In recent years, sprinkler systems have gone from being a niche solution in industrial buildings and commercial premises to becoming an important safety element in a wide range of buildings in Norway, including care homes, schools and private homes.
The expansion is driven both by national regulatory requirements TEK17, and increased awareness of fire safety. But a hidden enemy is now threatening the sprinkler wave: microbiologically influenced corrosion (MIC), which is corrosion caused by bacteria.
Corrosion damage already happening
MIC has already triggered major maintenance and repair costs, including at St. Olavs Hospital in Trondheim. This underlines the need to tackle the problem before it escalates further.
With TEK17, Norway introduced requirements for sprinkler systems in buildings where people with high vulnerability live, such as care homes and multi-family homes in 2017. The change in regulations has significantly increased the demand for sprinkler systems.
Globally, we see similar trends. Building requirements for sprinkler systems are being tightened and expanded in line with urbanization, increasing building density and more stringent safety standards.
Known phenomenon in water supply
MIC has previously been associated with cast iron pipes in marine clay, typically in municipal water supply networks, and steel pipes in the oil and gas industry.
However, research shows that MIC can also pose a challenge in water-filled systems such as sprinkler systems, especially where the water has been stagnant for a long time. Such conditions can accelerate corrosion processes, weaken the integrity of the pipe network and lead to costly repairs.
This finding indicates that issues surrounding MIC now need to receive much greater attention, both in research and in industry standards.
Millions of meters of pipes
Protecting sprinkler pipe corrosion by applying zinc coatings was approved in 2013. Since then, several cases of pressure increases, and in some cases ruptures or explosions in the pipes due to the formation of hydrogen gas, were reported.
Both SINTEF and Norway’s National Institute of Technology have investigated the phenomenon and concluded that the hydrogen gas is formed when the zinc coating inside the pipes corrodes.
Although the approval of zinc-coated pipes in sprinkler systems was withdrawn in 2021, one to two million metres of such pipes are still installed and in use. The safety of these systems is now handled by monitoring the pressure and releasing the hydrogen gas in a controlled manner.
FG Skadeteknikk has published a recommended procedure for this. Following their safety recommendations will ensure that the systems are safe to use.
Bacteria produce acids
Studies of zinc-coated pipes have shown that the zinc layer can provide sufficient protection against corrosion in neutral tap water, but that the pipes, on the other hand, may be exposed to MIC. Such corrosion occurs when bacteria produce acids and other aggressive compounds that attack the metal.
Sulphate-reducing bacteria, which thrive in anaerobic environments, play a particularly important role in MIC. They produce hydrogen sulphide, which is extremely corrosive to metals.
At the same time, the bacteria contribute to the formation of more hydrogen gas in the corrosion process. This creates a self-reinforcing effect in zinc-coated pipes, since hydrogen gas is food for the bacteria: More hydrogen gas is formed when the zinc corrodes, which feeds the bacteria, which in turn produce an aggressive environment and more hydrogen gas.
Even impacts buildings constructed to high technical standards
Examples of this problem in Norway, including St. Olavs Hospital, show that MIC can trigger the need for extensive maintenance and repairs even in modern buildings with high technical standards. But MIC can affect all types of sprinkler systems, and knowledge is still limited about how the phenomenon can best be prevented.
Currently, the extent of MIC in sprinkler systems is unknown, and understanding of the causal factors is limited.
Microbes are adaptable
Preventing MIC may require advanced water treatment to control bacterial growth. But it could also be that keeping the hydrogen pressure under control will be sufficient. Local water chemistry might also play a role.
International research has already shown that microbial communities adapt rapidly to different aquatic environments, and that controlling such communities requires carefully adjusted bactericides and additives.
Better understanding of how MIC develops and how the phenomenon is affected by water quality, temperature and flow patterns, will make it easier to anticipate problems and increase the lifespan of the system.
According to Norway’s Fire and Explosion Protection Act, sprinkler systems must be inspected annually by certified inspectors. Failure to follow up on such inspections can reduce fire safety and have financial consequences, such as reduced insurance payments in the event of a fire.
New knowledge needed
Over the next few decades, the demand for sprinkler systems in various building types will likely continue to grow. With increasing urbanization and increasingly complex building environments, it will also become all the more important to ensure that these systems are reliable over time.
Therefore, issues surrounding MIC need to receive greater attention in research communities and in industry standards – and to search for new knowledge about the phenomenon. Spotlighting prevention, monitoring and material selection can help reduce the risk of damage and ensure the reliability of sprinkler systems in an increasingly strict safety climate.
This post was first published in Teknisk Ukeblad and is reproduced here with TU’s permission.
