Fabrication of a Stainless-Steel Pump Impeller by Integrated 3D Sand Printing and Casting: Mechanical Characterization and Performance Study in a Chemical Plant

The emergence of additive manufacturing is renovating the landscape of available production technologies. In this paper, we describe the fabrication of a closed vane pump impeller (ϕ 206 mm, height 68 mm, weight 4 kg) by binder jetting 3D printing of a sand mould followed by casting using stainless steel 316 to create an identical copy of a part in service in a chemical plant in Tarragona, Spain. The original part was reverse engineered and used to create a sand mould by binder jetting 3D printing on which new impellers were fabricated by casting. Metallographic studies showed an austenitic matrix with 6.3% of ferritic phase and 40 μm × 8 μm ferrite grains without precipitated carbides. The impeller was put into operation in a centrifugal pump at a polyol/polyglycol plant belonging to Dow Chemical Ibérica SL from October 2020 to April 2021. Process variables related to the pump behaviour were compared with the same variables obtained in previous cycles with the original impeller for three different product viscosities (30, 180, and 500 cSt). At 500 cSt, the average current consumption was 9.34 A as compared with the 9.41 A measured with the original impeller. Similarly, the pump pressure remained essentially constant during process operation with both impellers (3.97 bar with the new impeller vs. 3.99 bar with the old). Other monitored parameters (product flow, tank level) were similar in both cases, validating the fabrication strategy from an operational point of view. This work further demonstrated that the implementation of additive manufacturing technologies in chemical process engineering is a useful solution to fabricate spare parts that are difficult to replicate with other technologies, providing consequent economic benefits.