Venting on the Subject of Clean Shop Air

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HomeResourcesWhite PapersVenting on the Subject of Clean Shop Air

Venting on the Subject of Clean Shop Air

If a company is laser or plasma cutting, its management should take a long, hard look at its ventilation practices.

Have you ever been in a metal fabricating shop that has the classic haze hanging just below the ceiling? It’s an image that continues to dog the industry as it tries to recruit a new generation into its ranks. Unfortunately, that picture is still reality in some work environments even today.

Shop owners likely aren’t trying to create an unhealthy workplace. They just haven’t been educated on the need for proper ventilation for thermal cutting operations.

In all likelihood, those shops have made the investments to ventilate welding fumes. The media has publicized the ongoing legal challenges for the welding industry brought by plaintiff attorneys looking to link exposure to welding fumes with illnesses such as Parkinson’s disease. So companies have to know that they need to protect their welders as much as they can.

When it comes to older thermal cutting equipment, however, the same companies might have antiquated ventilation equipment or none at all. There’s really never been a concern about the haze generated from the operation, so what’s the concern now, right?

Think again. These are five questions that every shop should ask itself about its ventilating efforts regarding regards thermal cutting operations, such as laser and plasma cutting.

1. Why Should My Company Be Concerned

Now Simply put, a company should be concerned about its employees. That concern should extend to the work environment, which can be polluted with large amounts of particulate generated from thermal cutting activities.

Think about it. If you have a 260-amp plasma cutting machine cutting ¾-inch plate without proper filtration equipment, the facility would fill with a haze in a short five minutes. The indoor environment actually would be worse than a welding shop that fails to ventilate its fumes properly.

If your company has invested in filtration equipment in the past, has it kept up with the latest upgrades in technology? Power supplies can generate 400 amps of power today; these higher amperages produce a wider kerf, generating much more metal displacement. Cutting tables that used to have a single head now have multiple heads on them, which might leave the original filtration installation struggling. With the advent of technology such as rack-and-pinion drives, gantries move much more quickly than they did in the past, and faster cutting means much more metal cut per hour. Tables are much larger today as well, with one table in the Midwest reaching up to 300 feet long; was the filtration upgraded with the new, larger table?

Of course, liability needs to be discussed as well. Exposure to certain compounds may not be an issue today, but may well be an issue tomorrow.

For example, manganese exposure likely will become more tightly regulated in the near future. The gray-white metal, which resembles iron, is widely used in steelmaking—particularly in stainless steel formulations and certain aluminum alloy. Overexposure to the element has been linked to nervous system damage in humans.

The potential risks linked to manganese exposure are not recent discoveries. Manganism was coined in the late 19th century to describe Parkinson’s disease-type symptoms found in miners and smelters who had been exposed to manganese. Burgeoning class-action lawsuits are been the new developments that should force metal fabricating management to realize the need for good filtration of thermal cutting activities.

Right now the Occupational Safety and Health Administration (OSHA) standard for permissible exposure limit (PEL) for manganese fume is 5 mg/m3, which is based on an eight-hour time-weighted average. The threshold limit value for manganese, determined by the American Conference of Governmental Industrial Hygienists (ACGIH®), a collection of occupational and environmental health professionals and safety officials, is 0.2 mg/m3. This numeric guidance should be noted because ACGIH limits often heavily influence OSHA when the time comes for revisiting PEL standards.

For those who are skeptical that OSHA would enact such a dramatic change in PEL standards, they only have to look back at the new standards for hexavalent chromium. The new OSHA PEL is 0.005 mg/m3 per eight-hour time-weighted average. This is down from the previous PEL of 0.052 mg/m3 that existed prior to February 2006.

2. How Do I Know If I Have a Problem?

Don’t rely on educated guesses. Don’t rely on the manufacturer of fabricating or ventilating equipment. Hire a third-party inspection firm, such as Bureau Veritas.

For a fee, the company will come in and set up monitors throughout your facility. Over an eight-hour period, the monitors gauge air quality. Upon completion of air monitoring, the company inspects the air filters and analyzes the contents. From there, areas of concern can be identified in the facility and discussion of remedying the situation can begin.

If you’re worried about your company having to pick up the tab for such testing, contact your insurance company. It may be interested in proactive steps that protect your company from having to cover huge payouts if something goes wrong in the future.

3. What Type of Filtration Setup Makes the Most Sense?

The key is air-to-cloth ratio. For thermal cutting operations, that means 1-to-1—1 square foot of filter media for a 1-cubic-foot-per-minute (CFM) application. For more aggressive environments where a shop might be cutting really thick metal and having longer periods of uptime, that ratio is 0.5-to-1. So a shop with a 2,000-CFM application would need 4,000 sq. ft. of media to stay on top of the cutting. The leader in welding air filtration 888-robovent You might opt for a 1.5-to-1 or a 2-to-1 ratio to minimize initial investments, but the cartridge filters are going to load much faster as they struggle to keep up with the cutting. As a result, the maintenance person is going to have to replace filters much more frequently, and the shop floor will have to schedule breaks between individual sheet cuts so that the cartridge filters have a chance to shed particulate with controlled pulses. 4. What Maintenance is Necessary to Maximize Ventilation Efforts? For a cartridge filter to have a nice, long life—six months to a year—the particulate matter has to get out of the pleat and into the collection device. This is accomplished with a periodic back-flush of compressed air that is sent through the filters, clearing them of particulate, which then falls into a bin for disposal. So time has to be allotted for “pulsing” to occur. If filters load up and airflow decreases, the filters become damaged and the system is unable to work properly until new filters are installed. Replacing filters can turn into a costly exercise. If filters have to be replaced every six weeks, you run the risk of spending several thousands of dollars, depending on the system size of course, on an annual basis. If given the opportunity, cartridge filters will do the job more than adequately. They are often rated 99.9 percent efficient and filter particles down to 0.5 micron. 5. Are There Any Other Safety Issues to Consider Other Than the Threat of Breathing in Metal-laced Fumes? For those metal fabricating shop cuts aluminum, you should realize the danger that aluminum dust presents. Aluminum is a reactive, flammable solid. Bulk aluminum metal is not combustible, but the hazard increases as the aluminum particle size decreases. Aluminum dust in contact with water may heat spontaneously. The reaction between the two substances creates flammable hydrogen gas as a byproduct, which can create a very dangerous explosion particularly if the fire occurs in a confined area. Aluminum dust that results from laser cutting operations that use nitrogen as an assist gas is especially risky because it’s pure aluminum. Aluminum cut without nitrogen turns the aluminum into an oxide, which is not as dangerous. A mixture of aluminum and steel dust also can create a problem. The steel dust can act as an ignition for the aluminum dust and trigger an explosion. That’s why it’s important that ventilation equipment have spark arrester controls and explosion vents if your shop is going to process multiple metals on the same equipment. Some metal fabricators actually have two dust collectors with a converter valve for aluminum and steel cutting, but that setup is still rare. Pat