Pushfit soil pipe as dust extraction

[sunnybob]

If I can inject a teeny bit of science in here?

The static comes from the wood chips scraping along the inside of the plastic pipe. Exactly the same effect as stroking a balloon across a woollen jumper and then sticking the balloon to a wall.
NONE of the pipes create static by themselves. The greater the flow speed, the more static produced.

Now, how are the pipes connected to the wall? if they are fixed with pipe clips, and you have left the rubber bumper pads on the clips, then the pipe is insulated.
If you have metal clips touching the pipe and then fixed to the wall in such a way that the metal clip stud is NOT insulated by a plastic wall plug you have earthed the pipe.
If the pipe goes into a metal container with a motor attached, its earthed through the mains lead.
So, most systems are earthed somewhere and will never produce shocks.
But if you have a powerful extraction system, into plastic hoses and plastic pipes and plastic cyclones, and the securing clips arent physically touching brick walls, guess what? you have static!
easy peasy innit?

On large installations I have heard of bare copper wire being threaded through the entire run and earthed through the pipe at each end.

 

[MikeK]

MikeK. I think you must be shopping at the wrong suppliers or someone saw you coming. The difference is not that big.

Your definition of purpose built is different than mine. The spiral duct in the link you provided is for low-pressure HVAC systems, not dust extraction systems, and is similar to spiral ducting available here at similar prices. The largest diameter available when I was shopping was 110mm, so this was already too small for my dust collection system. If you have a link to purpose built dust collection ducting that is similar in price to S&D pipe, I would like to see it.

Here is a link to the Schuko website that makes purpose built components for dust extraction systems that I installed. If you have a link to purpose built dust collection ducting that is similar in price to S&D pipe, I would like to see it.

https://www.schuko.de/en/products-syste ... components

The ducting I bought and installed is purpose built for dust extraction systems, with smooth interior surface and flange connections. Most importantly, it is not prone to collapsing like the thin wall HVAC spiral duct. According to the Bill Pentz website, the standard (for the U.S.) 30-gauge ducting can collapse if the blower is turned on with the blast gates closed. Since no one at any of the big box stores here could tell me how thick the metal was, and it would flex if squeezed, I passed on it.

 

[sumo2001]

If I run wire to my metal base extractor will that earth it ?

 

[sunnybob]

If you connect a copper wire direct to a bare metal area on the can and then to the earth connector on the appliance, then yes, its earthed.
Note BARE metal, paint will not conduct current.

 

[Trevanion]

the standard (for the U.S.) 30-gauge ducting can collapse if the blower is turned on with the blast gates closed.

Your usual spiral ducting here is twice as thick as that and it's still less than £5 a meter for 125mm, Mike Jordan is honestly saying the truth when he says there's barely anything in it between PVC and Spiral Duct.

Someone I know has just upgraded their dust collection set-up from a cowboy affair to spiral ducting and proper gates and such and buying everything new it cost him around £2000 and a few days to put it all up, and this was in a 4000sqft building with several machines to hook up to.

 

[Roland]

The problem with static isn’t getting a shock. There is a risk that a spark can ignite a dust/air mix, causing an explosion. Not common, but not a risk I’d like to take.

 

[MikeK]

Your usual spiral ducting here is twice as thick as that and it's still less than £5 a meter for 125mm, Mike Jordan is honestly saying the truth when he says there's barely anything in it between PVC and Spiral Duct.

Someone I know has just upgraded their dust collection set-up from a cowboy affair to spiral ducting and proper gates and such and buying everything new it cost him around £2000 and a few days to put it all up, and this was in a 4000sqft building with several machines to hook up to.

You are truly fortunate to have resources like that! The spiral ducting available at the big box stores here is useful for nothing more than low pressure ventilation. It would almost be cost effective to drive to the UK and load up my truck with your thicker ducting.

 

[Inspector]

The problem with static isn’t getting a shock. There is a risk that a spark can ignite a dust/air mix, causing an explosion. Not common, but not a risk I’d like to take.

Actually you can't get a big enough spark from a home DC until you use 12"+ diameter PVC (read that somewhere) and the DC big enough to move the air though it to build up the charge. Also you have to have the perfect concentration of dust which using home shop including drum sanders we can't reach. A big wide belt sander might get there but how many of us have 1 meter wide belt sanders in the shop?

The most common cause of DC fires is wood getting hot from friction with the wood pinching the saw blade or some other tool. The ember sits for some time in the bottom of the machine or in the DC and smoulders away until it starts to burn. The other reason is sucking up some metal and it hitting the impeller with that spark causing a fire.

The only reasons to try bleeding off the static is in some installations you can get an annoying zap and with the advent of CNC routers there is a possibility of the static discharging through the computer, frying some of the boards.

http://cliffsgarage.tv/articles/dustExplosion.html
http://www.woodcentral.com/articles/sho ... _221.shtml

Pete

 

[gregmcateer]

Gents,
I'm a little nervous of entering the ducting fray, which might head into a sharpening- style fracas before long, but here goes:

On the dustspares website, (thanks for the link- very useful), there are blast gates for 16 odd quid and also butterfly gates at just over 9 quid - is there a worthwhile advantage to the former?

Thanks in advance

Greg

 

[Inspector]

Blast gate when open is unobstructed so nothing for the shavings to hang up on. A butterfly valve always has the disc in the duct where shavings can hang up, eventually blocking the duct. Use blast gates.

Pete

 

[gregmcateer]

Cheers Pete,
I suspected as much - bit like proper water shut off and ball o fix style limiting flow.
Thanks
Greg

 

[Lons]

I'm a lot more concerned about my belt / disk sander causing a fire that my DC system as I've experienced it.
OK my own fault as I didn't clean it thoroughly enough, thought I had and I disconnected the DC outlet and connected a shop vac because I sanded some metal however there was a build up of sawdust in a corner which ignited due to metal sparks, it was a solid lump not fine dust, luckily saw it quickly but won't be doing that again in a hurry. #-o Pure laziness as I have several other means of grinding metal.

 

[Rorschach]

I am not really worried about fire from static (fire from sparks does worry me of course), I am only worried about the nasty shocks I was getting. Earthing solved this problem entirely (aside from shop vac) the potential fire prevention is an added bonus.

 

[gregmcateer]

I am not really worried about fire from static (fire from sparks does worry me of course), I am only worried about the nasty shocks I was getting. Earthing solved this problem entirely (aside from shop vac) the potential fire prevention is an added bonus.

Did you just run a bare copper wire down the inside and connect it at both ends to metallic parts?

 

[Rorschach]

I am not really worried about fire from static (fire from sparks does worry me of course), I am only worried about the nasty shocks I was getting. Earthing solved this problem entirely (aside from shop vac) the potential fire prevention is an added bonus.

Did you just run a bare copper wire down the inside and connect it at both ends to metallic parts?

No I used aluminium tape (the kind used for sealing ducts etc) and ran a strip down the length of the outside of the pipe and then connected to earth at the extractor end, it worked well.
My sandblaster has a copper wire clipped to the house earthing point and then I also wear an earthing strap on my wrist when using it, again it works perfectly, no shocks since.
I have not had any good ideas for the shop vac though as the hose is plastic as is the cyclone so earthing is tricky.

 

[gregmcateer]

That's helpful, thank you

 

[gregmcateer]

Gents, continuing this thread seems as good a place as any:

Blast Gates - 2 questions:

1. To avoid any jamming up with debris, should they be installed in the vertical pipe run, so they are horizontal, or in the horizontal runs so they are vertical?

Or doesn't it matter a hoot?

2. As close as poss to the extractor or as close as poss to the machine making the mess? (I assume the extractor, to minimise unnecessary 'pull'

Thank you in advance.

Greg

 

[Doug B]

If your blast gate is vertical it stands a chance of either dropping shut or falling open if it doesn’t have some sort of open/close fixing.
Usually gates are placed near the machine for ease of access especially if the extractor is the other end of the shop.

 

[gregmcateer]

Hi Doug, thanks for that.
I'll give it a go

 

[mindthatwhatouch]

Rorschach. Re: shop vac.
Try wrapping aluminium tape around the perimeter of the shop vac and have a little trailing bare conductive lead draped to touch the floor.