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Project location: Eastern Canada

Material: Calcium Carbonate & Calcium Sulphate

Material characteristics: Sticky, Corrosive and abrasive



To receive and store Calcium Carbonate and Calcium Sulphate discharged from a plate and frame press. The material drops from the press directly into individual storage hoppers, then transported via a conveying system, eventually discharged in-to a haulage container.

Issues to overcome:

Both the calcium carbonate and calcium sulphates are difficult to store for a period of time, due to the materials ability to adhere to itself and the transport equipment.

Once the material adheres to the spirals, the material just rotates within the spiral and does not transport.

When the material has been left in the hopper for a period of time and has had sufficient time to adhere to itself, the spirals will remove the material inside the spiral the material covering the spiral will not enter the spiral as it is stuck together, creating a tunnel or bridge.

Up-to this point in time, the client had studied several different options proposed by various equipment suppliers.

Due to the client’s previous experience, the client requested a (several day) demonstration of the Atara proposed equipment.

This demonstration proved beyond a shadow of doubt, that the equipment proposed by Atara could effectively store, transport and eventually discharge the carbonate products with ease.

The standard equipment selected by Atara to work in the Calcium Carbonate product:

  • (1) Twin live bottom: C/w Shaftless screws inside the storage hopper
  • (1) Crossing conveyor, inclined conveyor, out-loading conveyor all supplied with Shaftless spirals
  • Spirals are all manufacture in steel with a 250 Brinell hardness
  • Troughs, lids, gear-dive end plates, trough end plates, all in SS316
  • Connections: all axial

The equipment selected to work in the Calcium Sulphate product:

  • Quad live bottom: four 4) Shaftless screws inside the storage hopper
  • Crossing conveyor, inclined conveyor, transfer conveyor, out-loading conveyor shaftless Screws
  • Troughs, lids, gear-drive end plates all in SS 316
  • Connections: all axial


The above equipment has been successfully working for over 10 years.

Recent up-grades to-date:

  • Replacement of a local competitors spirals, the spiral material (steel) selected by the competitor was not rated for abrasive, corrosive applications and failed prematurely. The spiral profile design did not meet the axial loading requirements to move the material successfully.
  • Replacement quad live bottom liners.
  • Gear drive end plate, new live bottom flange, gear drive adapter, hold down devices, ceramic split seal for the inclined Conveyor, all in SS 316.

Atara replaced the competitors spirals in this application, with spirals manufactured Hardox 400, (400 hardness Brinell). The quality (grade) of steel, used in the manufacturing process of the spiral, has a direct impact on the stability and longevity of the spiral. Due to the fact that the spirals have a tendency to be the most expensive part of the conveying system, it is important to know the quality of the steel being supplied on the project, the majority of specification will name a Brand of steel or Brinell hardness required.

This can be confusing usually any brand name of steel will have several grades of steel within said Brand. It is therefore necessary to know which grade is being supplied and does this grade actually meet the specification.

The most common spiral material requested in the specification usually includes: Macro alloyed steel, HTMAS (High Tensile macro alloyed steel) again within these types of steel the actual Brinell hardness can vary between 150 to 350, sometimes reaching the Brinell hardness by a heat treating process.

To better understand what is the material of the spiral, you will need to know which grade of steel being used under which brand name.