How to Select a Welding Fume Extractor

Selecting Weld Fume Extractors is easier than it might seem.
Because of the May 31, 2010 deadline OSHA has established which tightens the welding requirements on Hexavalent Chromium exposure in the workplace, much attention has justifiably been directed at the dangers of welding stainless steel. But there are many other reasons aside from OSHA welding ventilation requirements for making sure all weld operations have the proper welding air filtration and extraction systems in place for weld smoke and fumes:

  • Health of Safety - Welding as a process most commonly applies high heat to a welding rod that serves as a metal filler for fusing other pieces of metal. Many of these welding rods contain a high amount of manganese because it strengthens the metals being joined. The action of heating and melting metals produces a gas, so when welders breathe in the smoke and fumes released in many welding processes, they are taking manganese toxins into their lungs which then very quickly travel to their bloodstream. Unfortunately, manganese is not the only hazard of welding and the often related process of torch-cutting. Go to lhsfna.org to see a list of the other common toxins listed by OSHA that are released during these operations. Correctly installing weld fume extractors and meeting recommended welding ventilation requirements can dramatically reduce these risks.
  • Recruiting the Best - Welding schools are now teaching their students that along with pay and benefits they need to consider workplace safety and welding ventilation requirements when comparing job offers. Highly skilled welders often have their choice of job opportunities.
  • Savings - Selecting the right weld fume extractors can directly translate into saving energy dollars. Insurance companies are often willing to lower premiums with documented improvement of the safety risks for workers and buildings when it comes to welding ventilation requirements. And finally, industrial ventilation systems that capture and remove particulates from work areas reduce the maintenance costs of power and electronic equipment.

Factors to consider when selecting the best weld fume extractors to fit your needs.

1. Type of Welding Fume Exhaust Systems

There are three primary types of protection from welding fume extraction:

  • PPE (Personal Protection Equipment) - For welders there are several pieces of PPE that are vitally important. But for the sake of the discussion of industrial air quality, the primary piece would be respirators. While respirators offer definite advantages they will only work, perhaps more than any other piece of equipment, if they are properly fitted, maintained - and used. Although of immediate value to the individual, respirators offer no benefit to surrounding air space and other employees.
  • Source Capture - Removing welding smoke and fumes before they reach a worker's breathing space, or source capture, is the optimum strategy for meeting welding ventilation requirements regarding welder safety. Essentially, the welding fumes are collected at the arc, filtered and then clean air is discharged back into the general air space, protecting all employees. Industrial Maid's line of weld fume extractors includes many styles of portable fume collectors such as downdraft tables or ones fitted with one or two flexible fume arms. Dual configuration and HEPA filter options increase safety and flexibility.
  • Engineered Systems - As manufacturers ourselves, we have a first-hand understanding that specific operations often have unique needs when it comes to industrial welding ventilation requirements. When source capture is not practical because of piece size, access to welding cells or other application challenges the engineers at Industrial Maid are ready to help design a system of weld fume extractors that fits your process and your budget. Our RH & RHV Series Hoods, EB 56 Side Drafts, and T-Series models can be ordered in standard sizes or custom designed and fitted with final Hepa’s filters (more about filters below).

2. The Filter

The importance of selecting the best type of filters for handling welding fumes and smoke can not be overstated. Welding fume hood filters are the first line of defense for welders and others who work in the welding area, and they need to meet certain welding ventilation requirements. Advanced technology in the industrial air filtration industry means the good news is that we have more choices, the confusing part can be that we have more choices. Gauging the type of filter you need for your weld fume extractors is the single most important factor to consider when putting together a fume extraction system.

Fortunately the rating of filters and their efficiency has a science. The Minimal Efficiency Reporting Value (MERV) is the industry standard for measuring the performance of filters. Testing results determine the assignment of a MERV number which reflects a filter’s efficacy based on the size of the particles it can capture.

A variety of filter media is available in the styles of Roll, Pleat, Bag, HEPA, Carbon and Cartridge to name a few. If you have questions concerning the best choice of filters for your application, consider taking advantage of the 30+ years of experience of the engineers on staff at Industrial Maid.

3. Airflow

Air flow measurement tells you how fast air is moving, so the CFM designation of weld fume extractors translates directly to how many cubic feet of air they move per minute.

Many factors go into the mix when calculating the amount of CFM required to meet welding ventilation requirements and insure proper air quality in the occupational work environment. Room size, types of processes, number of work stations and the configuration of a building's existing HVAC system are just a few. At Industrial Maid, design engineers work along side production managers so when you consult with our staff about selecting the best weld fume extractors, you get the benefit of insider knowledge and experience.

4. Other Considerations

After the selection of the appropriate equipment and filters, there are still important secondary welding ventilation requirements and issues to consider:

  • Installation and Fit - Filter bypass is a common problem found in many industrial air filtration systems and weld fume extractors. This occurs when air moves around the filter rather than moving through the filter resulting in a decrease of collection efficiency and defeating the intended purpose of the ventilation system. A 10 millimeter gap (less than ¼ inch) between filters can lower a filter’s MERV rating by at least two levels, thereby taking a high efficiency filter and moving it to a medium efficiency filter. Industrial Maid units are designed to address this problem in two ways: 1) standard replacement filters which makes for more convenience supply and lower cost compared to other manufacturer's who use OEM filters 2) factory added gasketing, filter clips, and optional gages to monitor pressure drop across the weld fume extractors' filter banks.
  • Maintenance - No matter which style you choose, please remember that no matter how high the MERV rating of a filter---if it is doing its job of capturing particulates---it will need to be cleaned or replaced in a timely manner in order to continue meeting welding ventilation requirements. See the box below for filter performance calculations. Having a quickly accessible filter goes a long way toward making it easier for personnel to stick to a regularly scheduled maintenance routine. Many Industrial Maid units are specially designed with easy access to doors where the filters are housed; here are a few examples, M36IAC, OM36V, EB Series, and FW Series.
  • Low noise - All Industrial Maid industrial air cleaners can be ordered with full carbon steel cabinets, but if the application does not require steel, most models can be manufactured using a high density polyethylene plastic. Not only are they environmentally-friendly for those businesses looking to "build green", they also make for a much lower noise of operation.
  • Portability - Along with models that can be hung, bracketed, or free standing Industrial Maid carries a full line of Portable Air Cleaners with Single or Dual Arms and Portable Downdraft Tables.

As employers continue their search for competitive advantages in finding and keeping skilled workers, maintaining a safe and healthful environment is an appealing incentive for new and current employees. Carefully selected industrial ambient or portable ventilation systems that meet welding ventilation requirements can extend equipment life, reduce insurance rates, and help manufacturers be in compliance with stringent federal regulations.

Pressure Drop Considerations
Fall 2003 issue of Air Media Author(s): Dave Matela, CAFS, Kimberly Clark Corporation

In response to the current situation, many facility managers (FM) are either moving to or have upgraded their levels of air filtration. Some FM’s are not fully cognizant of the fact that increasing efficiency without regard to pressure drop can result in dirtier air and increases in energy usage/cost. Additionally, there is an increase risk of system malfunction, compromising overall HVAC system performance caused by reduced airflow.

Three major components to life cycle costing formula are initial investment and maintenance, energy consumption, and disposal (Chart 1). Based on operating characteristics, we know the cost breakdown is:

Chart 1

Chart 1
Because energy comprises such a large portion of the cost and because pressure drop is the precursor of this energy usage, providing clean air depends most on efficiency and pressure drop.

Even before a FM can determine what level of cleanliness they want, they must look at the capabilities of the system they have (we are assuming this is a retrofit with no new addition of HVAC equipment). Most large HVAC commercial grade systems are designed to handle pressure drops of one inch, possibly more, for the air filter resistance. Matching filter initial, final and average resistance to the system is critical for proper air filtration and air exchange rates.1 Also, providing pressure drop reading devices such as manometers or electronic pressure sensors is an absolute requirement.

Next, examine the pressure drops of various types and efficiencies of filters to find one that meets the requirements, or retrofit the filter bank or filter to include more filter surface area to lower the resistance.

The Chart 2 shows the visual on the optimal change-out point of an air filter – that point where the pressure drop increases electrical consumption and overtakes the initial cost of the filter.

Chart 2

Chart 2
The equation used to derive the optimum final pressure drop is:

Energy Consumption
(kWh)= Q ΔP t η 1000

Q = Air Flow (m3/sec)
ΔP = Avg. Pressure Loss
t = Time in Operation (hrs)
η = Fan Efficiency

Putting the numbers in this formula, FM’s can expect to find lower overall electrical usage/operating costs for those filters that have lower average pressure drops. It can help determine the best time to change-out their filters.

Summary
System pressure is critical to the correct operation of the HVAC equipment. Facility managers can look to increase their level of air filtration efficiency and provide added protection for their building, but must also keep an eye on any added resistance to the system. Air filters that provide lower pressure drops through increased media area or newer synthetic medias can achieve the desired efficiencies and save energy. Working with a NAFA CAFS to determine the best recommended filter is critical to installing the correct filter for the system. Pressure drop reading devices are essential to determine optimum performance results and filter change-out frequency. Maintaining the HVAC air filter system with the proper measuring and monitoring devices will greatly assist the FM’s with managing the building’s air filtration systems.

Pressure Drop and Electrical Cost Considerations in Filter Performance
Pressure Drop; Fall 2002 issue of Air Media Author(s): Dean Arnold, Kimberly Clark Corporation; NAFA Staff

Running a filter to the final manufacturer’s recommended pressure reading could mean you are squeezing every last penny of cost from the filter. It could also mean you just wasted more money in energy costs because of the extra time it takes to heat or cool your facility due to lower supply velocities. So how do you know when it is the optimal time to change your filters?

The following equation will apply:

Energy Cost = HP x ($/KwHr) x Hours/0.746
Where HP (motor horsepower) = Average DP x CFM/Fan Efficiency x 0.001173
Final Pressure Drop

NAFA Guide to Filtration, 3rd Edition 2001
National Air Filtration Association, page 13.2 - 13.6

By utilizing this formula, you can determine where the optimal change out time is for your particular filtration system based on your specific electric rates, hours of operation and type of filter.

References:

1 NAFA Guide to Air Filtration, 3rd Edition 2001,
National Air Filtration Association, page 13.2- 13.6

References:
1 Chart 1: Carlsson, Thomas, "Indoor Air Filtration: Why Use Polymer Based Filter Media," Filtration+Separation, Volume 38 #2, March 2001, pp 30 - 32
2 Chart 2: R.H. Avery, Optimum Final Pressure Drop, NAFA Guide to Air Filtration, 3rd Edition, Chapter 13: Owning and Operating Costs.
3 ASHRAE Standard 62-2003, "Ventilation for Acceptable Indoor Air Quality"