Page 70 - Hub-4 Magazine Issue 58
P. 70

Asphalt Plant
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 300mm. This heavy slat chain assembly resists hydroplaning over the mix. Depending on required capacity, Astec offers either single or dual chain configurations. The drag conveyor discharges into a traverse conveyor atop the batchers.
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 over- lapping gates result in better gate wear resistance when compared to pinch- closed style gates. The double gates also centre 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 bi-directional airflow and equalize silo pressure as mix level changes during fill and loadout.
External coating & painting:
The outer casing is made of aluminium, completed with a coating that maintains the quality characteristics over time. The painting is either carried out in the official Astec colour or optionally in the customers colour choice.
Support structures:
The walls of the silo are made from rolled steel plate lined by structural weld. Jogged radial joints form a smooth inner surface, reducing wear at the joints. Standard silo legs provide 4.0m of clearance for trucks from the top of the weighbridge. 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 the installation location.
The advantages of a highly technological solution:
What are the advantages of a highly technological solution like the long-term storage silos from Astec?
The possibility of planning plant production 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, producers can cope with the peak loads, small supply requirements and intelligently use production plant downtime.
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 ability to store mixed material to overcome short to medium term interruptions to paving operations, without wasting mix. Where projects require high volumes of mixed material, production capacity can potentially be exceeded and necessitate the production of a buffer of material prior to the commencement of works. Disruption to paving operations either due to infield breakdown or changing weather conditions, can be mitigated by storing this material for up to four days without loss of quality.
The potential to maximise production plant capacity/efficiency. By filling either plant based or satellite storage facilities on Friday afternoon and then providing customers with high volumes of quality mix early Monday morning, without waiting for production plant startup.
Andrew concluded, “Astec long term storage silos revolutionized asphalt production methods in the USA. Allowing customers to take advantage of clean technologies for high capacity recycling of asphalt products such as the Double Barrel®, whilst maintaining the flexibility in supply to their customers. Recently our customers in Europe, by utilizing Astec silos for satellite storage applications, have taken these advantages one step further by consolidating production at highly efficient, environmentally responsible production facilities.
“Investment in long term storage solutions allows producers to position themselves differently in a competitive market, take advantage of clean efficient technologies and production methods whilst enhancing service to their customers.”
* polymer modified, open-graded and SMA mixes excluded
| p70 | September/October 2019 - Issue 58

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