Columbia L-24, Руководство пользователя, Страница: 25 / 60

24
Hot water boilers are subject to serious damage and failure if leaks develop in the hydronic system that
requires excessive make-up water. The make-up water introduces high levels of oxygen which will lead to cor-
rosion and component or system failure in a very short time. All boilers and systems should be checked for
leaks on a frequent basis. Leaks may be indicated by standing water under or around system components, rust
spots or drip spots. On a weekly basis, the system should be checked for hidden leaks. This is done by shut-
ting the make-up water supply isolation valve at a time when the burner is not operating. If pressure on the
boiler pressure gage falls, it is an indication that there is a leak in the system which should be located and
repaired immediately. Open the make-up water isolation valve after completing the test. Proper start-up and
verification that hot water boilers are leak free on a weekly basis is adequate to protect the hot water boiler.
Steam Boilers
Steam boilers operate at higher temperatures and have a steam region that can be subject to rapid failure due to
poor water quality. In addition, system operation can be adversely affected by poor water chemistry. The fol-
lowing terms and guidelines are for reference. Seek the advice of a water treatment specialist to best suit your
application. Use only chemicals approved in your locality/state.
PH
•
The PH factor is the most important factor influencing scale forming or the corrosive tendencies of the
boiler water. It should be adjusted to between a minimum of 10.5 and a maximum of 11.0 to prevent
acidic corrosion of the 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 condi-
tions, the steel gradually becomes thinner and thinner until its destruction. At a PH between 5 and 9.4,
pitting of steel plates will occur at a rate depending on the dissolved oxygen in the boiler.
Dissolved Oxygen
•
Dissolved oxygen is caused by the solubility of atmospheric oxygen into the supply water. Aeration of
city water supply is frequently used to remove other noxious gasses. 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 effects of dissolved oxygen can be accomplished both
directly or chemically.
• Dissolved oxygen: Direct (mechanical removal) or chemical (using additives) removal of the oxygen is
done through mechanical venting valves or 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 20 p.p.m. (parts per million)
Solids
•
Solids can be broken up into two categories of either suspended and dissolved. Suspended solids are
those which could be removed by filtration while dissolved solids are in solution with the water.
• The best test for the determination of 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.