HMA Storage Silos

Guaranteed Storage

Astec silos store mix for four days* without loss of mix quality. That's true storage. And we guarantee it in writing.

Use the silos as a conventional surge bin during the busy time of day. At day's end avoid time-consuming start/stop operations and begin filling silos while continuing loadout. The next work-day, begin selling mix right away from full silos. Nobody has to wait for mix. Uninterrupted production runs allow you to maximize equipment efficiency and reduce material waste. Incorporate multiple silos in your plant layout and you will be ready to meet customer needs for a number of different mixes. That's how Astec storage silos reduce operating costs and improve plant operating-efficiency.

*polymer modified and open-graded mixes excluded

Features & Benefits

  • Guaranteed four-day storage
  • Reduce operating costs and improve plant operating-efficiency
  • Ships complete with drag conveyors, traverse conveyors and batchers
  • Bucket elevators available
  • Standard design is to Seismic Zone IIA conditions and 150 miles per hour wind velocity
  • Structural engineering staff designs foundations based on soil conditions at site

    Ensure Mix Quality

    Astec's innovative batcher helps eliminate mix segregation. It is designed to ensure that the quality of mix that leaves the drum is the same quality stored in the silos.
    • The Astec batcher is designed to minimize segregation.

      Fill Silos Without Segregating the Mix

      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 clam gate into the silo and flattens on impact. Batchers with a single radial-type gate can off-center the drop. Our batcher clam gates center the drop into the silo and form a flattened mix surface, which prevents mix segregation.

    • The batcher releases a slug of mix that flattens upon impact, eliminating segregation.

      Automatic Batcher Gates

      The precisely activated batcher gates operate automatically. When the batcher is full the cylinder-operated clam gate opens. Mix discharges in bulk, and the gate closes just before the batcher is completely emptied. This way mix always collects in the batcher first and never falls straight from the drag conveyor into the silo. Sensors control the proper opening and closing of the batcher.

    • Air displaces through the batcher as the mix level rises, keeping the silo equalized.

      Keep Silo Pressure Equalized

      As the mix level rises, it displaces air in the silo. Vents in the batcher enclosure allow this air to escape and keep pressure in the silo equalized.

    • High and low bin indicators inside the silos relay mix information to the control house.

      Bin Indicators Show Mix Level In Silos

      Each Astec silo has a high and a low radio-frequency bin indicator. Mounted on top of the silo, the sensing rods extend down into the mix. The low bin indicator reaches deep into the silo; the high bin indicator is short. Both the high and low bin indicator information is transmitted to the control house so that personnel can track mix level. The high bin level indicator signal allows the operator sufficient time to finish loading mix already in the transfer conveyor, while the low signal informs the operator to begin filling the silo before the cone surface liners become exposed.

    Outstanding Cone Design

    The Astec silo cone is exceptional. It prevents segregation and mix build-up with its mass-flow slope, it is equipped to resist wear, protected from heat loss, and its gate seals the silo for storage.
    • Steep 66° angled cones allow mix to move by "mass flow" that prevents mix build-up on silo walls.

      Cone Design Prevents Mix Segregation

      Astec silo cones are taller and built with a steeper angle than other brands. The Astec design provides optimal material flow. Third party and Astec research shows the precise angle at which the entire column of mix flows down evenly to be 66°. The steeper angle of the cone provides true first-in/first-out inventory rotation, there is no mix buildup on silo walls, and mass flow loadout minimizes mix segregation. Mass flow occurs when mix flows out across the entire silo cross-section and that only happens with the correct cone angle.

    • Mass flow loadout minimizes mix segregation.

      Prevents Drops Into the Cone

      If the mix level falls below the top of the cone, the level indicator signals the silo discharge gate to remain closed. To open the gate and empty the cone in this situation, you manually override the gate controls. This is because if mix dropped from the batcher is allowed to impact the cone directly it can cause unnecessary wear, or segregate on impact against sloped cone walls.

    • Cone insulation and an electrical blanket surround the cone preventing excessive heat loss.

      No Heat Loss Through Astec Cones

      Unheated cones cause excessive mix heat loss. Our heating system operates during fill/run and storage modes. Together with the cone insulation the system works to keep mix in the cone hot.

      A silicone electrical blanket surrounds the cone. A heat indicating controller turns the blanket on when the temperature drops below a selected point. This sensor saves you 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.

      Four inches of insulation on the outside of the cone's bottom portion help hold in the heat. A partition covered with a six-inch layer of insulation forms a warm, dead-air space around the top portion of the cone for even greater energy savings.

    • Optional ceramic liners in the bottom of the cone help prevent excessive abrasion.

      Protect Critical Areas

      Mix can be abrasive and can wear on the area where the cylinder and silo cone meet. Astec lines this area with abrasion-resistant steel liners. Optional ceramic liners are available.

    Designed for Long-Term Storage

    Astec silos are insulated so well because they are designed as a storage system guaranteed to keep asphalt hot for up to four days. Many operators have even reported storing mix for up to a week with no significant loss in mix quality.
    • Twelve inches of insulation are installed in the top of the silos.

      Our Silos Keep Mix Hot

      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. These strong batts of insulation provide support the silo skin. The aluminum skin has a baked enamel finish that will look nice for years to come.

    • Four inches of insulation surround the cone.

      Store Mix Longer

      Astec uses thick, full R-value non-compressed insulation around the silo cylinder. Super insulation on Astec silos helps you to store mix for longer periods.

    • Astec's discharge gate is completely sealed with oil allowing no heat to escape.

      Seal Silos in Storage Mode

      In storage mode it is crucial to seal the silo. Oxidation, or premature hardening of the mix, happens in the silo when the mix is exposed to air. In storage mode Astec silos are completely sealed from top to bottom.

    • A tight seal keeps air from entering at the top of the silo.

      Seal the Top

      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. When filling operations begin again, the gate is opened and remains open until filling operations stop. An air actuated grease pump replenishes the grease and ensures a continued, perfect seal.

    • The oil reservoir pumps oil from the reservoir to the discharge gate.

      Seal the Bottom

      The exclusive design of Astec's discharge gate (U.S. patent number 3,949,907) 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. When the silo is taken out of storage mode, the pump is reversed and the oil is automatically withdrawn from the gate.

    Made to Last

    The Astec drag conveyor is tough. Formed from steel and lined with Ni-Hard, it is made to withstand the demands of asphalt production.
    • Extra-thick, high-capacity slats move the mix up to the batcher.

      Tough Roller Chains Hold Thick Slats

      The drag conveyor reaches from the mixer exit chute to the top of the silos. Strong, wear resistant, 6-inch roller chain runs from bottom to top, with 3/4-inch thick, 7-inch deep, steel, horizontal flights attached every 12 inches. This tough chain has an ultimate strength of 140,000 lbs and rollers hardened to Rockwell 57.

    • Idlers prevent the flights from skimming over the mix to help eliminate back-ups that could strain motors and reduce conveying capacity.

      Astec Drag Chains Ride Smoothly

      With wide idlers the flights don't skim or "hydroplane" over the mix. Mounted on floating hold-down bearings, these idlers also support the return portion of the chain and minimize vibration. As a result there is less wear to the sprockets, liners, and chain. Floating hold-down bearings have grease piping that lets you lube them from both sides of the conveyor stair.

    • Segmented sprockets can be replaced one piece at a time without removing the chain, greatly reducing time and effort.

      We Give You Segmented Sprockets

      The drag chain rides on segmented sprockets located at the head and tail shafts. Induction hardening to Rockwell C60 gives the sprockets a uniform, deeply hardened wear surface.

      Each sprocket bolts to a split hub. You can replace the sprocket one piece at a time without removing the chain, which drastically reduces the time and effort required. The bottom sprocket is adjustable so the drag chain can be tightened.

    • Flights have completely emptied mix by the time they reach the top sprocket.

      Astec Drag Conveyors are Unmatched

      The top sprocket is located a good distance above the conveyor discharge. This, plus the 9° backward slope of the flights, makes sure that flights are completely discharged by the time they reach the top sprocket. No mix residue is dropped on the sprocket, so the sprocket and chain last much longer.

    • The drag conveyor discharges into the traverse conveyor which deposits mix into the designated silo.

      Traverse Conveyors Load Batchers

      The drag conveyor discharges into the traverse conveyor installed atop batchers. The operator selects the silo to be filled, and the traverse empties its contents into the designated silo's batcher.

    Well Thought Out Features

    The engineers at Astec thought through the details to design silos that will stand up to the many tons of mix that you will store over time.
    • Silo walls are made from rolled 1/4" thick steel plate joined by structural welds.

      Heavy-Duty Construction Delivers Reliable Performance

      The walls of the silo are made from rolled 1/4 inch - thick steel plate joined by structural welds. Jogged radial joints eliminate destructive wear at the joints.

    • Silo legs provide over 13 feet of truck clearance.

      Legs and Support Frame

      Silo legs are 15 feet long, providing about 13-1/2 feet, of clearance for trucks from the top of the truck scale. Legs and the silo support frame is made of heavy, structural, wide-flange beams. Standard construction is to Seismic IIA conditions with stronger construction available wherever necessary.

    • Stairway provides access to drag components and silo tops.

      Stairs, Handrails, and Top Platforms

      A grated stairway runs parallel to the drag conveyor. It provides access to conveyor components and to the top of the silos. As an option, a second stairway can be supplied on the other side of the drag conveyor.

    • The spacious platform leaves room to work.

      Plenty of Safe Working Space on Top

      The Astec work platform atop the silos is big. Square corners increase its size even more over round platforms. Safety features include skid resistant paint on the platform surface and guard-rails made of welded square tubing. Each silo platform's kick plates join with the platform of the adjacent silo, preventing spillage from the top.

    Choose Options for Your Facility

    With an Astec silo, you will have an opportunity to configure your facility with options to better serve your customers and your community.
    • Blue smoke systems collect hydro-carbon vapors at mix transfer points.

      Optional Blue Smoke Packages

      Blue smoke (hydro-carbon vapor) is generated at mix transfer points. Blue smoke is actually a haze of petroleum droplets suspended in the air. The blue smoke collection system prevents the vapor from escaping when asphalt is transferred from the mixer to the storage silo. The blue smoke system captures the vapor and uses a fan to transport it back to the drum where it is incinerated by the burner flame. The result is extremely effective. Virtually no blue smoke escapes into the air during silo filling.

    • Load out tunnels capture unwanted vapors.

      Options for Environmental Compliance

      Load-out tunnels and fiberbed mist collectors can also be supplied for installations where environmental compliance is a priority.

    • Astec's truck scale is a totally electronic scale with a low profile.

      Low Profile, Electronic Scales

      The LPSII truck scale is a totally electronic scale with a low profile. It only needs small foundation pads at each load cell. Weigh sections have checkered-steel deck plates. The scale is wired in conduit. When a silo is used without a truck scale, Astec can provide an optional weigh batcher.

    • Manage all controls from one central location in the control house.

      Control All Silo Functions

      Motor starts and stops, filling operations and manual loadout are handled from one central location in the control house. The operator also monitors current draws, bin indicators and cone heating information from here. Choose either the latest, state-of-the-art TCII controls utilizing a computer screen, keyboard and mouse, or the traditional analog control panels.

    • The spacious platform leaves room to work.

      Silo Diameter and Capacity

      Astec silos are available in either a 12 ft. or 14 ft. diameter of the following capacities:

      Tons 100 150 200 250 300
      Metric Tons 91 136 181 227 272

      Capacities are based on 120 lbs/cu.ft. for mix (0.5 metric tons / cu. meter).