THINKSTOCK
PART 2 OF A 2-PART SERIES
Part 1  in the October issue of Today’s Motor Vehicles looked at how poor indoor air quality (IAQ) can negatively impact productivity, product quality, and worker health.
Part 2 covers IAQ mitigation options and the benefits 
of implementing a qualified, well-designed system.

Appropriate indoor air quality (IAQ) engineering controls are essential to protect worker health and maintain regulatory compliance. There are a lot of options for automotive manufacturers when it comes to dust and fume collection, from ambient air filtration systems to an array of source capture options. The best solution for any manufacturer depends on a combination of processes and facility characteristics.

IAQ mitigation options

No matter the processes used, IAQ mitigation options fall into a few broad categories. Manufacturers can think of these along a two-dimensional matrix:

  • Filtration vs. exhaust: Exhaust and makeup air systems push dirty air out of the facility and pull clean(er) air in. If particulate volumes are low, and heating and cooling costs are not a consideration, this option is inexpensive and easy to implement. However, if makeup air must be heated or cooled to indoor temperatures, exhaust systems can drain energy budgets. Depending on the type and volume of particulates, they may also put the facility out of environmental compliance. Filtration systems pull dirty air into a dust collector where particulates are filtered out before clean air is returned to the facility. Filtration is usually the better option for facilities with high volumes of particulates and temperature-controlled indoor environments.
  • Source capture vs. ambient: Source capture systems collect particulates close to the source as they are generated, before they escape into the ambient air. Ambient systems turn over air for the entire facility, suitable for automotive manufacturing processes that do not produce a large volume of particulates. For processes that produce larger volumes of particulates, source capture will be cheaper when it is feasible; the less air needed to move, the lower equipment and operating costs will be. Ambient systems can also be used with source capture solutions for secondary air quality control.
Source capture

Source capture is the best option for many automotive manufacturing processes, especially Tier I and Tier II suppliers manufacturing smaller parts. The best option depends on the type of process (e.g. dust-producing processes such as cutting and grinding, or fume-producing processes such as welding and plastic molding), the volume of particulates, the size of components, and whether human exposure is a concern.

  • Hoods and canopies can be placed over top of equipment such as robotic welders, injection molding machines, and laser cutting stations. Dust and fumes are contained within the enclosures, making it easy to capture and collect.
  • Fume arms use directed airflow to pull contaminated air from the immediate area. They work best for weld fumes and other thermally-generated fumes that rise in the air. Fume arms have a narrow collection zone, so they should be used for small, stationary components that allow the arm to be close to the source.
  • Backdraft or downdraft tables work well for manual grinding, cutting, or small-component welding. Like fume arms, backdraft intakes are best for thermal fumes. Downdraft tables can collect heavier dusts that tend to fall.
  • Fume guns offer source capture for many manual welding applications. They add fume extraction to the tip of the welding torch, so fumes are collected where they are generated.
Ambient options

Ambient filtration can be used as a stand-alone system when working with larger components that cannot be hooded, or as part of a hybrid system that also includes source capture. There are three main options for ambient filtration systems.

  • Ducted push-pull systems rely on a system of ducts near the ceiling that creates air currents in the building, moving air across the area. This continually dilutes the contaminated air with filtered air.
  • Ductless systems rely on standalone dust collectors that sit on the factory floor, creating their own circular local airflow patterns, pulling dirty air in and pushing clean air out. These are easier to install since they do not require overhead ductwork, but they do require some floor space.
  • Ductless, ceiling mounted systems, such as the RoboVent Vista360, combine ductless systems with the floor space savings of a traditional push-pull system and may work better in facilities with overhead cranes.
Automotive manufacturing

For each manufacturing process used in motor vehicle construction, there is a matching IAQ solution.

  • Welding: High-production robotic welding of smaller automotive parts is usually done under a hood. For larger weldments, robotic fume extraction is sometimes an option. However, resistance welding of frames and body components generally requires an ambient solution. Manual welding for small parts can be done on a backdraft table or beneath a fume arm to pull fumes away from the welder. For large manual weldments, a fume gun like the RoboVent Extractor may be best.
  • Machining: Machining precision automotive components usually involves lubricants. Metalworking fluids can create dangerous oil mists when heated by high-speed machining processes. Specialized collection equipment and filters must be used for oil mists as regular filters quickly become saturated and ineffective when oil mists mix with dry particulate. Packed-bed filters, also called coalescing filters, are most effective for most oil mists.
  • Cutting and grinding: Downdraft tables are effective for most manual cutting and grinding. Laser and plasma cutting produce large volumes of dust that must be controlled to avoid damaging equipment and to reduce combustion hazards. A hooded enclosure, ducted to a high-powered dust collector, can keep dusts under control.
  • Thermoplastic injection molding: IAQ planning must consider the process from raw material handling to final production of components. Plastic dusts are dangerous and combustible, so preventing buildup in the air is essential. High-powered ventilation can clean the air in areas where raw pellets or powders are moved, poured, mixed, and processed. If dusts can be contained to a smaller area, source capture filtration systems can use an intake plenum or hood over the processing point, ducted to an NFPA-compliant dust collector. Employees working inside the enclosed area should wear personal protection when working directly with the materials. Molding produces fumes rather than dusts, so an ambient filtration system can collect fumes as they rise. If the plastic processing area cannot be fully enclosed, partitioning and negative air pressure can create local containment, preventing fumes from escaping.
  • Rubber manufacturing: Ambient filtration is generally needed for rubber manufacturing to satisfy health and safety and environmental regulations regarding volatile organic compounds. Source capture can sometimes be used for enclosed processes.
Cost control

An experienced air quality engineer can help manufacturers find the best solution for their specific applications and challenges. Computer modeling can help companies avoid over- or under-engineering solutions in cost and effectiveness.

RoboVent’s VentMapping process optimizes placement of source and ambient capture equipment to meet the company’s air quality goals. Questions to ask during this process include:

  • What processes are used (e.g. machining, injection molding, grinding and polishing, welding), and what is the volume of particulates produced?
  • What are the sizes of components? Can processes be contained under a hood or on a bench?
  • Are processes manual or robotic?
  • When, where, and how are humans exposed to particulates?
  • What is the chemical makeup of the particulates, and what are the permissible exposure limits (PELs)?
  • Are the particulates combustible?
  • Where are the particulates generated, where do they end up in the facility?
  • What are the facility’s airflow patterns, and what factors influence them (e.g. HVAC or ventilation systems, facility layout, etc.)?
  • What mitigation systems are in place already, and how are they working?
  • How much flexibility is needed to reconfigure manufacturing lines?

Maintaining a safe and healthy manufacturing environment shouldn’t break the bank. A strategic approach to air quality system design can help vehicle makers get the best value for their money and take IAQ off their list of things to worry about.

RoboVent
www.robovent.com

About the author: Craig Widtfeldt is executive technical director at RoboVent. He can be reached at 614.498.1796 or info@robovent.net.