VMP IOM
19
Water Supply
Feed water contains solids and dissolved
gases. These may promote formation of
scale; foaming, priming, surging, and solids
in steam; corrosion and pitting; or caustic
embrittlement. To prevent this, feedwater
must be studied individually and treated
accordingly by reputable professionals
specializing in this field. It is strongly
recommended that a competent water
treatment company be consulted prior to
the installation of the boiler.
The purpose of this treatment should be to
provide quality feedwater to the boiler such
that corrosion and deposition in the boiler
will be minimized. Dissolved oxygen, high
TDS levels and low pH can all be major
causes of corrosion. Untreated hardness is
the major cause of scale deposits. Poor
quality feedwater will require increased
blow-down and increased chemical
treatment costs to prevent boiler corrosion
and scaling.
One way to lower the amount of dissolved
oxygen in the boiler feed water is the
feedwater preheating option. This option
injects live steam into the feedwater to
increase the water temperature to at least
180 degrees F (82 degrees C) which
removes oxygen from the water.
TDS can be controlled by increasing the
number and/or duration of blow downs per
day from one to four.
The Fulton Warranty does not cover
damage or failure that can be attributed
to corrosion, scale or sludge
accumulations. Oxygen is corrosive. See
the Warranty Section of this manual for full
details.
Recommended Water
Treatment
a. Following are recommendations for feed
water and boiler water. Contact your local
water treatment professional for testing
and treatment recommendations. It is
very important that a strict water
treatment program be followed.
Feedwater:
Dissolved Oxygen..............less than 0.05 ppm
pH Value.............................9-11 (tested at room
temperature)
*Hardness ..........................less than 25 ppm
in the form of CACO
3
Oil........................................none
Suspended Solids..............none
Organic Matter ...................less than 5.0 ppm
Total Dissolved Solids .......less than 300ppm
Boiler Water:
Alkalinity ........................less than 300 ppm in the
form of CACO
3
Chloride.........................less than 500 ppm
pH Value .......................9 to 11 (tested at room
temperature)
Total Dissolved Solids..... 2,000 ppm maximum
Hardness.......................less than 50.0 ppm
Dissolved Oxygen ........none
Suspended Solids.........40 ppm
ppm = parts per million; CACO
3
=Calcium
Carbonate; PO
4
=Phosphate; SiO
2
=silicon
dioxide; * 1 Grain Hardness = 17.118 ppm
Therefore: 70 ppm = 4.10 grains hardness
b. It is critical that the boiler pH be alkaline
(9-11) whenever water is in the boiler.
Solids that enter in with the feed water
concentrate in the boiler. Daily boiler
blow down is recommended to prevent
corrosion and/or deposits from forming.
Glossary of Water Supply
Corrosives and Inhibitors
DISSOLVED OXYGEN
Oxygen that is dissolved in the feedwater
will cause the steel in the boiler and the
feedwater system to be attacked by the
water in a manner described as “pitting”.
The pits that are produced can vary from
tiny depressions to holes large enough to
penetrate the boiler metal and are usually
covered with tubercles of iron oxide. Once
pitting starts, it may be extremely hard to
arrest. Pitting can proceed at a surprisingly
rapid rate and can occur not only in the
boiler proper, but also in pre-boiler
equipment such as economizers, feedwater
heaters, and feedwater lines.
SUSPENDED SOLIDS
Suspended solids are the undissolved
matter in water, including dirt, silt, rust and
any other insoluble matter. Normally
suspended solids are expressed in terms of
turbidity.The presence of suspended solids
in cooling water can increase impingement
type corrosion. Suspended solids may also
deposit in low velocity areas and create
differential aeration cells. Pitting can result.
The most common cause of high
suspended solids is high hardness
feedwater piping corrosion and inadequate
blow-down rate.
In line filters, or various types of
pretreatment can be used to lower the
suspended solids level. Various polymers
assist in holding solids in suspension. Boiler
blow-down is the best way to control
suspended solids.
ALKALINITY
Alkalinity is the capacity of a water to
neutralize acids. Common water alkalinities
consist of bicarbonate, carbonates,
hydroxide, phosphate, and silicate. These
alkalinities, especially bicarbonates and
carbonates, break down to form carbon
dioxide in steam, which is a major factor in
the corrosion on condensate lines. High
alkalinity also causes foaming and carry
over in boilers.
Both foaming and carry over cause erratic
boiler operation. When foaming occurs an
anti-foam should be added or increased.
The reason for the high alkalinity should be
determined. It may result from lack of
sufficient blow-down. Pretreated makeup
water and condensate should also be
checked. quite often the source of alkalinity
is an overdose of alkaline internal water
treatment chemical.
pH
pH is a measure of the degree of acid or
base of solution. Neutral pH ranges of 6.5-
7.5 will have negative influence on the
corrosion rate of carbon steel. A low pH can
result in corrosion of metals, while a high
pH can result in scale formation. Optimal
boiler pH is 9-11, slightly alkaline
In order to control boilers and equipment
used for the external treatment of make up
water, it is essential that frequent reliable
pH measurements be made.
Installation
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