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Boiler Systems Corrosion, Scaling and Deposition These can all reduce the operating efficiency of the boiler and all the systems connected to the water/steam cycle of the boiler.  It will reduce or create uneven heat transfer, cause equipment and piping failure and increase fuel costs to name a few (See Table and Example Below). On Small Boilers Treatment can be as simple as adding a blended chemical inhibitor which will look after all aspects of the boiler system and equipment. On Larger Boiler Systems treatment is divided into three segments. Pre treatment of the feed water entering the boiler, this is mainly mechanical. This includes softeners, reverse osmosis and de mineralizers which are all designed to remove minerals from the feed water. Internal treatment of the actual water in the boiler, this requires chemicals to control scale forming minerals, sludge conditioners, pH and oxygen scavengers. Condensate treatment of the condensed steam that is returning to the boiler, this requires a blended chemical of amines that are fed into the boiler. These amines flash off and are carried with the steam to all parts of the plant. When the steam condenses, the amines also condense and act to buffer the pH of the condensate to a less corrosive condition.

Water formed deposits result from the precipitation of minerals from the water to form scale. The most common forms of scale are calcium carbonate, calcium sulfate and silica scale. These particles are great insulators that inhibit heat exchange and cause the boiler to lose heat tranfer, therefore even a small loss of boiler efficiency can result in substantial increases in fuel consumption.

The graphs below represent the average heat loss caused by various types of scale.  Insulating properties of boiler scale vary with 
the mineral composition of different water thoughout Noth America.

Scale Thickness in Inches	Fuel Loss %
1/64 1/32 1/16 1/8	4 % 7 % 11 % 18 %

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Fuel cost vs Scale Thickness - What's it costing you?

Consider this example based on a Weil McLean 50 hp steam boiler (model LGB 17) used for heating a commercial building.

A 50 hp boiler producing steam at a rate of 1.7 million Btu/hr at 75% efficiency, and operating for 5040hrs/year 
(7 month Winnipeg heating Season) requires an energy input of 1.7 million Btu/hr x 5040 hrs/yr. x 0.75 = 6.426 million Btu/yr.

If scale only 1/64" thick forms on the heating surface, depending on the type of scale, expect an energy loss of approx. 4%.
Annual energy loss at 4% = 6.426 million Btu x 0.04 =  257.04 thousand Btu/yr.

Based on a heating value of gas at 1,000 Btu/cu.ft. and cost of $8.65/1000 cu.ft., by not keeping the boiler scale free will
result in an additional cost for natural gas in the amount of 257.04 thousand Btu/yr x 1 cu.ft./1000 Btu x $8.65/1,000 cu.ft. 
= $2,223.40/year

Water Treatment has a significant effect on utility costs, maintenance costs and equipment life. Properly applied water 
treatment costs a facility nothing, the money spent on products and services are paid for through reduction in energy costs 
and improved system efficiency.

Gas cost per 1000/cu.ft based on Winnipeg Centra Gas Small General Service (SGS) March 2002.
Btu rating model LGB 17 courtesy of Weil McLean.