Pushfit soil pipe as dust extraction

[OldWood]

I'm slightly reticent to entering this conversation (!) coming from a desire to fit such a system but no practical knowledge. Locic sasys to me plastic drain pipe as all fittings are immediately available at the local plumbers outlet, and how ever carefully you design something an immediate back up of parts is worth quite a lot of money.

I can understand the bare copper wire down the plastic pipe conducting away the electrostatic charge, but how do you get the wire out to earth it? Having just written that I realise a small hole at some point and silicone to seal it, or a 4mm bolt with earth tags inside and out.

But then I have difficulty with the option of placing of aluminium tape on the outside of the pipe - could I ask if Sunnybob could continue his discourse on static electricity to explain how the charge generated inside a plastic pipe gets to the outside, and further, referencing this tape, how it works when it will have an adhesive layer and possibly a plastic layer before you get to the conductive film on the surface.
Rob

Editted to say this is now an out of date request as I'm reading the article from Wood Central!!

 

[Chris70]

It was like déjà vu all over again.

Is that tautology?

 

[gregmcateer]

For info this is worth a read on the subject, it’s very thorough.

Grounding PVC and Other Dust Collection Myths

Thanks for sharing this - way over my little head scientifically, but reassuring to read.

 

[Sandyn]

Very interesting article. For me, the interesting line is " However, if you choose to use PVC ducting in your home shop, the risk of an electrostatic explosion due to the ducts is, at worst, extraordinarily small. From the research papers I have read, this risk is essentially zero "
so the risk is 'essentially zero'......but not zero

 

[MikeK]

Is that tautology?

Yes, but it's a quote attributed to Yogi Berra, and American baseball player for the Yankees. He was famous for nonsense quotes, such as "The future ain't what it used to be."

 

[Trextr7monkey]

Interesting thread I had a workshop with a commercially fitted extraction system which was mostly wood working machinery with about 14 points fitted. It was all installed using various diameters of spiral tube with flexible hoses to each applicance.
Couple of points
1) Over time equipment was moved around andthe system was modified in places with lengths of 110mm drain pipe as long lengths of flexible pipe get expensive and collect dust. The annual HSE inspection did not raise this as an issue.
2) Blast gates were fitted to all points and never got blocked there was one rotating butterfly valve attached to a sweep up hood for the cleaner and that occasionally caused problems.
3) The metal duct system replaced a plastic tube diy installation that had operated for many years the tubes appeared to function well it was the old plastic bags on the cyclones that made the system useless.
4) With all tubes shut off there was suitable suction to clear any minor blockages that could occasionally be heard bouncing up and down the dropper tubes. We were advised to just use one port at a time but in practice this didn’t always happen

 

[Inspector]

Sorry, my mistake, didn’t read the full thread thoroughly....

No sweat Richard. Everyone skims long threads at some point along the way and even when you do follow one over a period of time you forget some of what has been said and restate it again.

Plastic is an insulator and when it sparks only a small area near the contact point discharges. Trying to bleed all of it off so it doesn't build up is nearly impossible. Maybe wrapping the whole pipe with wire screen (chicken wire for instance) like a Faraday Cage might work but if going to that extreme one might as well get metal ducting.

I've said it before, maybe even in this thread , the only reason to try grounding is to reduce nuisance shocks and for dust collection to CNC machines to protect their circuit boards where a stray shock can fry them.

Everyone is free to make their own choices. Best if done after research rather than fear but we wouldn't be human if we did that all the time.

Pete

 

[Lard]

I replaced my flexible pipework with 110mm drainage pipe a few years back and, although screwfix is handy/local for immediate purchases, I bought the vast majority of pipe and fittings from an online company.

Cant remember the exact company but here’s a suitable web example to illustrate.....

Example price is ~£9 for 3m length of 110mm pipe (incl vat).....they charge a one-off delivery of ~£9 for orders below £90

https://www.plastics-express.co.uk/...MIz8G348e77QIV34BQBh3y6ATlEAQYBCABEgJ5lPD_BwE
Out of interest I‘ve also just completed a project for my cousins where the gf bathroom was a replaced with a brand new ff room which, obviously, involved some above ground drainage. I got them to buy online. Worked perfectly and saved a fair amount.

 

[DBT85]

Very interesting article. For me, the interesting line is " However, if you choose to use PVC ducting in your home shop, the risk of an electrostatic explosion due to the ducts is, at worst, extraordinarily small. From the research papers I have read, this risk is essentially zero "
so the risk is 'essentially zero'......but not zero

The risk of getting struck on the bonce by a meteor also isn't zero. Yet you don't walk the street wearing a Challenger 2 as a hat.

 

[gregmcateer]

The risk of getting struck on the bonce by a meteor also isn't zero. Yet you don't walk the street wearing a Challenger 2 as a hat.

Don't you????

 

[Sandyn]

The risk of getting struck on the bonce by a meteor also isn't zero. Yet you don't walk the street wearing a Challenger 2 as a hat.

Absolutely not. I just found the article slightly odd in some areas. It is a very good article. I'm taking a slightly tongue in cheek view of it and the poor wee soul spent ages in the library, but it's a bit dismissive of the problem,then goes into great detail how to counteract it.

The 'Myths'

1 " I do not know the explosive power of this volume of dust, but I do not think this is going to level your shop."
:-I read as ---he hasn't a clue, but has guessed it's not a problem. If you are going to produce 'the definitive guide to static in PVC'. one thing you can't do is guess, but we all do it...

2 " You simply can't ground an insulator."
:-Of course not, but if you have a charged insulator and put a ground near it, it will tend to reduce the charge. That's what lightning conductors can do. Charge will leak from earth via the conductor to cancel the charge on nearby clouds and can stop a discharge. The terminology 'grounding' is wrong, but it's literally what you do. You bring a ground to the insulator, just as a lightning conductor 'brings the ground to the sky'. He has to chill out about terminology.

3 " As seen above, the collected dust pile and the collection bag are greater hazards than the ducts. Fortunately, in practice home shop sized dust bags have shown themselves to pose little explosion hazard."
:-Totally irrelevant to PVC pipes and static.

4 "There is little or no static on the outside of the PVC unless you are rubbing the outside for some reason; the static is on the inside. The electric field due to the static charge in the pipe can cause a discharge on the outside"
:-It doesn't matter what the physics behind it is. People see effin big sparks from plastic tubes . He is being technically correct, but needs to chill out about terminology.


For me, static and dust explosions are not a concern, but I respect the concerns of other people who are worried about it. As for wearing protection against a meteor . NASA spends a fortune looking for meteors, so I don't need to wear Challenger 2 as a hat. ....and there are many people who do have disaster shelters for when the meteor strikes. I bought an extra toilet roll, so I'm OK!

When you start to quantify a problem like static in a tube, you are on to a looser, because there are so many variables but it is a non zero risk.
When it comes to health and safety, the risk has to be assessed see here, in particular the ducting requirement. I would say a better description is that the risk is 'not known'. not 'essentially zero' The risk in PVC pipe is apparently real if the HSE require conductive ducting.
I think that anyone who feels they need to do something about plastic pipe, are doing the correct thing for them. It seems there is no guaranteed way to completely prevent the possibility of discharge. Whether that causes a dust explosion is a completely separate problem and even more complex.

If anyone is really concerned, my advice now would be they should just follow the HSE advice and fit conductive ducting.

 

[Heluvaname]

Apologies if I've missed it, but does anyone use, or have a source for, clear rigid pipe for dust extraction?
Sure I've seen a systems somewhere, which seemed to make sense for easily spotting issues, and it looked cool to see the dust whizzing along!

 

[Inspector]

There are 2 1/2” size packages here at Lee Valley but nothing bigger that I know of. You can get clear PVC in larger sizes that have astronomical prices that make it too expensive to even consider.
Pete

 

[Sandyn]

Apologies if I've missed it, but does anyone use, or have a source for, clear rigid pipe for dust extraction?
Sure I've seen a systems somewhere, which seemed to make sense for easily spotting issues, and it looked cool to see the dust whizzing along!

There is some HERE, but a bit expensive. I would light it with blue LEDs

 

[Heluvaname]

Thanks, but at c£50/m I think I may give clear a miss!

 

[Heluvaname]

Would look great edge-lit with blue LED though

 

[Davey44]

I have a couple of new lengths of LARGE soil pipe (110mm I believe). Will check tomorrow if anyone's interested. It makes a relatively inexpensive means of installing a large extraction system, especially if you're using a high volume/ large power motor extractor. Spurring off a large primary with smaller secondaries gives one of the best options for an effective and efficient system.

 

[mikej460]

Yes, but it's a quote attributed to Yogi Berra, and American baseball player for the Yankees. He was famous for nonsense quotes, such as "The future ain't what it used to be."

Yes but then again he was smarter than the average Berra..

 

[Keith 66]

Just saw this on fb Oxford fire service called to a fire in an extraction system, I guess this is why metal ducting is a better choice.
,Facebook,

 

[Sandyn]

According to the report it was a spark from a saw that caused the fire in the metal ducting. I think it must have been clogged with sawdust. I think the metal ducting may have prevented the spread as it seems to have been limited to the extraction system