Dust Extractor advice needed.

[Bodger7]

I recently extended my workshop and, as a result, had to alter my dust extraction layout. I now find that, especially when I power sand, I am getting dust everywhere and not enough is being caught by the extraction system. My Draper 1hp extractor is housed in a shed that adjoins my workshop and 100mm piping leads to my lathe, sanding machine and bandsaw. From reading other posts on the subject I wonder whether the number of 90 degree bends in the system is contributing to the apparent lack of "suck". I have about 15 metres of pipe and 6 bends between the extractor and lathe which can't help. I have looked at rerouting the pipework to go across the ceiling instead of around the walls but the position of a new light would make that rather difficult. I am presently thinking about upgrading to a 2hp extractor, possibly a SIP but I see that there are two 100mm outlets and I only need one. Would blanking one off decrease the efficiency of the machine?
Any suggestions/advice would be appreciated. Thank you.

 

[Cabinetman]

The Inspector is the man you need.
From my limited experience blocking off one input on the machine just means that the remaining one gets all the suck. It does sound as if the pipework is a bit too long for the size of motor. Do you have blast gates on the unused bits of kit?
Ian

 

[Inspector]

My ears are burning. Hmmm.

Your 6 elbows assuming a 1R bend and smooth adds about the equivalent of 45ish more metres for a total of 60 metres.

Or using the calculator below using 425 CFM (optomistic) for your DC and what a 100mm duct can flow, 49 feet of PVC duct, and the 6 elbows the calculator shows a loss of 6.1 inches of water loss. Basically how much drag the system has. Probably more than your DC can muster.

No dust HVLP collector will have any luck pulling much through 100mm duct of that length, Even changing to a 2hp DC will not do much better because of the duct size.

Page 54 http://www.lorencook.com/PDFs/Catalogs/Cookbook_Catalog.pdf

http://www.63alfred.com/freecalc/ductloss.htm
Can you move the lathe close to the DC? If you kept the ducts short with the 2hp DC, used 150mm and made a bell mouth hood for the hose at the lathe you would get closer to this kind of draw.

Pete

 

[Bodger7]

The Inspector is the man you need.
From my limited experience blocking off one input on the machine just means that the remaining one gets all the suck. It does sound as if the pipework is a bit too long for the size of motor. Do you have blast gates on the unused bits of kit?
Ian

Thanks Ian. Yes, I do have blast gates on the unused ports and only use one at a time.

 

[Bodger7]

Can you move the lathe close to the DC? If you kept the ducts short with the 2hp DC, used 150mm and made a bell mouth hood for the hose at the lathe you would get closer to this kind of draw.

Hi Pete. I will read your reply again when I am more awake but I am going to consider reducing the length of pipe between DC and lathe by rerouting piping across ceiling rather than round walls. Changing to 150mm pipe woud be too much of a major change needing structural changes. Thank you for your advice.

 

[Jameshow]

Can you replace the 90° bends with soft bends? Might improve airflow?

 

[Myfordman]

3HP plus cyclone serves my 30 sqm workshop adequately with 110mm pipe and no bend/fitting greater than 45 degrees. ( two x 45 to make any 90s needed)

 

[Bodger7]

Thank you all for the additional replies. Following those replies I have looked at the situation again and by making a couple of structural alterations I can lose at least 4 metres of pipework and 2/3 90 degree bends as well as "softening" the other bends as suggested by using two 45 degrees instead of single 90 degree bends. I will then try the existing dust extractor before lashing out on a new 2hp one.
Pete, I didn't understand all the technical stuff but I did get the gist of it thank you. As seen above I will be reducing the effective pipe length quite substantially and hope that that will be sufficient. I am getting some suction with the present set up, just not enough.
Thank you all again.

 

[Inspector]

If you look at the Loren Cookbook page 54 link I put up above you can see that a pair of 45º elbows can have more drag than a single 90º elbow if it has a large enough radius. See what you have for elbows before changing them for the pair of 45ºs. The radius is measured along the middle of the elbow to the focal point where you would put a compass. Like this. 90 Degree Short Radius (1″ Centerline) – Conklin Metal Industries

Pete

 

[mindthatwhatouch]

It's quite easy to make nice gentle bends using a bandsaw and a length of pipe. Cut wedges and glue together.