FULTON FB-A 10, Instruction, Operation And Maintenance Manual

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38-G 1/01
pH: pH is a measure of the degree
of acid or base of solution. Normal
pH ranges of 6.5-9.0 will have little
influence on the corrosion rate of
cooling waters. If for some reason,
pollution, etc., the pH is lowered into
the acid range, increased corrosion
can be expected. The solution lies in
determining the cause of the low pH
and correcting that condition. A low
pH can result in corrosion of metals,
while a high pH can result in scale
formation.
In order to control boilers and
equipment used for the external
treatment of make up water, it is
essential that reliable pH measure-
ments be made.
Phosphates: Ground or surface
waters seldom contain large amounts
of phosphates. If present, it generally
indicates fertilizer runoff or pollution.
Phosphate from raw water can be the
cause of scale problems in open recir-
culating cooling water systems after
the water is concentrated.
Chlorides: Chlorides are involved in
most cooling water corrosion cells.
Other factors being equal, it can be
assumed the higher the chloride con-
tent, the more corrosive the water.
When pits or cracks occur on stain-
less steel or other metals, chlorides
are always suspect.
High chloride levels can cause severe
corrosion. Corrosion from chlorides
can be controlled by increasing the
amount of corrosion inhibitor or
changing to a more effective inhibitor.
Oil: Oil is not a natural constituent of
boiler water; still it can frequently enter
a system through leaks in a con-
denser or other heat exchanger. Oil
can also enter a system through the
lubrication of steam driven reciprocat-
ing 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.
Foaming is one indication of oil in
boiler water. Its presence can also
be confirmed by first shaking a bot-
tle containing boiler water. If oil is
present foam will result. To ensure
the foaming is being caused by oil,
add a small amount of powdered
activated carbon to the bottle con-
taining the boiler water and shake.
Little or no foam will appear if the
foaming is caused by oil.
Often oil in boiler water will origi-
nate in the condensate. This conta-
minated condensate should be
directed to the sewer until the
source of the oil is determined and
corrective steps taken.
Silica: Silica in boiler deposits is usu-
ally combined with other constitutents.
Silicates form a number of different
scale complexes with calcium, mag-
nesium, aluminum, sodium, and iron.
Since there is at present no effective
dispersant for silicate deposits, the
scale problem can be alleviated by
maintaining close control of calcium,
aluminum, and iron as well as silica.
Iron (oxides): Iron in any of its oxide
or complex forms is undesirable in
boiler water. It is very difficult to dis-
perse so that it can be removed the
bottom blow off lines.
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. Most
iron oxide originates outside the boil-
er. It does not concentrate in the boil-
er 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.
Water Hardness: Water hardness
is the measure of calcium and mag-
nesium content as calcium carbon-
ate equivalents. Water hardness is
a primary source of scale in boiler
equipment.
Feedwater: Feedwater is the com-
bination of fresh makeup and return-
ing condensate that is pumped to
the boiler.
Condensate: Condensate is con-
densed steam that is normally low in
dissolved solids. Hence, it does not
contribute to the dissolved solid con-
tent of the feedwater. In addition, con-
densate 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.
Description/Instructions