Alternate Heating WC100, Инструкция по установке и эксплуатации

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9
DISSOLVED OXYGEN
Aeration of city water supply is frequently used
to remove other noxious gasses, however,
efficient aeration results in saturation of the
water with oxygen. The majority of corrosion
problems are directly related to the quantity of
dissolved oxygen in the boiler water.
Elimination of the corrosive effect of dissolved
oxygen can be accomplished either directly or
chemically.
Direct or mechanical removal of dissolved
oxygen is done through the use of a de-aerator.
Chemical de-aeration is done through the
introduction of specific chemicals in the boiler
to react with the oxygen. The dissolved oxygen
content should be maintained at a minimum but
at no time should it exceed 0.007 mg/l.
SULFITES
Sodium sulfite is generally used for the
chemical removal of dissolved oxygen within
the boiler water. To assure the rapid and
complete removal of the oxygen entering the
boiler feed water system the concentration of
sulfite in the boiler must be maintained at a
minimum of 120 ppm. (parts per million).
SOLIDS
Solids can be broken up into two categories of
both suspended and dissolved. Suspended
solids are those that can be removed by filtration
while dissolved solids are in solution with the
water.
The best test for the determination of the solids
content of the boiler water is through a
conductance test. The conductance value of
boiler water varies by the various ionized salts
present. The conductance can be used to
measure the total dissolved solids in the boiler
water and to serve as an accurate means for the
control of solids through the use of blow down.
Another test that is sometimes used as a
measure of solids is to measure the chloride
present in the boiler water. The ratio of
chlorides in the boiler water to that of the feed
water can be used as a means to determine the
amount of blow down required. The chloride
test is unsuitable for feed water with low
incoming concentrations, and the concentrations
in the feed water must be averaged over time for
accuracy.
High boiler solids will lead to foaming, priming,
surging, and carry over. These conditions may
only be overcome by proper daily blow down of
the boiler.
ALKALINITY
The alkalinity of boiler water should be
sufficiently high enough to protect shell and
plates against acidic corrosion, but not so high
as to produce carryover. A minimum value for
alkalinity for adequate protection is 200 ppm.
High boiler alkalinity (in excess of 700 ppm)
should be avoided. Values higher than this can
cause the steel to become brittle.
PHOSPHATES
Phosphates are used to react with calcium
hardness in the boiler water. In order for this
reaction to take place it is important to maintain
a Ph at a minimum value of 9.50. It is desirable
to keep the concentration of phosphates in the
water to 30-50 ppm to enable the complete
reaction of the phosphates with the calcium
hardness entering the boiler through the feed
water.
HARDNESS
The hardness of water is caused by calcium and
magnesium ions. Water hardness will vary
greatly throughout the country depending on the
source of the water.
In boilers hard water can cause the formation of
scale and sludge or mud. The hardness must be
removed in the makeup water to the return
system. Total hardness should not exceed 50
ppm.
OILS
Every effort should be made to prevent oils
from getting into the boiler water. Oil causes
foaming or combines with suspended solids to
form a sludge, which can cause the overheating
of boiler plates. If oil does get into the boiler,
the boiler should immediately be taken out of
service and thoroughly cleaned.