Operating mix

According to the objective of the blasting process, one requires a defined and stable operating mix or, more precisely, a grain size distribution and composition within defined limits.
For example, blast cleaning to prepare the surface for corrosion protection coatings requires a broad distribution in order to achieve a defined and homogeneous surface roughness and cleaning effect.

The shot peening application, on the other hand, requires a narrow range of grain sizes in order to define the kinetic energy of the individual blasting shot grains and therefore to be able to control the required cold work process.

The range of grain sizes must be held constant by the air separator in the functional unit with the filter system. The air flow velocity determines the separation cut between undersized grains and grains of the required size, which should make up the operating mix.
The agglomerates / undersized grains with adhering material formed by oily blasting shot cannot be separated or can only be insufficiently removed by the separator. The actual range of grain sizes is shifted, or extended, in the direction of “grains that are too small”.
The blasting properties of the blasting shot are drastically altered with grains that are too small in size. For example, a change of 0.6 mm to 0.4 mm causes a loss in impact energy of around 70 %.

Corrosion protection coatings can only hold permanently if the surface preparation has been performed successfully for coating

Oily dust particles are transported by the dust extraction from the blasting room and the air separator to the filter media of the filter system. The filter is intended to serve the purpose of separating dust particles from the air, such as abraded metal, shattered grain, contamination, rust or scales, and ultimately eliminating these from the process.
However, oil and grease also cause dust accumulations with the filter media here. The sticky particles are no longer separated when passing through the purification stage of the filter, such as by an air pulse, and gradually and increasingly they clog the filter
This in turn reduces the air flow velocity in the cross current of the separator. The separation capacity of the separator continuously drops.  The fraction of dust and undersized grains in the operating mixture rises constantly. With the following consequences:

  • The blasting intensity is reduced, in spite of constant energy consumption
  • The roughness depth of the blasted surfaces is lowered
  • The degree of cold work is permanently reduced.

These processes occur gradually and uncontrolled. The process reliability can then no longer be maintained.

PantaTec can prevent all this.