The Alaska citizen., 1910-12-19

excerpts from Power and the En- gineer,' one of the best authorities | on the subject. in regard to boiler | explosions are printed:
 | II is an undisputed fact that boil CTS explode for want of sufficient strength to withstand the pressures carried
 The trouble may be due to faulty l design or poor workmanship in the 1 original construction. though more | frequently the weakening Is due to unequeal expansion and contraction, | to corrosiou CT to improper repairs. Should any part of the boiler be- ! come sufficiently weakened and rup- | ture occur. the steam pressure will
 be suddenly reduced and release the | energy stored up in the water The large volume Of water, thus relieved l of pressure, will instantly flash into
 steam, the sudden shock causing a 1 furjher opening of the rent and | producing destructive results. The fracture will not always fol- l low the path of the structural weak l ness. for new forces are set up 1 when the above shock occurs and 1 il Is alnOst impossible to predict i lie llIt Ol IdIuIb.
 IL is estimated that d cubic foot ] of water under 70 pounds pressure ] and heated to temperature cor l responding to steam at that pressure, i contains about the same energy as one 1 pound of gunpOWder. Further, that
 a plain cylindrical boiler of average l size with steam at loo pounds pres sue and filled with water to the proper level, has sufficient stored l ell rgy to project the boiler to a i height ot 3i2 miles.
 i lt is thus seen that the extent of m explosion depends not so much upon the amount Cf steam contained ] III tn boiler as to the amount of i hot waJer ready to flash into steam In this fact lies the greater safe i " of the Water-tube boiler over that i ol tn, fire tube
 All boilers if net properly cared for are liable to explode Due to the effects of unequal eX- ] pans on and contraction and perhaps ] causes beyond the control of the l engineer, the plates are liable to i become weakened to such an extent ] that the affected portion has to be removed and a patch substituted. l Here is where special care and l skill should be employed. For more boiler explosions have l h. en caused by improperly applied ] repairs 1han from defects in original 1 design.
 An engineer owes it to the public. i and 10 himself. to thoroughly under l stand the operations of his boiler i and how to properly make repairs. While boiler makers should always 1 be employed to make the repairs, the l engineer should be in a position to i judge the quality of their work. for
 dfler all, he is the one to whom all | responsibility is attached
 The circumstances causing the eX- l plosion Of steam boilers were for a
 long time not definitely understood and were attributed to one or an 1 other of the following reasons
 Electricity supposedly produced by ,rlction of the water on the boiler plates.
 The rapid generation of steam due
 10 an unknown chemical property of the water.
 OXyhydrogen gas supposed to be generated by the decomposition of 'l4G NditL III lHe DOlItf.
 Spheroidal condition of the water, etc.
 Later researches, however devel- ped the fact that every boiler ex- 1losion is accompanied by two occur rences; First. the steam pressure in the boiler is suddenly reduced
 by the rapid escape of steam in large quantities; second, the conse- Iuent reduction in pressure on the hot water causes it to suddenly flash into steam. While these fac tors are not the direct cause of the failure Of the boiler, they are, never -heless attending results which count for the disastrous effects of an ex- plosion.
 The violence of the explosion de bends principally upon three fac tors, viz: the size of the water space of the boiler, the steam pressure pre-
 'ious to the explosion and the size and position of the rent caused by he explosion. Ii in a boiler with a large water space, sudden reduc- ton in pressure takes place, the large quantity of water which is nus relieved of the pressure will generate large quantities of steam, which, of course, will do more dam age than smaller amount of steam II the steam pressure previous to the explosion were high, the correspond ing temperature of the water would also be high and more heat would be given up, thus generating larger amount of steam. But of still great CT influence is the position and size of the crack allowing the steam to
 scape. If for some reason a boil. CT ruptures in it's upper part, it's position will change very little or not at all depending entirely upon the lastenings and supports On the other hand, should boiler rupture m the lower part, it would tend to feoVlve or fly into the air.
 The sudden reduction of steam pressure sufficient to cause the dis astrous effects of an explosion can only take place when the boiler rup. lures. These ruptures, which are me initial cause of all explosions may be due to the following causes:
 OVerheating of the furnace or tubes, due to shortness of water, or less frequently to the accumula- tion of scale.
 Overheating of the shell plates of externally fired boilers due to the accumulation of scale.
 Oil in the feed water.
 Corrosion or wear and tear.
 Improper design or poor workman ship.