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Raw water problems

Raw Water Problems

In its natural form water contains dissolved gases and minerals. If the water comes from a river or lake it will probably also contain dirt. In some cases the water may even contain natural substances that act like a soap to produce bubbles and foam, for example industrial pollutants.

The two most common dissolved gases are oxygen and carbon dioxide which are absorbed from the atmosphere. If the water is drawn from deep springs or wells, methane or hydrogen sulphide may also be present. When carbon dioxide or hydrogen sulphide are dissolved in water, acids that can corrode the boiler and any part of the steam system are formed. The rate of corrosion is increased by high operating temperatures, and any dissolved oxygen. This means that it is important to significantly reduce the amounts of dissolved carbon dioxide, other potentially corrosive gases and oxygen.

Dirt held in suspension can settle out in pipework and inside the boiler. This can reduce equipment performance. Costly maintenance which will result in production losses will ultimately be required to make the equipment function correctly again.

Dissolved minerals such as limestone, chalk and calcium carbonate also cause problems. They can form scale deposits on the boiler surfaces or react with other substances to cause corrosion. Scale deposits act as an insulator, which can lead to the two problems described below.

Insulating scale reduces the transfer of heat. In boilers and heat exchangers this reduces performance and efficiency. In a heat exchanger this may mean that the required temperature cannot be achieved.

The insulating scale reduces heat transfer which means that the surface underneath becomes very hot. This can weaken the metal or accelerate corrosion so that the metal surface breaks. This in turn will cause leaks which can lead to even greater problems in extreme cases, this can cause catastrophic boiler failure.