compared with the exposure of the outer skin of the hull of the ship floating in salt water.
The effect of burning coal pickled in brine in the furnaces of modern boilers may possibly be injurious to the tubes; but that effect, at the worst, can only be very slight, and it is exceedingly doubtful if the products of the combustion of such coal which had been for years stored under salt water could have any deleterious effect on the boiler. It would take many years for coal submerged under salt water to have such quantities of chloride of sodium or other chemicals as to be injurious in a boiler.
In view of the removal of the coal depot from Dry Tortugas, it would seem that this would be a most opportune time for the re-erection of these coal sheds after their removal, with provision to fit them up as concrete water-tight cisterns.
The extra expense of constructing such water-tight cisterns for coal sheds in a tropical climate will be more than covered by the expense due to fires, loss of coal, gas, etc., in one year.
The Navy will suffer a great loss by being deprived of the coal depot at Dry Tortugas. But that is certainly an ideal spot for a national quarantine station and a place of refuge against yellow fever, because of the absence of mosquitoes at Dry Tortugas when mosquitoes are very thick on all the other keys of the Florida reefs.
Coaling depots are absolutely necessary for a fleet, and it is a narrow-minded view which claims that they must necessarily be protected by fortifications. Coaling depots certainly need protection, but that protection can only be afforded by the fleet itself. The Navy must have command of the seas, and coal is essential to the Navy. If the Navy has not command of the seas the coal is not needed at all.
But if the country demands the Navy shall give up the coal depot at Dry Tortugas, it is urgently necessary that the coaling facilities there should be transferred to Key West in order that this most important strategic point may be properly utilized. These coal sheds and the two piers can all be taken down and reerected at Key West, along the deep water-front, along the line running from Fort Taylor north to the present coal sheds. These piers in front of two additional coal sheds would be on the line of the quay wall to Fort Taylor, where the channel has thirty feet of water. The improvements contemplated at the Key West Naval Station will readily facilitate the erection of two additional coal sheds at that point.
The projected utilization of Fleming Key in Key West harbor as a torpedo destroyer depot makes it essentially important to have greater coal storage facilities at Key West, and at least as much additional as has been stored at Dry Tortugas.
The extension of the Florida East Coast Railroad to Key West (which will be in operation in February, 1907), greatly enhances the strategic value of Key NVest and emphasizes the urgent importance of not reducing the coaling facilities of this region by removing the coal depot from Dry Tortugas without re-erecting the same at Key West.
The argument of some, that the railroad along the Florida reefs will be exposed to destruction by an enemy's fleet, is absurd. The communications of an army in the field are always liable to attack by a flanking raid by the enemy; but the communication is not any the less valuable because of such a possibility. No one would think of removing New York back into the interior because it might be bombarded by a fleet off Coney Island, and the only wise defense of exposed points on the coast (and, in fact, the defense of the country itself) lies in having a navy thoroughly well prepared and adequate to command the seas. A raid by a cruiser might do some damage, but the damage caused is always in proportion to the strength of the force that makes the damage, and the repairing facilities of a railroad in operation are so great that any damage done by a cruiser to a railroad along the Florida reefs would only cause a temporary interruption, provided the strength of the squadron at Key West was as adequate as it should be. A few torpedo-boats and submarines at Key West would give adequate protection to the railroad along the Florida reefs, in cooperation with the battle fleet.
It would be very desirable if it were possible to ally the navy with the merchant marine as closely as is the case in Germany. The German navy does not need coaling depots in different parts of the world, because the German merchant marine provides the German navy with coaling facilities all over the world. It is a law of the German Empire that all German merchant steamships and steamship companies must at all times place their ships, supplies, and everything, at the disposal of a naval commander, so that in case any commander of a German naval vessel should want coal he may take it from the German steamer or the steamship's coal depot at Hong Kong or any other place, upon his receipt, and the German Admiralty will reimburse the steamship owners at the cost of the same. and the German Admiralty is the final judge as to the amount of compensation that shall be paid to the
private steamship companies. Claims for constructive or consequent damages by the government taking such private property of German steamship companies will not be entertained, and therefore the entire German merchant marine and all the resources of the German merchant marine are practically under the control of the German Admiralty whenever the German Admiralty wishes to take advantage of this law of the empire.
The German government does not subsidize its vessels, but this absolute control of all the property of private German steamship companies, in war and in peace, is better than any subsidy that could be devised.
In the absence of such a close alliance of the United States Navy and its merchant marine, it is absolutely necessary for us to have coaling depots. They need not be defended by elaborate fortifications, if we have a navy adequate to command the sea.
Owing to the condition of the coal mining industry, by which in one year there may be ample coal available from coal mines, and in the following year there may be a coal famine, it is highly important that there should be at least one depot in the West Indies—at the place of the greatest strategic importance, Key West—where coal could be stored for years, and by which we could. like Joseph in Egypt, be prepared tor coal famines in the future.
The writer begs to state that the foregoing paper is the result of his experience with the storage of coal at Key West and Dry Tortugas, Fla.
He does not claim to be infallible, and it is possible that some features in regard to the storage of coal have been overlooked and that a discussion of the subject will reveal the true solution of the problem.
The results of the British Admiralty experiments are being urged as necessary before we should undertake to solve this problem. But it is not wise to count upon getting all the information from the British Admiralty. It is clearly our duty to find these things out for ourselves, and it is possible that the British Admiralty may not care to divulge the knowledge they will obtain from their experiments. Therefore it would seem to be wise for us to provide for salt water storage for coal in any new sheds that may be erected. Money has been appropriated, and is avail able for building an additional coal shed here at Key West, and it would seem to be a simple matter to arrange this new shed for salt water storage by having concrete walls. This shed could be built with such concrete walls, and without the expensive fittings of ventilating pipes, etc., that I believe to be not only unnecessary, but also dangerous aids to combustion. Such a shed could be also used to store coal dry if salt water storage should be undesirable, and such a shed with concrete walls will have an advantage in keeping the mass of coal cooler than in the present style of shed with black steel walls. These black steel walls absorb the heat of the sun, which contributes considerably to increase the temperatures of the coal in the shed.
Here, then, is an opportunity to make this experiment without much, if any, additional cost. Surely one of the most practical elements in our preparedness for war is to have an ample supply of coal, and if we could store coal for years without detriment, the Navy could then be independent (in the case of threatened war, or in the first outbreak of hostilities) of coal strikes, etc., which at times make it difficult, and even impossible, to obtain any coal.