Read Ebook: Scientific American Supplement No. 363 December 16 1882 by Various

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COTTRAU'S LOCOMOTIVE FOR ASCENDING STEEP GRADES.

As well known, all the engines employed on level roads are provided with large driving wheels, which, although they have a comparatively feeble tractive power, afford a high speed, while, on the contrary, those that are used for ascending heavy grades have small wheels that move slowly, but possess, as an offset, a tractive power that enables them to overcome the resistances of gravity.

M. Cottrau's engine possesses the qualities of both these types, since it is provided with wheels of large and small diameter, that may be used at will. These two sets of wheels, as may be seen from the figure, are arranged on the same driving axle. The large wheels are held apart the width of the ordinary track, while the small wheels are placed internally, or as in the case represented in the figure, externally. These two sets of wheels, being fixed solidly to the same axle, revolve together.

On level surfaces the engine rests on the large wheels, which revolve in contact with the rails of the ordinary track, and it then runs with great speed, while the auxiliary wheels revolve to no purpose. On reaching an ascent, on the contrary, the engine meets with an elevated track external or internal to the ordinary one, and which engages with the auxiliary wheels. The large wheels are then lifted off the ordinary track and revolve to no purpose. In both cases, the engine is placed under conditions as advantageous as are those that are built especially for the two types of roads. The idea appears to be a very ingenious one, and can certainly be carried out without disturbing the working of the locomotive. In fact, the same number of piston strokes per minute may be preserved in the two modes of running, so as to reduce the speed in ascending, in proportion to the diameters of the wheels. There will thus occur the same consumption of steam. On another hand, there is nothing to prevent the boiler from keeping up the same production of steam, for it has been ascertained by experience, on the majority of railways, that the speed of running has no influence on vaporization, and that the same figures may be allowed for passenger as for freight locomotives.

The difficulties in the way of construction that will be met with in the engine under consideration will be connected with the placing of the double wheels, which will reduce the already limited space at one's disposal, and with the necessity that there will be of strengthening all the parts of the mechanism that are to be submitted to strain.

The installation of the auxiliary track will also prove a peculiarly delicate matter; and, to prevent accidents, some means will have to be devised that will permit the auxiliary wheels to engage with this track very gradually. Still, these difficulties are perhaps not insurmountable, and if M. Cottrau's ingenious arrangement meets with final success in practice, it will find numerous applications.

BACHMANN'S STEAM DRIER.

The apparatus shown in the annexed cuts is capable of effecting a certain amount of saving in the fuel of a generator, and of securing a normal operation in a steam engine. If occasion does not occur to blow off the motive cylinder frequently, the water that is carried over mechanically by the steam, or that is produced through condensation in the pipes, accumulates therein and leaks through the joints of the cocks and valves. This is one of the causes that diminish the performance of the motor.

The steam drier under consideration has been devised by Mr. Bachmann for the purpose of doing away with such inconveniences. When applied to apparatus employed in heating, for cooking, for work in a vacuum, it may be affixed to the pipe at the very place where the steam is utilized, so as to draw off all the water from the mixture.

As shown by the arrows in Fig 1, the steam enters through the orifice, D, along with the water that it carries, gives up the latter at P, and is completely dried at the exit, R. The partition, g, is so arranged as to diminish the section of the steam pipe, in order to increase the effect of the gravity that brings about the separation of the mixture. The water that falls into the space, P, is exhausted either by means of a discharge cock , which gives passage to the liquid only, or by the aid of an automatic purge-cock , the locating of which varies with the system employed. This arrangement is preferable to the other, since it permits of expelling the water deposited in the receptacle, P, without necessitating any attention on the part of the engine-man.

H.S. PARMELEE'S PATENT AUTOMATIC SPRINKLER.

The inventor says: "The automatic sprinkler is a device for automatically extinguishing fires through the release of water by means of the heat of the fire, the water escaping in a shower, which is thrown in all directions to a distance of from six to eight feet. The sprinkler is a light brass rose, about 1 1/2 inches diameter and less than two inches high entire, the distributer being a revolving head fitted loosely to the body of the fixed portion, which is made to screw into a half inch tube connection. The revolution of the distributer is effected by the resistance the water meets in escaping through slots cut at an angle in the head. The distribution of water has been found to be the most perfect from this arrangement. Now, this distributing head is covered over with a brass cap, which is soldered to the base beneath with an alloy which melts at from 155 to 160 degrees. No water can escape until the cap is removed. The heat of an insignificant fire is sufficient to effect this, and we have the practical prevention of any serious damage or loss through the multiplication of the sprinkler.

It is so simple as to be easily understood by any one. As soon as the sprinkler becomes heated to 155 degrees, the cap will become unsoldered, and will then immediately be blown entirely off by the force of the water in the pipes and sprinkler. These caps cannot remain on after the fusible metal melts, if there is the least force of water. A man's breath is sufficient to blow them off.

The arrangement commences with one or more main supply pipes, either fed from a city water pipe or from a tank, as the situation will admit. If desired, the tank need only be of sufficient size to feed a few sprinklers for a short time, and then dependence must be placed upon a pump for a further supply of water, if necessary. The tank, however small, will insure the automatic and prompt working of the sprinklers and alarm, and by the time the tank shall become empty the pumps can be got at work. It is most desirable, however, in all cases to have an abundant water supply without resorting to pumps, if it is possible.

In the main supply pipe or pipes is placed our patent alarm valve, which, as soon as there is any motion of the water in the pipe, opens, and moves a lever, which, by connecting with a steam whistle valve by means of a wire, will blow the whistle and will continue to do so until either the steam or the water is stopped. Tins constitutes the alarm, and is positive in its motion. No water can possibly flow from the line of pipes without opening this valve and blowing the whistle. We also put in an automatic alarm bell when desired.

From the main pipe other pipes are run, generally lengthways of the building, ten feet from each side and twenty feet apart. At every ten feet on these pipes we place five feet of three-quarter inch pipe, reaching each side, at the end of which is placed the sprinkler in an elbow pointing toward the ceiling. This arrangement is as we place them in all cotton and woolen mills, but may be varied to suit different styles of buildings.

The sprinkler is made of brass, and has a revolving head, with four slots, from which the water flies in a very fine and dense spray on everything, and filling the air very completely for a radius of seven or eight feet all around; thus rendering the existence of any fire in that space perfectly impossible; and as the sprinklers are only placed ten feet apart, and a fire cannot start at a greater distance than from five to six feet from one or more of them, it is assured that all parts of a building are fully protected.

Over each one of these sprinklers is placed a brass cap, which fits closely over and passes below the base, where it is soldered on with a fusible metal that melts as soon as it is heated to 155 degrees.

As soon as a fire starts in any part of a building, heat will be generated and immediately rise toward the ceiling, and the sprinkler nearest the fire will become heated in a very few moments to the required 155 degrees, when the cap will become loosened and will be forced off by the power of the water. The water will then be spread in fine spray on the ceiling over the fire, also directly on the fire and all around for a diameter of from fourteen to eighteen feet. This spray has been fully tried, and it is found to be entirely sufficient to extinguish any fire within its reach which can be made of any ordinary materials.

As soon as the cap on any sprinkler becomes loosened by the heat of a fire and is forced off, a current of water is produced in the main pipe where the alarm valve is placed, and as the passage through it is dosed, the water cannot pass without opening the valve and thus moving the lever to which the steam whistle valve is attached; by this motion the whistle valve is opened, and the whistle will blow until it is stopped by some one."

INSTRUMENT FOR DRAWING CONVERGING STRAIGHT LINES.

Then

whence

it suffices to take for CD a suitable value and to calculate AD.

or, again,

I describe the circumference C b i a, and arrange the instrument as seen in the figure, and measure the length C b.

It is visible that

and, consequently, the position of the needles which are found at A and B are determined.

and, consequently,

We shall have

It is evident that the lower sign alone suits our case, for d < r; consequently,

Having obtained C, we put the instrument in the direction A B C. Then each point of C F describes a circumference of the same center o.

or, as absolute value,

FEED-WATER HEATER AND PURIFIER.

In order to properly understand the requirements of an effective feed-water purifier, it will be necessary to understand something of the character of the impurities of natural waters used for feeding boilers, and of the manner in which they become troublesome in causing incrustation or scale, as it is commonly called, in steam boilers. All natural waters are known to contain more or less mineral matter, partly held in solution and partly in mechanical suspension. These mineral impurities are derived by contact of the water with the earth's surface, and by percolation through its soil and rocks. The substances taken up in solution by this process consist chiefly of the carbonates and sulphates of lime and magnesia, and the chloride of sodium. The materials carried in mechanical suspension are clay, sand, and vegetable matter. There are many other saline ingredients in various natural waters, but they exist in such minute quantities, and are generally so very soluble, that their presence may safely be ignored in treating of the utility of boiler waters.

Of the above named salts, the carbonates of lime and magnesia are soluble only when the water contains free carbonic acid.

Our American rivers contain from 2 to 6 grains of saline matter to the gallon in solution, and a varying quantity--generally exceeding 10 grains to the gallon--in mechanical suspension. The waters of wells and springs hold a smaller quantity in suspension, but generally carry a larger percentage of dissolved salts in solution, varying from 10 to 650 grains to the gallon.

When waters containing the carbonates of lime and magnesia in solution are boiled, the carbonic acid is driven off, and the salts, deprived of their solvent, are rapidly precipitated in fine crystalline particles, which adhere tenaciously to whatever surface they fall upon. With respect to the sulphate of lime, the case is different. It is at best only sparingly soluble in water, one part of the salt requiring nearly 500 parts of water to dissolve it. As the water evaporates in the boiler, however, a point is soon reached where supersaturation occurs, as the water freshly fed into it constantly brings fresh accessions of the salt; and when this point is reached, the sulphate of lime is precipitated in the same form and with the same tenaciously adherent quality as the carbonates. There is, however, a peculiar property possessed by this salt which facilitates its precipitation, namely, that its solubility in water diminishes as the temperature rises. This fact is of special interest, since, if properly taken advantage of, it is possible to effect its almost complete removal from the feed-water of boilers,

There is little difference in the solubility of the sulphate of lime until the temperature has risen somewhat above 212? Fahr., when it rapidly diminishes, and finally, at nearly 300?, all of this salt, held in solution at lower temperatures, will be precipitated when the temperature has risen to that point. The following table represents the solubility of sulphate of lime in sea water at different temperatures:

Temperature. Percentage Sulph. Fahr. Lime held in Solution. 217? 0.500 219? 0.477 221? 0.432 227? 0.395 232? 0.355 236? 0.310 240? 0.267 245? 0.226 250? 0.183 255? 0.140 261? 0.097 266? 0.060 271? 0.023 290? 0.000

These figures hold substantially for fresh as well as for sea water, for the sulphate of lime becomes wholly insoluble in sea water, or in soft water, at temperatures comprised between 280? and 300? Fahr.

It appears from this that it is simply necessary to heat water up to a temperature of 250? in order to effect the precipitation of four fifths of the sulphate of lime it may have contained, or to the temperature of 290? in order to precipitate it entirely. The bearing of these facts on the purification of feed-waters will appear further on. The explanation offered to account for the gradually increasing insolubility of sulphate of lime on heating, is, that the hydrate, in which condition it exists in solution, is partially decomposed, anhydrous calcic sulphate being formed, the dehydration becoming more and more complete as the temperature rises. Sulphate of magnesia, chloride of sodium , and all the other more soluble salts contained in natural waters are likewise precipitated by the process of supersaturation, but owing to their extreme solubility their precipitation will never be effected in boilers; all mechanically suspended matter tends naturally to subside.

Where water containing such mineral and suspended matter is fed to a steam boiler, there results a combined deposit, of which the carbonate of lime usually forms the greater part, and which remains more or less firmly adherent to the inner surfaces of the boiler, undisturbed by the force of the boiling currents. Gradually accumulating, it becomes harder and thicker, and, if permitted to accumulate, may at length attain such thickness as to prevent the proper heating of the water by any fire that may be maintained in the furnace. Dr. Joseph G. Rogers, who has made boiler waters and incrustations a subject of careful study, declares that the high heats necessary to heat water through thick scale will sometimes actually convert the scale into a species of glass, by combining the sand, mechanically separated, with the alkaline salts. The same authority has carefully estimated the non-conducting properties of such boiler incrustations. On this point he remarks that the evil effects of the scale are due to the fact that it is relatively a nonconductor of heat. As compared with iron, its conducting power is as 1 to 37 1/2 , consequently more fuel is required to heat water in an incrusted boiler than in the same boiler if clean. Rogers estimates that a scale 1-16th of an inch thick will require the extra expenditure of 15 per cent. more fuel, and this ratio increases as the scale grows thicker. Thus, when it is one-quarter of an inch thick, 60 per cent. more fuel is needed; one-half inch, 112 per cent. more fuel, and so on.

Rogers very forcibly shows the evil consequences to the boiler from the excessive heating required to raise steam in a badly incrusted boiler, by the following illustration: To raise steam to a pressure of 90 pounds the water must be heated to about 320? Fahr. In a clean boiler of one-quarter inch iron this may be done by heating the external surface of the shell to about 325? Fahr. If, now, one-half an inch of scale intervenes between the boiler shell and the water, such is its quality of resisting the passage of heat that it will be necessary to heat the fire surface to about 700?, almost to a low red heat, to effect the same result. Now, the higher the temperature at which iron is kept the more rapidly it oxidizes, and at any heat above 600? it very soon becomes granular and brittle, and is liable to bulge, crack, or otherwise give way to the internal pressure. This condition predisposes the boiler to explosion and makes expensive repairs necessary. The presence of such scale, also, renders more difficult the raising, maintaining, and lowering of steam.

The nature of incrustation and the evils resulting therefrom having been stated, it now remains to consider the methods that have been devised to overcome them. These methods naturally resolve themselves into two kinds, chemical and mechanical. The chemical method has two modifications; in one the design is to purify the water in large tanks or reservoirs, by the addition of certain substances which shall precipitate all the scale-forming ingredients before the water is fed into the boiler; in the other the chemical agent is fed into the boiler from time to time, and the object is to effect the precipitation of the saline matter in such a manner that it will not form solid masses of adherent scale. Where chemical methods of purification are resorted to, the latter plan is generally followed as being the least troublesome. Of the many substances used for this purpose, however, some are measurably successful; the majority of them are unsatisfactory or objectionable.

The mechanical methods are also very various. Picking, scraping, cleaning, etc., are very generally resorted to, but the scale is so tenacious that this only partially succeeds, and, as it necessitates stoppage of work, it is wasteful. In addition to this plan, a great variety of mechanical contrivances for heating and purifying the feed-water, by separating and intercepting the saline matter on its passage through the apparatus, have been devised. Many of these are of great utility and have come into very general use. In the Western States especially, where the water in most localities is heavily charged with lime, these mechanical purifiers have become quite indispensable wherever steam users are alive to the necessity of generating steam with economy.

Most of these appliances, however, only partly fulfill their intended purposes. They consist essentially of a chamber through which the feed-water is passed, and in which it is heated almost to the boiling point by exhaust steam from the engine. According to the temperature to which the water is heated in this chamber, and the length of time required for its passage through the chamber, the carbonates are more or less completely precipitated, as likewise the matter held in mechanical suspension. The precipitated matter subsides on shelves or elsewhere in the chamber, from which it is removed from time to time. The sulphate of lime, however, and the other soluble salts, and in some cases also a portion of the carbonates that were not precipitated during the brief time of passage through the heater, are passed on into the boiler.

Appreciating this insufficiency of existing feed-water purifiers to effectually remove these dangerous saline impurities, the writer in designing the feed-water heater now to be described paid special attention to the separation of all matters, soluble and insoluble; and he has succeeded in passing the water to the boilers quite free from any substance which would cause scaling or coherent deposit. His attention was called more particularly to the necessity of extreme care in this respect, through the great annoyance suffered by steam users in the Central and Western States, where the water is heavily charged with lime. Very simple and even primitive boilers are here used; the most necessary consideration being handiness in cleaning, and not the highest evaporative efficiency. These boilers are therefore very wasteful, only evaporating, when covered with lime scale, from two to three pounds of water with one pound of the best coal, and requiring cleansing once a week at the very least. The writer's interest being aroused, he determined, if possible, to remedy these inconveniences, and accordingly he made a careful study of the subject, and examined all the heaters then in the market. He found them all, without exception, insufficient to free the feed-water from the most dangerous of impurities, namely, the sulphate and the carbonate of lime.

Taking the foregoing facts, well known to chemists and engineers, as the basis of his operations, the writer perceived that all substances likely to give trouble by deposition would be precipitated at a temperature of about 250? F.

Having explained as briefly as possible the principles on which the system is founded, the writer will now describe the details of the heater itself.

In Figs. 1 and 2 are shown an elevation and a vertical section of the heater. The cast-iron base, A, is divided into two parts by the diaphragm, B. The exhaust steam enters at C, passes up the larger tubes, D, which are fastened into the upper shell of the casting, returns by the smaller tubes, E, which are inside the others, and passes away by the passage, F. The inner tube only serves for discharge. It will be seen at once that this arrangement, while securing great heating surface in a small space, at the same time leaves freedom for expansion and contraction, without producing strains. The free area for passage of steam is arranged to be one and a half times that of the exhaust pipe, so that there is no possible danger of back pressure. The wrought iron shell, G, connecting the stand, A, with the dome, H, is made strong enough to withstand the full boiler pressure. An ordinary casing, J, of wood or other material prevents loss by radiation of heat. The cold water from the pump passes into the heater through the injector arrangement, K, and coming in contact with the tubes, D, is heated; it then rises to the coil, L, which is supplied with steam from the boiler, and thus becomes further heated, attaining there a temperature of from 250? to 270? F., according to the pressure in the boiler. This high temperature causes the separation of the dissolved salts; and on the way to the boiler the water passes through the filter, M, becoming thereby freed from all precipitated matter before passing away to the boiler at N. The purpose of the injector, K, and the pipe passing from O to K, is to cause a continual passage of air or steam from the upper part of the dome to the lower part of the heater, so that any precipitate carried up in froth may be again returned to the under side of the filter, in order more effectually to separate it, before any chance occurs of its passing into the boiler.

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