Alternate Heating wood gun E100 SF, Инструкция по установке и эксплуатации, Страница: 33 / 72

e pH factor is the most important factor
inGuencing scale forming or the corrosive tendencies
of boiler water. It should be adjusted to between a
minimum of 9.0 and 11.0 to prevent acidic corrosion
of boiler tubes and plates and to provide for the
precipitation of scale forming salts.
Below a pH of 5.0 the water is acidic enough to
dissolve the steel boiler plates. Under these
conditions the steel gradually becomes thinner and
thinner until it is destroyed. At a pH between 5.0 and
9.0 pi7ing of steel plates is likely to occur at a rate
dependent upon the amount of dissolved oxygen in
the boiler.
Dissolved Oxygen
Aeration of city water supply is frequently used to
remove noxious gases, however, aeration results in
saturation of the water with oxygen. A majority of
corrosion problems are directly related to the
quantity of dissolved oxygen in the boiler water.
Elimination of the corrosive e:ect 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 speci c
chemicals in the boiler to react with the oxygen.
e
dissolved oxygen content should be maintained at a
minimum but at no time should it exceed 0.007 mg/l.
Sodium sul te is commonly 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 sul te in the boiler should be
maintained at a minimum of 120 ppm.
Solids (Primarily for Steam Boilers)
High boiler solids will lead to foaming, priming,
surging, carry over or boiler sludge in steam boilers.
Occasional blow downs of the boiler may remedy
these conditions. We recommend you utilize the
services of a local professional plumbing service for
this boiler maintenance task.
(See h7p://www.p2pays.org/ref/34/33 027.pdf)
Solids can be categorized as either suspended or
dissolved. Suspended solids are those that can be
removed by ltration while dissolved solids are in
solution with the water.
e best way to determine the dissolved solid
content of boiler water is a conductance test. e
conductance of boiler water varies proportionately
with the amount of various ionized solids present.
Another way to determine the dissolved solids
content is to measure the chlorides present in the
boiler water.
e chloride test is less sensitive than
the conductance test for measuring small
concentrations of dissolved solids.
e results of both
tests should be averaged for accuracy.
Alkalinity
e alkalinity of boiler water should be
su<ciently high to protect boiler steel against acidic
corrosion, but not so high as to cause carryover
(basic) corrosion. A minimum value for alkalinity for
adequate protection is 200 ppm CaCO3.
High boiler alkalinity (in excess of 700 ppm
CaCO3) should be avoided. Values higher than this
can cause the steel to become bri7le.
Phosphates
Phosphates are used to counteract hardness in the
boiler water. It is important to maintain a pH of at
least 9.5 to not hinder the reaction of the phosphates
with calcium hardness. Try to keep the concentration
of phosphates in the water to 30-50 ppm to enable
complete reaction.
Hardness
e 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. Total hardness
should not exceed 50 ppm.
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