by keeping the dissolved oxygen content of the boiler water as low as possible.

The watersides of naval boilers may be cleaned in two ways - mechanically, by thorough wire brushing of all drums, headers, and tubes; and chemically. by circulating chemical cleaning solutions through the boiler.

Mechanical Cleaning

Before mechanical cleaning of watersides is begun, the internal fittings must be removed from the steam drum. The fittings (particularly the steam separators and apron plates) must be marked or otherwise identified as to position in the steam drum to ensure their correct reinstallation. All internal fittings must be wire brushed and cleaned before they are reinstalled.

Cleaning the watersides of the generating tubes requires a special tube cleaner. There are several types available, but perhaps one of the most common is the pneumatic turbine-driven tube cleaner shown in figure 1-31. This type of cleaner consists of a flexible hose, an air-driven motor, a flexible brush holder, and an expanding wire bristle brush. The turbine-driven motor consists of a set of turbine blades made to revolve when compressed air is admitted through the hose. The turbine-driven motor, in turn, drives the wire brush. There are several sizes of brushes available (figs. 1-32 and 1-33). Figure 1-34 shows a brush refill for the type of brush shown in figure 1-32.

Before you start cleaning tubes, be sure that adequate ventilation and lighting have been arranged. Someone should also be stationed outside the drum to act as tender

Figure 1-32. - Wire bristle brush for cleaning generating tubes.

and to assist whomever is working in the drum. Keep a written checkoff list of all tools and equipment taken into the watersides and be sure that the same tools and equipment are removed.

With the air shut off, insert the tube cleaner in the tube until the brush is about even with the far end of the tube. Wrap friction tape, a rag, or some other marking

Figure 1-31. - Boiler tube cleaner (pneumatic turbine-driven type).