. The street railway review . ofmaking any, while, with the steam in greater or less pro-portions in the two drums, the result is a very rapid andpositive circulation in one direction, on account of thegreater specific gravity of the water in the external pipe,than that of the combination of steam and water in thetubes. On reaching the upper drum, the steam separatesfrom the water, rising to the top of the drum, while the water escapes through the external pipe. The water, itis estimated, circulates 218 times in the boiler beforefinally becoming steam, which secures, in addition to therapid an
. The street railway review . ofmaking any, while, with the steam in greater or less pro-portions in the two drums, the result is a very rapid andpositive circulation in one direction, on account of thegreater specific gravity of the water in the external pipe,than that of the combination of steam and water in thetubes. On reaching the upper drum, the steam separatesfrom the water, rising to the top of the drum, while the water escapes through the external pipe. The water, itis estimated, circulates 218 times in the boiler beforefinally becoming steam, which secures, in addition to therapid and steady circulation, an absolutely uniform tem-perature of water in all the tubes, as the fresh feedwater mingles with that already in the tubes, in whichthe temperature is always uniform, which relieves theboiler from any destructive strains from unequal expan-sion. The boiler rests on four iron brackets, riveted to thelower, or mud drum, supported on four piers of thefoundation, so that the entire structure stands without. 1 \HAM. \IKIIi\[ \\\IER TlBE BOILER. contact with the brickwork, which allows the boiler toexpand, without straining the brick setting. Pipe con-nections to the boilers, through the walls, are incased inexpansion boxes. The upper tube sheet has a circularopening in its center to permit the gasses to escapethrough the central opening of the upper drum, so thatthere is a central open space between the tubes, graduall}-narrowing to the bottom of the tube sheet. In thisopening, deflecting plates are introduced, which causethe gasses to be alternately thrown out and in,throughout the whole heating surface, giving them asweep at nearly right angles to the tubes, thereb}-abstracting their heat, until they come to very nearly thesame temperature as the water. In a test of ten hours 56 (^tetff^aikavS^vW on a direct fired boiler, using bituminous coal, the boilerwas run at an average of 30 per cent above its rating allthe time, and the average rating of the temperat
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Keywords: ., book, bookcentury1800, bookdecade1890, booksubjectstreetrailroads
