Static in PVC Pipe.

[Garden Shed Projects]

Hi all

I am looking to install a fixed extraction system for my workshop. I intend to install 3” pvc pipe with home made blast doors.

I understand that there can be issues with static build up on the pipe when the chips are flying through it. Can any one advise on how you have over come this in your workshop please? Or whether it’s a none issue for hobby use?

 

[Sandyn]

have a read of this thread. You might be able to find the answer. It's a slow start into the full discussion about plastic pipes in dust extraction.

 

[Jones]

4 inch will work better as the increased airflow can carry more debris and the fan won't be under as much strain. Using galvanised spiral ducting you won't have a static problem and though the pipe is about the same price as PVC the bends and joints are cheaper.

 

[Jonwar]

Hi all

I am looking to install a fixed extraction system for my workshop. I intend to install 3” pvc pipe with home made blast doors.

I understand that there can be issues with static build up on the pipe when the chips are flying through it. Can any one advise on how you have over come this in your workshop please? Or whether it’s a none issue for hobby use?

Check out John's video static in dust collection he is an electrician and hobby wood worker so you get the facts from an electrical point of view on static

 

[accipiter]

Another thumbs up for the John McGrath's "Main In Shed" video

 

[Insanity]

I think one guy solved the problem, I can't find the youtube video at the moment!.

Basically he put screws that have been cut down in the pipe all along the length, only so they just poke through as not to disturb any debris that flows through it. Then ran a copper wire wrapped round each screw head and then grounded that wire. Then think he hot glued around each screw to seal it up properly.

This is probably the best example I've seen of solving the issue. The idea is simply to create a point where static can flow to the outside of the pipe and then ground.

 

[Sporky McGuffin]

It does seem like a lot of effort compared to using steel ducting - and I'm not sure it's much cheaper, especially once you've added all the stuff to do the grounding, and even more so if you value your time in doing it.

 

[Garden Shed Projects]

It seems a contentious issue. From looking at the posts and videos it seems clear that there is an issue with static build up but how severe a problem it is is open to debate.

I have a large Kercher vacuum, maybe with a cyclone, and am likely to not be using anything that creates to large a chips. Only chop saw, track saw and evolution table saw are the creators of the largest chips. Which is why I was looking at 3” pipe as I don’t think the vacuum will pull enough air through. I also have the materials available.

Would running foil tape along the length and onto the body of the vac provide a ground?

 

[Insanity]

It seems a contentious issue. From looking at the posts and videos it seems clear that there is an issue with static build up but how severe a problem it is is open to debate.

I have a large Kercher vacuum, maybe with a cyclone, and am likely to not be using anything that creates to large a chips. Only chop saw, track saw and evolution table saw are the creators of the largest chips. Which is why I was looking at 3” pipe as I don’t think the vacuum will pull enough air through. I also have the materials available.

Would running foil tape along the length and onto the body of the vac provide a ground?

What size is the Kercher vacuum outlet? You really want to stick with the that size all the way through your collection system.
As for the foil tape, it might work if it was stuck on the inside of the pipe, but not on the outside.
I wouldn't worry too much about it. I haven't heard of a single report of a fire as a direct result of static in PVC pipes, and there is a LOT of people choosing it over the more expensive official duct work for vaccuum, myself included.

 

[RichardG]

Finally John McGrath has pointed out the complete futility of grounding PVC pipe. If you're worried about static then use metal ducting, it's not a great deal more expensive, otherwise just use the PVC pipe as is and enjoy your woodwork, it's a none issue.

 

[DBT85]

There was one poster here who called anyone using pvc a clown. Delightful chap.

The upside of using metal would be the static not making dust stick to the outside. I'd not be worried at all about the potential of having the right density and static buildup to cause an explosion which is why everyone else seems to worry about it.

 

[Jones]

I doubt explosion is a risk in any home setup, the only worry is that a small static shock might make you jump . Planer chips bouncing through corrugated flex duct seem to generate most static in my experience though the new hose with a spiral wire in it stops that. If it's only a small system with sawdust only I doubt you'll have any problems.

 

[RichardG]

The worst systems can be those that use metal ducting with a single earthing point and not physically attaching the joints and pipe together, either by drilling through the joint into the pipe and fitting a self tapper or bridging each junction with a cable. If the earth fails at any point, which it can on push fit joints, then you have an isolated conductive section where all the static can flow together and create a significant charge. However, even then the chances of this ever causing a problem in a home workshop is very slim.

 

[Sporky McGuffin]

The worst systems can be those that use metal ducting with a single earthing point and not physically attaching the joints and pipe together, either by drilling through the joint into the pipe and fitting a self tapper or bridging each junction with a cable.

I don't see how it'd work without drilling, screwing, and taping every joint - you lose too much performance.

 

[Old.bodger]

I’m sure I have contributed to these debates in the past, experience says that it all gets heated quite quickly. Suffice to say, if you are worried, thread a bare copper wire through your plastic ducting and ground. I did this in a school workshop and it’s been working without incident for 15 years now.

https://www.axminstertools.com/dust-extraction-system-grounding-kit-510412

 

[MorrisWoodman12]

.......... then you have an isolated conductive section where all the static can flow together and create a significant charge. However, even then the chances of this ever causing a problem in a home workshop is very slim.

My understanding of static is that it can only ever build up on non-conductive materials. There must be a means by which the positive and negative charges can remain separated. Otherwise they rush back towards each other and neutralise themselves. Thus static build up can never happen on a conductive material such as metal. A metal pipe is grounded purely for safety issues just in case it becomes live even if it's an extremely rare probability.

 

[RichardG]

My understanding of static is that it can only ever build up on non-conductive materials. There must be a means by which the positive and negative charges can remain separated. Otherwise they rush back towards each other and neutralise themselves. Thus static build up can never happen on a conductive material such as metal. A metal pipe is grounded purely for safety issues just in case it becomes live even if it's an extremely rare probability.

Think of a Van de Graaff Generator, what sits at the top, a metal sphere to store all the accumulated static charge. Static charge can accumulate on any isolated material. It's the process of one material donating an electron to another that generates the negative static charge, normally by friction.

If you look at industrial ducting or piping then they use bonding at regular intervals and also bond over joints or use conductive tape to ensure that the pipe remains connected together.

Reasonable article here that will explain it much better than my limited knowledge.

 

[RichardG]

I don't see how it'd work without drilling, screwing, and taping every joint - you lose too much performance.

Well a 100m duct has an area of 3.142 * 50mm squared or 7855 square mm, say a screw projects 3mm and is 3mm wide then it blocks the flow by 9 square mm or 0.12%. Say you have 5 joints in the way then 10 screws, so yes your flow would be reduced by 1.2%. Conductive tape is available.

Some industrial ducting has a spot welded tag on every pipe for the connection of bonding wire.

All I was trying to say is don't assume just because two metal pipes are loose pushed together they have a good long lasting electrical connection for life.

 

[Sporky McGuffin]

Well a 100m duct has an area of 3.142 * 50mm squared or 7855 square mm, say a screw projects 3mm and is 3mm wide then it blocks the flow by 9 square mm or 0.12%. Say you have 5 joints in the way then 10 screws, so yes your flow would be reduced by 1.2%. Conductive tape is available.

Some industrial ducting has a spot welded tag on every pipe for the connection of bonding wire.

All I was trying to say is don't assume just because two metal pipes are loose pushed together they have a good long lasting electrical connection for life.

Sorry! I just realised that I worded my post completely wrong.

I am strongly in favour of having two screws through each joint, and then taping it. What I meant to say is that I don't see how spiral ducting works (properly) without doing all of that - you lose too much performance to the leaks at each joint.

The way I wrote it does look like I was suggesting the complete opposite. Is there a facepalm smiley I can award myself?

 

[Spectric]

It seems a contentious issue. From looking at the posts and videos it seems clear that there is an issue with static build up but how severe a problem it is is open to debate.

The question to ask is how many home workshops have exploded over the last twenty or thirty years due to ignition of an explosive atmosphere within the extraction system, I cannot find anything. If the pipes are flowing gas or a powder then you will be under ATEX regs and then it is not just the ducting / pipework you need to be concerned with but all electrical fittings as well. As for the bonding, Sporky is correct in that if there is a need for bonding then just relying on a push fit pipe is not good enough, if in any doubt then read the machinery directive and electrical guides on bonding and protective conductors. A good example here is that any panel on an electrical system that is designed to be detached or opened must have it's own bonding conductor, you cannot rely on hinges or the fasteners.

So let's just get on with woodworking and stop worrying about the what if's, you are probably at more risk from being hit by a frozen cowpat from an aircraft than your extraction system exploding.