Extraction Ducting...

[themissingelf]

I'm struggling to determine the best ducting for my proposed fume and dust exhaust (to outside).

I'm proposing, from the existing 100mm hole in the wall, all in 100mm pipework:

90 degree bend > straight 2m > Y / T junction.

from the junction:

Route 1: > Non-return flap > flexible hose to dust vac exhaust.
Route 2: > Non-return flap > inline extractor fan > flexible hose > stayput hose.

"Route 1" allows the dust vac to exhaust to outside; ensuring the sub 0.5 micron dust that has passed through the filters is removed from the workshop.

"Route 2" will be used to:

• exhaust fumes from soldering and similar
• exhaust airborne dust to outside.
• drive airflow in warmer weather to keep the the shop cooler.

Grateful as ever for input!

Thanks

 

[will1983]

Ducting size is determined by the capacity of the blower.
Check out Phil Pentz's website, this has lots of interesting information about how to calculate this and other extraction related stuff.

On the face of it your initial description sounds fine but think about the following as these are common for all systems;
Use the biggest diameter possible for as much of the system as you can.
Understand the difference between HVLP and LVHP blowers, they require different duct sizing's.
Avoid T junctions like the plague
Replace 90 bends with two 45s is possible.
If splitting a route use a Y connection and do the CSA calculation for the in and out pipework.
Note that 2x 50mm dia pipes does not equal 1x 100mm dia pipe. 2x 50mm = 3927mm2, 1x 100mm = 7854mm2
Do not restrict the flow at the dust collection port of the machine or you will undo the good work done designing the rest of the system, open it up to match if necessary.

0.5micron sounds a bit optimistic for most filters to me, in reality you only need to capture the visible dust as you are discharging outside the workshop. Trying to remove any more than this is a wasted effort and will likely result in more maintenance of the system and cleaning of the filters.

Anyway, good luck and let us know how you get on.

 

[themissingelf]

Thank you for such a comprehensive reply. All useful info!