One of the types of boilers on this general plan is the "Heine," built by the Heine Safety Boiler Company, and illustrated in Figs. 61 and 62. Fig. 61 shows the construction of the boiler independent of its setting. The water legs arc made of flat plates stayed together by screw stays, as in locomotive-boiler construction, the perfectly flat parallel surfaces lending themselves to safe and adequate staying better than any other shape. The inner surfaces of the water legs act as the tube sheets, while holes a trifle larger than the tubes and exactly in line with them are cut through the outer surface of the water legs. These outer holes are closed when the boiler is in operation with a hand-hole plate, dog and bolt, but when the tubes are to be cleaned or removed these hand-hole plates are removed and give free access to the ends of the tubes.

Fig. 61. The Heine Boiler without its setting.

Fig. 62. The Heine boiler in its setting.

The screw stays should be called stay tubes and not stay bolts, because there is a hole through each of them large enough to permit the entrance of a half-inch pipe with a steam jet on the end, and as these stay-tubes are in the center of the space between the water tubes this permits the steam jet to pass down between the latter from end to end, and thus effectively to blow the dust off one-fourth of each of the four surrounding the space.

This is necessary with boilers in all industries, but is particularly necessary at blast-furnaces because of the great quantity of fine dust carried by the gas at the majority of plants.

The boiler in its setting is shown in Fig. 62, which also shows the baffling. It will be seen that the gases go to the rear, then to the front, and then to the rear again, passing around the drum on their way to the stack. For this reason the drum is covered with fire brick above the water line, and this is very important because I have seen the drums of this type of boiler badly burnt through failure to keep these covering bricks in place.

Fig. 62 shows a boiler adapted only for the burning of coal, but only two minor changes are required to adapt it to burning furnace gas also. First, it should be set a little higher above the grate, and a burner opening should be provided through the front wall between the bottom of the water leg and the top of the fire arch. Second, the tiles used as baffling immediately over the fire should be of the type which completely surrounds the tubes, covering their lower as well as their upper surface, as such tiling constitutes a water-cooled fire arch. The tiles become hot enough to help combustion, whereas the relatively cold tubes kill down the flame before the gas and air have a chance to mix sufficiently to produce complete combustion. When such gas has once been extinguished it will not reignite, but passes out of the stack unburnt and represents a dead loss.

Fig. 63. Wrought steel inclined header. B. & W. Boiler.

Fig. 64. Forges steel cross box.