Portable Dross Boss Processing Units – City Aluminum Foundry Co.

Portable Dross Boss Processing Units

1. Customer:

City Aluminum Foundry Co.
2505 Williams Dr.
Waterford, MI 48328-1869

2. Contact:

Chuck Juliarr Vice President 248-33s-8785
Customer Report

3. Melting Practices:

We pour primarily 356, 319 and 535. Our Hunter molding line has 4 Inductotherm I 300 pound resistance fumaces.

4. Practice Comparisons:

We typically get two batches from each furnace per day. We flux inject these furnaces. With a brick drossing table, we were generating around I drum of dross. weighing around 400 pounds, per day. With the DROSS BOSSTN4, we generate one drum of dross every three days. The difference is in recovered aluminum. It seems as though we are saving 800 pounds of metal every three days. It has been possible to reduce our loss by very diligently having the furnace tenders massage the dross and get it to drain, but once you stop watching them, they slip back into their old ways because of the time it takes and we again have a lot of lost metal. We consistently get good recovery with the DROSS BOSS rM.

5. DROSS BOSSTNt Practices:

The basic treatment cycle identified above was followed with the heats processed through the DROSS BOSSIM, with the exception of a two ounce addition of exothennic flux stirred into the dross that had been transferred into the reaction vessel. The rnanual stirring operation was accomplished in less than three minutes, with the recovered metal being returned at elevated temperature to tlte holding furnace. No significant change in metal chemistry had occurred during processing.

6. Customer Savings:

Using a conservative estimate of savings, the customer projected an approximate ($139/ day)* direct savinqs in metallics, rvith an additional saving in remelt energy by recharging tlie hot material to his melter. On that basis, their return on the capital investment was achieved in approximately three months.

*2013 prices

Click here to view full version.

Mercury Marine Company Report

Customer Report:   Mercury Marine Co.

750# Remote Station HD Dross BossTM Unit


Plant 17 of the Mercury Marine Company in Fond Du Lac WI, is the first American operator of one of the new family of larger Dross BossTM units.  The 750# Remote Station unit was commissioned in January 2015, and is recovering specification aluminum alloy from the hot aluminum drosses generated by five large Hearth Melters. The furnaces are skimmed twice a day, with the skims of hot dross and good alloy collected in portable Reaction Vessels (RV) for the recovery operation. The RVs are then transferred to the Mixing Tower, where they are given a small flux addition and processed in an approximate ten minute cycle. The intensive mixing promotes a gravity separation of the aluminum alloy and demetallized dross. The recovered alloy is under the floating dross, and may be conveniently drained into a sow mold and returned to the melting furnace while still at elevated temperature.


All functions are electrically powered and run by a Touch Control panel. A PLC executes the operating program, which is fully capable of running statistical optimization programs for metal recovery and processing time.


The average recovery of metal has been in the range of 50 – 60% of the weight of dross charged, with an occasional high of 70% reached.  The Mercury Plant staff is well pleased with the equipment, and is expecting a rapid return on their investment.              


Click here to view report externally: Mercury Marine Customer Report         

The Problem With Sectioned RPT Samples

sample1Sample One
The results of three cuts made through the same Reduced Pressure sample, illustrating the potential variations that might be found because of minor segregation in the bubble formation. The alloy is 356, and the samples were taken at the Kingsville Plant of ThyssenKrupp-Stahl Co.













Sample Twosample2
A similar result on a second sample with a much lower hydrogen level than Sample 1, above, and on a 319 alloy melt. If the target hydrogen production level is for a high sample density (low gas), the potential for error is obviously rather high, and scrap castings could result.


Note: In addition to the variations in bubble density that may exist between sections on the same sample, the subjective estimates of individual readers have been noted to vary by as much as two or three levels.

Reduced Pressure Testing of Aluminum Melts



The differential gage on the left, as used on most current RPT testers, measures a change in vacuum level from the current atmospheric pressure. As may be seen from the graph of atmospheric pressure in Madison, WI below, the pressure may vary over an average range from about 30.8 inches of mercury down to about 28.1 inches when high and low pressure weather systems pass through the area. By lowering the chamber pressure by 26 in.Hg, as measured with a differential gage, the actual chamber vacuum might vary over a range as much 4.8 in.Hg to 2.1 in.Hg (or the equivalent reading measured in mmHg) above a perfect vacuum.

For accurate testing of aluminum melts, the answer is to use the absolute vacuum gage on the right, which ignores variations in the current atmospheric pressure. With this type of meter, the test chamber may be always evacuated to a constant level, which is a major controlling variable in the size of the induced porosity in Reduced Pressure samples. The resulting process control accuracy that is achieved is one of the primary benefits of using a T.R.P. Tester (True Reduced Pressure).


Daily Averages of Mean Sea Level Pressure at Madison, WI1
Daily Averages of Mean Sea Level Pressure at Madison, WI1

This plot shows the daily average mean sea level pressure reported at the Dane County Regional Airport for the three year period covered. The net effect of these pressure changes can introduce significant errors to the test chamber vacuum level, as may be seen below.

The graph shows the resulting chamber vacuum level after pulling down the vacuum to the -26″Hg gage reading. The colored areas are zones of control error and represent the amount of improvement achieved by the TRP Vacuum tester.