By Craig Widtfeldt, RoboVent
The automotive industry has made tremendous progress towards greener, more sustainable manufacturing processes. But how green are robotic welding cells?
Robotic welding, by its nature, produces large volumes of toxic fumes that are dangerous to both human health and the environment. Manufacturers engaged in robotic welding of automotive parts must have an effective air quality system in place to meet OSHA (Occupational Safety and Health Administration) regulations. If these systems are not well designed, manufacturers may be wasting energy and putting their plant out of environmental compliance. Here are five steps to make the air quality systems more energy efficient and sustainable.
1. Opt for Filtration Over Exhaust
Typically, robotic cells for automotive parts are covered with a hood to contain welding fumes. This air must be removed from the hood so it does not build up and seep out into the ambient air of the facility. There are two main methods of removing weld fumes from the robotic hood:
Exhaust systems pull contaminated air out of the hood using ventilation fans. Clean(er) outdoor air must then be returned back to the facility to avoid negative pressure build up.
Filtration systems pull contaminated air through a filter media and return clean air back to the facility.
Exhaust systems are cheap to install, but generally not the best option for the large volumes of fumes produced by robotic welding applications. If the facility is heated or air conditioned, exhaust systems are literally blowing energy through the roof as indoor-temperature air goes out and outdoor-temperature air comes in. Exhaust systems also release toxic emissions into the environment, potentially putting the facility out of environmental compliance.
That’s why most robotic welding applications use filtration dust collection systems. Dust collectors filter dangerous particulates out of the air so air can be safely returned to the facility. This makes the air quality system more energy efficient and meets environmental standards and best practices for toxic weld fumes.
2. Size Fume Hoods for Maximum Capture Efficiency
CFM [cubic feet per minute] is one of the primary drivers of energy costs for dust collection: the more air the system needs to move, the more energy needed to move it. Greater airflow requires a larger (and more expensive) machine with a more powerful blower. The CFM required to control particulates produced by robotic welding is directly tied to the size of the openings into the hood used. The smaller the openings into the robotic welding chamber, the more airflow needed to capture the smoke inside the enclosure. The hood must cover the entire the robotic cell, and then enclose it on all sides so that there are the least amount of openings possible into the enclosure. Sizing the hood correctly for a given robotic welding application and making sure it is fully enclosed will improve capture efficiency and minimize opportunities for fumes and particulates to escape into the ambient air throughout the facility.
3. Size Filters to CFM
CFM drives filter sizing in addition to energy consumption. Air quality system designers look at filter velocity (or “air-to-cloth ratio”) to determine how much filter media is needed for a given application. This is the ratio of CFM to total area of filter media. The more air moving through the filters, the larger the square footage of filter media required.
Getting this ratio right will make the robotic welding system more sustainable. If there is not enough filter area, particulates are driven deep into the filter media before they can be pulsed off, quickly clogging the filter. This means higher energy costs as dust collectors try to compensate for filter loading as well as more frequent filter changes. On the other hand, systems with too much capacity will drive up initial costs and ongoing energy consumption. An air quality system specialist can help find the right balance.
4. Look for Energy- and Filter-Saving Technologies
|Clogged filters drive up energy costs and reduce collector effectiveness. Look for filter-saving technologies like dynamic pulse systems to extend filter life. Click to enlarge.|
Today’s dust collectors can be equipped with a variety of features to save energy and extend filter life. Here are a few:
High-performance blower wheels and low static pressure designs can significantly reduce the energy required to move air.
Pulsing systems extend filter life by blowing the particulates off the surface and into the collection bin before they become entrapped in the filter media.
Variable Frequency Drive (VFD) is an energy-saving feature that adapts blower speed to compensate for filter loading.
Smart control systems such as RoboVent eTell® reduce energy use and maintenance costs by making automated system adjustments.
5. Build Air Quality Into Production Lines From the Start
Weld fume control should never be an afterthought. Ideally, air quality systems should be planned in tandem with production lines. Air quality system designers can help evaluate physical concerns, such as floor space and the use of overhead cranes, and select the right approach for the volume and type of fumes produced. Options for robotic welding cells include:
Traditional ducted systems, in which ducts attached to each hood carry weld fumes to a centralized dust collector. These systems provide high energy efficiency because they require fewer dust collectors to do the work. Selecting a system with automated gating that closes off sections when welding cells are not in use can save even more energy. However, ducted systems may not provide the flexibility needed if production lines change often. The RoboVent Grid™ system is built with standardized, modular components to provide maximum flexibility in a ducted robotic welding system.
For greater flexibility, individual collectors can be directly attached to each robotic welding cell. If floor space is a concern, space-saving designs such as RoboVent Spire™ can help. Individual units may also be more desirable if overhead cranes and equipment or low ceiling heights make ductwork impractical.
Ambient systems are generally not used with robotic welding because of the volume of weld fumes produced. For robotic welding of small-to-medium sized parts, as is typical in automotive, it is generally much more energy efficient to put robotic welders under a fume hood. However, there are some applications where hoods may be impractical. In these cases, a traditional ducted push-pull system or a ductless ambient system such as RoboVent Vista360™ can provide fume control for an unenclosed space with several robotic welders. For some robotic applications, ambient air quality control can supplement a fume extractor tip that collects heavy fumes right at the torch head.
|Hoods are the most efficient method of fume extraction for most robotic welding of small- to –medium sized parts. Source: Robovent. Click to enlarge.|
|Applications that cannot be hooded may use fume extractor tips, ambient air quality control systems, or a combination. Source: Robovent. Click to enlarge.|
Considering these factors up front will help manufacturers choose the most energy- and cost-efficient system for their needs. An experienced air quality system designer can help make the right choices to save energy, reduce maintenance costs and make robotic welding facility more sustainable.
About the Author. Craig Widtfeldt is the Executive Technical Director at RoboVent. Craig has been designing, installing and servicing fume extraction systems for more than 20 years. He brings extensive experience in designing large, custom systems for world-class manufacturers, with a particular focus on source capture solutions and high-risk applications such as stainless steel welding processes.