The tubes of the distillate cooler, the air ejec-tor condenser, and the stage condensers operate with comparatively cool saltwater inside them and seldom require cleaning. The seawater in the saltwater heater, on the other hand, is at a higher temperature and its tubes will occasionally require cleaning to remove the hard scale on the inside of the tubes. A special tool is furnished for this purpose; this cleaning tool is shown in figure 7-6.

Figure 7-6.Tool for removing scale inside tubes.

The procedure for cleaning saltwater heaters is as follows:

1. Remove the waterheads.

2. Insert the special cleaning tool in the tube and drive it with a 250 to 300 rpm motor. The motor should be of the reversible type.

3. Feed a light stream of water into the opposite end of the tube to wash the scale from the cutting tool and out of the tube. A light stream of compressed air may be substituted in place of the water. Care should be taken not to drive the tool too fast and to be certain that the tool is straight when it is inserted into the tube.

An 8 to 10 psig hydrostatic test should be per-formed on the shell of the saltwater heater before replacing the heads. If a greater test pressure is used, the relief valve will have to be plugged or removed.