Looking under the hood
- Created: 2017-03-07
Raising the standards for indoor air quality requires a closer look at fume extraction considerations
by Jim Reid, managing director, RoboVent
Maintaining preferred supplier status for a top-tier automotive company like Ford requires strict adherence to occupational health & safety and environmental regulations. For manufacturers engaged in high-production robotic welding of automotive parts, balancing indoor air quality (IAQ) requirements and economic pressures can be a challenge. New options in air quality system design can help companies reduce the ongoing costs of weld fume control and ensure that their facilities meet both OSHA requirements and manufacturers’ expectations for supply chain partners.
A strategic approach to fume control can help high-production robotic facilities meet OSHA regulations while controlling costs.
Counting the costs
When evaluating options for controlling robotic weld fumes, companies need to consider not just the up-front costs of the system, but also the hidden costs that can add up over time. These costs include:
- Space considerations: For most automotive manufacturers, space is money – every square foot not directly tied to production is a loss. Large dust collectors that take up significant floor space reduce overall production efficiency.
- Energy use: The design of your air quality system has a big impact on the amount of energy it uses. Poorly designed systems increase energy costs and eat into your margins.
- Maintenance expenses: Total maintenance costs include not just consumables and parts but also the labor costs to maintain the equipment as well as production downtime. How much time will your system take to maintain each month? How often will you need to shut down production in order to maintain your air quality system?
All of these factors should be taken into consideration when calculating the total cost of ownership for an air quality system. Companies will need to balance all of these factors to make the right decision for their processes and facility.
In general, robotic welding will be conducted under a hood that contains weld fumes produced by the robot. There are two main approaches to controlling these fumes:
- Centralized ducted systems, in which multiple hoods are connected via ductwork to large dust collectors installed overhead or outside the facility
- Individual floor units, in which each hood is directly connected to a small collector
It may seem that centralized ducted systems provide a slam-dunk when it comes to floor space considerations, but this isn’t necessarily the case. High-efficiency, small-footprint dust collectors like the RoboVent Spire can handle fumes from one large or two smaller hoods and take up about the same amount of space as a wire barrel. Making the right choice requires balancing space with other considerations, including cost, flexibility and maintenance requirements.
A centralized ducted system maximizes floor space by keeping all equipment up overhead. These systems are also more energy efficient and require purchasing and installation of fewer (but larger) collectors. On the other hand, the ductwork is expensive to install, hard to reconfigure if your production line needs change and may interfere with overhead cranes or other equipment. These systems are also harder to maintain as they require ladders or lifts to clean out collectors and ductwork. And since all hoods are connected to one or two large collectors, the entire manufacturing line (or a large portion of it) will need to be shut down when units are down for repair or maintenance.
Space-saving floor units will take up a minimal amount of floor space and require purchase and installation of more individual collectors. However, they offer a high degree of flexibility: Manufacturers can easily move them when reconfiguring production lines or add another collector to expand capacity. They can also be easily maintained without lifts or ladders, and, since each unit only supports one or two robotic hoods, maintenance can be done sequentially without shutting down the entire line.
Space-saving individual dust collectors provide more flexibility than central ducted systems without giving up too much floor space.
Reducing energy costs
The total energy used by your air quality system is influenced by several factors.
Exhaust vs. filtration: Most facilities using robotic welding are now using filtration, but if you are considering a system that exhausts dirty air out of the roof instead of filtering it and returning it to the facility, you should be aware of the hidden energy costs. Exhaust-and-makeup air systems blow heated or cooled air out of the facility and suck in outdoor air that must then be heated or cooled to indoor temperatures. In very cold or very hot weather, these costs can be considerable.
Total volume of air moved: The No. 1 thing facilities using filtration systems can do to reduce energy costs is to reduce the volume of air that must be moved and filtered. For robotic systems, it is important to make sure that hoods are properly sized for the equipment and do not have air leaks. Dust collection equipment must be properly sized for total airflow needs for maximum efficiency. You need to maintain enough airflow for optimal capture efficiency; anything beyond that is wasted energy. If you are using a ducted system, consider one with electronic gates that can close off parts of the system that are not in current use. This can result in reduced operating costs of 20 to 50%, depending on production cycles.
Equipment efficiency: Dust collectors vary widely in energy efficiency. Look for energy-saving features like smart control systems that turn on or off with welding equipment or based on sensor data from air quality monitors rather than simply staying on all the time. Other energy-saving features include Variable Frequency Drive motors, which adjust blower speed to compensate for filter loading so the blower is never working any harder than it has to.
For ambient fume control, manufacturers may also want to consider new ductless celling-mounted units, such as the RoboVent Vista360, which provide the floor space savings of a centralized system without the ductwork.
Computer modeling can help companies find the most cost-effective solution for weld fume control.
Controlling maintenance costs
When it comes to maintenance, time is money. Dust collection equipment that requires frequent filter changes and other preventative maintenance may mean adding additional staff. If production lines must be shut down in order to maintain equipment, those costs must be taken into account as well.
There are several things companies can do to minimize maintenance needs.
- First, perform all recommended preventative maintenance (PM). Scrimping on PM will cost more in the long run through reduced efficiency, greater wear and tear on equipment, and unexpected downtime. If your staff does not have the time or expertise to manage required PM for the air quality systems, ask your manufacturer if they have a equipment service program that can help.
- Replacement filters are the No. 1 ongoing maintenance expense for dust collection systems. To maximize filter life, make sure you have a system with appropriate “air-to-cloth” ratio – that is, enough filter media for the volume of air you need to move. If you don’t have enough filter media to handle your CFM requirements, particulate is driven deep into the media instead of settling on the surface where it can be easily shaken off. This rapidly clogs filters, increasing energy use as well as the frequency of filter changes.
- Look for other filter-saving technologies such as dynamic pulse systems, which use multiple pulses to shake dust off filter surfaces and prevent re-entrainment on neighboring filters. Systems in which filters are oriented vertically rather than horizontally also extend filter life by reducing the amount of particulate that settles onto the filters.
- Smart control systems can also help to control maintenance costs by predicting maintenance needs and making proactive recommendations. For example, the RoboVent eTell control system monitors dust collector performance, automatically adjusts settings to optimize the equipment and tells operators when to order and replace filters based on actual performance rather than set time periods.
Balancing the initial, ongoing and hidden costs of air quality control isn’t always easy. Fortunately, companies can rely on computer modeling to evaluate factors, such as particulate size and volume, airflow patterns in the facility and other variables.
Engineers, therefore, can use the computer model to virtually consider different approaches and then select the optimal system design for their facility. This approach avoids over- or under-engineering to ensure that IAQ targets are met while controlling initial and ongoing expenses.
Understanding all of these factors and considering them in system design will help suppliers meet OSHA regulations and preferred supplier requirements in the most efficient and cost-effective way possible.