Purpose of Treatment. Boiler feedwater must be treated to remove
or modify harmful constituents to avoid damage to the boilers distribution
system and steam operated equipment and to improve heat transfer in the
boiler. The causes and effects of inadequate water conditioning are shown in
Table 16. Deposits must not form on transfer surfaces. Such deposits
restrict the design water circulation in the tubes and retard heat transfer,
thus raising the metal temperature. This reduction of heat transfer reduces
efficiency and may result in tube rupture. Depending on the type of scale, a
thickness of 1/8 inch (0.3175 m) may cause a loss of 2 or 3 percent in
efficiency in the area affected.
Choice of Treatment. The choice of treatment and treatment
facilities depends on the type of boiler, characteristics of water supply,
chemical constituents of the water, and economy of treatment. A full knowledge
of all these factors is essential to designing water conditioning facilities.
This knowledge can be gained only by surveys of feedwater conditions affecting
scale and corrosion in boilers and auxiliary heat exchange equipment. Seek
advice of qualified water treatment consultants.
Chemicals and Conversion Factors Used in Water Treatment. See
Kemmer, F.N., The Nalco Water Handbook (1979). Also, refer to Betz Handbook
of Industrial Water Conditioning, 1980.
Maximum Boiler Water Limits. For
boiler water limits, refer to
Table 17. For requirements to provide shore
steam and feedwater to non-
nuclear ships, see NAVSEASYSCOM requirements
outlined in NAVSEA technical
Testing & Treatment. The limits
manual (NSTM), Chapter 220, Boiler/Feedwater
of Table 17 can be obtained by the following
Intermittent or continuous blowdown
Raw makeup water treatment