Fig. 12 . This shows the comparison between standard and angled horizontal filter print.

print is fully flooded, including the slag trap. Some small beneficial eddy currents are still in the trap. By 10% filled (Figure 11), the filter print is fully stabilized and any inclusions that entered the slag trap will remain. Adding a small area to trap slag in the filter print inlet improves the flow characteristics of the runner design and the ability of the filter print to trap inclu- sions. Tese are significant benefits for a minimal reduction in yield.

Horizontal Filter Print Example For horizontal filter print designs,

some significant advantages to filtra- tion efficiency can be gained simply by placing the filter at an angle relative to the flow. Figure 12 shows a standard horizontal filter print compared to an angled filter print configuration. At 8.5% filled (Figure 13), the angled filter print flow profile is fully established and uniform throughout. A beneficial eddy current is visible within the filter print inlet which enhances the effectiveness of the slag trap. Te for- mation of the eddy current is a direct result of the angled filter. At 10% filled (Figure 14), both

filter prints are operating at steady state conditions and both produce a uniform flow pattern. Te angled design does a better job of distributing and minimiz- ing the flow energy at the filter inlet face and outlet face. Another advantage of angling the filter is to direct the flow across the filter inlet face to potentially dislodge any inclusions that may have become trapped on the filter itself. Tese dislodged inclusions then could get entrained into the eddy current and be mechanically moved into the slag trap Te benefits of the mechanical action of moving inclusions from the filter inlet face to the slag trap are two-fold. Tis action allows the filter to operate at maximum flow rate because fewer particles are

trapped on the surface of the filter restrict- ing the metal flow through the filter. In addition, for metal containing significant slag levels, this may also allow the filter to operate at higher capacity than standard filter print orientations because of the opportunity to pass more metal through the filter before becoming blocked or caked with slag or other inclusions. Overall, placing the filter at an

incline relative to the metal stream is beneficial to the filter flow rate capabil- ity and filtration efficiency.

Conclusions Alterations are sometimes made to

standard filter prints to improve yield

without careful analysis of the effect on the fluid flow properties on the gating system. Tis initial study evaluated the effect of several filter print design changes on the quality of metal flow in the filter print, the runner system and through the filter itself. Te general conclusions from the

study are: • Large reductions in filter print inlet and outlet areas, and sharp angles within the print itself adversely alter the flow characteristics resulting in non-uniform flow and turbulence

• A slag trap designed prior to the filter inlet face induces a counter- clockwise eddy current that washes the filter face and assists with the trapping of inclusions.

• In horizontal applications, angling the filter relative to the metal stream benefits the filter flow rate capability and filtration efficiency.

Tis is an edited version of paper 17-027 that was presented at the 2017 Metalcasting Congress.

Fig. 13. Here is the flow comparison for standard vs. angled horizontal filter print at 8.5% filled.

Fig. 14. This is the flow comparison for standard vs angled horizontal filter print at 10.0% filled. August 2017 MODERN CASTING | 39

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