Dust extractor issues

[mikec]

Yeah, thats what mine did :shock:

I was sucking stuff off the floor and it grabbed , the damn thing leaped across the floor and landed on top of me, I thought the aliens had landed :shock: :shock:


Mike C

 

[big soft moose]

lots of good advice here - mine is made out of 65mm rainwaterpiping for the narrow runs and 100mm drainpipe for the larger ones. Axminster blast gates will fit onto these pipes with a bit of "persuasion"

the other thing i'd say re the jumping dust extractor is bolt it to something - then the worst that will happen is the tube pulling loose rather than the DE learning to fly - mine is fixed to the 'shop wall with rawl bolts while the one at work (which is supposedly freestanding and movable) is bolted to the floor with anchor bolts and a piece of steel plate

also if using rigid pipe it is a good idea to earth it by running a copper wire through the pipe then to a copper water pipe or ground pin (ie a bit of rod banged/drilled into the ground), otherwise the movement of dust inthe system can set up a static charge which can then result in a spark and dust explosion. Its never happened to me but I know a guy who blew the back wall out of his shop as a result of a dust explosion (though admittedly his was from a sparking bush in a drill being used for sanding) so it isnt a risk worth taking.

 

[loz]

also if using rigid pipe it is a good idea to earth it by running a copper wire through the pipe then to a copper water pipe or ground pin (ie a bit of rod banged/drilled into the ground), otherwise the movement of dust inthe system can set up a static charge which can then result in a spark and dust explosion. Its never happened to me but I know a guy who blew the back wall out of his shop as a result of a dust explosion (though admittedly his was from a sparking bush in a drill being used for sanding) so it isnt a risk worth taking.

Thanks for that, something else i hadn't even considered.

 

[Jenx]

Good Point BSM :wink: ...

Its astonishing and something which really surprised me .. 'Dust' in general is considered explosive.
I did a fire-fighting course a few years ago, and the instructing fire officer demo'd a cloud of basic 'flour' ( like for baking ), exploding, when exposed to a suitable source of ignition.

Up until that time, its something I'd not considered.


Loz - B&Q sell earthing rods ( solid copper ones about 3 foot long ) and they're not horrendous, price wise.
Good spot by the Moose this one... something well worth doing. 8)

 

[mikec]

Yeah,

In a previous life :wink: I had a cannon and we managed to get some good secondary explosions wadding a blank charge with flour. Once the flour was dispersed to a critical level in air it would ignite :twisted:

Regards,

Mike C

 

[robo hippy]

I think I am following what you said. One, flex pipe is lousy for dust collectors. The coils reduce your air flow a lot. If you do use the flex pipe, run rigid pipe to the machine, and then use short sections of flex pipe to hook up to the machine, and get the heavy duty type. The cloths dryer type will collapse, as can the thin metal duct pipe used for home heating systems. The size is determined by whatever size port there is on your collector. Run that size to your machine, and then step it down if you need to, or fix the port on your machine to match the size of your hose/pipes, and you will get better air flow. I know there is one book out there about dust collecting in your wood shop, but can't remember the author.

There has been a lot of debate about grounding your collection lines. There is some static build up, more with plastic than with metal. Most of what I have read is that there isn't enough build up to generate a big enough spark that can start a fire. I used metal duct work for mine, and it is grounded to the machine. I asked some of the installers of those centralized home vacuum systems if they had to ground their lines and they had no idea of what I was talking about, and all of those systems use plastic ductwork.

robo hippy

 

[big soft moose]

There has been a lot of debate about grounding your collection lines. There is some static build up, more with plastic than with metal. Most of what I have read is that there isn't enough build up to generate a big enough spark that can start a fire. I used metal duct work for mine, and it is grounded to the machine. I asked some of the installers of those centralized home vacuum systems if they had to ground their lines and they had no idea of what I was talking about, and all of those systems use plastic ductwork.

robo hippy

its not about starting a fire but triggering an explosion - dust mixed with air is highly explosive and it doesnt take much of a spark to light it off - far less than would be needed to start a fire.

and re the comparison with centralised home vacuum systems - these pose a far lower risk because a) they arent left running for hours at a time (which is what causes the static build up) , and b) general household dust, fluff, animal hair, grit etc isnt particularly combustible or explosive - however workshop systems are run for long stretches of time , and are full of fine cellulose and lignin (aka wood) dust - which is far more combustible/explosive

another point to note about dust explosions in the 'shop is that they tend to trigger a positive feedback loop - that is the initial , relatively small, explosion throws up a much larger cloud of dust which then iginites as a bigger secodary - that then liberates all the dust you have kicking about on walls , shelves, ceilings etc which goes off in a massive tertiary - add in all the solvents, waxes etc the average turner has kicking about and pretty soon the police are wondering what you did to upset Al Quadea.

the risk of it happening is fairly low , but given the potential seriousness of the consquences if it does , it makes sense to mitigate the risk as far as possible - especially as earthing the system is cheap and easy to do.

 

[Bodrighy]

And there'sme thinking all I had to worry about with this hobby was cnacer, friction burns, and a few cuts and bruises. Think I'll take up Offshore powerboat racing, it's safer.

pete 8-[

 

[mikec]

Hi Loz,

Here are the photos. The 100mm pipe from the DC connects to the yellow pipe. The smaller pipes can be positioned in any position. The black one has various end collectors.

All the pipes are fixed in place with hot melt glue. The box is made of scrap 18mm ply and mdf sealed on the inside with sanding sealer

Hope this helps

Regards,

Mike C

 

[loz]

Ah thanks Mike,

Makes all clear now - good idea. That black pipe semi rigid ?

 

[mikec]

Hi Loz

Yes, each segment of the black pipe is rigid but can swivel relative to the previous segment. The grey pipe is a twist type that locks when twisted.

Regards,

Mike C

 

[Jenx]

And there'sme thinking all I had to worry about with this hobby was cnacer, friction burns, and a few cuts and bruises. Think I'll take up Offshore powerboat racing, it's safer.

pete 8-[

:lol: :lol: Classic ! very good, Pete .. I like it !!

and pretty soon the police are wondering what you did to upset Al Quadea.

:lol: :lol: :lol: :lol: :lol:



Loz - that semi-rigid bit is called a 'poseable hose' ... you can bend it into virtually any shape you like, and it is self supporting.
They're 'right handy' :wink:

 

[boysie39]

Loz.I should add that the record 5ooo has a metal bracket from which it can be fixed to a wall which I have done now after learning the Tango,The Miliatery two step, and some Ceidalhe and Sumo. All I have to watch out for is not to stand on any mats that I'm hoovering.
I dont know if all the 5000's are the same but the inlet is on the front of the container which makes it take up more space than is nessesary. But its one hell of a sucker. REgards Boysie