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Cold aggregate bins are manufactured in modular structure with capacities between 9 – 24 m3 each. The extracting belt motors are equipped with frequency control devices to ensure accurate proportioning of the components. Special belts with flat rubber strips on both sides allow a maintenance free operation. Extracting belts, collection and transfer conveyors are equipped with special belt scrapers and “no-material warning” alarms.

High thermal efficiency, low fuel consumption, effective use of heat and high mechanical stability are the most significant superiorities of SIGMA dryer. The drying drum is thermally insulated and covered with stainless steel sheets on the outer surface. The drum rings are manufactured out of special forged steel. Drum drive is friction type with four rollers that are individually driven through shaft mounted gear motors, enabling easy regulation of dryer rotation. Shapes and configurations of the blades inside the drum are optimally designed for efficient heating.

Monoblock SIGMA Hi-Tec burners, feature optimized design for efficient burning, high thermal yield and minimum pollution. Varieties of different fuels such as diesel, heavy oil, gas or combination of them can be utilized at SIGMA burners.

The dust collection system comprises of pre-separator and filtration sections. The pre-separation process increases the lifetime of filter bags significantly by collecting the bigger particles and letting only the tiniest particles into the filter bags section.
SIGMA reverse flow filter with elliptical ARAMID bags is widely dimensioned for efficient operation to comply with the environmental standards. The central computer controls the cleaning of filter bags by automatically opening the lateral gates in pre-determined time intervals.
The recovered dust is collected at the hopper below and the screw conveyor extracts the dust to be used as recovered filler. Pre-separator section, outer surface of the filter and the collecting hopper are insulated with rockwool for maximum heat efficiency.

The hot recovery filler collected at the bag filter is conveyed by a screw conveyor and bucket elevatör into the buffer bin above the filler scale. The excess amount of filler is transferred to the recovery filler silo through an overflow pipe. For storing outsourced mineral filler, a tower type silo can be used. This silo which has a mineral filler storage section on top and the recovery filler section below. Depending on customer’s requirement, a separate mineral filler silo can be utilized as well. Priority is given to the usage of hot recovery filler, thus heat energy is conserved.

For trouble-free and continuous operation, bucket elevators are one of the key components of the asphalt plant. SIGMA aggregate and filler elevators feature a fully bolted, robust structure and are equipped with high quality components leading to an excellent performance. Heavy duty chain, high strength drive and tail pulleys, buckets with wear protection are some of the distinguished features of the hot aggregate elevator.

High efficiency screening is considered to be one of the key factors influencing the asphalt plant performance. As per the latest technology, the “semi-inclined” SIGMA screen combines the advantages of horizontal screens and inclined screens. The linear oscillating motion of the screen is generated by two vibrating motors with adjustable counterweights.
The screen is equipped with pneumatic bypass and oversize material chutes. Aggregates can be separated into 4, 5 and optionally 6 classifications. The sliding front chute and larger back doors facilitate easy screen mesh replacement.

Aggregate scale, bitumen scale and filler scale are equipped with 3 load cells, rubber anti-vibration mounts and constrainers, thereby ensuring accurate and fast weighing of all ingredients. In order to ensure maximum precision of dosage in aggregate scale, fine aggregate discharge gates of the hot silo are equipped with double stage pistons to enable fine/ coarse dosing. The recovered and mineral filler is fed to the filler scale by a special extracting screw and a pneumatic flap gate to obtain reliable and constant weighing. The weighed filler is distributed uniformly to all zones of the mixer by a screw conveyor.

The mixer is the main component of the asphalt plant determining the quality of the asphalt produced. SIGMA asphalt mixer is developed as the result of 40 years of experience in double horizontal shaft mixers. With SIGMA mixer’s larger internal dimensions and effective mixing arm design, homogenization of the product is ensured with reduced rate of wear at the blades and liners. The reliable, low noise and low maintenance drive system of the mixer comprises of double synchronized planetary gearboxes drive system and V-belt.

In order to meet special requirements of our customers, SIGMA hot mix storage silos can be manufactured in various capacities and concepts. Standard SIGMA hot mix silos have one or two compartments. In two compartment product silos, two different types of asphalt can be stored at the same time. Also, the optional direct discharge chute allows discharging directly onto trucks. As the silos are modular in structure, higher capacities can be achieved by adding extra modules or by placing additional silos in front, rear or sides. Outer surface of the silos are insulated with rockwool and covered with aluminum sheets for efficiently preserving energy.

Compact and reliable SIGMA fiber dosing system is used for the production of stone mastic asphalt (SMA) or other special asphalt types. The system can also be installed to existing SIGMA asphalt plants. The cellulose fiber in big bags are loaded into the feeding hopper, then weighed accurately by the electronic scale at the required amount for each batch and finally transferred into the mixer by the pneumatic conveying system. Liquid additive system for adding chemical solutions to the mix is also optionally available.

Horizontal or vertical type bitumen tanks with thermal oil or electric heating are available at desired capacities. External surfaces of tanks are insulated by rock wool and covered with aluminum, galvanized or corrugated steel sheets. Bitumen and thermal oil feeding systems are designed by our Italian specialists for best performance. Complete feeding lines are manufactured and installed including thermal oil jacketed or electrically heated piping, transfer and circulation pumps, valves, along with all sophisticated control devices.

Milled asphalt pavement from old roads is used by feeding to the asphalt plant after being processed. Due to the protection of the environment and cost advantages, usage of RAP (recycled asphalt pavement) is becoming quite widespread in the recent years. In SIGMA cold recycling system, the RAP material is weighed at the recycling tower and dosed into each batch of the mixer at the required ratios.