VOL 23 ISSUE #2
The Vaccari Group operates one of the largest aggregate mining operations and asphalt production facilities in Italy’s Northeast Sector. Continued market growth required the purchase of a 200 ton satellite silo system for storing asphalt mix.

Having a clear market vision is anything but simple, especially at a time when trends and responses are rapidly changing.

But the Vaccari family, owner of Vaccari Antonio Giulio S.p.A. (Vaccari), is certainly not discouraged and on the wave of continuous corporate investments has asked some fundamental questions.

The evolution of the market demand requires an increasing flexibility with how asphalt mix is produced and stored based on the relatively limited shelf life of the finished product. To be successful, producers need to formulate a strategy that meets the demands of the market, while limiting excess production of unused asphalt mix.

The modularity of the Astec system allows the implementation of elements throughout the life of the plant.
The modularity of the Astec system allows the implementation of elements throughout the life of the plant.
The elevator conveyor feeds a three tonne per meter load for each silo whose function is to prevent the segregation of the asphalt mix.
The elevator conveyor feeds a three tonne per meter load for each silo whose function is to prevent the segregation of the asphalt mix.

The average cost of starting a plant to produce asphalt mix fluctuates approximately 400 Euros ($262 USD). That cost often discourages the supply of small quantities on days when the plant is not operating, not to mention when the production facility is engaged in some large supply where it is difficult to place small orders, especially when different mix designs are required to fill the smaller orders.

But the market the Vaccari family serves features a portfolio of small and medium-sized jobs that are often not as programmable as one would like. Small quantities that are difficult to manage in a rational way represent an important part of the overall volume the producer turns out.

A problem that is difficult to solve

 
The Astec solution seemed the most convincing on paper, and we have validated this assumption.

— Nicola. Vaccari, Vaccari Antonio Giulio SpA

 

And it’s just talking to Nicola Vaccari, sales manager of Vaccari, which highlighted the problems of an organizationally difficult job.

“Our problems partly relate to the preservation of the product packaged for long periods,” explains Vaccari.

“The demands of the market often present a fragmentation of supplies with many small jobs, often non-programmable, that require small amounts of asphalt mix,” he adds, while touring the Montecchio Maggiore plant, “and for us it is difficult to satisfy every single request. We therefore decided to understand what opportunities the market offered to be able to produce and store the two main types of asphalt mix most marketed to always have quantities ready for loading. We collected data, examined various technical solutions and visited a production site in Northern Europe that works in difficult conditions. We evaluated all the available technologies, and the Astec solution seemed the most convincing on paper, and we have since validated this assumption.”

The choice of the Vaccari Group has indeed fallen on the long-term storage silos of the satellite storage system designed with Astec long-term silos, which have particular characteristics and allow the producer to insulate the material for four days with the guarantee of preserving the technical characteristics of the mix.

The Vaccari Group has chosen the design of filling through the hopper in order to keep flexibility over time as high as possible.
The Vaccari Group has chosen the design of filling through the hopper in order to keep flexibility over time as high as possible.
The truck dump hopper feeds a three ton batcher for each silo whose function is to prevent the segregation of the asphalt mix.
The truck dump hopper feeds a three ton batcher for each silo whose function is to prevent the segregation of the asphalt mix.

Modularity and technology

“At first sight they look like simple silos,” explains Nicola Vaccari, “but, they are real machines with a very sophisticated technology that comes from a deep knowledge of the material and its dynamics of oxidation and loss of the original features.”

The choice of Vaccari fell on two long-term storage silos with a capacity of 100 tons each.

“The system developed by Astec focuses on modularity and integration,” explains Vaccari, “and the sizing with the total 200 tons of load capacity allows us to have that organizational autonomy necessary to satisfy a wider market in a much more linear and optimized way. The combination with the production plant can take place without any problem,” illustrates Nicola Vaccari, “leaving us ample operational space.”

“We were definitely convinced when we saw a plant in Belgium at work where the asphalt mix was produced and stored on Friday and then loaded perfectly intact with all its best technical characteristics on Monday morning,” he says.

“Even in the middle of winter, with very low temperatures, the stored asphalt mix that contained milled material that was soaked from heavy winter rains proved the ultimate challenge for producing and storing an exceptionally high quality of the outgoing materials, but we were able to remove any remaining doubts regarding the technologies developed by Astec.”

The advantages of a highly technological solution

 
Even in the middle of winter, we proved we could produce and store an exceptionally high quality of asphalt mixes.

— Ing. Vaccari, Vaccari Antonio Giulio SpA

 

What are the advantages of a highly technological solution like the long-term storage silos from Astec?

The possibility of planning the production of the plant in a more linear way is certainly the first and most obvious advantage. By storing up to four days of material with Astec’s guarantee of the quality, you can cope with peak loads, small supply requirements and intelligently use system downtime.

The second is certainly that of being able to provide maximum availability to all of your growing customer base, which need supplies of small quantities at any time.

But the other big advantage consists of being able to logically schedule when to start a plant and when to shut it off. With the silos, it is possible to cope with the first load flow very quickly, as well as, shorten the loading times thanks to the material that can be prepared continuously and loaded quickly when the trucks arrive.

“The purchase of the two silos from Astec,” explains Nicola Vaccari, “represents a revolutionary way we approach the market, our customers and the way we organize our work. From the analysis we performed, it was decided to store the materials subject to the greatest purchase, especially in small quantities and in a less programmed way. The silos come into action to serve customers who need ordinary mixes.”

And he continues, “In the event there are jobs of a certain size, nothing removes the use of the silos also as a regulator of the flow of cargo, preparing the material in the dead times and loading it quickly when the vehicles arrive. In short, it is an investment that allows us to position ourselves in a very different way than in the past, opening new niches to service customers with certain delivery times and loading capabilities.

“We are a structured company with three mining and processing sites. In addition to having the asphalt mix system here in Montecchio Maggiore,” explains Ing. Vaccari. “Being organized and efficient for us is fundamental from every point of view. The two Astec silos will allow us to increase our efficiency even further. We have seen how Astec builds plants with truly cutting-edge technologies and these silos could be the first step to evaluate future expansions.”

Much more than simple silos

Filling through the hopper takes about ten minutes, making it very productive.
Filling through the hopper takes about ten minutes, making it very productive.

The long-term storage silos are real machines, with technology based on a deep knowledge of the asphalt mix. They are not just insulated containers but a storage system in which all the elements, starting from the loading hopper, passing through the elevator conveyor and the transverse conveyor up to the silo batcher to the silo and lower cone, are designed to optimize the process.

The main elements that make it a unique technology are:

  • INSULATION: Twelve inches of insulation at silo tops, four inches around the cone, and six inches along the cylinder keep the mix hot. Batchers are insulated as well, because uninsulated batchers are a major source of heat loss. Two layers of stiff sheet insulation are staggered to eliminate heat-leaking seams along the silo cylinder. Astec uses thick, full R-value, non-compressed insulation.
  • TOP SEAL: In storage mode, the cylinder-operated gate at the top of the batcher is completely sealed. The gate runs in rails which tightly wedge it against a ring of grease. This forms a tight seal and keeps air from entering at the silo top.
  • BOTTOM SEAL: Astec's patented discharge gate completely seals the bottom of the cone when the silo is in storage mode. The heated and insulated discharge gate closes to completely cover the cone opening. Oil is pumped into the gate to seal the bottom silo opening. The oil reservoir is located by the silo legs, and a motor-driven pump moves the oil from the reservoir into the gate. A sensor monitors the oil level in the gate and controls the pump.
  • LOWER CONE: The lower cone has a specific inclination of 66° and a higher shape, which naturally prevents segregation and build-up of the material. To prevent wear caused by the material, the interior is coated with wear-resistant steel and, on request, ceramic liners can be used.
  • HEATING OF THE WALLS OF THE CONE: A silicone electric heating blanket surrounds the lower cone section. A thermostat activates the blanket when the temperature drops below set point. This sensor saves money, because the energy to heat the cone is used only when required. Hot-oil heating is available as an alternative to the electric blanket.
  • TRANSPORT OF THE MATERIAL: The drag conveyor reaches to the top of the silo. Strong, wear-resistant, roller chain runs from bottom to top, with deep, steel slats attached every 12 inches. This heavy slat chain assembly resists hydroplaning over the mix. Depending upon required capacity, Astec offers either single or dual chain configurations. The drag conveyor discharges into a traverse conveyor installed atop batchers.
  • BATCHER: The mix moves by drag conveyor or bucket elevator into a three-ton batcher atop the silo. When full, the batcher releases the slug of mix. Mix drops through the rapid-opening double-clam gate into the silo and flattens on impact. Astec's double-clam gates are not like conventional pinch-closed style double-clam gates. Astec's overlapping gates slice through material flow as the gate closes. This slicing action and overlapping gates result in better gate wear resistance when compared to pinch-closed style gates. The double gates also center the drop into the silo and form a flattened mix surface, which prevents mix segregation.
  • SILO PRESSURE EQUALIZED: As mix level rises, it displaces air in the silo. Integrated vents inside the batcher enclosure allow bidirectional airflow and equalize silo pressure as mix level changes during fill and loadout.
  • EXTERNAL COATING AND PAINTING: The outer casing is made of aluminum, completed with a coating that maintains the quality characteristics over time. The painting is carried out either in the official Astec color or, as in the case of the silos purchased by the Vaccari Group, in the company colors chosen.
  • SUPPORT STRUCTURE: The walls of the silo are made from rolled steel plate joined by structural weld. Jogged radial joints form a smooth inner surface, reducing wear at the joints. Standard silo legs provide 13-1/2 feet of clearance for trucks from the top of the truck scale. Legs and the silo support frame are made of heavy, structural, wide-flange beams. Silo support structures are designed to meet the site specific design criteria at your location based on the current building codes in your states.
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