Tech Tips: managing manganese
- February 15, 2016
Looming regulations on lower limits may pose problems in the welding shop
Dealing with welding fumes has been a common challenge in the industry for many years. However, a recent recommendation change from the American Conference of Governmental Industrial Hygienists (ACGIH) regarding acceptable levels of respirable manganese (Mn) levels has brought a new focus to handling welding fume. The ACGIH has lowered the recommended respirable manganese exposure limit by a factor of 10, from 0.2 mg/m^3 to 0.02 mg/m^3.
Since Canadian provinces look to the ACGIH for guidance in setting their regulations, this is a potential issue. Some Canadian provinces are far ahead of other jurisdictions in lowering allowable respirable manganese levels, creating confusion.
Manganese is a key factor in giving steel ductility and in tying up sulphur to reduce cracking tendency. Most steels contain approximately one to two per cent manganese. However, as manganese does not travel well across the welding arc, it makes up a greater proportion of the total fume, typically in the range of five to ten per cent.
Can we afford this when productivity is key to survival?
In our experience, lowering manganese exposure levels to 0.02 mg/m^3 is not going to be accomplished with one solution on its own. The claims of many fume reduction solutions are based on an ideal or ‘used properly’ situation, which may not be realistic. Is a new welding consumable offering lower manganese levels going meet new requirements alone?
Solutions specific to the shop environment should be evaluated and tested before being implemented. Most shops will likely need two to three solutions to get where they want to be.
So, how do we do this?
First, benchmark your current exposures by conducting individual and ambient air testing by an industrial hygienist. Next, determine where you want to be in the future and develop a plan for how to get there. The best practice is to start at the source and work outwards, ending with Personal Protective Equipment (PPE) like respirators or Powered Air Purifier Respirator (PAPR) helmets. Make sure the solutions chosen will be effective in your
work environment, so test them first when possible to make sure the strategy is sound.
Here are some guidelines to help better manage manganese levels in your welding shop.
• Reduce the welding fume at source. This means evaluating and implementing alternative welding consumables and/or welding processes. Make sure to do this under the direction of a qualified welding engineer to be sure the application requirements will be met.
• Advanced Pulse Modes can significantly lower welding fumes in certain circumstances, but may reduce travel speeds. Solutions that offer welding fume reduction as well as welding productivity can pay for new welding power sources.
• Fume extraction guns are evolving quickly into lighter more accessible tools that can often reduce fume by 50 per cent or more.
• Fume extraction arms can be effective, particularly if parts are smaller. With small to medium sized repeatable parts, downdraft tables or backdraft panels of various sizes are typically more practical.
• There are also general fume extraction solutions, such as fume hoods. However, Fume Hoods often require additional lighting and are difficult to use with cranes. Hoods work well in robotic welding systems, which can be a solution in itself.
• A potentially powerful general fume control solution is a Push-Pull ventilation system. These systems filter and segregate welding fumes in the upper regions of the facility where nobody is working.
• The last option is PPE. PAPR helmets have improved over the years and can be battery powered or used on a central tethered system. These are often implemented to protect workers that are closest to the source. However, this solution is only effective for workers using the PPE, and do not protect other workers in the area.
In summary, don’t believe anyone’s claims for fume reduction unless confirmed in your application (or workplace), by an industrial hygienist. Start at source and work outwards. Solutions for welding fume reduction are specific to your environment. Spend wisely. SMT
Rob Ritchot is district sales manager for Manitoba/Saskatchewan for Lincoln Electric Company of Canada.