Carbon Steel
When specifying any product, cost, longevity and sustainability are key issues. Carbon steel over the past decade has been increasingly used as a greener alternative to mild steel. Carbon steel is up to 50% lighter than traditional mild steel pipe. This means that not only is installation easier but as carbon steel uses fewer materials it produces less CO2 during manufacture. It’s usage also plays a significant part in the recycling of mild steel. Traditionally mild steel screwed pipework has been the fail-safe for applications like closed-circuit heating or chilled water.
Carbon steel with press-fitted connections is now widely used thanks to its corrosion resistance in closed heating and chilled water systems. Boasting enhanced eco credentials plus money-saving benefits, as long as it is installed correctly, carbon steel makes for a convincing alternative. One of the key benefits of carbon steel is its anti-corrosive nature in closed-circuit systems. However correct storage, handling, installation and commissioning is vital to illuminate any damage caused by corrosion.
However serious problems can develop when the manufacturers guidance is not followed.
There are 4 key points to take note of with Carbon steel:
- Keep it clean: Prior to fitting the piping must be protected from dirt and damage. Carbon-steel products should not be stored alongside stainless-steel items otherwise contact corrosion can occur.
- Moisture Free: It is absolutely critical that the pipe is protected against moisture and the influence of weather. For chilled-water applications a vapour barrier must always be maintained in areas where condensation is likely to occur.
- Oxygen free: Crucially, the probability of corrosion is increased if oxygen is present in the circuit; concentrations in excess of 0.1 g/m3 indicate a greater probability of corrosion. This can occurs through compression glands, screw connections or automatic air-valves, however there is little risk of corrosive damage from oxygen when filling and supplementing with water since the amount of oxygen is very low.
- Correct commissioning: This may seem an obvious point however many contractors have fallen down because they haven’t followed the correct commissioning procedures. Installers Should not be tempted to test sections of pipe with water as they go along, draining them down in between. Residual oxygen and water in the pipework can begin the corrosion process, which once started is almost impossible to stop. The system can be purged with Nitrogen if left empty.
