1850.1 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



291 



INCRUSTATION IN STEAM BOILEKS. 



On the Incrustation which forms in the Boilers of Steam-Engines, 

 in a letter addressed to Dr. G. Wilson, F.R.S.E. By Dr. J. Davy. 

 On entering on this inquiry, which I did after my return from 

 the West Indies in December, 1848, and after communicating 

 a short paper to the Royal Society "On Carbonate of Lime in Sea- 

 water " it appeared to me desirable to collect as many specimens 

 as possible of incrustation from tlie boilers of steam vessels, now 

 so widely employed in home and distant navigation By applica- 

 tion to companies and to friends in our sea ports, as Dundee, Hull, 

 Southampton, Hayle, Liverpool, A^Hiitehaven, I have succeeded in 

 nrocuring specimens of incrustation formed by deposition in 

 voyages from port to port, in the British and Irish Channels and 

 the North Sea, between Southampton and Gibraltar, in the Medi- 

 terranean and the Black Sea, and in the Atlantic Ocean, between 

 Liverpool and North America, and between Southampton and the 

 West Indies. I am promised specimens from the Red Sea and the 

 Indian Ocean— hut these I have not yet received. 



The character and composition of the incrustation, whether 

 formed from deposition from water of narrow seas or of the ocean, 

 I have found very similar— with few exceptions, crystalline in 

 structure, and, without any exception, composed chiefly of sulphate 

 of lime; so much so, indeed, that unless chemically viewed, the 

 other iAgredients may be held to be of little moment, rarely 

 amounting to 5 per cent, of the whole. From two specimens of 

 incrustation from the boUers of steamers crossing the Atlantic, 

 one of which you sent me, in which you had detected a notable 

 portion of fluorine, judging from its etching efl-ect on glass,— 1 

 also procured it, it was in combination with silica; and procured 

 it also so combined from two obtained from steamers navigating 

 our own seas, one between Dundee and London, the other between 

 Whitehaven and Liverpool. Of this I had proof, by covering 

 with a portion of glass or platina foil a leaden vessel charged with 

 about 200 grains of the incrustation mi.xed with sulphuric acid, 

 and by keeping the glass cool by evaporation of water from its 

 surface, and by supplying moisture for the condensation of the 

 silicated gas by a wet band round the mouth of the vessel. After 

 about twenty-four hours under this process, a slight but distinct 

 deposition was found to have taken place, corresponding to the 

 margin of the vessel— a deposition such as that produced by sili- 

 cated fluoric acid gas under the same circumstances, f hu-^ it was 

 not dissipated by heat nor dissolved by water, and yet admitted ot 

 removal by abrasion, either entirely or in great part; the former 

 in the instance of the platina foil, the latter in that of the glass. 

 Besides the ingredients above-mentioned, I may add that, in many 

 instances oxide of iron, the black magnetic oxide, was found to 

 form a part of this incrusting deposit, collected in one or more 

 thin layers, and further, that in some, especially of steamers navi- 

 gat"ng^the narrower and least clear part of the British Channel 

 the depositions presented a brownish discolouration produced by 

 the admixture of a small quantity of muddy sediment. Ii«usta- 

 tions so discoloured, 1 may remark, are reported to be most difii- 



''"i* have^'^said that the incrustations, with few exceptions were 

 similar in their structure, and that that was crystalline; it was 

 not unlike the fibrous variety of gypsum of the mineralogists. 

 The specimens received, as might have been expected varied very 

 much in thickness-viz., from one line and ess to half an .nch I 

 have endeavoured, by a set of queries which I had distributed, to 

 obtain information respecting the exact time in which the incrus- 

 tations were formed, and under what circumstances; but with 

 partial success only, owing to a want of exact observation In 

 one instance, that of the North American mail-ship i?«>opa, 

 which arrived at Liverpool on the 15th of November at 4 p.m., 

 having left Boston on the 7th of the f^e month at 9 am an 

 incrustation was found in her boiler of about one-hftieth of an 

 inch in thickness; and it is stated that an incrustation of about 

 the same thickness was found on her outward voyage. Ihis 

 example may aid in giving some idea of the degree ot rapidity 

 with which the incrustation is produced, at least in the Atlantic, 

 with the precaution of "blowing-oif " every three hours, and with 

 the "brine pumps" kept in constant work. In other seas, especi- 

 ally contiguous to shores, and more especially of shores formed by 

 volcanic Eruptions, it is probable, cMeris paribus the rate of the 

 deposition of the incrusting sulphate of lime will be more rapid. 

 The results of the trials of several portions of sea water taken up 

 on the voyage from the West Indies to England noticed in the 

 paper of mine already referred to, are in favour of this conclusion. 



To endeavour to prevent the deposition of the incrusting matter 

 or to mitigate the evil, various methods, it would appear, have been 

 had recourse to— some of a chemical kind, as the addition ot • 

 muriate of ammonia and sulphate of ammonia to the water in tlie 

 boiler— without success, as might be expected; others, ot a me- 

 chanical kind, with partial success— as the introduction ot a cer- 

 tain quantity of saw-dust in the boiler, or the application ot tallow 

 or of a mixture of tallow and plumbago to its inside, to prevent 

 close adhesion, and the more easy separation of the incrusting 

 matter either by percussion, using a chisel-like hammer or by 

 contraction and unequal expansion, by means ot .'^^^S/'", /^^ 

 with oakum, after emptying the boiler and drying it. Ut all tne 

 methods hitherto used,' that of "blowing-off —that is the dis- 

 charging by an inferior stop-cock a certain quantity of the concen- 

 trated water of the boiler by the pressure of steam, after the 

 admission above of an equivalent quantity of sea water ot ordinary 

 density, appears to be, from the reports made, the most easy in 

 practice, the least unsuccessful, and the most to be relied on. But, 

 as in the instance given of the North American steamer, it can be 

 viewed only as a palliation. , 



Considering the composition of the incrusting matter and tne 

 properties of its principal ingredient— the sulphate of lime, a 

 compound soluble in water and in sea water, and deposited only 

 when the water containing it is concentrated to a certain degree, 

 there appears to be no difficulty theoretically in naming a preven- 

 tive The certain preventive would be the substitution ot distilled 

 or rain water in the boiler for sea water. Of this we have prcot 

 in the efficacy of Hall's condenser, which returns the water usett 

 as steam, condensed, after having been so used; but, unfortunately 

 for its practical success, the apparatus is described as being too 

 complicated and expensive for common adoption, lurther proot 

 is afforded in the fact, that the boilers of steamers navigating 

 lakes and rivers in the waters of which there is little or no sulphate 

 of lime, month after month in continued use, remain free from 

 incrustation. This I am assured is the case with the steamers that 

 have been plying several summers successively on the lake ot 

 Windermere. And it may be inferred, that in sea-goiiig steamers 

 in which sea water is used in the boiler-or, indeed, any water 

 containing sulphate of lime, the prevention of deposition may be 

 effected with no less certainty by keeping the water at that degree 

 of dilution at which the sulphate of lime is not separated from the 

 water in which dissolved. i i, ♦„ 



From the few trials I have made, I may remark, that sulphate 

 of lime appears to be hardly less soluble, if at all less, in water 

 saturated with common salt than in perfectly fresh water. Ihis 

 seems to be a fortunate circumstance in relation to the inquiry as 

 to the means of prevention, and likely to simplify the Foblem 

 If these principles be sound, their application under different 

 circumstances, with knowledge and judgment on the part of tne 

 directing engineer, will probably not be difficult. His great object 

 will be in sea-going steamers to economise the escape of water in 

 the form of steam, and thereby also economise heat and fuel; also 

 when fresh water is available, to use it as much as possible; and 

 further, to avoid using sea w.ater as much as possible near coasts 

 and in parts of seas where sulphate of lime is most abundant. 

 From the incrustation on the boilers of sea-going steamers, the 

 attention can hardly fail to be directed to that which often forms, 

 to their no small detriment, in the boilers of locomotive- railway 

 engines, and of engines employed in mines and in the multifarious 

 works to which steam power is now applied. These incrustations 

 will of necessity be very variable, both in quantity and quality, 

 according to the kind of ingredients held in solution in the water 

 used for generating the steam. , r ■ ^ ►•„„„ 



Hitherto I have examined two specimens only of incrustations 

 taken from the boilers of locomotive engines, and a single one 

 only from the boiler of a steam-engine employed on a mine-a 

 mine in the west of Cornwall. The latter was fibrous about halt 

 an inch thick, and consisted chiefly of sulphate of lime, with a 

 little silica and peroxide of iron, and a trace of fluorine. 1 he 

 former were from one-tenth of an inch in thickness to one inch. 

 They were laminated, of a grey colour, and had much the appear- 

 ance of volcanic tufa; they consisted principally of •'f :bo"ate and 

 sulphate of lime with a little magnesia, protoxide f ';«"' "'"'^' 

 and carbonaceous matter-the last two, the ^'l'*^^ ''"f, ';^'^^~°n f 

 matter, probably chiefly derived from the s™''''^ °V wouW aonear 

 the dust in the air. From the engineers f P^^* i* ^f a„tnch!l 

 that the thinnest-the incrustation of about one-tentl^^of an inch- 

 had formed in about a week, during which t>me the locomotive 

 had run about 436 miles, and consumed about 10,900 gallons ot 

 water. 



39* 



