An economical suction-type cabinet is ideal for everyday maintenance and light-duty jobs. Compressed air (released by operator pedal or trigger gun) enters gun and creates a vacuum that draws and expels abrasive onto the workpiece.
Blasting uses the Venturi principle of sucking media from a hopper. Air jet diameter is half the interior diameter of the nozzle and, as the air stream passes through both, it creates suction which pull the media from the hopper into the air stream. Media acceleration distance from nozzle to workpiece is short (approximately 4 to 14 inches). The suction system works fine and can continuously blast as long as there is blasting media in the hopper.
However, suction systems have limits on suction capacity and propelling heavier media. Very heavy blasting media (larger steel media) cannot be conveyed into air stream with suction blasting. Nonetheless, most industrial blast cabinets use suction systems due to their lower cost and because they work well for most applications.
For rapid results in hard-to-reach areas, high performance pressure-type cabinets have 1.3 cubic foot pressure vessel that forces media through blasting hose and nozzle.
The pressure pot contains media that pressurizes the pot as it is energized with compressed air. When air/media mix is released from the pot, it accelerates through at least 5-10 feet of hose and then picks up even more speed as it travels through the Venturi of the nozzle. The acceleration rates of air/media mix are much higher in pressure blasting than suction blasting.
When pressure pot empties of media, it must be depressurized to be refilled with media. Pressure blasting systems are much more productive than suction systems. Additionally, pressure systems can blast all types of media regardless of weight or size, but require a minimum of 25 psi to operate.