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shelved in favor of weight per volume measurement.


• Results from flowcoating are more consistent using the weight per volume method. If temperature biasing is added, engineers expect variability will be reduced again.


• Mold wash penetration is on the order of 0.100-0.125 in. from flowcoating with a surface layer of 0.010-0.015 in.


Fig. 5. The penetration with the olivine/magnesite wash (left) was improved with the magnesia wash (right).


• Mold wash pooling can occur if care is not taken to inspect every mold and brush or blow down drips and puddles


• Because of the change to the MgO wash, the pH of the heat treat quench water has gone up to 10pH or more. As a result, castings have a bluish color com- ing out of the quench with little surface rusting. It is not known yet if the high pH quench water has long-term implications. Lenoir Magnetic Separation System Monitoring:


Other than the routine daily XRF checks, the separator is inspected daily for an even flow of sand from the distributor to the upper vibratory pan feeder. If the flow is obstructed by debris from the attrition mill, the blocks are cleared and the attrition mill is inspected for holes in the screens and plates. A layer of fine dust and metallic particles builds up on


the discharge lip of the lower vibratory pan feeder that can alter the presentation of sand to the phased array roll. Te lower pan is inspected weekly and cleaned as needed. Te chromite/silica separation plate was set during


start-up in March 2014 and has not been changed. Te sand throughput was increased by increasing the vibration parameters of the two pan feeders and slightly opening the distributor gate. By using a mouse-hole type distributor gate, as shown in Figure 4, the process can tolerate more debris from the attrition mill without having to check for uniform flow multiple times per shift. Mechanical Reclamation Control (Attrition Mill): Te


controls of the attrition mill have been upgraded to monitor sand availability and process time by adding three ammeters, which are used to measure the current in circuits. One meter is set to a high threshold, one is set to a low threshold and one verifies the vibrator motor is running. Te mill starts and stops the shaker/conveyor and feed belt, and sleeps/wakes on a fixed time interval to check for sand. Tese upgrades mean operators no longer rely on optical switches for sand pres- ence verification, and the mill does not shake itself empty for long intervals. Troubleshooting: Te new system has not totally been


without problems. About six months after conversion, engi- neers found that the magnetic separator could be mistakenly switched to manual mode when sand level probes were deacti- vated. Te magnetic separator would keep running when there was no room in the reclaimed silica sand silo to accept sand transports. Te result was that the reclaimed silica bin could overflow into the reclaimed chromite bin, which then could be


February 2016 MODERN CASTING | 35


transported into the reclaimed chromite silo. Layers of reclaimed chromite contaminated with high levels of reclaimed silica could be used as facing sand. Te end result was a small number of castings scrapped for severe metal reaction/penetration. Narrow flangeway areas of trackwork castings required


new chromite facing to avoid metal penetration. To achieve the cost savings of facing with a blend of 90/10 reclaimed/ new chromite, engineers changed from an olivine/magnesite flow coating to a pure MgO flow coating, as noted previ- ously. Figure 5 shows flangeway penetration with the 90/10 reclaimed/new chromite and the olivine/magnesite wash on the left, while the the improved surface achieved with the magnesia wash is on the right.


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