For the airflow techies...

[dgardner]

I was looking up a blower spec on the Dresser Roots site and came across this cool table:

http://www.dresserroots.com/documents/MISC/friction_loss_chart.pdf

It shows some neat parameters at a glance. For instance, I can see that, at 200 CFM, 2" hose drops over 4.5"hg per 100 foot run, while 2.5" hose only drops about 1.8"hg.

If I want to look at velocity, I can see I need about 170 CFM to maintain my desired 5000 FPM in a 2.5" hose, about 130 CFM for 2", all the way down to 50-ish CFM in a 1.25" hose (which explains why my little single vac Mytee spotter came with that size).

Anyway, if you find this table as interesting as me, you probably need to get out more....

 

[Shawn Forsythe]

Just remember, that chart is for straight smooth bore pipe. Convoluted bore, coiled and bent hose has rather different characteristics.

 

[dgardner]

Somewhat worse, in terms of pressure drop, I assume?

 

[Bob Savage]

Thanks, Dan, for your post.

Yep, distance is definitely the enemy of a vacuum system.

It's also surprising how much of that dirty water/air mixture we actually recover , just fine, without needing mega CFM and lift, as long there is a balance within the vacuum system corresponding to the maximum hose lengths and ID sizes we use.