1840.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



3(17 



ON CLOTfflNG OF STEAM BOILERS. 



Report ttpon the advantages to be derived from Clothing Steam Boilers, 

 Pipes, Cylinders, ^-c, with the Patent Felt, mannfaclured by JMessrs, 

 Borradaile, IFTtiting, and Company. 



By Thos. Wicksteed, Mem. Inst. Civil Eng., Hon. Mem. Roy. Cornish 

 Polytech. Soc, &c. &c. 



[We feel mucli pleasure in being able through the kindness of 

 Messrs. Borradaile and Co., to give to our readers the following very 

 valuable report on Clothing of .Steam Boilers and Cylinders, and which 

 we are sure will be perused with much interest. We must here ob- 

 serve that too much praise cannot be given to those gentlemen for the 

 spirited manner they have had the experiments made, which could 

 rot have been done excepting at a very large outlay. We think after 

 a careful study of tliis report by those who have a steam engine not al- 

 ready clothed, they will hesitate no longer iu adopting that very essential 

 requisite, which we are sorry to say has been, heretofore, most shame- 

 fully neglected. The experiments were conducted under the direction 

 of Mr. Wicksteed, the eminent engineer of the East London Water 

 Works, whose abilities are too well known to the profession to need 

 any praise on our part for the very elaborate manner he has performed 

 his task.] 



Upon the 25th of April last, Mr. Francis Whiting called and re- 

 quested me to give an opinion as to the advantages of using Borra- 

 daile's Patent Felt as a non-conductor; and to state what I considered 

 was the actual amount of saving in fuel obtained in the use thereof 

 as a clothing for steam-boilers, cylinders, &c. I stated that, although 

 I never had had the opportunity of trying experiments, I was satisfied 

 it was a good non-conductor, and as the amount of saving stated as 

 having been obtained by those that had used it varied from 6 to 17 

 per cent., I thought it would be advisable to try a series of experi- 

 ments upon a large scale, continued for so long a time that the expe- 

 rience obtained should put at rest all question as to the actual amount 

 of saving. 



Mr. Whiting approved of this suggestion, and gave me instructions 

 to try any experiments 1 thought proper. 



In pursuance of these instructions I determined to ascertain the 

 quantity of water evaporated by a given weight of coals, when the 

 boiler, steam-pipes, and flues were exposed, or not clothed, and also 

 when they were clothed with one, two, three, and four couts of the 

 Patent Felt respectively ; having been in the habit also of using hop 

 sacking as a covering for the boilers, I determined to ascertain the 

 evaporative power of tlie boiler when clothed with three and five coats 

 of hop-sacking respectively, these experiments would give me the 

 proportionate amount of fuel required to evaporate a given weight of 

 ■water under the dilferent circumstances before stated. 



To ascertain the saving obtained by the use of the Patent Felt in 

 clothing the cylinder, nozzle, and steam-pipes, I determined to ascer- 

 tain the quantity of water that was required to pass through the 

 cylinder in the form of steam, to do the duty of one horse, when the 

 cylinder, steam-pipes, &c., were exposed, or not clothed, and when 

 clothed partially, or wholly, with Patent Felt, as described in Table 

 No. IV. appended to this report. 



The boiler on which the experiments were tried was made by 

 Boulton & Watt; it was of that form called wagon-headed, with a 

 flue passing through the centre, the fire being underneath; the di- 

 mensions were as follow : 



Ft. In. 

 Length of boiler . . . . 21 U 



Depth . . , . .88 



Width in widest part . . . 5 11 



Width of flue passing through the centre .26 

 Depth of ditto ditto . 3 



The engine, which was a single pumping-engine, was made by the 

 same parties, the cylinder GO inches in diameter, and average stroke 

 7ft. llin. ; the cylinder had a steam jacket around it. 



A long series of experiments was made, the details of which are 

 given in Tables Nos. 1, 2, 3, and 4, appended to this report. 



Before commenting upon the experiments, I will give an expla- 

 nation of the Tables, to show in what way the ditFerent results have 

 been arrived at. 



Table No. I. 



The columns 1 and 2 require no explanation. 



Column No. 3, shows the number of hours the engine was at work per 

 diem of 24 hours. 



Column No. 4, gives the bushels of coals consumed, which were accurately 

 weighed, each bushel weighing 84 lb., being the weight of the imperial 

 bushel. 



Column No. 5, gives the weight of water in hundred weights introduced 

 into the boiler every 24 hours, the way in which this was ascertained was as 

 follows : — There were two cisterns of given dimensions placed one above the 

 other, the top one communicating with the feed pump of the engine, having 

 an overflow, or waste water-pipe attached to it, and a valve in the bottom to 

 let water into the lower cistern when required ; the lower cistern communi- 

 cated with the boiler, supplying it in the ordinary way adopted for low pres- 

 sure boilers ; the lower cistern was gauged, the gauge being divided into 

 hundred weights, the divisions being obtained by actually weighing tlie water 

 into the cistern ; the lower cistern was filled with 21 cwts. of water, and 

 when that was exhausted in feeding the boiler, the feed valve was closed, 

 and the cistern was refilled with 21 cwts. more, so that the actual quantity 

 evaporated was most accurately obtained. 



Column No. 6, represents the mean teraperatnre of the water in the lower 

 cistern before evaporation, and was thus obtained : the temperature of the 

 water each time the cistern was filled was taken, and again when it was nearly 

 empty, the mean of all these temperatures is represented in column No. 6. 

 The mean temperature in the line of Totals was otjtained by multiplying each 

 weight of water, given in column No. 5, by the corresponding temperature iu 

 column No. 6, the products being added together, and divided by the total 

 weight of water, which gives the true mean temperature of the whole water 

 evaporated. 



Table No. II 



Column No. 1, refers to the totals in Table No. 1. 



Columns Nos. 2, 3, 4, 5, & 6, require no further explanation than has been 

 already given. 



Column No. 7, represents the pounds weight and decimals of a pound of 

 water evaporated by the consumption of one pound of fuel ; the water before 

 evaporation being at the corresponding temperatures given in column No. 6. 



Column No. 8, represents the cubic feet and decimals of a cubic foot of 

 water evaporated by the consumption of 1 12 tb. of coal, under similar circum- 

 stances to those given in column No. 7. 



Column No. 9, represents the cubic feet and decimals of a cubic foot of 

 water, that would have been evaporated, if the temperature of the water ad- 

 mitted into the boiler had been equal to 212^ of Fah., and is obtained thus :* 

 The latent heat of steam was stated by Mr. Watt to be equal to 950°, the 

 sensible heat at the boiling point is 212°, the sensible and latent heat together 

 being equal to 1162°, but as the water to be evaporated (see experiment No. 

 1,) had already 80'9° of beat in it, the number of degrees of heat required to 

 be communicated to the water to convert it into steam would be 1081-1° 

 only, and if the temperature of the water had been 212°, it would have re- 

 quired only 950° of heat (equal to the latent heat) to be communicated to it 

 to convert it into steam, hence 



Heat. Coal. Heat. Coal. 



As 1081-1° : n2tb. :: 950° : 98-4 tb. 



Thus if the temperature of the water had been 212° Fah. before it had been 

 admitted into the boiler, 98-4 tb. of coals would have evaporated as much 

 water as 112 tb. of coals would have done, the temperature being 80-9, hence 

 Coal, Water. Coal. Water. 



98-4 tb. : 13.43 cubic feet ; : 112 tb. : 15-28 cubic feet, 

 in other words, 112 tb. of coal will evaporate 15-28 cubic feet of water from 

 212° Fah., and only 13-43 cubic feet from 80-9° Fah. 



The oljject of column No. 9, is to show a fair comparison betweefi all the 

 experiments, reducing them to one standard, which is rendered necessary from 

 the circumstance of the temperatures given in column No. 6, varying in each 

 series of experiments. 



Column No. 10, shows the amount of saving in fuel under different states 

 of clothine, or exposure of the boiler, steam-pipes, &c., as described in column 

 No. 11. 



Table No. HI. 



Columns Nos. 1, & 2, require no farther explanation tlian has already 

 been given. 



Column No. 3, represents the weight of water passing through the cylinder, 

 or into the steam jacket in the form of steam, in the time stated in column 

 No. 2. 



Column No. 4, represents the number of strokes made by the engine in the 

 time stated in column No. 2, which is necessary to be recorded, that the 

 power of the engine may be ascertained. 



Column No. 5, is the pressure under which the engine worked, or the 

 height to which the water was raised, and was obtained by noting down 

 every 15 minutes during the time the experiments lasted, tlie pressure, indi- 

 cated by a mercurial syphon-gauge attached to the pump, then taking the 

 mean of the pressures so noted down, and adding to it the height from the 

 level of the water in the engine well to the datum line of the mercurial 

 gauge ; the mean pressure in the line of totals was obfamed by multiplying 

 the figures in columns No. 4 and 5 together, and dividing by the total num- 

 ber of strokes, which gives the true mean of the observations made every 

 15 minutes. 



Table No. IV. 

 Column No. 1 refers to the totals in Table No. 3. 



* Vide Mr. Parke's paper on the evaporation of water from steam boilers. 

 Trans.ictions of the Institution of Civil Kngineers, vol. 2. page 172. 



3 D 2 



