The factors affect to the quality of the boiler water


1. Conductivity:

The sum of all dissolved substances (conductive) in water can be determined by conductivity (taken as a standard temperature of 250 C)


The conductivity depends on the temperature and the conductivity increases as temperature increases


Conductivity of water is determined by the solutes such as salts, acids (including carbonic acid), bases, and some silicon organic material but does not affect the conductivity of water.


The aforementioned water soluble largely dissociate into ions with different charges depending on their valence. The positively charged ions called cations (such as Na +, Ca + +, Fe + +) and negative charge called anions (Cl-, SO42-, PO43-). Even a very small part of the country also dissociate into cations H + and anions OH-, so that the electrical conductivity of pure water as well. At 250 C, the conductivity of pure water about 0.055 microseconds sent / cm


The conductivity of the water affect corrosion, the higher the conductivity, the greater the corrosion rate


2. PH

Very low separation of pure water decide average value PH 7, PH lower than 7 is acidic with a characteristic acidity increases when pH decreases to 0, and pH greater than 7 are characteristic of each Basic (or alkaline) with alkalinity increases as the pH increased to 14. It should be noted that each of the PH level as a result of changes in concentrations 10 times.


Water moderately alkaline (pH 9 -12) are the ideal conditions to protect iron from corrosion.


Acid or acidic water will dissolve the protective magnetite and destroyed iron / steel


3. Hardness:

Water hardness (mainly calcium and magnesium compounds) are classified as carbonate hardness and non-carbonate hardness.


Carbonate hardness (calcium, magnesium carbonate) hardness is only soluble in water with a small amount of carbonic acid (CO2 dissolved in water).


If CO2 is removed by boiling or reduced by the injection of air or heated, calcium carbonate (limestone) will precipitate and form carbonate deposits.


The tropical and subtropical areas often have heavy rain, there are only few limestone formed, so carbonate hardness of the raw water is relatively low.


Non-carbonate hardness (calcium, magnesium, chloride, sulphate, nitrate, etc.) can be dissolved in water, only calcium sulphate (gypsum) scale formation if its concentration is greater than 2 g / l = 2000 mg / l. Raw water contaminated by sea water or brackish water with non-carbonate hardness higher than sea water has a very high concentration of NaCl, CaCl2 and MgCl2 also even more.


When silica in water (acid, silica, silica), both carbonate and non-carbonate hardness scale formation of calcium / magnesium silicates (silicon residue) and reduce the heat transfer coefficient.


Path easy, safe, and most commonly used to remove the hardness of water is applied to water softening equipment, it convert the calcium and magnesium compounds of sodium compounds are soluble in water


4. Alkalinity

Alkalinity is an important parameter in the operation of the boiler, it allows us to identify the different components of the water by titration with 0.1 N acid in determining the value of alkalinity m / p positives and Basic 0.1 N when determining the value of alkalinity m / p sound. Alkalinity are classified as total alkalinity, alkalinity, mixed alkali NaOH


Total alkalinity (alkalinity m positive) is caused by alkaline bicarbonate (eg sodium carbonate or bicarbonate hardness (reaction product of carbonate hardness in the water softening process), it includes mixed alkali where (alkalinity p positive) and alkaline NaOH if any.


If only positive alkalinity m of water ie water containing bicarbonate (as carbonate hardness or NaHCO3), this is the basic characteristics of the raw water or water after softening.


If water alkalinity m negative expression acidic with a pH lower than 4.3 and is determined by titration with NaOH 0.1 N.


Alkaline mixture (alkalinity p positive) caused by all compounds with alkaline pH> 8.2 as carbonate (soda), Na3PO4 and free alkali (caustic soda NaOH) and it supersedes alkalinity measurements NaOH. Alkaline mixture including alkaline NaOH.


Trj alkalinity p negative (-p) PH <8.2 and show a weak acid or alkaline environment, it is determined by titration with NaOH 0.1 N.


NaOH just alkaline to know the amount of free alkali in water, but it should be determined by a special process before titration determined alkalinity p (phenolphthalein indicator)


Indicator is used to determine alkalinity m is methyl orange, it turns at PH = 4.3


Indicator is used when determine alkalinity p is phenolphthalein, it turns at PH = 8.2


This means that only alkaline water when the it contain p value.


For horizontal steam boiler must check the alkalinity mixture of p and total alkalinity of the boiler water


5. Silicon

The countries of the tropical and sub-tropical areas often have heavy rain, rough water, usually with silicon (silica) or silicates (silicon compounds with calcium, magnesium, aluminum such as aluminum, silicon, clay ) from medium to high river water especially after heavy rain.


Both silicon and silicate are derived from the underground minerals such as granite, mica, clay, basalt .. limestone because almost completely dissolved in rainwater.


Silicon and silicates may exist in the soluble or semi-soluble (colloidal) and very difficult to eliminate or reduce water treatment by


Mechanical water filters and water softeners can not get rid of silica and silicates.


6. Iron, manganese

Of iron and manganese compounds are found in surface water and well water if low oxygen levels.


This phenomenon occurs mostly in the soil with organic matter such as river sediment, in some cases including H2S.


The compounds of iron and manganese can create sediment layer on yellow pipe, After exposure to oxygen (air) it will create a brown foam residue. This is the cause of scale formation on the pipeline as well as reduce the activity of the resin softens water by complex membrane on the surface of the plastic to soften brown. Iron salts make fabrics stain.


So before the water softener should treat water wells and water treatment


7. Organic compounds:

The organic matter in the raw water can be of natural origin (such as plant material decomposes, peat) or from human activities or industrial (such as sewage, industrial origin) even periodic condensed media can also be contaminated by organic products (such as milk, vegetable oils, solvents). Many organic compounds capable of forming foam in steam boilers to affect the quality of steam and water pot.


A number of organic substances such as sugar and alcohol decomposed into organic acids and reduce the PH of the water pot.


Oils and fats can also make the control system can not work, it creates a film on the glass surface and can form dangerous residue class. Hydrocarbons boiling below 130 0 c do not cause adverse effects to the boiler


8. Gases (oxygen, nitrogen, carbon dioxide, etc.)

Oxygen, nitrogen, carbon dioxide is dissolved in water if exposed to air. Solubility of all gases in water depends strongly on the temperature.


Oxygen-oxygen causes corrosion on carbon steel or alloy steel if the pH is too low or if the steel does not provide the protective magnetite.


Nitrogen is not harmful to the operation of the boiler. Carbon dioxide reduces the pH and cause acid corrosion on carbon steel


Oxygen and nitrogen in the water can be removed easily by using boiling hot and in terms of them almost equals 0.


Some chemicals, such as sodium sunphit and hydrazine capable of redox. Carbon dioxide can only be removed by heating with PH of water under conditions 7-8 or pH> 8.