Water Treatment for Boiler Feed Water
Feed water
for steam generation
Feed water forms the basis for safe and efficient steam generation in thermal processes. Its quality directly influences the performance, cost-effectiveness and service life of boiler systems. A key parameter is conductivity, which, depending on the pressure stage, must often be below 10 µS/cm. Even small quantities of dissolved salts, gases or solids can lead to deposits, corrosion and impaired heat transfer.
Targeted treatment and conditioning of the boiler feed water is therefore crucial to ensuring trouble-free operation, high energy efficiency and a long service life for the plant.
Boiler feed water
requirements
Boiler feed water is subject to stringent quality requirements, which vary depending on the pressure level and application. It is crucial to reduce hardness components, salts and dissolved gases, as these promote scaling and corrosion. The pH value must also be precisely adjusted and is typically maintained in the alkaline range between 8.5 and 9.5 to protect materials. This requires multi-stage treatment processes as well as targeted chemical conditioning to ensure safe, long-term operation.
Only through the combination of treatment and conditioning can a consistently high feedwater quality be achieved. Herco offers solutions for the safe, economical and long-lasting operation of steam generators.
Typical challenges
in feed water treatment
In practice, inadequately treated feed water leads to significant problems in boiler operation. Deposits caused by hardness components impair heat transfer and increase energy consumption. For this reason, total hardness concentrations in feed water > 0,1°dH are critical and unacceptable. At the same time, dissolved gases such as oxygen and carbon dioxide promote corrosion, which can lead to damage to components and unplanned downtime.
The loss of water that has already been heated and treated is particularly costly. This results not only in water losses but, above all, in unnecessary energy costs. Optimised water treatment addresses precisely these issues and reduces risks and operating costs in the long term.
How to protect your steam boiler
Our methods for safe feed water
The following techniques protect your steam boiler from corrosion, scale build-up and efficiency losses:
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Pre-treatment
Removes all particles and turbidity to stabilise subsequent processes. Target values such as turbidity < 1 NTU and an SDI < 3 ensure the reliable operation of the entire system.
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Water softening
Removes hardness-causing substances to prevent deposit formation. Typical target values are residual hardness levels of less than 0.1 °dH.
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Reverse osmosis
Removes dissolved substances using membrane technology. Salt rejection rates of >95–99% enable permeate qualities with conductivities in the range of 5–20 µS/cm.
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Degassing
Corrosive gases such as CO₂ are removed using membrane degassing processes to protect the plant. The aim is to achieve a CO₂ content of < 2 ppm.
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Conditioning
Systems for dosing suitable conditioning chemicals are calibrated to stabilise the system. A pH value of 8.5–9.5 and the complete removal of residual oxygen ensure that the boiler plant remains corrosion-free in the long term.
Technical requirements for boiler feed water
Appropriate water quality depending on the application
High-pressure / Electric boiler
E.g.: Turbine operation in power station (fuel oil, gas or H2ready)
Deionised water:
- Conductivity 0,06-1 µS/cm
- Total hardness ≈ 0 °dH
Recirculation boiler
E.g.: High-specification process steams, refineries
Low-salinity water:
- Conductivity < 30 µS/cm
- Total hardness < 0,1 °dH
Large-capacity boilers
E.g.: Basic process steam supply, food industry
Saline water:
- Conductivity > 30 µS/cm
- Total hardness < 0,1 °dH
More water treatment expertise and knowledge
Softening
In water softening, calcium and magnesium ions are replaced by sodium ions through ion exchange. This ensures consistently soft water for reliable system operation.
Reverse osmosis
In industrial reverse osmosis applications, water is forced through membranes under high pressure, thereby being desalinated.
Membrane degasser
Membrane degassing is used to reduce the amount of dissolved CO2 in the permeate of a reverse osmosis unit, or potentially between the first and second stage of a reverse osmosis unit.
pH value
The pH value is the abbreviation for “potential of hydrogen”. It is defined as the negative common logarithm of the H⁺ ion concentration and is a measure of the acidity or alkalinity of aqueous solutions.
Questions and answers on the subject of feed water
What is the difference between boiler water and boiler feed water?
Boiler feed water is the treated water that is fed into the steam boiler. It must meet certain requirements to prevent corrosion and scale formation. Boiler water, on the other hand, refers to the water that is already in the boiler and participates in the evaporation process.
Is boiler feed water the same as desalinated water (VE water)?
Not quite. VE water (fully desalinated water) is completely free of dissolved salts using ion exchange or reverse osmosis. Boiler feed water may contain deionised water, but is additionally conditioned – for example, by raising the pH value or binding oxygen – to meet the specific requirements of the steam boiler. This means that deionised water is a basis, but not a ready-to-use boiler feed water.
Which requirements apply to boiler feed water in steam boilers?
The requirements depend on the boiler pressure rating and the plant technology. Important parameters include conductivity, total hardness, pH value, oxygen and silicate content. Only treated feed water ensures high operational safety and extends the service life of steam generators.
Why is conditioning so important?
Conditioning prevents deposits, corrosion and efficiency losses. Targeted dosing and coordinated water treatment systems keep water quality stable – for safe, energy-efficient operation.
Which processes are suitable for treating feed water for steam boilers?
Processes such as softening, reverse osmosis, degassing and conditioning are combined for treatment. The selection depends on the raw water quality and the plant requirements. Modern systems from Herco ensure that the boiler water parameters remain within the optimum range at all times.
What are the advantages of professional boiler feed water treatment from Herco?
Herco develops tailor-made systems for the conditioning and treatment. These reduce corrosion, minimise maintenance costs, increase energy efficiency and extend system service life – for sustainable and economical operation.
Downloads
Product Guide 2026
Our Industrial Water Treatment Solutions – Complete Catalogue
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