Martin Engineering
In order to achieve controlled and consistent flow on conveyors handling large volumes of bulk material, transfer chutes and vessels must be designed not just to accommodate but to actually facilitate the flow of the cargo they will be handling.
However, various conditions can impede effective flow, and designing a conveyor and chute system suitable for every material condition is nearly impossible. Modest changes in moisture content can cause adhesion to chute or vessel walls or agglomeration at low temperatures, especially if the belt is stagnant for any period of time. Additionally, during operation or under storage conditions, materials can compact, often due to natural variations in material properties. These accumulations negatively impact system efficiency, potentially infiltrating scrapers, damaging the return side, contaminating rollers and pulleys, or, in the worstcase scenario, causing complete blockages due to minor but widespread changes in flow characteristics.
To overcome these issues, a variety of devices collectively known as flow aids can be employed.
What Are Flow Aids?
Flow aids are components or systems installed to promote the transport of materials through a chute or vessel, controlling dust and spillage. These aids come in various forms, including rotary and linear vibrators, high and low-pressure air cannons, aeration devices, low-friction liners, and specially designed chutes that enhance material flow.
These modular systems complement one another, enhancing overall performance. The components are suitable for nearly all bulk materials and environments, including hazardous tasks and extreme temperatures. One of the primary advantages is that an operation can obtain a level of control over the material flow that is not possible any other way.
When employing flow aids, it’s critical that the chute and support components are sound and the flow aid be properly sized and mounted, because the operation of these devices can create potentially damaging stress on the structure.
A properly designed and equipped with correctly sized and installed flow aids, can function efficiently without sustaining damage.
Best Practices
Flow aids should only be used when the discharges are open and the material is flowing as intended. The best practice is to use flow aids as a preventive solution to be controlled by timers or sensors to avoid material buildup, rather than waiting until material accumulates and restricts the flow. Flow aids should only be used when the discharge points are open and the material is flowing as intended.
Air Cannons
One solution for managing material accumulation in chutes and vessels is the low-pressure air cannon, originally developed and patented by Martin Engineering in 1974. Also known as an “air blaster,” it uses a plant’s compressed air to deliver an abrupt discharge to dislodge the buildup. Cannons can be mounted on metallic, concrete, wood or rubber surfaces.
12 Martin® Hurricane Air Cannons, each with a 70-litre tank, were placed at strategic points.
The basic components include an air reservoir, fast-acting valve with trigger mechanism and a nozzle to distribute the air in the desired pattern to most effectively clear the accumulation.
Air cannons operate by providing a controlled burst of compressed air to remove material accumulations. The system functions when compressed air (or another inert gas) stored in the tank is suddenly released via a valve, directing the air through strategically placed nozzles. Often installed in a series and precisely sequenced for maximum effect, the network can be timed to best suit process conditions or material characteristics. The air blasts break down material accumulations and clear blocked pathways, allowing solids and gases to resume normal flow.
To facilitate installation in high-temperature applications without production downtime, new air cannon technologies have been developed. These advancements allow units to be mounted on kilns, preheaters, clinker coolers, and other high-temperature areas while production continues uninterrupted.
Air cannons significantly enhance efficiency in various industries by effectively managing material accumulation. A real-world example of the benefits of this technology can be seen in the RHI Magnesita Eskişehir Plant.Vaka Çalışması: RHI Magnesita Eskişehir Fabrikası
Case Study: RHI Magnesita Eskişehir Plant
RHI Magnesita Türkiye Refractory Trade Inc. operates in İnönü District, Eskişehir, producing raw magnesite, sintered magnesite, gunning mix, and slide gate plates. The facility houses three vertical and two rotary magnesite kilns. However, material adhesion and buildup in the smoke chamber areas of rotary kilns have led to production losses, reducing equipment efficiency and disrupting production continuity.
To address this issue, Martin Engineering Türkiye conducted a thorough analysis of the areas where material adhesion was most pronounced. Based on these findings, the installation of an Air Cannon system was recommended to prevent buildup and ensure continuous material flow.
Smoke Chamber of Rotary Kilns
A system comprising 12 Air Cannon units was implemented on all affected wall surfaces. Once activated, the system significantly mitigated the buildup problem in the smoke chamber area. Additionally, the frequency of opening the kiln cleaning hatch, which previously occurred every shift (every 8 hours) for approximately 15-30 minutes, was reduced to once every two days. This reduction resulted in energy savings and enhanced operational continuity.
The process of opening the kiln hatches for cleaning increases natural gas consumption. By minimizing the cleaning frequency, the plant saved approximately 500 sm³ of natural gas per day. Moreover, eliminating the need for manual cleaning reduced labor costs and minimized occupational health and safety risks.
Engineered Vibration
One of the traditional methods for breaking loose blockages and removing accumulations from chutes and storage vessels was to pound the outside of the walls with a hammer or other heavy object. However, this approach can worsen the situation, as hammer impacts create protrusions that serve as new accumulation points.
A more effective solution involves using engineered vibration devices designed to reduce friction and facilitate material movement without damaging the hopper or chute. The technology is often found on conveyor loading and discharge chutes but can also be applied to other process and storage vessels, including silos, bins, hoppers, bunkers, screens, feeders, cyclones and heat exchangers.
Flow aid devices deliver force through the chute or vessel and into the bulk material. Over time, components will wear, or even break, under normal conditions. However, most of these devices are rebuildable, and their service life can be extended with regular maintenance. It is recommended that flow aid devices be repaired by the manufacturer or that plant maintenance personnel receive specialized training to service them properly.
