A method of discharging fine sand at high velocity to remove rust, dirt and scale from a surface before welding, painting, or finishing.
When welding, if more than one layer of metal is to be deposited, the oxide and scale should be: removed from each layer before the next layer is applied. Sand-blasting is probably the fastest and most efficient method of producing a thorough cleaning job.
A portable sandblaster consists of a sheet metal tank provided with a filling hole and a pipe T-outlet for an air-operated siphon. The siphon consists of a pipe from the vertical of the T to the bottom of the tank; the horizontal outlets of the T are fitted with a sand nozzle and an air control valve. The sand nozzle tip should be replaceable because it will wear quite rapidly. A sandblaster of this type will operate well with an air pressure of about 620 kPa (90 psi).
Care should be exercised when sandblasting to avoid entrapping sand in crevices or embedding sand in the surfaces of soft metals and alloys. Particles of sand can result in contamination of subsequent weld passes, and can lead to other problems in the weldment.