September/October 2003
More air bags in cars has meant more air bags in the scrap stream, posing safety concerns for scrap processors and consumers. Here’s how the industries are meeting the challenge.
By Robert L. Reid
The number of air bags in American cars and light trucks is growing dramatically, both in overall figures and in how many air bags are installed in each vehicle. The shapes of these air bags and their materials are also changing. While all this is good news for driver and passenger safety during the useful life of the car or truck, it poses greater and sometimes unexpected challenges for scrap processors and consumers once these vehicles enter the recycling stream.
Consider how much the use of air bags has grown in recent years. In the summer of 2000, an estimated 95 million cars and light trucks on American roads were equipped with driver air bags and more than 68 million of them had passenger air bags. By May 2003, however, the numbers had increased to 137 million driver air bags and more than 115 million passenger air bags out of a total fleet of 215 million cars and light trucks, or more than 63 percent of the total vehicles on U.S. roads, notes the Insurance Institute for Highway Safety (Arlington, Va.). Moreover, another 1 million new vehicles with air bags are being sold each month.
The number of air bags in each vehicle is also on the rise. Today’s recyclers generally handle older scrapped cars that might contain just one or two air bags. But newer cars can feature anywhere from six to more than a dozen air bags—in a variety of shapes and sizes—that will likely enter the recycling stream over the next decade or so.
For scrap processors and consumers—specifically, secondary aluminum smelters—these facts mean that an increasing number of recycled vehicles and shredded nonferrous metal will contain a growing number of air bags now and well into the future. Already, air bags in the scrap stream have led to rejections of scrap shipments by major secondary smelters with “zero-tolerance” policies, the establishment of new sorting efforts by scrap processors, as well as a revision to a key ReMA specification for the aluminum scrap produced by automobile shredders.
While these challenges mostly affect the nonferrous side of the scrap industry, ferrous consumers also need to watch the issue. That’s because the metal canisters used in air bags—which for years were made from aluminum—are increasingly being made out of steel.
Safety Concerns
Safety has long been the chief concern in processing or consuming scrap that contains air bag canisters—ironic, given that air bags themselves are a safety device. But over the years, the nature of this potential safety problem has shifted somewhat.
When scrap processors first began to worry about air bags and safety back in the 1980s and 1990s, the issue mostly involved the safety of their own workers. The air bag units being installed during those years usually included an explosive propellant called sodium azide that, when detonated, would produce nitrogen gas to rapidly open the protective bag. Unfortunately, sodium azide is a hazardous substance that recyclers feared might put scrap yard employees and the environment at risk if too much accumulated, explains Scott Horne, ISRI’s counsel and managing director of government relations.
Sodium azide only poses this problem if the air bag has not already deployed. When the air bag deploys, the sodium azide is completely consumed, and any residual powder is at most an irritant, explains an OSHA hazard information bulletin. Moreover, many undeployed air bag canisters are removed by automobile dismantlers for reuse. But scrap processors worried—rightly so, it turned out—that an unknown number of canisters would arrive at their facilities intact and undeployed, even in dismantled or flattened car hulks. Shredder operators also feared that an undeployed canister could detonate inside the shredding chamber, possibly contaminating the equipment or starting a fire by igniting other material.
As more and more scrapped vehicles with air bags entered the recycling stream, however, neither sodium azide exposure nor canister explosions inside shredders turned out to be actual problems, Horne says.
Instead, he explains, sometime around late 2000 and early 2001, “we started hearing that undeployed air bag canisters were making it through the shredding process intact.”
One air bag manufacturer actually tested this problem by running a batch of canisters through a shredder. Not a single canister deployed and only half of them were even damaged, the manufacturer told an ReMA gathering.
This unexpected turn of events created two new potential problems: First, a canister that has survived the rough treatment inside a shredder can be unstable. One recently detonated in a processor’s eddy-current system, Horne notes. So if a scrap yard worker picks a canister off a conveyor or carries it across the scrap yard, the device could detonate in his hand. The potential injury depends on various factors, including which type of air bag inflator it is and how the employee is carrying it, Horne says. And while an electrical charge is needed to detonate the device, there are reports of static electricity being enough to set one off, he adds.
Consequently, workers should always wear protective gloves and avoid situations that could generate static electrical charges while handling undeployed canisters, experts note. Eye and ear protection—because of the loud explosion that occurs during deployment—is also useful, as is holding the canister so that the cover plate won’t strike the worker holding the device or anyone else in case of an unexpected deployment.
The other new potential problem also emerged in the 2000-2001 time frame when scrap processors “started hearing the first reports of explosions at secondary aluminum smelters that were tied back to air bag canisters,” Horne says. Again, the key concern was worker safety, though this time it was the smelters’ employees who were potentially at risk.
Because an undeployed air bag canister is a sealed, airtight unit, it acts like a “bomb” inside a secondary smelter’s furnace—with the resulting explosion inside the metal bath causing anything from a firecracker-like pop to a violent reaction in which either molten aluminum can splash out of the furnace or the canister itself “shoots out like a rocket,” one smelter explains.
Deployed canisters or partially shredded units can also cause problems because of moisture trapped inside the now-open containers, processors and smelters note. Larry Berry, vice president of sales for Huron Valley Steel Corp. (Belleville, Mich.), a heavy-media separator, says his firm finds both deployed and undeployed canisters, but “because of moisture, the deployed canisters will act like an undeployed canister in a secondary’s furnace.” Berry adds that deployed canisters “even get moist if they’re exposed to high humidity.”
Inspecting and Rejecting
Though no canister seems to have caused a serious personal injury yet, there are reports of minor burns, equipment damage, and downtime losses, ISRI’s Horne says. Moreover, the potential hazards were great enough for one smelter—Audubon Metals L.L.C. (Henderson, Ky.)—to redesign the charge wells around its furnaces. Audubon closed off those wells with metal walls about two years ago, creating a barrier between the metal bath and the surrounding area “to minimize any danger to the furnace operators or any bystanders that might be walking by,” explains Jim Butkus, Audubon’s president.
Other smelters responded with zero-tolerance policies under which an entire load is rejected if a single air bag canister is discovered. IMCO Recycling Inc. (Coldwater, Mich.) made zero-tolerance its policy this past January, accompanying that rule with a new inspection effort as well as an extra level of processing on certain incoming scrap, says Dave Riddell, director of purchasing, metal management.
IMCO always inspected incoming shipments, Riddell explains, but the procedure used to involve dumping the material on the ground and then sorting through it with a material handler. As the number of canisters in shipments began to rise in recent years, that dump-and-inspect effort caused problems and delays when an air bag canister was discovered after the supplier’s truck had already left, Riddell says. In response, IMCO began “walking the truck,” a procedure in which an employee walks over the load in the open truck to visually examine the shipment.
Though this allows the smelter’s inspector to look over only the uppermost level of scrap, such examinations have found canisters and resulted in rejections, which reduces the number of times a truck must be called back to retrieve a dumped load, Riddell says. IMCO also dumps and examines the shipments that pass this initial truck-walking inspection, and it doesn’t hesitate to reject a load and call back the truck if a single canister—even a deployed one—is found in the material. While IMCO hasn’t experienced any furnace explosions from deployed canisters, the firm rejects them anyway “because any type of canister is not tolerable according to the policy,” Riddell notes.
As an extra safety precaution, IMCO will run material through its own shredder to chop up any undiscovered canisters into pieces small enough that they won’t cause problems in the furnace. This additional processing mainly shreds nonferrous material that comes directly from auto shredders. Shredder residue that’s processed through a heavy-media separation system before being sent to the smelter usually doesn’t need to be reshredded, Riddell explains.
For that reason, IMCO has also increased its purchases of material from heavy-media separators and decreased its purchases directly from auto shredding operations, though there are exceptions. Specifically, auto shredders that use their eddy-current systems to produce a “long-throw” product do manage to keep canisters out of their shipments, giving IMCO trust in their product, Riddell says.
No system is perfect, though. Audubon Metals operates its own heavy-media separation system yet still needs to put pickers on a line to remove canisters just before the material is introduced to a furnace, explains Butkus.
Recyclers Responding
Though the problem of canisters in scrap shipments seemed to be getting worse a few years ago, several smelters say they’ve seen a great improvement more recently. Not long ago, Audubon received a couple of hundred pounds of canisters every month, notes Butkus, whereas today his people usually find less than half that much. Finding canisters is “more the exception than the rule today,” he says.
Other smelters report similar progress by their scrap suppliers, an improvement they credit to a number of factors, including their own policies of rejecting canister-containing loads, efforts by the scrap processing industry to keep canisters out of shipments, as well as ISRI’s recent revision of its Twitch specification for fragmentized aluminum scrap, which was rewritten this April to exclude “air bag canisters, or any sealed or pressurized items.”
Audubon’s Butkus—who prefers to downgrade shipments that contain canisters rather than reject a load entirely—believes the zero-tolerance stand taken by various smelters “woke a lot of people up and certainly put the onus on the auto shredders to do a better job of assuring that their product is canister-free.” Even some processors understand the rationale behind the rejections.
“I could argue with the secondaries about a lot of different rejects for different reasons, but quite honestly this is one where you can’t argue,” notes Randy Goodman, director of nonferrous marketing for Hugo Neu Schnitzer Joint Ventures (Jersey City, N.J.). Such rejects make sense, he explains, “because if they find one air bag [in a shipment], there might be more.”
Hugo Neu is one shredder operator that produces the sort of long-throw product that smelters such as IMCO find acceptable. Basically, long-throw is generated by operating an eddy-current system so that the heavier, denser air bag canisters fall short of the collection point for desired aluminum scrap. In addition, any shipment destined to go straight to a secondary smelter—without undergoing heavy-media separation—will be hand-picked, with increased inspections both at the time of production and before loading, Goodman says.
Other suppliers have added pickers and even widened the conveyors coming off their eddy-current systems so that the material is spread over, say, a 5-foot belt instead of just a 2-foot belt, making it easier to find and remove canisters, notes IMCO’s Riddell. Another useful approach was identified by Bill Monaghan, senior purchasing manager for secondary smelter Wabash Alloys L.L.C. (Cleveland), which also has a zero-tolerance policy. Monaghan recalls one supplier who was certain his shipments didn’t contain any canisters because material had been hand-sorted—until Wabash spread out a load and let him see for himself. This scrap processor then put in a special bonus program. “For every load that wasn’t rejected because of air bags, they put money in a pool,” explains Monaghan, “and for every load that was rejected, a huge amount came out of that pool.”
The monetary incentive seems to be working, he adds, “because we’ve only had one load from them in the last year that was rejected.”
Reshredding canisters to break them down into smaller pieces can also help, as can sending the canisters through a drying process to eliminate moisture, a process that can reportedly deploy the canisters if done at high enough temperatures. Neither effort works all the time, however. Huron Valley, for instance, experimented with drying but didn’t get good results, says Larry Berry, so the company now reshreds. Newell Recycling of Atlanta Inc. (East Point, Ga.), on the other hand, abandoned reshredding after sending the same batch of canisters through its equipment several times without success.
Installing smaller shredder grates might improve the chances of breaking apart canisters, some suggest, but Frank Goulding, Newell Recycling’s vice president, has another concern. Newell Recycling runs its own heavy-media separation plant, which is where the unshredded canisters are sorted from the shredder residue. Though the canisters that make it through the auto shredding process on the first pass often remain easily recognizable, Goulding wonders if repeated attempts to reshred them will change their appearance enough to make it harder for sorters to identify the devices, which in turn increases the possibility that canisters will end up in aluminum shipments.
Others worry that reshredding undeployed canisters in one large batch—to avoid potentially contaminating other material with sodium azide—could renew concerns over shredder explosions and worker exposure to sodium azide given the volume of canisters that might be processed simultaneously. Such concerns are legitimate, notes Audubon’s Butkus, who says his operation minimizes the risks by reshredding a small number of canisters within a much larger overall load of aluminum.
An Uncertain Future
Despite the scrap industry’s apparent success today in responding to smelters’ concerns over air bags, the challenges presented by these safety devices aren’t going to go away and potentially will only expand. As noted before, the number of air bags per vehicle is growing. So, too, are the sizes and shapes of these devices, which will only make it more difficult for sorters to recognize all the different types of air bag canisters in future end-of-life vehicles.
The material in the canisters is changing as well. Whereas approximately 80 percent of the canisters manufactured in the early 1990s were made of aluminum and 20 percent from steel, those numbers completely reversed in the second half of the decade, noted ReMA President Robin Wiener in a 2001 speech to steel manufacturers. Thus, she stated, “by 2005 the large majority of these units will be made out of steel and may pose a threat to steel mill melt shops.”
Though some air bag manufacturers are starting to use less-toxic propellants to deploy the air bags, that won’t make much of a difference if the sealed canister still makes it intact into a smelter’s furnace, industry watchers note.
Likewise, some see China’s huge labor pool as the hand-sorting solution to getting canisters out of nonferrous shredder residue. Hugo Neu’s Randy Goodman, however, cautions against “coming up with a solution to a problem by pushing that problem onto another country.” In other words, sell nonferrous shredder residue to China for marketing reasons, he says, not to solve a potential safety or environmental concern.
Some see the heavy-media separators as the best point at which to capture canisters. But Huron Valley’s Larry Berry challenges the fairness of “putting the onus on someone downstream who bought the scrap.” Instead, industry watchers see the automakers themselves as the ones who need to find a solution.
Among the ideas being floated within the recycling industry is a centralized connection system to simultaneously deploy all air bags prior to dismantling a vehicle, as well as a system to let shredders visually verify that such deployment has taken place, even if the vehicle is already flattened. Japanese automakers are reportedly developing such a simultaneous-deployment system, and at least one U.S. carmaker seems to be considering the idea, says ISRI’s Scott Horne.
Such systems could help solve many of the issues surrounding air bags, but certainly not all (don’t forget the
concerns over moisture in already-deployed canisters). Moreover, these innovations are years from being widely implemented and even farther from showing up in the recycling stream, notes Randy Goodman.
“We have to work on solutions for today and long-term solutions for tomorrow,” he stresses. •
Robert L. Reid is managing editor of Scrap.
More air bags in cars has meant more air bags in the scrap stream, posing safety concerns for scrap processors and consumers. Here’s how the industries are meeting the challenge.