311 



GAS, MANUFACTURE OF. 



GAS, MANUFACTURE OF. 



311 



the most respectable MM! moat experienced gas-fitters should be em 

 ployed. No doubt many of the sad accidents recorded, of explosion* 

 in houses, are to be attributed to the use of inferior composition 

 service-pipes for the distribution of gu. 



In arranging the dimensions of the mains of a gas distribution it is 

 to be observed, first, that there is an economy of working expenses 

 in making the mains rather larger than would theoretically be requirec 

 to deliver the quantity of gas they are originally intended to supply 

 because, in such a case, the gas might be made to work under a 

 diminished pressure, and thus the leakage would be diminished. The 

 diameters of the mams are to be ascertained by dividing the district 

 to be supplied into certain sub-districts, according to their relative 



consumption, and then applying the formulas 



__. n 



= / 2 y ; 



p = - t*; the former for the purpose of determining the velocity oi 



the gas due to a certain pressure ; and the latter, the pressure for a 

 given velocity. In these formula;, p= the pressure ; r= the velocity 

 ;/ the force of gravity = 32'19 ; 8 = the weight of a cubic foot oi 

 the gas in pounds ; but no attention is paid to the retarding effects ol 

 friction in the mains, or to those produced by bends, or other incidental 

 causes. Taking the friction alone into account, it has been considered 

 that the total pressure at the end of a pipe may be represented by the 



formula />= fT--t-n/-) sr*; in which the new terms, M = a 



efficient determined by experience to be = 00011 ; I the length oi 

 the main ; c = the inner circumference of the pipe ; and a = its area. 

 Clegg enters at length into the mathematical reasoning on this subject , 

 and the reader is referred to his work for further details upon it ; but 

 it may suffice for present purposes to state that he finally quotes, for 

 ascertaining practically the quantity discharged by a pipe, the formula 



<J = I860 tP A/ ; in which Q = the quantity sought ; d = the 



diameter of the pipe in inches; A = the working pressure in inches; 

 I = the length of the pipe in yards ; and = the specific gravity of the 

 gas compared to that of atmospheric air as unity. Provided the radius 

 of the bends upon a length of main be large, there is little necessity 

 for taking them into account; and indeed the simple precaution ol 

 making the diameter of the pipe rather larger than would theoretically 

 be required, would obviate any necessity for so doing. 



Under any circumstances, when a town U characterised by great 

 irregularities of level, it is desirable to insert, upon the leading mains, 

 species of receivers provided with governors at the points where the 

 marked changes of level occur. When, on the contrary, the town is 

 (like those of Holland) nearly upon a dead level, and close to the 

 water line of the district, it becomes necessary to insert numerous 

 syphons in order to relieve the mains of the tar and other liquids 

 which may find their way into those mains ; and in towns of this 

 character it is desirable to give an inclination of about 1 in 600 towards 

 the syphons. It is of course necessary to maintain an efficient seal in 

 the syphon box, and to provide a small discharge pipe to draw off any 

 excess of tar or water. Another detail of pipe laying, which requires 

 to be considered, is the position of the valves to be placed for the 

 purpose of shutting off the gas during the repairs of the mains. These 

 valves must be placed so as to interfere with the service in the 

 smallest possible degree ; but no definite rule can be laid down in any 

 of the matters of local detail. 



In laying the pipes great care should be exercised in forming a 

 regular and incompressible bed, and in rigidly adhering to the rates 

 of inclination prescribed. As a general rule, the pipes for convey- 

 ing gas may be laid at the depth of 2 feet from the surface ; but 

 of course the latitude of the locality considered may render it advis- 

 able to modify this law. If any water-pipes should be laid in the 

 some street as the gas-pipes, the latter must be kept as far from them 

 u possible, and under any circumstances they must be placed above 

 the water-pipes; serious accidents have indeed occurred from the 

 neglect of these precautions, for occasionally the gas has found its 

 way into water-pipes, by the singular action known by the names of 

 endosmose and exosmose, and explosions have taken place at the outlet 

 The greatest possible care should be taken in laying the main* to 

 ensure the tightness of the joints, as it is at such places that the gas 

 most commonly escapes. 



The following tables may be considered to represent, first, the 

 dimensions and weights of gas-pipes of various diameters; and 

 secondly, the quantity of gas which pipes of the respective diameters 

 will deliver, under ordinary circumstances, with the pressure of 

 1 inch. 



Table I. Dimtnnmt and Welyhtt r,f Pijti. 



Column No. 1 represents the diameter in inches ; No. 2 the number 

 of belt* in the length of pipe ; No. 3, the thickness ; No. 4, the mean 

 weight of each pipe ; No. 6, the tolerated deviation of weight of 

 each pipe; No. 0, the net length of the pipes ; No. 7, the ordinary 

 price for laving and jointing, without earthworks, calculated per yard 



i.: .J. 



Table II. Skmeing Discharge through Pipei. 



With respect to the consumers' fittings, it may be as well to observe 

 that the public lampe in streets should be made to consume at the rate 

 of 5 feet per hour on the average of the night ; and that gas coin 

 would tiiii I it desirable to use regulators upon these lamps, both fur 

 the sake of checking the waste of gas, and of improving the light 

 them. As a rule, the lamp-posts in the streets of populous towns 

 should be placed alternately on either side of th< i at a 



distance of from 22 to 30 yards (measured on the axis) ; though in the 

 less frequented districts, the distance asunder of the posts (measured 

 as before) may be carried, without inconvenience, even to 60 yards. 

 The height of the flame in the lamps should be about 12 feet above 

 the ground line. 



In private houses, the character of the fittings, and the quantity <>f 

 gas burnt to light a given space, depend so much upon the task 

 consumer, and the details of the burners are exposed to such constant 

 changes from the whims and fancies of the gas fitters, that it is im- 

 possible to lay down any positive rules with respect to them, other 

 than a few general ones derived hum the ordinary principles of 

 lighting. Thus, it is preferable to distribute the light of a room by 

 means of a number of burners consuming small quantities of gas, 

 rather than to concentrate it in one central burner consuming a large 

 quantity ; because the effect of artificial light diminishes in tin 

 nearly of the square of the distance from its source. Of the various 

 kinds of burners used, the ordinary Argand burner seems, quan- 

 gos for quantity, to be the most convenient and the most econ- : 

 The bats-wing burners ore the next in the order of relative economy ; 

 and the fish-tail burners the last. The so-called solar lamps are 

 admirably adapted for lighting large rooms, wherein it may not be 

 desirable to distribute the sources of light, or wlieivin it is desired to 

 establish an active upward ventilation ; but they are expensive, and on 

 account of the heat they evolve, they render it necessary to adopt 

 certain precautions in the construction of the building. 



Whatever description of burner be used, attention must be paid to 

 regulate the escape of the gas, in such wise as to prevent its issuing 

 with too great a pressure, because in the latter case a large portion of 

 the gas would only be partially burnt, and would thus cause mm h 

 smoke. As to the asserted injury to furniture, books, Ac., from the 

 use of gas in dwellings, it is curious that in on old French work, pub- 

 lished at Lausanne in 1770, precisely the same accusation was brought 

 against the use of coal in fire-places as is now brought against gas ; 

 and the inference to be drawn from this tale is, that certainly the 

 latter cannot be at fault, whilst probably there may be exaggeration in 

 both cases. The heat of gas is also at times objected to, but if the 

 same amount of light were obtained by any other method of artificial 

 lighting, even greater heat would be evolved ; and in either case atten- 

 tion is required to ensure an efficient ventilation. This is the more 

 senary from the fact, that by whatever means artificial light is 

 ained, its brilliance can only be secured by the consum; : <, . i 

 rgen ; and therefore it is essential that an ample supply of fresh air 

 mid be introduced to maintain the combustion, if for no 

 am 



A great deal of attention has lately been directed to the question of 

 gas-meters, and a special act of parliament has been passed (22 & 23 

 Viet. c. 66) to regulate them. It may suffice here to say that meters 

 ire of two sorto, dry or wet; and that the latter work satisfactorily, if 

 -pt properly filled, for a longer period than the former, both of 

 them, however, must now be made with such accuracy that they 

 should only have a range of error of 2 per cent, above, or below, the 

 nathematic.il quantity indicated : and if the best compensating meters 

 >c used, there need be no fear of any subsequent tampering on the 

 art of the gas companies. It is usually calculated that the con- 



