FIG. 12.Ventilator
FIG. 13.Cross section plan of ventilator
Various forms of ventilators, belonging to the first-named class, have been introduced into many ocean-going passenger vessels within recent years, the result being a considerable improvement in the sanitary condition of the more confined portions of vessels. One of the most approved of these, receiving specially extended adoption, amounting as it does to a highly perfected system, may be noticed a little in detail. This is the form of ventilator patented and introduced by Messrs R. Boyle & Son, the well known ventilating engineers ofLondon and Glasgow, consisting of upcast and downcast shafts fixed above deck, communicating with the interior of vessel by a system of piping led to the various compartments. The upcast, or “air pump” ventilator, as the patentees term it, consists of a fixed head having an ingenious arrangement of louvre webs, whereby the wind impinging upon it from any direction, creates a current and exhausts the air from the cylinder of which the head is part, the foul air from below immediately ascending to supply the place of the air extracted. A continuous and powerful upward current is thus induced, and the head is so devised as to effectually prevent down-draught or the inlet of water. The elevation and plan of this ventilator is shown by Figs. 12 and 13. In Fig. 13, 1 represents cylindrical chamber communicating with shaft below; 2, deep lip to prevent the possibility of water passing into cylinder and down the shaft; 3, curved plates to deflect and compress the air over outlet openings or slits; 4, creates an induced current and exhausts the air from the cylinder; 5, radial plates to deflect air off centre of slits; 6, curved baffle plate or guard, to concentrate the current, and prevent the wind blowing through the slits opposite. The downcast ventilator, though necessarily more simple, is arranged, by means of similar louvered webs to prevent any water passing below, lodging it on the open deck instead. By means of up and downcast ventilators of this type, it is possible to have the ventilationgoing on between decks without interruption when there is a storm blowing and seas sweeping the deck, whereas under ordinary conditions, and in similar weather, everything would be battened down and the ventilationnil. The inventors, of course, are able to point to other advantages possessed by these ventilators, but the above are the salient features, which have won for their system marked recognition and pretty wide adoption. As evidencing its efficiency, it may be stated that Messrs Boyle’s system was awarded the “Burt” prize of £50, offered for international competition by the Shipwrights’ Coy. of London in 1882 for the best system of ship ventilation.
Having regard to the great importance of first providing means whereby foul air may be extracted from compartments rather than first attempting to put fresh air in—at least by other than mechanical means—it has become the practice with several steamship companies to fit a series of pipes from the rooms throughout the ’tween decks all leading into a common main, carrying this main into the boiler funnel, and thus utilising the powerful draught existing there when the vessel is under way. The efficiency of this method is all that could be wished, but its action is necessarily impaired when the vessel is in port and the boilers not in use. For steamships having long runs its value is very considerable; but in steamers having short passages and long port delays its merits are not so pronounced, and it is, of course, of no account when sailing ships are concerned.
Two systems of ventilation much alike in principle and equally applicable to the steamer and sailing ship may be shortly referred to. One is the Norton Ventilator, in which the dipping motion of vessels is utilised in effecting their own ventilation; the action in ocean-going vessels, of course, being continuous and automatic. Two cylinders, closed at the upper ends, are placed on each side of the stern post at such a distance as not to interfere in any way with the action of the rudder, and sufficiently close under the stern to be well out of harm’s way. As the vessel rises the water drops in these cylinders, which are partly submerged, and in its fall causes a vacuum,to fill which the air is drawn from all parts of the ship. The sinking motion of the vessel again fills the cylinders and forces the foul air collected, through the discharge pipes. The ventilator admits also of being actuated by steam or other power on board steamships, the exhausting and forcing device in this case consisting of a water bell or air chamber to which a vertical reciprocating motion is imparted by a beam or other attachment operated upon by the mechanical power adopted. The other method referred to is that now being pretty extensively introduced by Messrs Mosses and Mitchell, of London. It consists of two small cylinders, placed on either side of a ship, in-board, and connected by a pipe. The cylinders are partly filled with water, and, as the vessel rolls, the water rushes from the elevated to the depressed side of the ship, from one cylinder to the other, and, by creating a vacuum, draws up the foul air from between decks, or out of the hold, by pipes leading below. The air which is pumped up by this self-acting process goes out through a discharge pipe over the side, and such is the force of its exit that it serves to blow a foghorn when required. The cylinders can be placed so as to be worked by the pitching as well as the rolling of the vessel, and there is always a sufficient movement of the water to keep these pumps in action.
Systems of the other class—those involving the aid of mechanical power—are as much available as the automatic systems, but the greater expense of fitting, maintaining, and working them are considerations, apart from the question of their greater efficiency, which stand in the way of their general adoption. In vessels chiefly intended for passenger or emigrant carrying, artificial ventilation by mechanical means has been provided, and the practice is greatly on the increase, but systems in which natural agents are more largely brought into requisition have advantages which appeal most effectually to ship owners in general.
In several modern steamships engaged in cargo and passenger service, hydraulic machinery designed to take the place of the usual deck steam equipment has recently been introducedwith great advantage. This embraces machinery used for steering the vessel, loading and discharging cargo, heaving anchors; for performing, indeed, all the work on board excepting that of propulsion. From experience of the well proved utility and durability of hydraulic power on shore, it seems quite a natural consequence that it should take its place on board ship. Indeed, the system has so many advantages both from the point of view of the passenger and of the steamship owner, the wonder is that its introduction has been so long delayed. Its perfect noiselessness, as compared with the rattling, hissing, steam machinery now in vogue, is an advantage which will appeal strongly to the sea voyager. The great speed of the system, as well as the absence of jar and noise, the reduction in wear and tear, and the obviating of well-known disadvantages incidental to steam pipes, are merits of the system which are bound to appeal to the steamship owner.
It has been well pointed out by Mr A. Betts Brown, of Edinburgh, the patentee and manufacturer of this class of machinery, in a paper read by him before a recent meeting of the Institution of Naval Architects that—“With all the noise of steam engines at work on deck, running at piston speeds of as much as 1000 feet per minute, the cargo is lifted from the hold at a rate of only from one to two feet per second, which cannot be considered as keeping pace with the general progress made in other departments of steamship economy. In short, vast sums are spent on fuel to gain half a knot extra speed on a passage, while hours may be wasted in port in consequence of the primitive nature of the present system of deck machinery for discharging cargo.” Previous to 1880, Mr Brown had supplied and fitted hydraulic machinery on board the paddle-steamerCosmos, built by Messrs A. & J. Inglis, of Glasgow, intended for South American river service, but it was only in that year that he had an opportunity of fitting a large ocean-trading steamship with the system. This was theQuetta, built by Messrs Denny, Dumbarton, to whom, with the managers of the British India Association Steam Navigation Company, who own the vessel, Mr Brown ascribes credit for the opportunityafforded him of fitting his firm’s system on a complete scale. TheQuettais 380-ft. in length, 40-ft. breadth, depth of hold 29-ft., and 3,302 tons gross, and is fitted with a complete system of hydraulic machinery performing the following functions:—Steering, heaving the anchor, warping by capstans fore and aft, taking in and discharging cargo, lowering the derricks to clear cargo over side, hoisting ashes, reversing main engines, and shutting tunnel water-tight door in engine-room. For detailed descriptions of these various appliances, the reader is referred to the before-mentioned paper. The most for which space is here available is a very general outline of the principle on which they are supplied with motive power. The prime mover consists of a pair of compound surface-condensing pumping engines of 100 indicated horse-power, situated in the engine-room of the vessel. These engines pump water (or in winter non-freezing fluid) from a tank into a steam accumulator. The pumping engines are started and stopped by the falling or rising of the steam piston in the accumulator; and since the piston falls when the hydraulic power is being utilised, and rises to its former level when the power is not in use, it follows that the apparatus is perfectly automatic. Once started, it does not require the supervision of an engineer, and it maintains a steady pressure of 800-lbs. per square inch in the hydraulic mains or pressure pipes. These are carried up from the engine-room, and extend fore and aft the ship. Alongside the pressure main a similar return main is laid, which discharges into the tank. From the pressure mains branches are connected to the various hydraulic machines. After having done its work, the water is discharged into the return mains, being thus used over and over again. The experience obtained in the working of theQuettashows that a donkey boiler of the usual size, just sufficient for steam winches, enables the cargo to be discharged in half the time: in other words, does double the work on a given coal consumpt with compound surface-condensing pumping engine, and the hydraulic system.
The advantages of hydraulic machinery have been thus summarised:—A pair of engines in one place do, with nonoise and half the consumption of fuel, the work usually performed by perhaps a dozen donkey engines, while about £30 or £40 a voyage is saved in wear and tear. The increase of speed obtained in loading and discharging cargo practically ensures a quicker voyage. The rapidly working machinery necessitates double gangs of men in the hold; but though the hands are more numerous they are paid for a shorter time, and the cost of labour per ton of cargo is thus less than usual. The prime outlay is considerably greater than under the ordinary system, but it is calculated that in at least three years the extra expense will have been saved.
Notwithstanding the considerable increase in cost (more than double that of steam equipment) of the hydraulic system, the British India Association have seen their way to fit the succeeding steamers they have built, similarly to theQuetta, namely, theBulimba,Waroonga, andManora, the two intervening ships having their emigrant quarters ventilated by fans driven by hydraulic engines, as well as the usual deck equipment. In addition to the above, there have already been nine other steamers fitted successfully by Mr Brown’s firm with hydraulic machinery—including the Union Steamship Coy.’sTartar, of 4340 tons—and there is every prospect now of its taking the place of the noisy steam machinery in at least our most important passenger lines.
The regard which is had to comfort and luxury in modern passenger steamers has manifested itself—like the attention devoted to swiftness and safety—in various propositions and designs of a more or less novel kind. These, indeed, have very often consisted of designs embracing the whole of the qualities named; comfort and luxury being coincident with the more important properties of speed and safety already noticed; but not a few propositions and actual undertakings have consisted of vessels in which comfort has largely been the dominant and regulating condition of design. This subject receives happier illustration from the history of steam service between Englandand France, than perhaps from any other service that could be instanced. The thought and speech expended on “an efficient Channel service” at the meetings of the various societies concerned with shipbuilding and marine engineering, and the space devoted to the subject in the technical journals, has been no more than commensurate with the number and variety of projects for its accomplishment, submitted from time to time. Many of the schemes have not been quite of a marine character, and these, of course, lie beyond the province of the present review; but so far as ships are concerned, it is interesting to note to what extent comfort has been the dominant and regulating condition in the designs. In theCastaliaand theCalais-Douvres, employed in Channel service, features of considerable novelty—notably the double hulls—were adopted, and it was to the desire for increased comfort as much as speed that their introduction was owing.
In the steamerBessemer, however, built at Hull in 1875, this subject finds happiest illustration. This steamer, which involved some very interesting and novel problems in shipbuilding—in which the matters of propulsion and steering were largely concerned—was designed for the special purpose of practically testing an invention of Mr Henry Bessemer’s, having as its object the alleviation of the evils of sea-sickness. Mr (now Sir Henry) Bessemer’s invention, as applied in this case, consisted of a saloon supported on longitudinal pivots, which was to be made unsusceptible to transverse oscillation by the application to it of machinery wrought by hydraulic power. It was the intention of the eminent inventor to have applied this system to the correction of longitudinal as well as transverse oscillation, but on considering that the steamer was to be of large dimensions and performing a service in comparatively small waves it was thought desirable to limit its application to transverse motion, at the same time having regard to the longitudinal motion by reducing the height of the vessel for a distance of 50-ft. at each end, thereby inducing depression at the extremities, through the vessel’s not rising to, but being overswept by, the waves.
Although an influential company was formed to work theBessemerand other vessels embodying her novel features, which it was thought might follow, she was virtually abandoned afterone or two trialsacross the Channel. Her failure was assumed without exhaustive and conclusive trials being made of the many novelties embodied in her construction, some of which were obviously of an experimental character. This is the more to be regretted because of the beneficent issues involved in the project, and also in some degree because of the extent to which the faith of some intrepid and experienced men was pledged to its success. Nevertheless, it was always a matter of grave doubt, even when the fullest measure of mechanical success was allowed for, whether the idea of the pivoted saloon was calculated to secure that immunity from the effects of ship motion in a seaway, for which the celebrated patentee felt induced to hope.
It is maintained by many who profess to have given the subject attention, that sea-sickness in its most virulent forms, and in the majority of instances, is less attributable to the transverse and longitudinal oscillations—known respectively, as the “rolling” and “pitching” motions—than to the vertical movement termed “dipping,” which in its descent from the summit of one wave until upborne by the wave next following, the vessel undergoes. Now, this is a condition for which, in the Bessemer project, there was no provision, nor indeed well can be under any circumstances, save in the simple but costly expedient of adding to the dimensions or bulk of vessels, irrespective of form. The Czar of Russia’s yachtLivadia, built some years ago, exemplified in her extraordinary dimensions and great bulk the truth of such reasoning. The actual rolling and pitching of this remarkable vessel, as observed in the height of a gale in the Bay of Biscay, and in the midst of very heavy seas, was exceeding small. This never exceeded four degrees for the single roll, or seven degrees for the double roll, nor beyond five degrees for the forward pitch, or nine degrees for the double pitch, so to speak. This horizontal steadiness appeared to experts, who were on board at the time, mostremarkable, and Sir E. J. Reed, in a communication to theTimes, commented amongst other things on the agreeableness of the contrast the voyage on theLivadiaafforded, with his experience of voyaging at sea in ordinary ships.
After all, it must be acknowledged that attempts hitherto made to obviate the evils of sea-sickness by novelty in design fall very far short of attaining the beneficent results sought after. TheBessemer, theLivadia, theCalais-Douvres, and otheruniquecraft primarily conceived with regard to this end, are now, it would seem, exemplifying in their latter fate the futility of the endeavour. Such attempts, however ill-advised they may possibly appear in the light of the knowledge their very failure or their partial successes yield, have still their creditable and praiseworthy aspects. The spirit which has prompted some of them is not wholly one of money-making, and their histories enrich the general fund of experience far more than libraries of untried theories. Shipowners are too ready to shut their minds against everything which seeks theacmeof comfort and safety by other means than those which guaranteeeconomicalsuccess, or those which consist in increasing the size and power, and enhancing the accommodation of conventional types of vessels. These novelties and innovations, on the other hand, represent more of the intrepidity essential to genuine advancement than is forthcoming in a thousand merchant ships of the conventional type.
Happily the need for such enterprise as is involved in at once departing from tried types, has within recent years been largely, if not altogether, obviated, through improved procedure in the work of design. The more thoroughly analytic process of investigation and experiment now in vogue, greatly curtails the number of novelties introduced, or which reach the constructive stage. Many present-day projects never get beyond the “paper stage,” which in times not so far distant would have spelled out “failure” to the very last letter. Since the system of model experiment has begun to be practised in a reliable manner, and since theoretical prediction generally has become better appreciated, over-sanguine inventors have beenspared the penalties of failure in actual practice, and ingenuity has been reclaimed or warned away from channels that would inevitably have proved chimerical.
List of Papers bearing on the safety and comfort of modern steamships, to which readers desiring fuller acquaintance with thetechniqueand details of the subjects are referred:—
On the Necessity of Fitting Passenger Ships with Sufficient Watertight Bulkheads, by Mr Lawrance Hill: Trans. Inst. N.A., vol. xiv., 1873.On Water and Fire-tight Compartments in Ships, by Mr Thomas May: Trans. Inst. N.A., vol. xiv., 1873.On Causes of Unseaworthiness in Merchant Steamers, by Mr Benjamin Martell: Trans. Inst. N.A., vol. xxi., 1880.On Modern Merchant Steamers, by Mr James Dunn: Trans. Inst. Naval Architects, vol. xxiii, 1882.On Bulkheads, by Mr James Dunn: Trans. Inst. N.A., vol. xxiv., 1883.On Pumping and Ventilating Arrangements, by Mr Thomas Morley: Trans. Inst. N.A., vol. xvii., 1876.On Sir Wm. Thomson’s Navigational Sounding Machine, by Mr P. M. Swan: Trans. Inst. N.A., vol. xx., 1879.On Steamships for the Channel Service, by Mr John Grantham: Trans. Inst. N.A., vol. xiv., 1873.On Channel Steamers, by Mr John Dudgeon: Trans. Inst. N.A., vol. xiv., 1873.On High-speed Channel Steamers, by Mr H. Bowlby Willson: Trans. Inst. N.A., vol. xv., 1874.On the Ark Saloon, or the Utilisation of Deckhouses for Saving Life in Shipwreck, by Rev. W. R. Jolley, R.N.: Trans. Inst. N.A., vol. xv., 1874.On the Bessemer Steamship, by Mr E. J. Reed: Trans. Inst. N.A., vol. xvi, 1875.On the Bessemer Channel Steamer: Naval Science, edited by Mr E. J. Reed, 1873.On Electric Lighting for Ships and Mines, by Mr Andw. Jamieson: Trans. Inst. Engineers and Shipbuilders, vol. xxv., 1881-82.Electricity on the Steamship(Series of Papers): the “Steamship,” vol. I., 1883.On the Ventilation of Merchant Ships, by Mr Jas. Webb: Trans. Inst. N.A., vol, xxv., 1884.On the Comparative Safety of Well-Decked Steamers, by Mr Thos. Phillips: Trans. Inst. N.A., vol. xxv., 1884.On the Application of Hydraulic Machinery to the Loading, Discharging, Steering, and Working of Steamships, by Mr A. B. Brown: Trans. Inst. N.A., vol. xxv., 1884.
On the Necessity of Fitting Passenger Ships with Sufficient Watertight Bulkheads, by Mr Lawrance Hill: Trans. Inst. N.A., vol. xiv., 1873.
On Water and Fire-tight Compartments in Ships, by Mr Thomas May: Trans. Inst. N.A., vol. xiv., 1873.
On Causes of Unseaworthiness in Merchant Steamers, by Mr Benjamin Martell: Trans. Inst. N.A., vol. xxi., 1880.
On Modern Merchant Steamers, by Mr James Dunn: Trans. Inst. Naval Architects, vol. xxiii, 1882.
On Bulkheads, by Mr James Dunn: Trans. Inst. N.A., vol. xxiv., 1883.
On Pumping and Ventilating Arrangements, by Mr Thomas Morley: Trans. Inst. N.A., vol. xvii., 1876.
On Sir Wm. Thomson’s Navigational Sounding Machine, by Mr P. M. Swan: Trans. Inst. N.A., vol. xx., 1879.
On Steamships for the Channel Service, by Mr John Grantham: Trans. Inst. N.A., vol. xiv., 1873.
On Channel Steamers, by Mr John Dudgeon: Trans. Inst. N.A., vol. xiv., 1873.
On High-speed Channel Steamers, by Mr H. Bowlby Willson: Trans. Inst. N.A., vol. xv., 1874.
On the Ark Saloon, or the Utilisation of Deckhouses for Saving Life in Shipwreck, by Rev. W. R. Jolley, R.N.: Trans. Inst. N.A., vol. xv., 1874.
On the Bessemer Steamship, by Mr E. J. Reed: Trans. Inst. N.A., vol. xvi, 1875.
On the Bessemer Channel Steamer: Naval Science, edited by Mr E. J. Reed, 1873.
On Electric Lighting for Ships and Mines, by Mr Andw. Jamieson: Trans. Inst. Engineers and Shipbuilders, vol. xxv., 1881-82.
Electricity on the Steamship(Series of Papers): the “Steamship,” vol. I., 1883.
On the Ventilation of Merchant Ships, by Mr Jas. Webb: Trans. Inst. N.A., vol, xxv., 1884.
On the Comparative Safety of Well-Decked Steamers, by Mr Thos. Phillips: Trans. Inst. N.A., vol. xxv., 1884.
On the Application of Hydraulic Machinery to the Loading, Discharging, Steering, and Working of Steamships, by Mr A. B. Brown: Trans. Inst. N.A., vol. xxv., 1884.