B1 - Ensure that the correct air pressure is used.
Optimum blasting pressure is at least 100 psi. If lower pressures are used, productivity will almost certainly be reduced.
Air pressure should be measured at the nozzle, rather than at the compressor, as there will be an unavoidable drop in pressure between the compressor and the nozzle, especially when long hose lengths are used.
Nozzle pressure should be measured with a hypodermic needle gauge inserted into the blast hose, directly before the nozzle.
B2 – Use the correct blast hose for the job.
Good quality blast hose should always be used and the correct diameter selected in order to ensure that friction losses are minimised.
A rough guide to sizing, is that the blast hose diameter should be between 3 and 5 times that of the nozzle. Hose lengths should be kept as short as site conditions will allow and correctly sized couplings fitted in order to avoid unnecessary pressure loss throughout the system.
B3 – The blast nozzle.
The size of the blast nozzle orifice will affect the productivity of the blasting operation. The larger the bore, the bigger the area blasted, facilitating faster production rates.
However, in order to achieve the desired surface finish, the volume and pressure of the air supply needs to be high enough to ensure that abrasive velocity is maximised.
Hence, there needs to a balance between compressor, hose and nozzle sizes.
There are standard tables available from equipment manufacturers which indicate appropriate nozzle and compressor sizes.
Nozzle type also affects the blast pattern and productivity. Straight bore nozzles produce a narrow blast pattern, commonly used for spot blasting.