Shop Dust Extraction

[John Saxton]

Righto, in the course of re-vamping the workshop I need to get the dust extraction hoses off the floor and at least tidy the place up a bit so..........I am contemplating doing so using pvc ducting overhead.
I know of a couple of sites that do go into some detail in this but do you dry fit the pvc tubing or glue it in place?Is there a rule of thumb for placing the earth wire for the static electricity produced?Has anybody had any experience dealing with this type of system?
Cheers http://ubb.ubeaut.com.au/ubb/smile.gif

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Johnno

[Rod Smith]

HiJohno
Have a look at this site, http://www.gis.net/~dheaton/woodworking/articles/DC_myths.shtml#top lots of info there and it does seem to agree with the bulk of opinion regarding fires and static/earthing.
I have a 1400 cu ft dust extractor that I'm gonna duct to all machines (one of these days), I was thinking it would be best to dry fit the PVC in case of blockages. I doubt that any significant leakage would occur, maybe some duct tape would be adequate? Rod

[Gary]

Hi Jonno
Check out the JET website at jettools.com (http://jettools.com) go to the help center then go to the quick tips and you will find quite a lot of info on setting out your shop,plus hints on grounding the poly pipe etc. It is in PDF format so you can download it and print it out if desired.
Gary

[This message has been edited by (edited 28 August 2000).]

[John Saxton]

Thank-you Rod,Gary,two very good sites that give an in depth answer to my query.

Rod, I was thinking along the lines of a dry fit primarily with the thought of being able to add or change the layout but you have given me another reason to consider which I had'nt thought of but it stands to reason that you would want to be able to clear the lines easily and I thank you for that in fact you have helped me decide. http://ubb.ubeaut.com.au/ubb/biggrin.gif

Gary the Jet site is full of info that I did'nt know was there and it gave me access to a couple of other questions that I had so thanks to you for that.

Cheers

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Johnno

[John Saxton]

Rod, a further post to say that I have fitted pvc ducting, being ceiling mounted, but have glue fitted all in place to ensure minimal leakage.I still have to seal the external joints for full measure!
I put in place at varying intervals some Y section fittings with threaded ends with a screw cap on the unused portion of the Y for easy access in the event of a blockage but I may be lucky as there is plenty of suction with blast gates on all machines to ensure same giving upwards of around 1200cfm with a total demand on any one machine of no more than 400cfm.
There is still the Static Earth wire to assemble .......still getting around to it!
Cheers http://ubb.ubeaut.com.au/ubb/smile.gif


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Johnno

[Iain]

Recall reading somnewhere (hope it was not here) about installing static wire in PVC, attache fishing line to a rag, switch on DC and insert rag at end. After the rag and line have passed through tie wire to line and pull through.

[John Saxton]

Yeah cheers Iain,thanks for that little tip.
The Jet tools website has a page on installing ducting and was a big help also.
Apparently there is a need to wire the outside of the ducting as well as the inside.
The outside wire is coiled around the length of the ducting whilst the inside is is earthed to each take-off or machine.
Haven't got around to doing this yet have just put the last piece of ducting in place today ending at the lathe.
Cheers http://ubb.ubeaut.com.au/ubb/smile.gif

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Johnno

[JackoH]

Did I read somewhere that static electricity in poly ducting was a bit of a furphy?
Regards. John H. http://ubb.ubeaut.com.au/ubb/frown.gif

[Iain]

I read that too but I have also seen a van de graf generator, new ones, lots of plastic....and static.

[Rod Smith]

Thanks for the update John (S). The access points should work well. Interesting all that stuff about static and grounding in insulators such as PVC. Did you read the article at the link I posted? Rod

[Mal]

I have a mate who went to the local salvage yard and picked up some 4" metal down piping. He reckons it's pretty good. One interesting point he noticed was that he never gets any blocks at the bend because metal pipe tends to have gentler corners. The only plastic is the little bit of flex at each machine.

[John Saxton]

Yeah Rod I read that post of yours with interest which goes right into the nitty-gritty of the topic.
By some accounts there have been fires in the workshop due to the fact that the ducting(pvc)hasn't been effectively earthed and with the static energy created, some the residue of dust and shavings within the dust extractor have smouldered and ignited.
It goes without saying that a job worth doing is a job worth doing properly.
Must get in there and finish mine off properly!
Cheers http://ubb.ubeaut.com.au/ubb/smile.gif

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Johnno

[Rod Smith]

Actually John, I got the opposite message from that and many other articles I've read on the subject. That is that, 1- no one was able to provide instances of fires caused by static in pvc pipe. 2- PVC is an insulator therefore it can't be effectively earthed. 3- It is far more likely for fires to start due to sparks entering the stored dust when metal is struck, causing a smoldering fire. So more important to have this outside or empty daily.
One observation I have made is that static is greatly increased when mdf is used. Also, occassionally there is a spark (external I think) from my small DC plastic collection bag to the stand.
If I ever get around to installing a ducted pvc system I won't be attemting to insulate it, unless I get a boot, then I'll replace it with metal duct. Anyone else got any thought on this? Cheers. Rod

[RETIRED]

Gooday.

I have not entered into this discussion, (waiting to see how it panned out) but I am about to put my 2cents in.

I have to agree with Rod on this one. In 15 years of using PVC pipe on Dust extraction Systems, I have never had a fire caused by static discharge.

My theory on the subject is that the average extractor does not have the capacity to get enough dust up the chute to get a combustible ratio. Also, to ignite the interior dust where is it going to arc to? It can't arc to itself in the pipe because PVC is an insulator. If it arcs to the outside, it can't ignite the dust inside the pipe because it is sealed.

We used to extract straight into a metal dump master bin. I have had a shock off the PVC pipes but a 6 volt battery gives me a shock.

We have had fires in caused by heated material off our overhead routers drilling holes but we expect that. http://ubb.ubeaut.com.au/ubb/smile.gif

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Ian () Robertson
"We do good turns every day"

[John Saxton]

Rod,,I have to admit that I had the wrong slant on a couple of points on my previous post.
Rod I had read your post with the in depth explanation behind it some time back and it was the time lapsed plus a few too many Bushmills last night in company that lead me from the straight and narrow.(thats my excuse and I'm sticking to it )
Thanks , for putting all straight as someone working with the system in place can only do.
So armed and with recovery Bushmills in hand I look towards a less frightening prospect in the workshop!
Cheers http://ubb.ubeaut.com.au/ubb/smile.gif


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Johnno

[RFNK]

Metal downpipe/ducting is pretty cheap, you don't have to earth it, it's not going to explode, so, why bother with PVC?

[Rod Smith]

Dunno RF, I spose its strong enough? How tight are the bends, no worse than pvc I expect. I've heard of yanks using metal heater duct. Can you get 5 or 6" for main runs. Certainly would take the static out of the equation. You definately would want make sure its earthed through the DC. This may be achieved by the way its connected. Food for thought. Checkya. Rod
PS I do hate static shocks.

[John Saxton]

What size doe's that metal downpipe come in?
The recommendations in the readinds on the subject suggest no less than 100mm dia.for max effect.

[outback]

Really John you need 150mm ducting.




























































I think craigb needs a hug after this. :D :D















Not that I think its funny digging up old threads and answering them. :D

[Felder]

You couldn't find an older thread, Outback?:confused::p

[John Saxton]

Since Outback has dredged this from the very bowels of the BB I'll add that all Pvc 100mil is in place and doing as intended.

end of thread

PS and a thanks to all respondants

Cheers:)