UFC 3-240-13FN
25 May 2005
Figure 2-3. Duplex Softener
2-2.5.1
Sodium Ion Exchange. The sodium ion exchange process is used on
most military installations. It is preferred to other softening processes because the
equipment is compact, easy to operate, relatively inexpensive, and produces a makeup
that is suitable for use in industrial water systems. This system exchanges (removes)
hardness (cations) from incoming water with sodium ions contributed by the sodium
chloride (salt) used in regenerating the cation ion exchange resin.
2-2.5.1.1
Service Cycle. The normal operating cycle during which hardness is
removed from the makeup water flowing through the softener is determined by
calculating the amount of water that can be softened by a given ion exchange material.
The operator must consider several factors:
2-2.5.1.1.1 Sodium Ion Exchange Process. The sodium ion exchange process
depends upon the exchange of sodium ions in either the zeolite material or synthetic ion
exchange resins (whichever is used) for calcium and magnesium ions in the makeup
water, as shown below:
→
+
Sodium salts
+
Sodium
Calcium/Magnesium
Calcium and
in water
Zeolite
Zeolite ion exchange
Magnesium
Resin
Hardness in
Water
2-2.5.1.1.2 Water Softener Capacity. The softening capability or capacity of an ion
exchange softener is usually given in units of grains (grams) of total hardness of
calcium carbonate (CaCO3). The operator needs to know how much water can be
softened before regeneration is necessary. The volume of water that can be softened
18
Previous Page
