A full range of impeller materials
Customers often ask us: “What's the best impeller material?” Unfortunately, there is no standard answer because there is no such thing as standard wastewater....
Duplex Stainless Steel Since there are different types of wastewater, material choice for specific sewage applications is critical for ensuring long pump life. Occasionally – although this is rare in municipal wastewater applications – a low pH level causes corrosion and justifies the extra cost of stainless steel, which is why we have now added duplex stainless steel impellers to our range. However, wastewater is by definition anaerobic: containing very little oxygen, therefore corrosion is seldom a problem.
Managing the nitty gritty More often than not, the problem is not corrosion but erosion. If the wastewater you pump contains high concentrations of abrasive particles, hard iron is a better choice in the long run over cast iron or duplex stainless steel. As you can see in Fig. 1, the wear resistance of duplex stainless steel impellers is about the same as cast iron. Significantly harder and better than either – and less expensive than duplex stainless steel – is our proprietary alloy Hard-Iron™.
Five times more wear resistant than stainless steel Hard-Iron™ is not the same as hardened iron, which is only slightly harder than duplex stainless steel. Flygt Hard-Iron™ is a high chrome alloy that is as much as five times more wear resistant than duplex stainless steel.*
Less erosion, less maintenance In accelerated wear tests, Hard-Iron™ kept working efficiently and showed minimal wear after pumping water with a very high concentration of highly abrasive particles. Field testing has demonstrated that, despite salt and sand infiltration, Flygt N-pumps with Hard-Iron™ impellers continue to deliver sustained efficiency without erosion or corrosion. In other words, by choosing Hard-Iron™ you can reduce the time and money spent on maintenance.
* Hard-Iron™ is a high-strength alloy containing 25% chromium and 3% carbon. During the solidification process, the chromium and carbon transform into very hard carbides. This makes Hard-Iron™ highly resistant to abrasive wear and erosion-corrosion
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