Weld fume management, step by step

Weld fume management has always been a concern for busy welding shops, but with new American Conference of Governmental Industrial Hygienists (ACGIH) recommendations being passed into law in many provinces a few years ago, the ability to meet strict manganese fume targets in particular has pushed shops to change their approach to fume management substantially.

Basically, the regulations require that exposures to manganese in welding fume be kept below 0.1 mg/m3 for inhalable particles and 0.02 mg/m3 for respirable particles. This represents a ten-fold reduction from the previous TLV of 0.2 mg/m3.

Of course, the importance of fume management can’t be stressed enough.

“Weld smoke is a pernicious little evil out there because it’s such a fine particle,” said Tom Miller, regional sales director for Canada and central U.S. at Donaldson Torit. “It’s an oxidized metal particle that tends to remain aloft in the plant atmosphere very easily, which allows it to flow everywhere and get into the surface of everything in a facility. These are superfine particles in the range of 0.1 to 1 micron that are highly respirable.”

The question is, how should a company proceed to find the best solution for their needs? Ultimately, no single system that will solve all your weld fume management challenges on its own, but as a number of experts have explained, the variety of tools available to reduce operators’ weld fume exposure continue to grow.

PPE

Eric Sommers, product manager for weld fume controls at Miller Electric Mfg. Co., stressed that if a shop has concerns about its weld fumes, it should first engage an industrial hygienist to do sampling work in the facility.

“Once you understand the exposure you are dealing with, then you can work through the generally accepted occupational health and safety hierarchy of controls to get to a solution that is appropriate for occupational health and safety, and what is feasible for your budget,” Sommers explained.

Although personal protective equipment (PPE) is often touted as the very last resort for weld fume management, many shops adopt this first to protect the most exposed immediately while they assess other options that will be more practical in the long term. In the long term, of course, employers and welders should turn to PPE (a PAPR - powered air purifying respirator - or other similar air-supplied respirator) only if it has been determined that other methods of controlling fume are insufficient to keep the exposure levels below those mandated by the regulations.

While the combination of a PAPR with a welding helmet can be heavier than standard helmets, Sommers noted that even this technology is being advanced to make it more comfortable to wear on the job. Miller’s T94 series helmet, for instance, has been designed to be lightweight and better balanced, while also providing customizable airflow.

Employers and welders should turn to PPE (a PAPR - powered air purifying respirator - or other similar air-supplied respirator) only if it has been determined that other methods of controlling fume are insufficient to keep the exposure levels below those mandated by the regulations. Photo courtesy of Lincoln Electric Canada.

“The airflow has been split at the back so that the air actually targets either side of the face rather than running down from above your face,” said Sommers. “It’s also been made adjustable so that you can change where the air blows on your face for your personal comfort.” So while wearing PPE isn’t ideal, it can be made manageable with the right technological applications.

Weld Wire

Regarding the hierarchy of controls, the substitution of one technology or material for another can make a significant difference for operators. One of the newest advances being developed is low-manganese wires.

“A lot of welding engineers are very reluctant to adopt this technology because it is so new, but we are starting to see it being used in more non-critical applications,” said Robert Ritchot, district manager for Lincoln Electric’s Winnipeg office. “It has been a few years since they were first introduced and they are starting to gain acceptance. However, they do have their limitations. Some require only high-argon gases, for instance. But there is a large market that can benefit from them.”

Sommers noted that Hobart’s Element™ low-manganese wire reduces manganese exposure by as much as 60 to 90 per cent. “That’s in lab conditions, of course, but it can be a very good start in reducing manganese exposure,” he said. “You still require some manganese content for the toughness that welds require.”

Although it will likely take shops longer to adopt low manganese welding wire, it’s a relatively economical option. It can be as simple as merely switching wires, but Ritchot stressed that such a change should first be cleared with your welding engineer.

Fume Guns

Another popular solution being adopted in the field is welding fume guns that collect the fume at the nozzle.

“They are now as light, if not lighter, than traditional guns because they can use the cooling effect of the suction to cool the gun,” said Ritchot. “The newest technology uses standard gas nozzles on the guns that allow the fume suction system to be further away from the fume to minimize the risk of gas integrity issues. For instance, the suction point might be 65 mm away from the nozzle, whereas it was previously positioned just 30 mm away, which can cause trouble with welds, particularly in tight corners.”

Technology has evolved quickly within this space. All major equipment providers have come up with and are refining these designs, from Lincoln’s Magnum® PRO fume guns, to Tweco’s Smoke Master® 250, to Bernard’s FILTAIR™ fume extraction gun.

Weld fume arms can be problematic when they have to be moved regularly to follow a weld. Miller Electric’s Capture 5 system was designed to create a stronger draw for a larger area. Image courtesy of Miller Electric Mfg. Co.

However, Ritchot emphasizes that while a fume gun may be part of your overall welding fume solution, a fume gun by itself may not remove all of the welding fume.

Inverter Technology

Modern inverter technology, which allows you to create a pulse waveform that stabilizes arc length and reduces spatter, can create a cleaner weld while producing less fume.

“By controlling the arc transfer through this new waveform technology, you may be able to improve your overall fume management, including your manganese exposure,” said Ritchot.

Ritchot also notes that if you start using an advanced pulse waveform, you will generally have to switch to a wire with a larger diameter because it often lowers your voltage. You have to maintain the current to make the weld similar to that which you would get using a smaller diameter wire.

Fume Extraction Arms

Fume extraction arms can be very effective tools provided they are properly positioned for the work at hand. However, they may not be appropriate for all welding environments and projects, so an analysis of your specific welding situation is necessary.

“Welders may resist moving an arm along a fixed part all day, but the local exhaust ventilation units that are currently available can make this easy to do,” said Ritchot. “But for those situations when it may not be feasible to continuously move the fume extraction arm, welders can consider other engineered fume extraction solutions, as well as some of the other solutions mentioned here, to ensure welder safety,” continued Ritchot.

For those looking for a fume extraction arm that has a bit more power, technology is being developed to address that problem.

Miller, for instance, has developed what it calls its Capture 5, which resembles a traditional mobile fume extractor but has a capture distance of up to 5 ft.

“You can think of it as a double-walled pipe,” said Sommers. “You’ve got the inside pipe that acts as the intake for the fumes. That air is brought to a filter. Then the exhaust air, instead of being blown out the back of the system, is blown out through the hood between the double wall. It exhausts at a 90-degree angle from the capture hood, creating a negative pressure zone around that hood, which helps create a collection zone up to 5 ft. away from the hood.” With such an extension of the fume arm’s collection capability, there is less need to move the arm.

“The arm interaction is really the biggest pushback from a safety perspective,” said Sommers. “With this you get better compliance because the operator doesn’t have to move the arm very often, if at all, and better productivity for the same reason.”

Ambient Fume Collectors

While having the ability to collect fumes right at source is the ultimate goal for any shop, the two main methods mentioned previously have their downsides. An ambient fume extraction system is by no means a fool-proof system either, but if it is properly maintained, it is a system that the welders themselves don’t have to think about when they go on the shop floor.

“There is no one best solution,” said Donaldson Torit’s Miller. “Source-capture systems are sometimes difficult to apply in the field because most welding is happening on large weldments that can’t be contained successfully. And with fume guns, the hose carries weight, which can become a fatigue point. An ambient system, meanwhile, is set up based on the physical geometry of the space of the weld shop, and will take into consideration ergonomic conflicts such as bridge cranes potentially conflicting with airflow and ducting.”

Like other welding-related technologies, ambient fume collectors have been refined to be less obtrusive on shop floors. They can either be ducted systems that carry all the fume to a remote dust collector, or modular systems in which the air is filtered in one fully integrated system on the shop floor, with numerous such systems being placed where necessary.

Miller said that some shops are finding novel methods to contain and extract weld fume to manage the cost of such systems.

“A large equipment manufacturer in the Midwest that welds truck chassis-sized weldments had a welding bay that was surrounded on three sides by an assembly area, cutting and forming, and a series of paint systems,” Miller explained. “To avoid airborne contaminants moving into these other areas, they hung curtains from the roofline down to a level that would still allow forklift traffic but isolated the weld fume in that area. That is a space 100 ft. by 300 ft. in a plant that is probably 12 times that size. We only had to filter the air in that one area, which meant a large reduction in total airflow through the extraction system and smaller fans, controls, ducts, and filters.”

Miller suggested that with an ambient system you consider carefully how your processes work, what the goals of the fume extraction approach will be for the plant, and what other processes need to be considered at the same time.

“A shop may be highly focused on weld fume, but there may be ancillary processes that should also be addressed in a rollout,” Miller said. “For instance, grinding and finishing also produce airborne contaminants and also need to be considered.”

Miller’s advice is to ensure that the ambient system’s filter media is up to the job of capturing these small particulates. “Some systems will extract air efficiently, but due to the inefficiency of their filter media can return up to 30 per cent of the contaminants back to the plant atmosphere,” he said. “Look for a filter media that is efficient to 0.3 micron that can also sustain service for well over 2,000 hours.”

It’s also important to ensure that a system is easy enough for your team to maintain. “Without the right maintenance, a system can eat up horsepower while doing little to nothing for the facility,” Miller said.

Ultimately, it will likely be the implementation of some combination of several of these technologies that will enable you to comply with exposure limits and create a cleaner weld shop in your facility. Make sure you find the right mix for your shop.

Editor Robert Colman can be reached at rcolman@canadianfabweld.com.

Donaldson Torit, 800-365-1331, www.donaldsontorit.com

Lincoln Electric Canada, 416-421-2600, www.lincolnelectric.ca