tms wrote:
Hey Gene,
I'm going to have to disagree with you on the virtue of 6" pipe over 4". The critical parameter is not the velocity but the volume (and corresponding mass) of air. The amount of solid material that can be conveyed is dependent upon the ratio of ratio of solid mass to gaseous mass. A 6" pipe will have less parasitic drag (from surface to volume), and will convey more air, and thus more solids.
In fact, velocity can work against you. That is the mechanics behind a cyclonic separator, the air speed continues to exceed that of the solids until the solid drop out.
Cheers,
Tom
If the impeller intake were 6" I'd agree. However, I think her's has 2 4" intakes so that would be the determining restriction as to volume of air moved I believe. If she combines the 2 intakes into a single 6" pipe, then the volume would obviously be greater, and 6" pipe would be beneficial.