Part 24 (2/2)
In houses ofThe two syste the heated water most commonly used are--(1) The _tank_ system; (2) the _cylinder_ systera 192 The boiler is situated at the back of the range, and when a ”daases pass under it to a flue leading to the chi water rises to the top of the boiler and thence finds its way up the _flow pipe_ into the hot-water tank A, displacing the soh the _return pipe_ to the bottom of the boiler
Water is drawn off froh the bottom of A, so that the hottest portion of the contents may be drawn off first A tank situated in the roof, and fed froh the siphon pipe S The bend in this pipe prevents the ascent of hot water, which cannot sink through water colder than itself From the top of A an _expansion pipe_ is led up and turned over the cold-water tank to discharge any steaenerated in the boiler
A hot-water radiator for war the house may be connected to the flow and return pipes as shown Since it opens a ”short circuit” for the circulation, the water in the tank above will not be so well heated while it is in action If cocks are fitted to the radiator pipes, the aoverned
[Illustration: FIG 192--The ”tank” systee of the tank systeh to supply all flows, is sometimes so far from the boiler that the water loses much of its heat in the course of circulation Also, if for any reason the cold water fails, tank A may be entirely emptied, circulation cease, and the water in the boiler and pipes boil away rapidly
THE CYLINDER SYSTEM
(Fig 193) is open to neither of these objections Instead of a rectangular tank up aloft,have a large copper cylinder situated in the kitchen near the range The flow and return pipes are continuous, and the cold supply enters the bottoh a pipe with a siphon bend in it As before, water is drawn off from the flow pipe, and a radiator may be put in the circuit Since there is no draw-off point below the top of the cylinder, even if the cold supply fails the cylinder will re before there is any danger of the water in it boiling away
[Illustration: FIG 193--The ”cylinder” system of hot-water supply]
Boiler explosions are due to obstructions in the pipes If the expansion pipe and the cold-water supply pipe freeze, there is danger of a slight accumulation of steam; and if one of the circulation pipes is also blocked, steao,”[38] which is naturally the boiler assu that the pipes are quite full to the points of obstruction, the fracture would result froenerate unless there be a space above the water But the expanding water has stored up the heat which would have raised steay is suddenly let loose Stea the effects of the explosion Froathered that all pipes should be properly protected against frost; especially near the roof
Another cause of disaster is the _furring up_ of the pipes with the lime deposited by hard water when heated When hard water is used, the pipes will sooner or later be blocked near the boiler; and as the deposit is too hard to be scraped away, periodical renewals are unavoidable
HOW A LAMP WORKS
Fro, and first to the ordinary paraffin las to notice about this are the wick and the chi made of closely-woven cotton, draws up the oil by what is known as _capillary attraction_ If you dip the ends of two glass tubes, one half an inch, the other one-eighth of an inch in diameter, into a vessel of water, you will notice that the water rises higher in the slass plates and lay thehtly apart at the other by soed perpendicularly, the water will rise between the plates--furthest on the side at which the two plates touch, and less and less as the other edge is approached The tendency of liquids to rise through porous bodies is a phenomenon for which we cannot account
Mineral oil contains a large proportion of carbon and hydrogen; it is therefore terhted wick, the liquid is heated until it turns into gas The carbon and hydrogen unite with the oxygen of the air Some particles of the carbon apparently do not coh the fiery zone of the flahly luht-rays that we use a lamp, and to burn our oil efficiently we en, with more than it could naturally obtain So we surround it with a transparent chilass The air inside the chimney is heated, and rises; fresh air rushes in at the bottoh, the flaen
If the wick is turned up until the flame becomes smoky and flares, the point has been passed at which the induced chien to combine with the carbon of the vapour, and the ”free” carbon escapes as s 194) performs exactly the saer scale The plate prevents air passing straight up the chih the fire itself to replace the heated air rising up the chi how a blower-plate draws up the fire]
GAS AND GASWORKS
A la hydro-carbon as-jet burns gases produced by driving off hydro-carbon vapours froned for the purpose Gas-hting, so ilance at the processes which it includes Coal gas may be produced on a very small scale as follows:--Fill a tin canister (the joints of which have been ) with coal, clap on the lid, and place it, lid doards, in a bright fire, after punching a hole in the bottoins to issue from the hole This is probably at first only steahtedthat coal gas proper is co time When it dies the canister may be removed and the contents examined Most of the carbon rehter than coal, for the hydrogen, oxygen, and other gases, and some of the carbon have been driven off by the heat The coke itself burns if placed in a fire, but without any smoke, such as issues from coal
[Illustration: FIG 195--Sketch of the apparatus used in the as yields a s to the presence of certain ien, and carbon bisulphide A gas factoryrid of these objectionable constituents Turning to Fig 195, which displays very diagraas plant, we observe at the extreht the _retorts_, which correspond to our canister These are usually long fire-brick tubes of D-section, the flat side at the bottom Under each is a furnace, the flames of which play on the bottom, sides, and inner end of the retort The outer end projecting beyond the brickwork seating has an iron air-tight door for filling the retort through, iases Tar, which vaporizes at high temperatures, but liquefies at ordinary atot rid of This is effected by passing the gas through the _hydraulicthe whole length of the retorts The end of pipe A dips below the surface of the water, which condenses as now passes through pipe B to the _condensers_, a series of inverted U-pipes standing on an iron chest with vertical cross divisions between the mouths of each U These divisions dip into water, so that the gas has to pass up one leg of a U, down the other, up the first leg of the second pipe, and so on, till all traces of the tar and other liquid constituents have condensed on the inside of the pipe, froe is the passage of the _scrubber_, filled with coke over which water perpetually flows The aas is here absorbed There still reen and the carbon bisulphide, both of which are extremely offensive to the nostrils Slaked liht compartment called the _lime purifier_, absorbs as is then fit for use On leaving the purifiers it flows into the _gasoe cake-like form of which is a very faasometer is a cylindrical box with a domed top, but no bottom, built of riveted steel plates It stands in a circular tank of water, so that it as The levity of the gas, in conjunction eights attached to the ends of chains working over pulleys on the fra the holder, suffices to raise the holder
[Illustration: FIG 196--The largest gasholder in the world: South Metropolitan Gas Co, Greenwich Gas Works Capacity, 12,158,600 cubic feet]
Soasometers have an enormous capacity The record is at present held by that built for the South Metropolitan Gas Co, London, by Messrs Clayton & Son of Leeds This196) is 300 feet in diah When fully extended it holds 12,158,600 cubic feet of gas Owing to its immense size, it is built on the telescopic principle in six ”lifts,” of 30 feet deep each The sides of each lift, or ring, except the topmost, have a section shaped somewhat like the letter N Two of the members form a deep, narrow cup to hold water, in which the ”dip”above it rises and falls
[Illustration: FIG 197--Drawing retorts (_Photo by F Marsh_)]
AUTOMATIC STOKING