Fulton FB-S Horizontal Firetube Boiler - Manual (Page 24)

The Fulton Companies*FB-S Series Manual*Version 2010-0820 rev. 3/5/13
Page 24
caustic embrittlement. In order to control boilers and equipment used for the
external treatment of make up water, it is essential that reliable pH
measurements be made. RO/DI water will have a pH of 6.0 - 6.5 and will require
neutralization if used in a carbon steel vessel.
f) Chlorides: If chloride levels are high enough to cause severe corrosion, they can
be controlled by limiting the cycles of concentration and increasing boiler
blowdowns. Corrosion from chlorides can also be controlled by increasing the
amount of corrosion inhibitor or changing to a more effective inhibitor. Reverse
osmosis is another method of pretreatment to reduce chlorides. Chlorides are a
major concern in a stainless steel vessel.
g) Oil: Oil is not a natural constituent of boiler water; still it can frequently enter a
system through leaks in a condenser or other heat exchanger. Oil can also enter
a system through the lubrication of steam driven reciprocating equipment.
Whatever the source, the presence of oil in boiler water is undesirable. Oil can
act as a binder to form scale. In high heat-transfer areas oil can carbonize and
further contribute to the formation of scale and low pH. Foaming is one indication
of oil in boiler water. Its presence can also be confirmed by first shaking a bottle
containing boiler water. If oil is present foam will result. Often oil in boiler water
will originate in the condensate. This contaminated condensate should be
directed to the sewer until the source of the oil is determined and corrective steps
taken.
h) Iron (oxides): Iron in any of its oxide or complex forms is undesirable in boiler
water. Iron in its various forms can originate in the raw water makeup,
condensate return water, or form directly in the boiler as a result of corrosion. It
can concentrate in the boiler and it tends to collect in stagnant areas. If a boiler
is using raw water makeup, iron is almost certain to be a major component of
developing scale or create fouling.
i) Water Hardness: Water hardness is the measure of calcium and magnesium
content as calcium carbonate equivalents. Water hardness is a primary source
of scale in boiler equipment. Hardness is removed by softening.
j) Feedwater: Feedwater is the combination of fresh makeup and returning
condensate that is pumped to the boiler.
k) Condensate: Condensate is condensed steam that is normally low in dissolved
solids. Hence, it does not contribute to the dissolved solid content of the
feedwater. In addition, condensate is very expensive to waste. It's been
chemically treated, heated, pumped, converted to steam, and condensed. This
costs money and when condensate is returned to the boiler, money is saved.