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LIVERPO

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Originally appearing in Volume V27, Page 409 of the 1911 Encyclopedia Britannica.
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LIVERPO L '7x It-i ii1-it-s.eAii :6inibiiii iiui ii See also:

age a (From a See also:diagram in Proc. Inst. Ciro. Eng.) into the See also:chimney from the See also:fan has a See also:line parallel to that of the fan-See also:shaft and of the fan-See also:blades, and, as a consequence, as each blade passes this shutter, the stoppage of the See also:discharge of the See also:air is instantaneous, and the sudden See also:change of the pressure of the air on the See also:face of the blade whilst discharging and the reversal of the pressure, due to the vacuum inside the fan-casing, cause the vibration hitherto inseparable from this type of ventilator. As an See also:illustration of the effect of the pulsatory See also:action of the Guibal shutters the following figures may be given: a fan having ten arms and See also:running, say, sixty revolutions per See also:minute, and working twenty-four See also:hours per See also:day, gives (10 X 6o X 6o X 24=) 864,000 blows per day transmitted from the tip of the fan-vanes to the fan-shaft; the shaft is thus in a See also:constant See also:state of tremor, and sooner or later reaches its elastic limit, and the consequent injury to the See also:general structure of the fan is obvious. This difficulty is avoided by cutting a A-shaped opening in the shutter, thus gradually decreasing the See also:aperture and allowing the air to pass into the chimney in a continuous stream instead of intermittently. The action of this regulating shutter increases the durability and efficiency of the fans in an important degree. In towns like See also:Liverpool and See also:Birkenhead any pulsatory action would he readily See also:felt by the inhabitants, but with the above: arrangement it is difficult to detect any See also:sound whatever, even when See also:standing See also:close to the buildings containing the fans. The See also:admission of the air on both sides is found in practice to conduce to smooth running and to the reduction of the See also:side-thrust which occurs when the air is admitted on one side only. The fans are five in number: two are 4o ft. in See also:diameter by 12 ft. wide, and two 3o ft. in diameter by See also:loft. wide, one of each See also:size being erected at Liverpool and at Birkenhead respectively. In addition, there is a high-See also:speed fan 16 ft. in diameter in Liverpool which throws 300,000 cub. ft. The following table gives the result of experiments made with the ventilating fans of the See also:Mersey railway: Fan at z n ti A Y,t - C c o ff; c s ~~ c E o c« c4.a oy ~[ a, `w 'OC o g C ~... a .

ie h a y ~ 3 ~ ~ E a ES E c o o lfamilton See also:

Street, 30 10 47 113 I.30 1895 214,135 Birkenhead See also:Shore Road, 40 12 45 41 2.50 32881 134,685 Birkenhead 1 See also:James Street, 40 12 45 72 2.45 2465 178,880 Liverpool . James Street, 30 10 6o 6o 2.30 2062 123,720 Liverpool . Bold Street, 162 — — — — — 300,000 Liverpool . See also:Total 951,420 • i The central point of the See also:Severn See also:tunnel (fig. 15) lies toward the See also:Monmouthshire See also:bank of the See also:river, and See also:ventilation is effected from that point by means of one fan placed on the See also:surface at Sudbrooke, See also:Monmouth, at the See also:top of a shaft which is connected with a See also:horizontal Ventilating Fan 4oxret--__ Monmouthshire ®2Jy` heSn otSevern ( too 7 in 3 4 7 See also:miles '*----Total:englh of Tunnel 4 miles 624 yards . heading leading to the centre. This fan, which is 40 ft. in diameter by 12 ft. in width, removes from the tunnel some 400,000 cub. ft. per minute, and draws in an See also:equivalent See also:volume of fresh air from the two ends. About 1896 an excellent See also:system was introduced by Signor Saccardo, the well-known See also:Italian engineer, which to a See also:great extent has minimized the difficulty of ventilating See also:long tunnels under See also:mountain-ranges where shafts are not available. This system, which is not applicable to tunnels in which underground stations exist, is illustrated in fig. 16, which represents its application to the single-line tunnel through the See also:Apennines at Pracchia. This tunnel is one of fifty-two single-line tunnels, with a gradient of I in 40, on the See also:main line between See also:Florence and See also:Bologna, built by See also:Thomas See also:Brassey. There is a See also:grey See also:deal of See also:traffic which has to be worked by heavy locomotives.

Before the See also:

installation of a ventilating system under any See also:condition of See also:wind the state of this tunnel, about 3000 yds, in length, was See also:bad ; i In the See also:case of this circular See also:drift-way a velocity of 4000 ft. per minute was subsequently attained. 2 See also:Quick-running fan.but when the wind was blowing in at the See also:lower end at the same See also:time that a heavy goods or passenger See also:train was ascending the gradient the condition of affairs became almost insupportable. The engines, working with the regulators full open, often emitted. large quantities of both See also:smoke and See also:steam, which travelled concurrently with the train. The goods trains had two engines, one in front and another at the See also:rear, and when, from the humidity in the tunnel, due to the Fan (From the Proc. Inst. Cis. Eng.) steam, the wheels slipped and possibly the train stopped, the state of the air was indescribable. A heavy train with two engines, conveying a royal party and their See also:suite, arrived on one occasion at the upper exit of the tunnel with both enginemen and both See also:fire-men insensible; and on another occasion, when a heavy passenger train came to a stop in the tunnel, all the occupants were seriously affected. In applying the Saccardo system, the' tunnel was extended for 15 or 20 ft. by a structure either of See also:timber or See also:brickwork, the inside line of which represented the line of maximum construction, and this was allowed to project for about 3 ft. into the tunnel. The space between this line and the exterior constituted the chamber into which air was blown by means of a fan. Considering the length of tunnel it might at first be thought there would be some tendency for the air to return through the open mouth, but nothing of the See also:kind happened. The whole of the air blown by the fan, 164,000 cub. ft. per minute, was augmented by the induced current yielding 46,000 cub. ft. per minute, making a total of 210,000 cub. ft.; and this volume was blown down the gradient against the ascending train, so as to See also:free the See also:driver and men in See also:charge of the train from the products of See also:combustion at the earliest possible moment.

See also:

Prior to the installation of this system the drivers and firemen had to be clothed in thick woollen garments, pulled on over their See also:ordinary clothes, and wrapped See also:round and round the See also:neck and over the See also:head; but in spite of all these precautions they sometimes arrived at the upper end of the tunnel in a state of insensibility. The fan, however, immensely improved the condition of the air, which is now pure and fresh. In the case of the St Gotthard tunnel, which is 91 M. in length and 26 ft. wide with a sectional See also:area of 603 sq. ft., the Saccardo system was installed in 1899 with most beneficial results. The railway is See also:double-tracked and worked by steam locomotives, the cars being lighted by See also:gas. The ventilating plant is situated at Goschenen at the See also:north end of the tunnel and consists of two large fans operated by See also:water See also:power. The quantity of air passed into the narrow mouth of the tunnel is 413,000 cub. ft. per minute at a velocity of 686 ft., this velocity being much reduced as the full See also:section of the tunnel is reached. A See also:sample of the air taken from a See also:carriage contained 10.19 parts of carbonic See also:acid gas per 10,000 volumes. In the Simplon tunnel, where See also:electricity is the See also:motive power, See also:mechanical ventilation is installed. A See also:steel sliding See also:door is arranged at each entrance to be raised and lowered by electric power. After the entrance of a train the door is lowered and fresh air forced into the tunnel at considerable pressure from the same end by fans. The introduction of electric See also:traction has simplified the problem of ventilating See also:intra-See also:urban See also:railways laid in tunnels at a greater or less distance below the surface, since the See also:absence of smoke and products of combustion from See also:coal and See also:coke renders necessary only such a quantity of air as is required by the passengers and See also:staff. For supplying air to the shallow tunnels which See also:form the under-ground portions of the See also:Metropolitan and See also:District railways in See also:London, oren staircases. See also:blow-holes and sections of uncovered track See also:ate relied on.

When the lines were worked by steam locomotives they afforded notorious examples of bad ventilation, the proportion of g 7 SFr Chamber ~I II IY111ii ~l4 Air Chamber See also:

Gloucestershire carbonic acid amounting to from 15 or 20 to 60, 70 and even 89 parts in Io,000. But since the See also:adoption of electricity as the motive power the See also:atmosphere of the tunnels has much improved, and two samples taken from the cars in 1905 gave 11.27 and 14.07 parts of carbonic acid in Io,000. When deep level " See also:tube " railways were first constructed in London, it was supposed that adequate ventilation would be obtained through the lift-shafts and staircases at the stations, with the aid of the scouring action of the trains which, being of nearly the same See also:cross-section as the tunnel, would, it was supposed, drive the air in front of them out by the openings at the stations they were approaching, while See also:drawing fresh air in behind them at the stations they had See also:left. This expectation, however, was disappointed, and it was found necessary to employ mechanical means. On the Central London railway, which runs from the Bank of See also:England to Shepherd's See also:Bush,adistance of 6 m., the ventilating plant installed in 1902 consists of a 300 h.p. electrically driven fan, which is placed at Shepherd's Bush and draws in fresh air from the Bank end of the line and at other intermediate points. The fan is 5 ft. wide and 20 ft. in diameter, and makes 145 revolutions a minute, its capacity being See also:Ioo,000 cub. ft. a minute. It is operated from I to 4 a.m., and the openings at all the intermediate stations being closed it draws fresh air in at the Bank station. The tunnel is thus cleared out about 2t times each See also:night and the air is left in the same condition as it is outside. The fan is also worked during the day from II a.m. to 5 p.m., the intermediate doors being open; in this way the atmosphere is improved for about See also:half the length of the line and the cars are cleared out as they arrive at Shepherd's Bush. Samples of the air in the tunnel taken when the fan was not running contained 7.07 parts of carbonic acid in 10,000, while the air of a full See also:car contained IO'7 parts. The outside air at the same time contained 4.4 parts. A See also:series of tests made for the London See also:County See also:Council in 1902 showed that the air of the cars contained a minimum of 9.6o parts and a maximum of 14.7 parts.

In some of the later tube railways in London—such as the See also:

Baker Street and See also:Waterloo, and the Charing Cross and See also:Hampstead lines—electrically driven exhaust fans are provided at about half-mile intervals; these each See also:extract 18,500 cub. ft. of air per minute from the tunnels, and discharge it from the tops of the station See also:roofs, fresh air being conveyed to the points of suction in the tunnels. The See also:Boston system of electrically operated subways and tunnels is ventilated by electric fans capable of completely changing the air in each section about every fifteen minutes. Air admitted at portals and stations is withdrawn midway between stations. In the case of the See also:East Boston tunnel, the air leaving the tunnel under the See also:middle of the See also:harbour is carried to the shore through See also:longitudinal ducts (fig. 3) and is there expelled through fan-See also:chambers. In the southerly 5 M. of the New See also:York Rapid Transit railway, which runs in a four-track tunnel of rectangular section, having an area of 65o sq. ft., and built as close as possible to the surface of the streets, ventilation by natural means through the open See also:stair-cases at the stations is mainly relied upon, with satisfactory results as regards the proportions of carbonic acid found in the air. But when intensely hot See also:weather prevails in New York the tunnel air is sometimes 5° hotter still, due to the See also:conversion of See also:electrical See also:energy into See also:heat. This condition is aggravated by the See also:fine See also:diffusion through the air of oil from the See also:motors, dust from the See also:ballast and particles of See also:metal ground off by the See also:brake shoes, &c. Volume of Air Required for Ventilation.—The See also:consumption of coal by a See also:locomotive during the passage through a tunnel having been ascertained, and 29 cub. ft. of poisonous gas being allowed for each See also:pound of coal consumed, the volume of fresh air required to maintain the atmosphere of the tunnel at a See also:standard of purity of 20 parts of See also:carbon dioxide in 10,000 parts of air is ascertained as follows: The number of pounds of See also:fuel consumed per mile, multiplied by 29, multiplied by 500, and divided by the See also:interval in minutes between the trains, will give the volume of air in cubic feet which must be introduced into the tunnel per minute. As an illustration, assume that the tunnel is a mile in length, that the consumption of fuel is 32 lb per mile, and that one train passes through the tunnel every five minutes in each direction; then the volume of air required per minute will be 32 lb X 29 cub. ft. X 5o0 =185,600 cub. ft. 21 minutes.

Corrosion of Rails in Tunnels.—Careful tests made in the See also:

Box and Severn tunnels of the Great Western railway, to ascertain if possible the loss that takes See also:place in the See also:weight of rails owing to the presence of corrosive gases, gave the following results: Box TUNNEL (1 m. 66 chains in length). Percentage of See also:Wear per annum. lb per yard Down line, gradient falling I in too— % per annum. At east mouth 0'439 = 0'377 28 chains from east mouth 1 Boo =1.540 48 chains from east mouth 2.110=1.810 1 m. 8 chains from east mouth 2.88o =2.48o At See also:west mouth o.64as= =c2Up line, gradient rising 1 in too At east mouth 0.620=0.575 t m. 8 chains from east mouth 1.500=1.380 t m. 28 chains from east mouth ..

End of Article: LIVERPO

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