Equipment Focus: Metal Analyzers

No portable, handheld metal analyzer is perfect for all scrap-identification tasks. This review can help you select the right one for your needs.

By Jim Fowler

If you’re in the market for a portable, handheld metal analyzer, the first fact you need to know is this: “There’s no portable piece of equipment that can do it all,” asserts one analyzer manufacturer. “There isn’t one technology that’s a panacea.”
   There are two technologies, in fact, that are used most commonly for analyzing materials in scrap facilities—X-ray fluorescence (XRF) and optical-emission spectrometry (OES). Both technologies are useful in scrap-analysis tasks, though they differ in the elements they can identify effectively.
   OES, for instance, can reportedly analyze a broader range of elements, particularly light elements such as aluminum, aluminum alloys, silicon, carbon, and magnesium.
   XRF is more commonly used to analyze high-alloy materials, such as stainless steels, nickel alloys, and cobalt. While the latest XRF units can analyze some aluminum alloys—many more than they could two years ago—they “can’t do them all,” notes a vendor. Titanium is generally the lightest element a portable XRF can realistically measure. As an XRF manufacturer points out, “We all have what we call an aluminum model in our instruments, but what that’s really measuring is copper, zinc, and tin in the aluminum. It’s not measuring aluminum, silicon, or magnesium—the primary alloying elements in an aluminum alloy. To do aluminum, you need an OES instrument.”
   So, which technology—XRF or OES—is best for you? The answer, in short, depends on which types of scrap you’ll be analyzing. “A scrap recycler who handles large volumes of aluminum will want an OES system, while one that handles large volumes of stainless will want XRF,” suggests one manufacturer, noting that “if the company handles large volumes of both, they’ll most likely want both systems.”
   As another producer adds, “you have to look at what sampling range is most important to you—what type of material you’re going to use it on.” 
   Aside from the basic XRF/OES question, here are some other issues to consider in your search for the right metal analyzer:
Technological Features: Computer technology is incorporated in all handheld systems these days, and most can be integrated with personal digital assistant (PDA) technology, with wireless capability to feed information back to a computer. Ask the various analyzer vendors to review the technological features and capabilities of their units. Make sure you understand the benefits of such features and capabilities—especially why they’re important to your operation.
Analysis Speed: “Speed is important to scrap processors,” says one analyzer producer. “When you’ve got huge piles of material with lots of pieces, the quicker you can sort through that pile, the more money you can make out of it. It’s a dollars issue.”
   XRF units can reportedly provide an analysis in two or three seconds for sorting purposes and 10 seconds (or less for some materials) for good analytical chemistry. OES instruments operate at about the same speed as XRFs, a vendor says, maintaining that “they’re roughly the same. Once you click the trigger, both will give you a reading in a few seconds. Both systems are designed for instant readings.”
   Another manufacturer concurs, stating that “for purposes of sorting metal in a productive way, I think they’re all about the same.” In his view, “When you’re talking about a second here or a second there, it really doesn’t matter. There are other time issues, such as how long it takes the operator to put the tested piece into a barrel or the time to grind a corroded piece of material to get a good test. That alone blows away any testing time differential.”
Sample Preparation: Both XRF and OES systems require the analysis sample to have a reasonably clean surface. In general, anything that isn’t representative of the material—such as paint or heavy scale—needs to be removed. “If you have corrosion or scale on a piece to be tested, you need to knock it down with a grinder,” a vendor says, adding that “scrap processors want to do as little prep as they can get away with because time is money.” Notably, high-temp alloys don’t corrode and are generally clean enough that little or no prep is required.
   With XRFs, the practice of shot-blasting a sample can present problems, a manufacturer notes. “Some scrap recyclers will shot-blast material, and the tiny iron shot impregnates iron into the surface of the material,” he explains. “When you test, you’ll get a high iron content. To avoid that, we recommend hitting the piece with a small grinder before testing.”
   According to another producer, “OES is more sensitive to surface grime because it’s an optical technique—it’s a less-forgiving technology than XRF. For example, if you don’t have the OES gun in just the right position, where the spark is going to reflect just right, then you don’t get a good measurement.”
Sample Shape: Curved or complex shapes typically aren’t a problem for XRF instruments since they generally have geometrical normalization programs built in, sources note. As a result, XRF instruments are ideal for testing turnings and odd shapes, says one manufacturer.
   In contrast, while “OES instruments with air devices can be used on some curved surfaces,” he notes, “you can’t do turnings. For turnings, you have to melt a ‘button’ and then test it.”
User-Friendliness: Compared with stationary, laboratory-scale analyzers that require a highly trained technician to operate them, today’s portable, handheld analyzers are designed for quick and easy operation by virtually any worker.
In general, manufacturers claim that XRF instruments are easier to use than OES units. As one vendor explains, “You turn an XRF on, hit a button or two, and you’re ready to start pointing at material, pulling the trigger, and getting answers—point and shoot.”
   With OES analyzers, he says, “you have to make sure your calibrations are tuned up, you have to do the right sample prep, you often need argon gas for the test, and you have to make sure you’re getting a good burn on the sample. OES is a significant step upwards in terms of complexity for the user.”
   Though another manufacturer acknowledges that “the operator needs to know more when using an OES and that the XRF is designed to be a bit more foolproof,” he notes that the downside of XRF units is that “you can have someone go out and make a ton of shots with an XRF who doesn’t realize that the unit’s analysis source is starting to fail. OES is more stable, but it requires an operator who knows the OES system to be sure it’s calibrated.”
   With an XRF instrument, one vendor continues, the user doesn’t need to know the type of material being tested. The instrument will determine the type of material and analyze it correctly. In contrast, he says, “OES devices are more complex. You have to know the type of material you’re testing—you have to know whether it’s aluminum, or copper, or titanium—and you have to set the unit in the correct mode to get a reasonable analysis. OES systems require more operator training.”
   When using an OES unit, a scrap processor will often have an employee who becomes well-versed in that technology and instrument—“and that person can make it sing,” one producer notes. “An OES instrument generally requires a person with a higher technological competence. It’s also a more complex technology in terms of the data being analyzed.”
   While the point-and-shoot simplicity of an XRF analyzer is enticing, that feature only matters if the unit can do the analysis job you need. As one manufacturer notes, “Since XRF doesn’t see silicon, carbon, or sulfur, if you need that ability, it won’t do the job for you.”
Destructive vs. Nondestructive Testing: OES is considered a “destructive” technology in that “the arc spark from an OES makes a tiny burn spot less than a millimeter in size where it vaporizes a tiny bit of the material,” explains one producer. XRF analyzers are “nondestructive” in their analysis. This distinction, however, is a nonissue in the scrap industry, manufacturers agree. The sample damage caused by the OES analysis is “inconsequential,” states one vendor. “The little burn mark is not a big deal for a scrap processor.”
Durability and Maintenance: It’s a given that portable, handheld metal analyzers must be rugged to withstand the scrap environment. Aside from coming in tough cases that can survive drop tests, units need to be watertight as well as dust- and soil-resistant. Also, shielding and padding inside the unit are important to absorb shock and prevent the internal components from breaking if the instrument is dropped.
   When it comes to maintenance, manufacturers strive to make their analyzers as “care-free” as possible. Users still need to keep tabs on some maintenance points, however. With OES, for instance, “you’re burning metal and have an electrode that corrodes, so you have to maintain it,” a vendor notes. 
   On the XRF side, one source maintains that such radioisotope-based instruments “have fewer components that are subject to failure and are, therefore, more rugged.” Still, cadmium sources used to power older XRF instruments need to be replaced every couple of years. Sometimes, operators complain that they’re not getting a signal, but the problem is that the cadmium source has become so weak. “You need to maintain the source—replace it—for the instrument to function properly,” a manufacturer states. “They don’t last forever.”
   Another notes that XRFs that use X-ray tubes as their analysis source must have the tubes replaced every three to five years. As one manufacturer explains, X-ray tubes consist of an anode and cathode encased within a vacuum-sealed vessel. When the vacuum is lost, the tube will no longer function and must be replaced. (For more details on X-ray tubes and other analysis sources, see “What’s New in OES and XRF?” on page 90.)
Flexibility: “Ask if the system can be upgraded,” advises an analyzer source. “Pick a system that not only does what you need to do now, but one that you can easily add to if you start handling a new group of materials in a year or two.”
Cost: The cost of metal analyzers is certainly less today than in years past. The new OES portable, handheld units are around $20,000, but be sure to ask how many calibrations are included with the unit. [For reference, the larger transportable, wheeled OES systems, which include a laptop, run $35,000 to $45,000, depending on the number of calibrations.] XRF handheld instruments, meanwhile, run $30,000 to $35,000 on average.
   Due to the limited market that prevents economies of scale, manufacturers don’t expect analyzer prices to decrease. As one vendor says, “One of the big expenses is amortizing design and the required support, and those costs are personnel-related. If anything, personnel expenses will increase.”
   Finally, after considering all of the above factors, ask the manufacturer for a demonstration of its analyzer in your operation. As one manufacturer states, “Scrap processors should absolutely insist on a demonstration that provides an opportunity for the individual in their yard who is going to use the instrument to try it out. That person needs to walk around with it and sort metal with it.”

Analyzing the Future
Though some manufacturers don’t see analyzers changing dramatically in the coming years, others see the relentless progress of technology at work.
   “We’re all trying to make improvements in detection limits and analytical capabilities,” says a producer. “I think you’re going to see improvements in the analytical range of instruments and possibly a combination XRF and OES. There’s a big demand for an analyzer that will do everything. While there’s no single technology that does everything well, we’re trying to find a way to cover the full analytical range.”
   Smaller is always a goal, but as one manufacturer points out, his firm’s unit already weighs only 1.7 pounds, in-cluding a battery as large as the system. “Battery technology is improving, but these systems take a lot of power to cool the detector, move sources, and crunch data,” he notes. “The battery may be the limiting factor as to the size you can make the instrument.”
   Another producer points out that at some point “a lot lighter or a lot smaller doesn’t really add a lot of benefit. I think the focus will be on lower and lower limits of detection in alloys. I bet in five years there’ll be a handheld XRF system that will do aluminum, silicon, and magnesium. But, to accomplish that, there’ll have to be some significant breakthroughs in a handheld system that will be rugged in the field.”
   Then there’s this final optimistic note from a vendor: “I don’t think we’re near the technical apex. Ten years ago we couldn’t imagine the point we’ve now reached. With the improvements in battery technology, microprocessors, and electronics, it’s hard to say where we’ll be five years from now.” 

What’s New in OES and XRF?
For OES systems, the newest development has been the introduction of portable, handheld units. Previously, OES systems were available only on carts that were wheeled around the work site. The advantage of these larger “transportable” units is that they have a better optical system than handheld models. “The larger the optical system, the better results you get,” a manufacturer notes. “It’s very reliable and can do anything a lab-grade system can do.” Such wheeled units were difficult, if not impossible, to use in scrap plants, however—thus the development of a portable, handheld OES analyzer. As the manufacturer points out, “Scrap dealers want the ease of operation you get from a handheld OES instrument.” 
   XRF analyzers, in contrast, have been available in portable, handheld versions for at least six years. The biggest developments in the XRF niche have been in the types of analysis sources used in the instruments. Traditionally, XRF units used radioisotopes—commonly Cadmium 109—as their analysis source. Today’s XRF analyzers are also available with either specially designed and patented radioisotope sources or X-ray tubes, which were first introduced about three years ago.
   As with any new technology, there were some initial problems with X-ray tubes. Manufacturers addressed these problems by imposing strict testing procedures. “When we get our tubes in, we don’t just stick them in an analyzer and ship the instruments out,” a vendor explains. “We burn them in and test them a couple of months. We have a huge amount of data from this testing, and we’ve seen dramatic improvements in the reduction of early tube failures and their overall reliability. Early on it was a problem and their use was a question mark, but the reliability of these tubes has improved tremendously over the past two years.”
   Notably, both radioisotope-based and X-ray tube-based XRFs are regulated, though manufacturers disagree on which technology faces more regulatory hassles. One tube-based vendor suggests that federal regulations on isotopes are only going to get worse, but a radioisotope XRF producer counters that some states have stricter rules for tube-based instruments and that, in Canada, the regulatory costs, paperwork, and training requirements are more burdensome for tube-based units than radioisotopes.

The Analyzer Experts
Angstrom Inc., 800/395-5393, www.angstrom-inc.com 

Innov-X Systems Inc., 781/938-5005, www.innov-xsys.com 

Metorex Inc., 609/406-9000, www.metorex.com 

NITON L.L.C., 978/670-7460, www.niton.com 

Oxford Instruments America Inc., 847/439-4404, www.oxford-instruments.com 

Spectro Analytical Instruments Inc., 978/342-3400, www.spectro-ai.com 

Thermo Electron Corp., 505/428-3534, www.thermo.com 

Verichek Technical Services Inc., 412/655-3491, www.verichek.net or www.was-ag.com

Jim Fowler is retired publisher and editorial director of Scrap.