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Boiler Houses

Trimming Energy Costs with Online Water Quality Monitoring

Enhance Energy Efficiency: Elevate your facility's boiler performance through water quality monitoring. Recent research demonstrates that optimizing parameters like water hardness, carbonate hardness, and conductivity via online monitoring can lead to substantial annual savings in energy and downtime expenses. Additionally, this practice extends boiler lifespan, translating to significant capital equipment and investment savings.

What are the effects of lime scale?


Even in small amounts, lime scale's presence hampers heat transmission, causing an immediate drop in heating capacity—a significant contributor to increased energy expenses. As lime scale accumulates, it not only diminishes pipe cross-sections but also heightens flow resistance, affecting overall system efficiency. Furthermore, its build-up on heat transfer surfaces can cause local overheating and surface cracks on tubes, reducing longevity.

For instance, a mere 0.04 inches (1.0 mm) of lime scale diminishes heat transfer coefficients in plate or tube heat exchangers by around 80%, resulting in up to a 30% decrease in heat transfer efficiency. Even an inconspicuous layer measuring just one-hundredth of an inch can lead to a surprising 12% spike in energy expenses.

Energy Loss Caused by Lime Scale

Source: Verein Deutscher Ingenieure (The Association German of Engineers), Guideline 2035

What happens in boilers in which feed water is not monitored?

Low heat transfer and thus relatively significant energy losses occur under the following operating conditions at a constant water hardness rate of just 2 ppm CaCO3:

Example: 15 t/h boiler:


Condensate returns (45%)       238.4 ft³/hr
Feedwater b
ackfeed (55%)      291.3 ft³/hr [1,748,076 ft³/yr total]
Hours of operation                  6000 hrs/year
Water hardness                     2 ppm/m³ = 2 g/m³ CaCO3
Heating surface                     3,230 ft²

At an input quantity of 200 lb of CaCO3 (lime) annually and a heating surface of 3,230 ft², a lime scale layer of approximately 0.005 inches develops in the first year alone. This corresponds to around 2% additional energy costs.

The additional costs of an electric power price of 2 cents per KWh add up to approx. $2,440/year

With higher levels of water hardness, energy costs rise even more significantly:

Water hardness        Limescale per year            Additional energy costs

                                                                          (At an electric power price of 2 cents /KWh)

    2 ppm CaCO3         0.005 in (0.1 mm)                     $2,440 / yr
  9 ppm CaCO3         0.02 in (0.5 mm)                       $6,100 / yr
  18 ppm CaCO3         0.04 in (1.0 mm)                      $12,200 / yr

Monitoring boiler feedwater with a Heyl Brothers Testomat ECO® analyzer prevents this additional energy usage. The return on investment of a Testomat ECO® is thus realized after just one year. Return on an investment in the basic Testomat® 808 analyzer model is realized even earlier.

Does water hardness have other effects on boiler performance?

Beyond energy losses caused by calcium salt-based lime scale, water hardness triggers harmful deposits from various sources. Silicates, sulfates, and calcium phosphate in boiler feedwater contribute to surface scaling. Excessive presence of these substances can incur expenses of up to $27,000 annually. When combined, these factors lead to substantial costs stemming from energy loss, descaling efforts, and potential equipment damage.

Energy losses due to build-up of calcium-carbonate, sulfate and calcium-phosphate:

Build-up of 0.04 inches       Energy loss           Oil or gas usage
Ca-Carbonate                        ~ 11%                    18,823 ft³ / yr
Sulfate                                   ~ 9%                      15,397 ft³ / yr

Ca-Phosphate                       ~ 4.5%                     7,699 ft³ / yr

Do down-times for boiler maintenance really affect typical operating costs?

Plant down-times are an essential cost factor in the decision to better monitor water quality with an online analyzer. Plants or facilities have to be shut down when a boiler needs to be cleaned. This occurs more frequently if water hardness has lead to increased lime scaling. Plant operators and facility managers can significantly lower these costs through monitoring water hardness with a Testomat 2000®, Testomat ECO® or Testomat® 808.

Down-times                              Frequency                        Days/year             Production loss

                                                                                                                           (For a 15t saturated steam boiler in industrial usage)

Without hardness monitoring       approx. 2-3 times/year    approx. 8-12          approx. $15,000 – 90,000

With hardness monitoring           1 time/year                       approx. 4               approx. $6,300


Testing water hardness in heating systems and boilers enhances plant cost-effectiveness.

How do Heyl Brothers instruments help control boiler water quality?


The Testomat analyzes feed water hardness on a quantity- or time-controlled basis. When high hardness levels are exceeded, the Testomat sends a signal to the Softmaster MMP2 and the Softmaster will change the filter and regenerate depleted filter. Both devices send signals to a main control unit over a 4-20 mA interface. Both devices have alarm signal outputs in case of unexpected events (e.g. low water pressure, low filter capacity etc.).

Online monitoring of water quality with instruments from Gebrüder Heyl
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