Horizontal Water-Tube Boilers - Root Water Tubes Nearly Horizontal Steam and Water Drums Horizontal Straight-Tube Single Tube Sectional

HORIZONTAL WATER-TUBE BOILERS - ROOT: WATER TUBES NEARLY HORIZONTAL, STEAM AND WATER DRUMS HORIZONTAL, STRAIGHT-TUBE, SINGLE TUBE, SECTIONAL The above brief outline indicates that the Boot water-tube boiler is, in its main features, like the Babcock and Wilcox. In fact the difference is in detail of construction only. Fig. 46 shows the general appearance when a part of the brickwork is removed. It will be seen that there is a large steam drum (cross type) at the top in addition to the small steam and water dram over each section.

Construction. The Root water-tube boiler is composed of 4-inch lap-welded wroughtiron tubes. These tubes are expanded into cast iron headers as shown in A, Fig. 45. A vertical section is formed by placing one pair upon another as shown at B, Fig. 45. One tube of each pair is connected to one above it by a flexible bend, by means of which is obtained an uninterrupted circulation from the bottom to the top of the section. A metallic packing ring (see C, F), and E, Fig. 45) insures a tight joint between the bend and the header. F, Fig. 45, shows an enlarged end of a bend.

To form the boiler several of these vertical sections are placed side by side. These vertical rows are not rigidly connected because the lower tubes being nearer the fire expand more than those above.

Circulation.Each section has its overhead drum into which the water and steam is discharged from the tubes. At the rear of the boiler and at the end of each steam and water drum, a verdeal pipe leads to a cross drum beneath; this drum is a common reservoir for all the sections. The feed water enters this drum and meets the hot water coming from above. The mixing of the water results in a temperature which prevents any trouble from unequal expansion. The cross drum (reservoir) is also connected by vertical pipes to another drum which is below and parallel to it; this is the mud drum. From the feed reservoir, the mixture of feed and circulating water descends to the mud drum in which the solid impurities are left. The circulating water then flows from the top of the mud drum into the lower end of the tubes. As these tubes are surrounded by hot gases, the water becomes heated and rises through the tubes to the steam and water drums. This heated water contains bubbles of steam which leave the water and collect in the steam drum. The water flows through the steam and water drum and descends to meet the entering feed water. The water level is at about the ladle of the steam and water drums.

The hot gases from the fire pass among the tubes three times in practically the same manner as in the Babcock and Wilcox boiler.