A Brief Guide to Boiler Water Treatment

One can prolong the life of one’s physical assets and maximize process productivity through optimization of the chemistry of a boiler system and monitoring of TOC (Total Organic Carbon) levels for preventing corrosion in the boiler system.

What is boiler water treatment?

No matter what kind of boiler one owns, there is always a risk of corrosion. Corrosion is typically caused by unsuitable pH control or oxygen. These can make holes in economizers, feedwater piping, or boiler tubes, causing boiler leaks and expensive repairs. Therefore, there is a need for boiler water treatment or preventive maintenance programs.

It is vital to note the amounts of different harmful materials that can be permitted in the boiler water without risking damage. Corrosion may take place in the feedwater system because of water of low pH and the accumulation of dissolved Carbon dioxide and oxygen.

Corrosion can be countered by proper design, regular cleaning, and consistent and continual control of dissolved solids, oxygen, and pH. The best mode of ensuring optimal performance level of boiler is through constant control and making use of automated feed of chemicals for ensuring use of feed water of high quality. One may even use de-aerators to lower oxygen levels and heat feedwater.

The major parameters for water treatment are as follows:

•  the pH of feed water of the boiler
•  Dissolved solids
•  Dissolved oxygen
•  Silica content

Automated systems of feedwater offer the following benefits to any program of water treatment for preventive maintenance:

•  Very little or no handling of chemicals by employees (avoiding spill of chemicals)
•  No chemical overdosing
•  No chemical underdosing
•  Capacity to track and monitor the consistency of the system

Damages caused by corrosion

Even a few minutes of imbalances in the program for water treatment can result in problems. Hence, the fewer are the fluctuations in the water feeding and treatment program, the better it proves for the equipment. If a system is not constantly tested for accuracy and subject to treatment, there can occur chemical imbalances that result in the quantum of scaling and corrosion amounting to many days. Take note that corrosion is simply a symptom and the real cause is the inconsistency of feedwater.

Importance of water quality

• There exist dissolved salts in water. When water evaporates, it leaves scales on the surfaces of heat transfer. Such scales have much less capacity for heat transfer compared to steel. This leads to failure and overheating of boiler tubes. Also, scale reduces flow area that enhances pressure drop in piping and tubes of boiler.
• Low dissolved oxygen or pH in the water damages steel. These cause pitting or reduction of steel tube thickness, causing rupture of boiler tubes.
• Corrosion assisted by flow takes place in the pipes of carbon steel because of the continual removal of the protective layer of oxides at high flows.
• When impurities are carried along in the steam, they cause deposits on the blades of turbines, which lead to a reduction in efficiency of turbines, failure of blades, and high vibrations. All such contaminants can also result in eroding of blades of turbines.

Maintenance needs of boiler

• In the first step, the make-up water is subject to the steam cycle with maximum purity.
• In the second step, a protective layer is formed on the insides of the tubes that help protect the metal surface from any potential corrosion.
• In the third step, this layer is maintained all through the plant’s life. In case water quality deteriorates, the protective layer will be damaged, and the tubes will be attacked by corrosion.

In sum, even the highly aggressive modes of preventions cannot prevent the eventual occurrence of minor corrosion. However, with the proper approach, one can minimize the impact of corrosion and prolong the life of the boiler. This is the crux of boiler water treatment.

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HydroChem Joined: December 10th, 2020