Hard Iron Versus Cast Iron Impellers For Non-Clog Sewage Pumps

By Sherry Heinly, KSB North American Marketing Manager

When specifying the impeller material for a non-clog sewage pump, how do you know whether to select cast iron or hard iron material?

Usually, a hard iron material is only required if your non-clog pump utilizes a semi-open impeller. A semi-open impeller does not have a shroud on the suction side and rotates against an adjustable suction wear plate, which results in a high amount of wear on the impeller. Semi-open impellers rely on a sharp leading edge to cut material in the wastewater, which allows them to remain clean and help prevent clogging; therefore a hard iron / chromium / nickel alloy is required to keep the semi-open impeller’s leading edge sharp. Without that harder material, the leading edge will dull more quickly, diminishing the pump’s ability to stay free of clogs over a long period of time.