271 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[Septeuder, 



iiicrea-ieil power miirlit be obtained from tlie same expenditure 

 of steam, and consequently of fuel, if the vacuum were improved 

 so as to be as fjood as the averaj^e of the six expansive eng^ines, 

 or lO.U'). per inch throui;hout the stroke. This vacuum lias been 

 obtained in the two eni;incs, Xos. 12 and 17, which have been 

 altered as before described, although in these enjrines the altera- 

 tion was carried out only to a limited extent, and at a compara- 

 tively triflinpf expense; but if it were carried out efficiently by 

 attachino; expansive year in addition to the alterations tliat have 

 been made, a much better effect would be obtained by using the 

 same volume of steam exjiansively. 



In many cases the expansive action is accomplished by the addi- 

 tion of a separate expansion valve in the steam I)ipe, which is 

 worked by a cam, so as to cut off the steam at any portion of the 

 stroke that may be desired, this valve openina; and shutting twice 

 for each double stroke of the entjine; the steam and eduction 

 valves are worked by a common eccentric motion, the top and 

 bottom valves o])ening and shuttinjr together. But this is an 

 imperfect mode of obtaining expansion, because the steam filling 

 the side pipe and the two steam chests expands after the cut-off 

 valve is shut, and this steam forms a considerable proportion to 

 the contents of the cylinder. 



The only efficient mode of applying expansive action, is by 

 lifting each valve by a se]>arate cam, so adjusted as to shut each 

 steam valve at whatever point of the stroke may be desired, whilst 

 the eduction valve is lield open till t!ie termination of the stroke; 

 by which means the full effect of the expansive action is obtained. 

 The difference in effect between these two modes of cutting off 

 the steam, is shown by the Diagrams Nos. 46 and 47, Plate X., 

 which are taken from a pair of blast engines working coupled 

 together, and with no difference between tliem except that in No. 

 V6 the steam is cut off by a separate expansion valve in the steam 

 pipe, and in No. 47 the valves are lifted by separate cams. 



But independent of the loss sustained by not working expan- 

 sively, tlie loss of power in the engines described being 1930 

 horse-power, as shown before, the annual loss in money by extra 

 consumption of fuel in these engines, calculating 20 lb. of slack 

 per hour, for one-horse power, at a cost of 3.s. per ton, will amount 

 to 18,610/., or 2/. Is. Id. per horse-power per annum. 



The total power of the steam engines employed in the manufac- 

 ture of iron in the district, may be computed to be fully ten times 

 the nominal power above named; and the total annual loss to the 

 proprietor from the causes described in the present paper, may be 

 therefore taken in round numbers at 180,000/. per annum, as the 

 more expansive engines described above may be considered a fair 

 average of the engines in the district. 



It has been generally considered hitherto, that the impi-ovement 

 of expansive action of steam was not applicable advantageously to 

 the engines of this district, because of the small cost of the fuel 

 employed; but this will be seen to be an erroneous conclusion from 

 the actual results of the alterations described above, where the 

 imjjrovement was only effected in the vacuum, and the expansive 

 principle was not carried out, which would have effected a still 

 i^reater saving. The total quantity of fuel consumed at present is 

 so large, that although the price ])er ton is insignificant, the total 

 amount of saving effected by the per centage on the whole is very 

 important. 



In addition to the saving in cost of fuel consumed, a very im- 

 portant saving would also be effected in the tear and wear of the 

 boilers, which is fully in proportion to the extra fuel burnt under 

 them, and the repairing of which is invariably attended with 

 serious inconvenience and expense. 



The description of boilers in general use in the district, and the 

 further saving to be effected by improvements in their construction 

 and mode of setting, is also an important practical suhject for con- 

 sideration, and is intended to form the subject of another paper, 

 to be laid before the Institution at a future meeting. 



Remarks. — Mr. M'Conneli, said, he believed the writer was quite 

 within bounds when he estimated the saving in fuel which might 

 be effected in that district alone, at 180,000/. per annum; n(u- was 

 the subject of im])ort:mce in that light merely, l)ecause it was found 

 to prevail as a general rule, that the amount of destruction in ma- 

 chinery and boilers was nearly in pro])ortion to the quantity of fuel 

 consumed. lie had remarked at a former meeting on the practical 

 importance ot obtaining comparative accounts as complete as pos- 

 sible of the consumjition of fuel, an{l economy of working of the 

 steam-engines in the different districts of the country, and he 

 thought that all information of that kind was of great practical 

 value. 



Mr. Bowman inquired whether, in most of the engines mentioned, 

 the ]iroportions of Boulton and \^'att were observed iu the con- 

 denser? 



.Mr. VV. Smith replied, that speaking generally he believed that 

 was the case, but the bad working of the engines was accounted 

 for by the extraordinary pressure of the steam used. The error 

 was, that engines intended and proportioned for 3 lb. steam were 

 worked up to I2lb. or I6lb. per inch throughout the stroke, and 

 co'isecpiently, they were very imperfect in their condensing; as 

 there was so much larger quantity of steam to be condensed at each 

 stroke, when the cylinder full of high pressure steam expanded 

 down to the same pressure as the low pressure steam. 



Mr. Bowman observed, that this would seem to imply that the 

 size of the condenser should be regulated by the pressure of the 

 steam in the cylinder. 



Mr. CowpER said, the pressure of the steam was certainly a ne- 

 cessary element to be taken into consideration, as well as the size 

 of the cylinder, in determining the size of the condenser. There 

 was not only a greater quantity of steam to condense when a higher 

 pressure was employed, but also a greater quantity of air to pump 

 out at each stroke of the air pump. He mentioned a case which 

 came within his own observation in that district, where 18 lb. steam 

 was employed; there was no barometer guage, but the parties were 

 satisfied that they had a good vacuum ; however the fact was, that 

 the injection water was forced into the condenser by means of a cis- 

 tern at the top of the engine house, 22 feet in height. 



Mr. Slate remarked, that he fully concurred in the results 

 obtained by Air. Smith, but feared they were so startling that 

 there would be a disinclination to give them credence in the dis- 

 trict. It was highly important then that the truth of the deduc- 

 tions should be practically admitted 



Mr. T. Thorneycroft, as an iron-master of the disti'ict referred 

 to, felt extremely obliged to the author of the paper pointing ont 

 the means whereby any saving conld be effected, more especially 

 at a time when, owing to the state of the trade, economy in the 

 manufacture was so essential. 



Mr. VV. Smyth said, it had often occurred to him, that a steam 

 engine was like no other machine. A time-piece, if out of order, 

 was sent hack to the maker to be repaired ; and in the case of ma- 

 chines of other descriptions, if they did not do their work well 

 they were immediately stopped, because they wasted and injured 

 the material iipon which they were employed. But when the old 

 steam-engine, after twenty or thirty years' of hard labour, showed 

 some symptoms of disorder, it could not be stopped, so with an 

 extra application of the coal shovel, and some hammering at the 

 cotters, &c., it was set to work again, and with its powerful steam 

 arm it wound round all the complicated machinery. This, how- 

 ever, was done at an enormous expense to the proprietor of the 

 engine, and it would be much better if he were to renovate its 

 constitution. He trusted that the exertions of the members of the 

 Institution would have some influence in showing to persons of the 

 description referred to, the necessity of carrying out these things 

 on more efficient principles than they had hitherto been con- 

 ducted. 



Mr. Bowman thought it a matter of great importance tliat the 

 injection water should spread itself out amongst the whole quantity 

 of steam immediately on its passage into the condenser, and the 

 altei-ation made by Air. Smith in the mode of injection was very 

 advantageous. 



Mr. CowpER observed, that they ought all to add their testimony 

 to the value of the Indicator Figures produced by Mr. Smith, 

 because they showed the character of the engines much better than 

 any judgment which could be formed with reference to them, inas- 

 much as it was the character of each engine written by itself, and 

 could not be erroneous, fie had not the slightest doubt, that a 

 loss of 180,000/. at least, as stated by Mr. Smith, was sustained in 

 that district, because the mode of condensing ordinarily ado])tcd 

 was exceedingly defective. It had occurred to him many years 

 ago, that a valve might be put at the side of the condenser, and 

 connected with an injection pump, so that a gush of cold water 

 might be injecteil at every stroke, at the very moment of the 

 entrance of the steam into the condenser, and shut off again imme- 

 diately, by which means the greatest possible use might be made 

 of the injection water, and the condensation of the steam effected 

 with a smaller quantity of injection water. He then explained tlie 

 drawing of an improved injection valve which he had constructed, 

 and found to work very successfully ; the object wi:s to maintain 

 the full pressure of the water at the point of entrance into the 

 condenser, and to obtain a more efficient distribution of the jet of 

 water without danger of its getting choked. In fig. 5, \ is the 



