This can be written as.
Boiler water hardness limit.
This value will limit the silica content of the steam to 0 25 ppm as a function of selective.
Hardness compounds predominantly calcium and magnesium salts collect on heat transfer.
Some impurities such as hardness iron and silica are of more concern for example than sodium salts.
Crystals form crystals from scale.
A boiler that makes up 4000 gal day of water having 100 ppm of hardness has a potential of accumulating over 1000 pounds of scale per year.
Feed water boiler water characteristics as per is 10392 1982 1 feed water parameters upto 20 kg cm2 21 kg cm2 to 39 kg cm2 40 kg cm2 to 59 kg cm2 unit total hardness 10 1 0 0 5 ppm as caco 3 ph value 8 5 9 5 8 5 9 5 8 5 9 5 dissolved oxygen.
Scale is a buildup of solid material formed on internal boiler surfaces when the concentration of impurities in the boiler water exceeds their solubility limit and precipitation occurs.
In order for this reaction to take place it is important to maintain a ph at a minimum value of 9 50.
Total alkalinity 600 ppm maximum.
Maximum flow velocities in water systems water velocities in pipes and tubes should not exceed certain limits.
For boiler water the conductivity increases at the rate of approximately 2 of the value at 25 c for every 1 c increase in temperature.
Steam boiler rating and feed water temperature boiler output and feed water.
Total hardness 1 ppm maximum.
A serious loss of boiler efficiency and possibly boiler failure.
Deposition from low less than 1 0 ppm hardness boiler feedwater is eliminated with chelant programs and can be reduced by up to 95 by a good polymer phosphate treatment program.
Alkalinity test in natural waters alkalinity is most commonly the result of bicarbonate and carbonate ions.
The purity requirements for any feed water depend on how much feed water is used as well as what the particular boiler design pressure heat transfer rate.
Total silica 150 ppm maximum.
Conductivity control in the boiler.
A boiler water sample has an unneutralised conductivity of 5 000 μs cm at 25 c.
Phosphates are used to react with calcium hardness in the boiler water.
Small amounts of hardness and iron can get into the boiler.
Water treatment recommendations vary depending on the operating pressure of the boiler the application steam or hot water and other parameters.
Iron oxide is of particular concern in today s boiler water treatment programs.
Presented by cleaver brooks steve connor.
Feed water purity is a matter both of quantity of impurities and nature of impurities.
In treated waters alkalinity may also be contributed by hydroxide phosphate silicate and.
Feed water treatment to avoid corrosion make up water to steam boilers should be treated with oxygen scavengers to avoid serious corrosion problems.
General guidelines to prevent corrosion and scaling in low pressure boilers are as follows.
Asme limits conductivity 7000 umhos neutralized.
