## 3 Results and Discussion
### Performance Tests of BJ Impeller in a Chemical Plant  
The performance of the manufactured BJ impeller was then tested in a real scenario. The BJ impeller was mounted in a centrifugal pump located in a production plant of Dow Chemical Iberica in Tarragona Site, Spain. This plant produces aqueous polyol/polyglycol solutions of different concentrations and viscosity by adjusting the proportions of feed materials (a polyol/polyglycol precursor and an antioxidant solution) in a discontinuous process. The pump (P) is located immediately after the reaction tank T and pushes the  
Figure 10: Microstructure images of (**a**) BJ impeller, (**b**) KSB impeller.  
Figure 9: SEM images of BJ impeller surface showing (**a**) large (\(\sim\)400 \(\upmu\)m) and (**b**) small (\(\sim\)50 \(\upmu\)m) shrinkage voids due to metal contraction.  
product mixture towards distillation column D (see Figure 3), and it is remotely supervised from a control room that collects several process parameters.  
For the purpose of this study, the process parameters were first collected using the original KSB impeller during specific periods of time for three product recipes of high, medium, and low viscosity, as indicated in Table 1. Afterwards, the KSB impeller was substituted (on 30 October 2020) for the BJ, which was set to operate in identical operational conditions for the three recipes in order to compare its performance with that of the KSB impeller.  
Figures 11-13 show the results obtained for both impellers using the three recipes. Panels (**a**) and (**b**) in these figures show the dependence of pump ampere (current) on pressure and product flow, with typical values between 9 and 10 A. Since, in normal operating conditions, the electric tension of the pump is constant, a decrease in the current indicated a malfunction of mechanical parts of the pump in which the impeller was located and was thus an indirect measure of the performance of the pump. The average values in all cases were between 9.3 and 9.4 A, with low standard deviations, indicating similar behaviour of both impellers.  
On the other hand, panels (**c**) and (**d**) in Figures 11-13 show comparisons of the data obtained with both impellers for one typical production cycle. Average values and standard deviations are also indicated over each trace. A normal run lasted about two days, and parameter readings were taken continuously every 20 min. Pump P was continuously monitored to maintain the level of tank T at \(\sim\)40%, and the variations in pressure and product flow observed in the figures correspond to adjustments in the production according to the desired specifications and production volume. Although we did not carry out a detailed statistical analysis of these results, it was evident that the parameter readings with the BJ impeller were comparable to, and in some cases slightly more stable than, those obtained with the original KSB impeller. This general trend was observed for all production cycles monitored, and no failure of the BJ impeller was observed throughout the performance study.  
The results obtained indicated that there were no differences between the original and the new BJ manufactured impeller and further demonstrated that the manufacturing strategy was technically validated, from a design/manufacture point of view to an operational/process point of view.  
Figure 11: _Recipe 1_. (**a**,**b**) Dependence of pump average (current) on pump pressure and polyol flow for two consecutive production cycles. (**c**,**d**) Tank level, polyol flow, and pump pressure, read continuously for a complete production cycle. KSB impeller (**a**,**c**), BJ impeller (**b**,**d**).  
Figure 12: _Recipe 2._ (**a**,**b**) Dependence of pump average (current) on pump pressure and polyol flow for two consecutive production cycles. (**c**,**d**) Tank level, polyol flow, and pump pressure, read continuously for a complete production cycle. KSB impeller (**a**,**c**), BJ impeller (**b**,**d**).