386 TRANSACTIONS OF THE 



[London Artizan, August, 1858. 



ON BOILER EXPLOSIONS. By Edward Strong, 

 Extracts by H. Meigs. 

 The theory that hydrogen gas is produced in a boiler (whether of iron or 

 copper) by too much heat decomposing water— or, secondly, that over- 

 heating causes water to take a spheroidical form, are mysteries. Engi- 

 neers have often said that when the metal is heated to redness from short- 

 ness of water, the gas is formed and exploded, with force equal to that of 

 gunpowder. Hydrogen gas is generated in the boiler but it is harmless 

 until mixed with certain amount of air, or of oxygen gas, neither of which 

 should be present in boilers when working. Iron, red hot, decomposes 

 water, but red hot copper does not, nor will do it at any temperature, how- 

 ever high. A copper fire-box, with tubes of brass, cannot decompose 

 water. Copper has proved to be superior to iron for raising steam, and it 



will not blow up. 



Water in the Spheroidical form.— If a plate of iron be heated to boiling 

 water, it gives steam, but when heated beyond 212^ Fahrenheit, water on 

 it does not form steam, but takes the spheroidical form, at U0°, rolling in 

 globular forms ; when the heat diminishes to 212°, then steam is formed. 

 It is said that the heat being reduced to 212°, after the water has taken 

 the spheroidical form, steam is produced so as to produce explosion of the 

 boiler. This theory has never been proved. The ordinary working pres- 

 sure on locomotive boilers, is 120 lbs. per inch. Such pressure requires 

 343° of heat, at which the water must be in spheroidical form, so that 

 whenever the pressure falls to 110 lbs. per inch, that form ceases and we 

 ought to have an explosion, which, however, does not take place. Further, 

 engines have been worked at 200 lbs. with perfect safety, with temperature 

 of 385°. These facts show the absurdity of the theory of explosion from 

 the spheroidical form of water. Locomotives are frequently so inclined as 

 to have part overheated without explosion ! The two theories being dis- 

 posed of, the rest is simple ; it is the mechanical strength of the boiler 

 only ! The boiler maker, therefore, should not merely make it strong 

 enough while it is new but allow enough to allow for tvear during the 

 mimber of years which it is decided to be workable It should first be 

 tested by hydraulic pressure of at least double its working pressure ; and 

 the boiler should be so tested once, at least, every year of its employment. 

 Neglected leakage leads to mischief, for it rapidly reduces the strength of 

 the plate there. Dirt, &c., bad. 



•SAFETY VALVES. 



Every boiler should have one. On no account should two or more boil- 

 ers (as is sometimes done,) have but one for all. Each boiler is fitted with 

 a stop cock, so that if one cock should happen to be closed that boiler 

 would inevitably explode. This one valve for several boilers, is, however, 

 allowed in government service even, sometimes. The valve, sometimes, 



