Choise of the mode of projection

Treatment by compressed air blast
The treatment by compressed air blast is the only "technically universal" solution because it allows treating as well the locks doors set up as a brake pad.
The material using the compressed air can also be portable, it is handy, easy to use and various in so far as it allows treating parts of very varied shapes. This is its main advantage.
The investment is low if it is portable (building site) and more important if it is fixed (cabin in workshop). Both objections which weight at the time of the choice are the labour and the compressed air consumption which are fundamental economic data.

Choice criteria
The first choice criterion is the variety of parts to be treated and the diversity of shapes.
The second choice criterion is the average production capacity which should not exceed in cabin for 4 operators maximum: 40m2/h in SA 3 or 120m2/h SA 2 for a compressor power of 75kW.
This in order to avoid compressed air consumption too important which would require the investment in a "small air station" and the high cost of labour which would put a serious strain on the cost price of the treatment.

Treatment by mechanical blast wheels
The blast wheels treatment would be a perfect process if it was not blind.
Contrary to the manual or mechanized jet which follows precisely the part geometry, the blast wheel projects in a fixed point and in an invariable direction a few tens, even hundreds of kilos of abrasive per minute whatever there is a part to be treated or not in the impact area.
If the manual jet follows the part, the blast wheel being fixed, this is the part which must move in the projection area.
The blast wheels machines have a real interest only if they can be specialized in their work (i.e. sheets, sections, tubes, or parts with regular and repetitive shapes). The relatively universal machines, like suspended load or apron machines, also know operational limits related to the dimensions and the parts shapes.

Choice criteria
The first choice criterion is the specificity of the parts to be treated and the regularity of the shapes.
The second choice criterion is its large production capacity, since a small machine equipped with a blast wheel of 7.5 kW can treat 40m2/h at 100% in SA 3, that is to say the equivalent of 4 manual operators at a lower energetic cost, except writing off the equipment cost.