Corrosion

Image of pitting corrosion in a steam system (tank)

Pitting corrosion in a tank.

Corrosion is one of the most common problems in steam systems. It causes premature degradation of equipments and can be responsible for production downtime. In a badly-designed steam system, it spares no kind of equipment: heat exchangers, steam traps, pumps, pump traps, condensate return piping, deaerator, etc.

The most prevalent forms of corrosion are caused by O2 (oxygen) and CO2 (carbon dioxide) :

  • Oxygen corrosion, also known as ‘pitting’, creates small holes that can eat through a steel pipe in less than two years.
  • Carbon dioxide in steam causes corrosion when it dissolves in the condensate. Condensate pH drops rapidly with increasing concentrations of CO2. Acidic condensate eats through pipes, causing a characteristic trough at the bottom of pipes. Byproducts of corrosion are then returned to the boiler where they can create iron deposits.

O2 and CO2 are called noncondensable gases because, as opposed to water (H2O), they can’t condense and get eliminated from the steam system with the condensate. On top of accelerating corrosion, noncondensable gases degrade heat transfers by acting as a thermal insulator in heat exchangers.

Mechanical noncondensables eliminator

In a conventional steam system, corrosion is usually controlled by injecting chemicals in the system, such as sulfite for O2 and a neutralizing amine for CO2.

In a Lalonde Systhermique SCCS®, noncondensable gases are eliminated mechanically with an exclusive device, throughout the whole steam system. Mechanical elimination of oxygen and carbon dioxide drastically reduces consumption of corrosion-control chemicals. In most of our projects, this decrease exceeds 50%. In many cases, it reaches 95%!

Learn more about the importance of eliminating noncondensable gases.