Abrasives

Three (3) important factors to be considered  in evaluating the  performance of abrasive used for general cleaning  are:

1. How fast cleaning can be completed
2. Uniformity of appearance
3. Cost of achieving desired finish

These factors are determined by the abrasive particle size and shape, the abrasive breakdown characteristics (metallurgy and hardness) and the abrasive-size distribution in the machine. Maintaining an operating mix of the optimal sizes will permit  a consistent and cost  effective operation. Choose the smallest size shot or grit that will do the job. Choose shot over grit whenever possible to minimize wear. Balance the use of faster cleaning hard steel abrasives against their higher wear and breakdown rates.

The impact Power and coverage of steel abrasive is governed by its mass and velocity in accordance with equation of kinetic energy.

Ke = ½ MV2  (Where Ke = Kinetic Energy  M=Mass  V=Velocity).

The impact force delivered to the work piece will change only if the mass factor (i.e. the abrasive size) is altered.  The relationship of abrasive size to both impact power and coverage is shown in figure The economy and performance of blast cleaning depends upon the abrasives used. The proper size and type of  abrasives and its quality which is most important.

The following four factors should be considered while selecting the abrasives:

€¢  Area of job surface these can clean  
€¢  Quality of work produced   €¢  Cost of the shots