Blast Hose Sizing
To efficiently convey air-driven abrasive from the blast machine to the nozzle, blast hose should have sufficient inner diameter and be kept as short as possible.
*Blast hose inner diameter should be 3 to 4 times the size of the nozzle orifice.
Using a blast hose with an inner diameter that's smaller than the blast machine outlet diameter greatly reduces the amount of air and abrasive flowing to the nozzle. A blast machine with 1 ¼-inch piping (32mm) feeding a ¾-inch (19mm) blast hose must overcome a 64 percent in capacity. Air and abrasive are now being forced into an area that has one-third the capacity of the blast machine's external piping. This is not a problem if you also switch to a smaller nozzle – appropriate for the size of the hose. If you switch to a smaller hose and still try to use a nozzle that has a large orifice, nozzle pressure will drop drastically.
For use with most abrasives, the blast hose inner diameter should be a least 3 times (preferably 4 times)the size of the nozzle orifice. For example, a 3/8 -inch (9.5mm) nozzle demands a minimum hose ID of 1 1/8-inch (28.5mm). There is no 1 1/8 -inch blast hose, so use the next larger size: 1 ¼-inch (32mm).