Process improvements

The challenge with sorting aluminum alloys using a handheld X-ray fluorescence (XRF) device is that it can take as long as 30 to 60 seconds to identify many grades. While that has been the case historically, using the best detector and tube combination and applying them strategically, it can be possible to drastically reduce test times.

XRF is a proven, indispensable technology for alloy identification and sorting. While most alloys can be identified in a second or two, aluminum grades can take considerably longer because of a number of special challenges. Here is why.
 

Issues for analysis

Beyond the fact that aluminum grades specifications have an uncommon amount of overlap, the central problem is that some of the key elements used for identification are difficult for XRF technology to analyze. The table on page 104 identifies the key alloying elements for identifying aluminum grades.

This table (based on 618 aluminum grades listed in the Unified Numbering System for Metals and Alloys, or UNS) lists magnesium (Mg), copper (Cu), silicon (Si), manganese (Mn), zinc (Zn) and chrome (Cr) as the primary elements for sorting aluminum. In many cases, such as cast aluminum grades—6000, 5000, 4000 and 1000 series—Mg and Si are the key elements for proper sorting. Likewise, Mg and Si are the two most challenging grades to measure accurately.

In relation to other alloy types, aluminum grades require longer XRF test times, have poorer precision (especially on the key elements of Mg and Si) and have more challenges related to surface contamination. These factors can cause aluminum to take 10 times as long as other alloys to identify. And, for all the effort and time required, the reliability (analytical confidence) can be quite a bit worse as well. Plainly stated, sorting aluminum grades can take 10 times the work and can produce five times the mistakes.

Olympus, based in Waltham, Massachusetts, spent years listening to customers, studying the problem and devising a smart strategy for streamlining the sorting of the 50-plus most common aluminum grades. While we apply this approach to more than just aluminum grades, aluminum is the alloy base that benefits the most from this process. SmartSort, a sorter-friendly smart logic, can cut test times to one second for half the common aluminum grades. For the remaining grades, the same smart logic identifies whether the test can finish in six seconds or needs to be extended past eight seconds. On average, test times run approximately six seconds. This approach often can be more reliable, faster and more productive than conventional XRF sorting approaches.

The logic that allows this accelerated approach breaks the common 53 grade aluminum library into three grade types: 26 Smart Grades that take one second to identify, 18 Quick ID grades that require six to eight seconds to identify and nine full-test grades that require eight to 20 seconds to test.

The average test length for these common aluminum grades, if presented equally in a sorting process, would be less than six seconds.

The key to this rapid processing is the SmartSort logic that is guiding the sorter through the process. The key factors of this expedited process are:

• relativity – Sorting is a relative question more than an absolute analysis. So, the more focused the operation or the list of grades being processed, the simpler and more efficient the sorting process.
• informing the process as it goes – Starting with the trigger pull, the XRF data inform a simple and automatic logic that progressively guides and speeds the sorting process. The result is an accurate and rapid ID for each grade in the absolute minimum test time—simple, fast, definitive aluminum sorting with the convenience and economy of handheld XRF.
  
   

Go with the flow

Display messages on the sorter guide the user through the fastest possible process to analyze aluminum grades:

• Half of the library grades can be accurately identified in one second, encompassing grades from automotive, aerospace and consumer sources.
• Another 30 percent of analysis is completed in as little as six seconds, including cast 319 and 380 grades.
• Only the most challenging grades—the final 20 percent of the library—require more than eight seconds to sort, usually to accurately identify small alloying differences in magnesium.
• All of the library grades are correctly tested using the SmartSort’s logic and messaging process.

Further fine-tuning

While this approach is effective for most scrap operations, any further tuning of the logic and guidance messages based on site and process specific requirements is a simple process.

If your yard handles large volumes of aluminum, SmartSort can be a game changer, allowing more rapid and confident completion of aluminum sorting projects.

Ken Smith is director of XRF process and OEM analyzers at Olympus, Waltham, Massachusetts. More information is available at www.olympus-ims.com.