Abrasive cleaning in shot blasting

Any blasting machine that recirculates the abrasive —whether a wheel blasting machine or a compressed-air blast room— needs to condition it between cycles. The abrasive circulating inside the equipment becomes contaminated and degrades with use, and the cleaning system performs two essential functions:

• Condition and clean: it recovers the usable shot for reuse and discards the contaminants generated during the process —dust, mill scale, fine shot, sand, bolts—. It also removes the particles that, because of their reduced size, no longer have the mass to impact with enough energy and have stopped contributing to blasting.
• Store: it deposits the clean, reclaimed abrasive in a silo, ready to recharge the equipment.
It is worth remembering that these systems do not remove grease or oil: surfaces must therefore be cleaned before blasting, so as not to contaminate the abrasive.

Cleaning the abrasive is not only a matter of cost: it directly affects the durability of the coating.

When fine contaminants are not removed from the mix, they settle between the peaks and valleys of the blasted surface profile. When paint is applied, that dust is trapped between the coating and the steel and reduces the adhesion the two surfaces should have. If the contaminant also penetrates the paint, it can create corrosion cells in the steel, increasing the likelihood of premature coating failure.

The effect on costs is measurable. It has been shown that, in the blasting and desanding of castings, the presence of just 2% sand in the shot considerably increases the wear of the parts compared with the same process using contaminant-free shot. Coarse contaminants can also damage the blasting nozzle and even the parts being processed.
A well-regulated cleaning system makes it possible to:
• Keep operating costs under control.
• Achieve blasted parts free of contaminants.
• Maintain controlled roughness profiles.

The type of cleaning is chosen according to the weight of the abrasive. Heavy abrasives —carbon or stainless steel shot— are conditioned with mechanical cleaning systems, which combine screening and air flow to separate fines and coarse material. Light abrasives —aluminium oxide, glass bead— require cyclonic cleaning, which classifies the abrasive without damaging the delicate particles. This principle governs the recirculation of any equipment, wheel or compressed air; the capacity, models and selection criteria are covered on the abrasive purifiers page.

The abrasive cleaning and reclaim system is not an accessory but a fundamental part of the blasting process. Properly sized and regulated, it controls costs, protects the equipment and ensures clean parts with stable roughness profiles, ready to receive the coating. Underestimating it means giving up quality and missing one of the clearest ways to optimise the process.