Piped extraction

[The Bowler Hatted Turner]

So after all that (now that I am done with the jelly) have we come to an agreement? Should I earth plastic extraction pipes or not?

[Les Symonds]

...Have you ever got out of a car and got a shock when your foot touched the ground?...

Yes, at Death Valley, ye gods was that tarmac hot!

On a less flippant note, this is becoming another of those interesting, informative threads on the forum. It is somewhat curious that the links which Bryan posted seem to suggest that earthing is essential, yet what you, Paul, and others are saying makes perfect sense and suggests that earthing plastics is a waste of time. I think that I shall go with the latter.

Les

[Bryan Milham]

Les,

My first post on this thread was to say somewhere I had read an article that says earthing dust extraction was not necessary, but could not find it again.

The documents I posted had useful information if you (BHT) wanted to go ahead anyway. If you don't need it and fit it, its no big deal. More belt & braces.

I do not know the answer.

[johnanthony]

Hello The Bowler Hatted Turner

I did exactly what you proposed in your first post about ten years ago except that I used the grey piping. Worked a treat and easy to use. However, in the first five years I had two dust explosions in the piping which was suspended from the ceiling and ran the full length of the workshop. Fortunately, the explosions were only powerful enough to blow the blanking plugs out of the ends, and frighten the life out of me.

I then ran a bare copper wire down the inside of the pipe and earthed it to the body of the wall-mounted extractor - that was five years ago and I haven't had an explosion since.

Fine dust and shavings being sucked along a plastic pipe are ideal conditions for static build-up, it works similar to a Van-de-Graff generator and in very dry conditions the resulting discharges can cause an explosion - both of mine happened mid-summer.

So, I would highly recommend just adding a wire down the inside of the pipework when you build it. It doesn't have to be copper, steel fencing wire would be fine, just make sure it runs down all the pipework and is then earthed to the metal body of your extractor, or to a mains earth.

I guess the guys who have never had an explosion using plastic pipe got away with it because home workshops are notoriously damp places.

Fortunately/unfortunately, mine isn't! :-)

Cheers - John

[The Bowler Hatted Turner]

John thankyou so much for this. I stand justified for posting my original question. I too have seen dust explosions in industry but was usure about the plastic piping. Once I get round to it I will run a wire all the way through. At the end of the day if I don't need to , nothing will be lost apart from a bit of copper wire, I never throw " it will come in useful oneday" stuff away so I have all the old copper wire from when I rewired the house, that will do the trick. And if I do need to it will be done.
Thanks everyone that took part in this post, I think it was very enlightening.

[johnanthony]

Just a final comment on industrial dust explosions ...

Many decades ago, my father worked at an animal food company ‘Up North’. It would import hard, dried, products from around the World and grind them into coarse granules and then mix them into cattle food and other animal feed.

The big grinders generated lots of dust which ended up in the empty ‘attic’ space of the multi-story mill. There were big shutters at each end of the attic to allow the dust to be carefully cleaned out periodically. Unfortunately, after working fine for many years, the cleaning lapsed for quite a while.

When someone finally realised it needed cleaning out, a relative newcomer went up and opened the shutters wide at each end - the resulting fierce wind that blew through the attic lifted enough dust into the air to reach critical density and it exploded, killing the hapless employee and demolishing much of the roof structure. It could have been much worse.

John

[Paul Hannaby]

The moral of this story - if you suffer from wind don't do the dusting!