fire-tube boiler has the same disadvantages as that of the horizontal-tube design - limited capacity and furnace volume.

Before selecting a vertical fire-tube boiler, you must know how much overhead space is in the building where it will be used. Since this boiler sits in an upright position, a room with a high ceiling is necessary for its installation.

The blowdown pipe of the vertical tire-tube boiler is attached to the lowest part of the water leg. and the feedwater inlet opens through the top of the shell. The boiler fusible plug is installed either (1) in the bottom tube sheet or crown sheet or (2) on the outside row of tubes, one third of the height of the tube from the bottom.

Horizontal Return Tubular Boiler

In addition to operating portable boilers, such as the Scotch marine and vertical fire-tube boilers. the Utilitiesman must also be able to operate stationary boilers, both in the plant and in the field. A STATIONARY BOILER can be defined as one having a permanent foundation and not easily moved or relocated. A popular type of stationary fire-tube boiler is the HORIZONTAL RETURN TUBULAR (HRT) boiler shown in figure 1-4.

Figure 1-3. - Cutaway view of a vertical fire-tube boiler.

Figure 1-4. - Horizontal return tubular (HRT) fire-tube boiler.