63mm dust extraction from a chip extractor

[MattRoberts]

Hi all, it's anyone having success running 63mm extraction ducting from a larger system?

I have 125mm ducting coming from a 2hp extractor for my larger machines, but it's like to plumb in my smaller machines (disc sander etc) via 63mm ducting. I'm concerned that if I step down from 125mm to 63mm it will just starve the impeller.

My only other solution is to use my shop vac, but that's 32mm so a similar problem but at the other end of the scale.

Cheers

 

[morturn]

Matt, there are pressure relief valves around. I have not used one but understand that will stop pipes collapsing

 

[PAC1]

If your 2HP system is a vacuum system HPLV you should be able to connect 63mm pipe quite well. If the 2HP system is LPHV then there is not much hope as you will lose to much air flow stepping down from 125mm to 63mm as you have 1/4 of the cross sectional area so you will have virtually no flow.
You would be best with a vacuum system for smaller tools/connection sizes in any event. As long as your vacuum generates enough pressure a 63mm pipe and connection should suck enough to deal with sander dust.

 

[MattRoberts]

Sorry, should have clarified, it's an HVLP extractor.

I thought it wouldn't work. Looks like I'll need to try the shop vac, and if that doesn't work I guess I'll need to get a larger shop vac.

Thanks for the replies

 

[sunnybob]

Youre not thinking laterally.
If you run the large pipe right up to nearest point of the machine, put in a tee and full size extra gate on the side outlet. then you can open the side gate and step down the straight tube. Then when the machine is running you can fine tune the amount the side gate opens so the machine in question operates properly but without straining the extractor.

 

[MattRoberts]

Youre not thinking laterally.
If you run the large pipe right up to nearest point of the machine, put in a tee and full size extra gate on the side outlet. then you can open the side gate and step down the straight tube. Then when the machine is running you can fine tune the amount the side gate opens so the machine in question operates properly but without straining the extractor.

Interesting idea Bob. I had considered running 2+ pipes in parallel (even if one wasn't in use), but the side gate idea is really nice. I might have to give that a go, cheers!

 

[PAC1]

Bob. It does not work like that. Low pressure systems work by moving a large volume of air. If you have a 125mm pipe and then restrict it to 63mm that restricts air flow to one quarter as that is the relative cross sectional area. What happens is that the fan is starved of air. The air does not miraculously squash up and all race through the 63mm pipe to make up the short fall.

 

[sunnybob]

PAC, you dont seem to understand my suggestion.

The 125 mm side gate when fully open will allow sufficient air for the extractor to work at full efficiency.
The side gate will only be closed enough to allow a quarter of the suction to be diverted to the 63 mm pipe.
Side gate = 75%
63 mm gate = 25%
together = 100% of flow.

 

[PAC1]

Bob I follow but probably should have also said the air flow at the sander would not be sufficient to extract the dust. Your plan increases the air going to the fan but not the air extracting at the sander. My experience of restricting low pressure systems is that flow rate also drops so if the flow is 4000ft per minute at 125 diameter it might only be 750 63mm so on top of the limited cross section you also suffer a slower flow rate. At that point there is insufficient air moving too slowly to effectively extract the dust

 

[sunnybob]

I still dont see your reasoning. What I'm suggesting is in essence a Y joint with unequal diameters. The flow on the main trunking will not change, the flow in the two unequal tubes can be balanced by adjusting the larger opening. Quite possibly the speed of air in the smaller tube will increase, but surely thats a good thing.

Theory is good, but practice sometimes confounds it.
Hopefully he will try it and let us know.

 

[MattRoberts]

Pac, the assumption is that 63mm is sufficient to extract from the sander (as that is its port size). Therefore if you use the blast gate method Bob suggests, the sum of the 63mm and the partially open 125mm blast gate should give the extractor the air it needs

 

[sunnybob]

63 mm works well for all of my machines
4" belt sander, router table, bandsaw, combi mitre saw (home made Y branch in 63 mm tube, sleeved down to 50 mm tubes, one at the rear and one on the side when in table saw mode), 63 mm hose for vacuuming the floor. The hose also goes across the workshop and plugs into a record bobbin sander and even an axminster 12" benchtop thicknesser. I had to enlarge the holes on those last two as they came with bloody silly little tubes.
Dust, chips, nuts and small bolts, even pencils are not safe when that thing is working. The only time the 63 mm blocked was when I tried to vacuum up plane shavings. The large curls blocked at the 90 degree bend.

 

[PAC1]

Bob I thought you had a vacuum high pressure extractor in which case 63mm is fine with a decent vacuum.
Matt no. It does not work like that with low pressure extractors. Read Siggy’s thread or Bill Penz website.

 

[sunnybob]

Matt, youve just been volounteered as the guinea pig. (lol)

 

[MattRoberts]

It appears so! Challenge accepted!

 

[TopCat 32]

PAC, you dont seem to understand my suggestion.

The 125 mm side gate when fully open will allow sufficient air for the extractor to work at full efficiency.
The side gate will only be closed enough to allow a quarter of the suction to be diverted to the 63 mm pipe.
Side gate = 75%
63 mm gate = 25%
together = 100% of flow.

i got what you mean bob , and that would be my 1st choice to try , if that didn't work ,what have you lost ? a Y joiner and blast gate , which could come in handy for a later project, if it doesn't its back to the drawing board

 

[PAC1]

Matt, out of interest did you ever test this theory?

 

[MattRoberts]

I didn't unfortunately. I bought the 100mm to 63mm adapter from axminster, and then my 63mm belt and disc sander died, and the replacement I got one has a 32mm port instead. I am planning on extracting from it via my main 125mm ducting (using a rectangular intake), so it doesn't appear as though I need a 63mm system after all.

I have a bunch of 63mm ducting, blast gates and whatnot that I bought from another member ages ago, so perhaps I need to move on and sell them.

 

[sunnybob]

You just cant the staff any more (sigh).

 

[MattRoberts]