Dust control, inventory management and environmental stewardship are an essential consideration in the management of dry bulk stockyards, writes Claire Cowie from WeatherSolve Structures.
 
Technologies used to optimize stockyard operations are diverse and offer the ability to streamline operations, lower costs, and reduce the overall environmental footprint of a site. Of these technologies, wind fences emerge as a transformative asset for stockyards; capable of tackling hazardous dust emissions and reducing the loss of valuable product all while improving safety and regulatory compliance.
 
UNDERSTANDING WIND FENCES
Wind fences are barriers that are constructed to alter wind patterns and reduce fugitive dust. They are typically constructed by erecting a porous material that acts as a barrier between the wind and the area to be protected. In general, wind fences have two mechanisms of action to reduce dust: an upwind fence or a downwind fence. Upwind fences dramatic ally lower wind speeds and minimize dust dispersion and movement, while downwind fences act as a ‘catch’ fence for dust that is still moving. In a downwind fence, there is a small sheltered area in front of the fence that functions as a drop-out zone for dust when the fence is perpendicular to the wind direction. Some dust also passes through the downwind fence causing dust to drop out in the same manner as an upwind fence in a protected area that extends one to two shelter heights downwind. As dust erosion studies have shown, the majority of dust does not generally exceed 1m above the ground, meaning any height of a downwind fence can be effective, although this is dependent on each individual site and its dust control strategy. It should be noted that with changes in season and wind directions, an upwind fence may function as a downwind fence and vice versa.
 
The porous material that is used for wind fences allows a small amount of wind to pass through, thus substantially reducing the turbulence which is seen with solid barriers. A quality well-designed wind fence creates a sheltered area on the leeward side where the wind speeds are typically reduced by 50% to 80% depending on the shelter patterns the fence designer is working towards.
 
The aerodynamic porosity and the porous opening dimensions of the material also impact the effectiveness of the wind fence. The aerodynamic porosity is the porosity the wind ‘sees’. It is different than the visual porosity. For example, consider the 1” x 4” timber slats used on snow fences — a different type of wind fence — (with a slat, then a 4” gap, then another slat). Visually these are 50% porous. Aerodynamically, the porosity is closer to 25% as the corners of the slats create micro-turbulence that decreases the porosity. This is good for slowing wind but bad for controlling dust as dust would pour through the 4” gap. In fact, that is why snow fences are built that way — so snow will go through the gaps and settle out into a mound behind the fence. Clearly fences with large porous opening dimensions are not good for containing dust in a downwind mode though they may be efficient in an upwind mode.
 
In general, materials with porous opening dimensions greater than 1” and fences that do not go all the way to the ground are very poor at containing dust. Tightly meshed woven fabrics such as high-density polyethylene or polypropylene as tested and utilized by the industry experts at WeatherSolve Structures have been shown to be an effective wind fence fabric choice as they function efficiently in both upwind and downwind mode.
 
 
REAL-WORLD SUCCESS STORIES
There is an abundance of real-world examples that illustrate the effectiveness of wind fences in reducing dust emissions and improving operations for dry bulk stockyards. For instance, in one stockyard in Florida, a custom designed wind fence (with a unique stress-release clip system to protect the structure during extreme weather events) was developed to reduce bagasse (dried and pulped sugar cane stalk) erosion and dust. The source of the erosion and dust was due to incoming winds as well as loaders shifting the pile. The stockyard had originally been using a bunker system to control the dust, however; the turbulence created by the wind moving up and around the solid barrier reduced its effectiveness and resulted in a loss of the bagasse product not to mention the dust wreaking havoc on the site and surrounding community.
 
The stockyard’s primary goals were to reduce unwanted dust and product loss, as well as protect the surrounding community from the effects of air borne particulate matter. In this instance, an upwind and a downwind fence were custom designed to meet the needs of the site and effectively reduce dust emissions. The implementation of this wind fence technology resulted in substantial cost savings and a positive impact on the surrounding environment.
 
Another example of the real-world efficacy of wind fences in optimizing dust suppression in stockyards takes us to Australia where a cement manufacturer maintained multiple stockpiles of limestone. This site had historically used surfactants as their primary method of dust suppression but were plagued with significant dust plumes when the pile was disrupted causing a negative impact on operations and nearby neighbourhoods. In many cases, a wind fence can be used with other methods of dust suppression such as surfactants, foam, water and other sprays to optimize their effectiveness. When utilized alone, these other methods of control do not provide the dust containment that a well-designed wind fence can provide — especially on a dynamic stock pile. A tailor-made portable wind fence was designed and implemented that would allow the site to customize wind fence placement based on the shifting location of pile activity and wind direction. When not required for dust suppression, the fence could be moved along the perimeter of the site as not to interfere with operations. The result was a smaller environmental footprint, significant reduction of dust, and happier neighbours.
 
FINAL THOUGHTS
The integration of wind fences into dry bulk stockyard management represents a reliable and effective way to address the challenges of dust management and operational efficiency. As evidenced by real-world examples, a well-designed custom wind fence that addresses the specific needs of a stockyard can mitigate hazardous dust emissions and reduce the impact of said dust on the surrounding environment. The adaptability and effectiveness of wind fences showcase their ability to transform dust mitigation strategies even in the harshest environments. As regulatory pressures and environmental concerns continue to rise in industry, the technology of wind fences is crucial for stockyards who prioritize environmental stewardship and safety.