Context

The customer is a cement manufacturer who requires a screw conveyor emptying station to transfer salt initially contained in big bags.

Project constraints

One of the main constraints of this project is the nature of the product. Salt can have a some disadvantages. Firstly, although the salt is purified and dried, the big bags can be exposed to a humid atmosphere during storage or transport. The product is likely to agglomerate due to its ability to absorb moisture. Wet salt tends to become slightly sticky and lose its fluidity, making it more difficult to flow. In addition, the corrosive nature of salt places additional stress on industrial equipment, particularly steel equipment, which requires greater protection and maintenance.

The entire emptying station must then be installed indoors with limited headroom. This is an important parameter to consider at the design stage.

The proposed solution

The customer’s requirement was to supply a big bag unloading and transfer unit using an Archimedes screw, taking into account the constraints associated with the product and the ceiling height available on site.

The big bag emptying station is equipped with :

  • A low frame and a high frame with a steel monorail.
  • A low-loss hoist for handling the big bag.
  • A pneumatic massage system to assist product flow. It consists of 2 pneumatic cylinders with deflector and linear guide. This system takes over from the vibrating hopper when the product forms lumps. Lumps of product can form at the outlet of the big bag, preventing the product from being discharged properly. The system is pneumatically operated.
  • A 316L stainless steel vibratory hopper isolated from its support structure by 4 silentblocks. Driven by an unbalanced motor, it empties products stored in Big Bags that have been compressed by transport and/or have little natural flow.
  • A 316L stainless steel access chamber, fitted with a safety open/close sensor and a flexible sleeve.
  • A weighing system consisting of 4 load cells and a weighing indicator.
  • A flexible sleeve for adaptation to the process.

The transfer screw

Salt transfer is ensured by a dosing screw conveyor with the following characteristics:

  • Length approximately 4000 mm.
  • Required capacity: between 50 and 200 kg/h.
  • Continuous sealing on spiral.
  • Equipped with gear motor and rotation sensor.

This Archimedean screw is made from 316L stainless steel, a material highly appreciated for its exceptional resistance to corrosion, particularly in aggressive environments.

Finally, to finish all the equipment, the steel was shot blasted before being coated with a 60 micron dry film anti-rust paint. Stainless steel parts were pickled, passivated and shot blasted.

Assembly and on-site testing were carried out by ISERCO.

Bulk information

  • Industry: Cement factory
  • Product: Purified and dried fine salt
  • Density: 1.2
  • Conditioning: Big bags of 1m3 with a maximum weight of 1200 kg.