ChemFlow builds centrifugal pumps for chemical processing. A line of pumps handling mildly corrosive fluids was coming back for volute replacement far too early — the coated cast-iron volutes were corroding at the seal faces and internal surfaces, and a corroded volute means lost efficiency and eventually a failed pump.
The wrong material for the fluid
The volute is the spiral casing that surrounds a pump impeller and converts its velocity into pressure. Its internal surface finish and the flatness of its sealing faces directly set the pump's efficiency and whether it leaks. In a corrosive fluid, material chemistry sets how long all of that lasts.
ChemFlow's coated cast iron was a cost choice that didn't survive the chemistry. Once the coating was breached, the iron corroded, roughening the flow path and eating the seal faces — early failures that were hurting ChemFlow's reputation for reliability.
Cast it in the right stainless
The established answer for corrosive pump service is a CF8M casting — the cast equivalent of 316 stainless, with molybdenum for resistance to chlorides and many process chemicals. Investment casting produces the complex volute geometry with a good as-cast surface, and the critical flange and seal faces are then machined true.
Getting there meant switching from iron to a corrosion-appropriate stainless, cast to net shape and finished where it seals.
The part we built
We investment-cast the volute in CF8M stainless, pickled and passivated it to establish a clean corrosion-resistant surface, and machined the mounting flange and seal faces to a CT8 tolerance grade so the pump assembles and seals correctly. We pressure-test and finish the castings before they ship, so ChemFlow receives a ready-to-assemble part.
Because we can cast, machine, and test in-house, ChemFlow deals with one supplier for the finished volute instead of coordinating a foundry and a machine shop.
Service life, restored
In the same corrosive service that had been eating iron volutes, the CF8M castings hold up — the flow path stays smooth and the seal faces stay true, so the pumps keep their efficiency and stop coming back for early volute replacement. ChemFlow could stand behind the pump's service life again.
Matching the casting alloy to the fluid is unglamorous engineering, but it's the difference between a pump that lasts and one that doesn't.
“We were replacing corroded volutes under warranty. In CF8M they just hold up — the pumps keep their efficiency and stay in service.”
Bill Ferrante, Chief Engineer, ChemFlow Process