Thread: Smooth Bore v Spiral Flexible Ducting

after you read this Bill's Cyclone & Dust Collection Research - Ducting you'll probably switch to 6" PVC sewer pipe

Thanks Ian,

I already have straight 6" mains made from stormwater/sewer pipe. I'm after some input regarding the short flexible ducting lengths to the machine/s.

G

To help quantify the difference, earlier this week I tested some 4" smooth bore flexy and yesterday I dug up some 4" fully corrugated flexy from underneath my junk pile on the drive way and will be running a comparison test maybe next week.

Excellent, thanks Bob. Will keep an eye out for the results.

Originally Posted by BobL

To help quantify the difference, earlier this week I tested some 4" smooth bore flexy and yesterday I dug up some 4" fully corrugated flexy from underneath my junk pile on the drive way and will be running a comparison test maybe next week.

Unfortunately it turns out not to be 4" flex but 90 mm storm water (square corrugations) but I tested it anyway.

Summary
NB: The measured flow rate drop-offs relate only to when connected to a 3HP CFM with 6" ducting pulling ~1250 CFM
A 4" inlet can draw no more than ~400 CFM
4" smooth wall flex loses ~20 CFM/m
90 mm fully corrugated ducting loses ~56 CFM/m
I would expect 4" fully corrugated to be somewhere between these two values

The loss rates per metre only apply for the first few meters of use after that the flow-rates/m will reduce slightly but it won't take much to reduce the flow stuff all.
In short keep any amount of flexy as short as possible and if it is corrugated keep it really short.

Thanks Bob,

Appreciate the testing and reporting of results.

G