# Dust extraction / cyclone pressure release valve



## MattRoberts (29 Jul 2016)

*EDIT - **** AES has posted details of an automatic design later in this thread *****


So we were discussing the issue of when shop vacs with cyclones get blocked, it creates a huge amount of pressure on the system. This will cause the weakest component to implode, which usually means the container that the dust is falling in to. 

You can create a simple pressure release valve which will trigger when the pressure inside the container gets too much. I can't take credit for this I got the idea from Peter Parfett. This is a pretty simple solution though. 







Get a bit of plastic pipe around 40mm in diameter, and cut a 20mm slice off the end. Next, make a cut in this slice with a saw. Now cut a hole into the lid of your dust container, but make it a slightly smaller diameter than your pipe. This will ensure the slice of pipe is a snug fit in the hole. 

All you need then is to cut a couple of small bits of wood. One will be the cap, so it needs to be wider than the pipe. The other needs to be a bar shape, so when it sits on top of the other end of the pipe it still allows air to flow through. 

Epoxy a bit of metal to the cap piece (or even better, use a metal lid as the cap). 






I connected mine using a few cable ties, threading one through a magnet (you can get countersunk magnets which have holes in them). Our you could just epoxy a magnet to the bar piece. 

That's about it. When the pressure is too much for the magnet to hold the cap, it pops off. After fixing the blockage, the slack in the purple cable tie allows you to yank the cap back on without having to open the container of even switch off the vac.


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## Steve Maskery (29 Jul 2016)

Thank you very much. I wish I'd read that a fortnight ago.


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## AES (29 Jul 2016)

Thanks Matt. Bookmarked.

AES


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## Alexam (31 Jul 2016)

Great idea Matt. It prompted me to look at Peter Parfit's video, which shows just what you have done. 
http://cyclonecentral.co.uk/AssemblyInstructions/


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## pike (11 Nov 2016)

Thanks Matt,

Slightly older thread but I'm wondering when are pressure valves needed? Are they for small hose HPLV (vac) or large hose HVLP (chip extractors)? Or both? I've read contradictory comments on which one needs it. I thought it would only be the vac as they are higher pressure?

I see this one is for your vac. Did you bother for your large 100mm extractor thien container?

Cheers,
Carl.


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## sunnybob (11 Nov 2016)

If you just have a vacuum machine and the hose that came with it, theres no need for anything else.
If you start fitting cyclones and dust pails into the system, if the hose blocks the weakest link will collapse. Thats usually the bucket.

Calling it a pressure valve is misleading, its an anti suction valve. Pressure valves stop things blowing up (very dangerous) an anti suction valve stops things imploding, possibly spectacular, but not so dangerous. 

But its one of those things that is not needed on most systems. If you watch peter's video, he has a large plastic cyclone to protect. Thats a couple hundred quid's worth. If youre using an old paint bucket, big deal.

Also, when a hose blocks, the vacuum noise increases alarmingly and in 99% of cases you are near enough to a kill switch to stop anything imploding.


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## pike (11 Nov 2016)

Hi sunnybob, I'm in the process of setting up cyclones for both my vac and my HVLP chip collector, so I'm wondering which one needs the valve.

The vac separator container is a metal drum. The chip cyclone is going to be one of those big blue barrels people tend to use from amazon/ebay.


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## MattRoberts (11 Nov 2016)

You need to consider the weakest point of your extraction system, as that is what will implode if there is a blockage. If your weakest point is a cloth bag, you don't need a pressure relief valve. If your weakest point is a plastic container or thin plastic cyclone, you probably do


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## pike (11 Nov 2016)

I read somewhere that High volume low pressure (chip extractor) hasn't got the pressure to implode something? I suppose the weakest point on my chip extractor would be the plastic bag or the filter cartridge?

I understand blockages can cause a container to collapse but have a few things I'm not too sure about:

1. Is a metal drum for a vac cyclone strong enough to mean I don't need the valve?
2. Do I need a valve for a chip extractor (using a plastic drum, a plastic bag and a filter cartridge)?


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## pike (11 Nov 2016)

Just reread your comment Matt and realise "waist" point shouldve said "weakest" 

So I suppose my chip extractor probably won't need a valve (as there is a plastic bag and low pressure involved) and my vac cyclone might do (as it's high pressure), but might not as I'm using a metal drum for that?


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## AES (11 Nov 2016)

FWIW gents, I've just been rigging up a cyclone to go with my shop vac (a Karcher which sucks very well, but which is annoying-ly loud).

Following advice here I specially bought a metal dustbin. OK, it's a cheapo, and the basic material (galvanised sheet steel) is only about a quarter mil thick (about 32 SWG). But although it does have various stiffening rings and grooves pressed into it I can assure you that if the gets hose blocked then it does definitely suck well enough distort the sides of the bin - quite a bit actually - I haven't been able to knock all the "dents" out with a heavy rubber mallet!

Being one who likes to "re-invent the wheel" I've designed my own valve (set into the lid of the dustbin), and FWIW I call it a pressure relief valve. The difference with mine is that it resets itself automatically as soon as the hose blockage is cleared - so no stopping the vac, clearing the hose, and then re-setting the valve before you can start again.

As is my wont, it's more complicated than it needs to be, but as I've been away from the shop and the PC on health grounds it was at least something I could sketch out while laid up in bed and a chair.

I've got some pix and an (over-complicated) drawing which I'll post within the next few days just in case anyone's interested.

AES


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## pike (11 Nov 2016)

Cheers AES. I think a few people have also posted pics of diy valves. I read on another forum it's a good idea to put it in a connector/hose above the cyclone itself.

I want to avoid having one unless I really need it. I'd like to believe my chip extractor doesn't need one. Although my vac setup is a single plastic piece cyclone (not a thin plastic sheet diy thing) and I'm using a proper metal drum, I suspect I should have a valve for it as the vac is powerful. I'd be happy to just buy one if it was say a tenner.


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## Terry - Somerset (11 Nov 2016)

The numbers are a bit old school - but....

A drum 30" high by 18" diameter will have a surface area of 2200 sq inches including sides top and bottom. A 1 PSI difference is equal to 10 large blokes squashing it - albeit not all in one place. I'm also not sure at what pressure difference the fan will actually stall - so pressure difference would not increase indefinitely.

It is little surprise that even small pressure differences can implode dustbins!!.


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## graduate_owner (11 Nov 2016)

I like this idea so I am making a reply so that I can find it easily. I don't know how to bookmark.

K


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## NazNomad (11 Nov 2016)

graduate_owner":14vl6d6e said:


> I like this idea so I am making a reply so that I can find it easily. I don't know how to bookmark.



PM'd you the link to this thread so you don't lose it. :-D


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## AES (11 Nov 2016)

@graduate owner:

If you go to the very top LH side of this page (or any other page for that matter) you'll see a couple of little white boxes ("Post reply", etc).

1 row below that you'll see a horizontal blue line across the whole page width. That's divided into several boxes on which you can click with the mouse. One of those is called "Bookmark". You click on that and then you'll find a list of all the threads/topics you've bookmarked in your private profile page. That way you can find the stuff you're interested in again easily.

At least, that's how it looks n works on my PC setup - "your mileage may ...... "

I'll be posting details of my auto pressure relief valve soon. I'll add it to this thread.


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## MattRoberts (11 Nov 2016)

pike":32taxwit said:


> Just reread your comment Matt and realise "waist" point shouldve said "weakest"
> 
> So I suppose my chip extractor probably won't need a valve (as there is a plastic bag and low pressure involved) and my vac cyclone might do (as it's high pressure), but might not as I'm using a metal drum for that?



Hah, whoops. Correct, your chip extractor will implode the bag before anything else. 

Your vac setup doesn't sound like it needs one, but if there is a blockage and you don't realise for a while, it could put a lot of strain on the motor


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## MattRoberts (11 Nov 2016)

AES":2nt8ofg2 said:


> I'll be posting details of my auto pressure relief valve soon. I'll add it to this thread.



Look forward to seeing it!


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## AES (11 Nov 2016)

Edited to delete duplicate post & 1st 2 pix.

AES


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## AES (11 Nov 2016)

Well, here goes Matt.

As said, I'm slowly doing something about dust in my cellar workshop (it's shared with the resident domestic authority!) so I bought a cyclone extractor from Steve Maskery of this parish earlier this year.

There's no doubt that I just like "complicated" (but hopefully also "elegant") solutions sometimes - Whatever floats yer boat, and all that .......... So I thought that if I was going to need a pressure relief valve in my DE system, then I wanted one that I would not have to re-set manually after every vac hose blockage

And my other excuse for this thing below is that while recently unable to do much at all in either the cellar or on my PC for health reasons, I was at least able to sit & lie about thinking & sketching all sorts of weird and wonderful ideas.

Following the advice from Steve and others here, I bought a steel dustbin especially to go with his cyclone. But after the first run without a valve it was clear that even with a dustbin rather than a plastic bucket collector, the setup would need a pressure relief valve for when the hose gets blocked - it's a thin gauge sheet galvanised steel dustbin with various stiffeners pressed into it, but when I tried a quick hose blockage as a test the dustbin walls deformed quite dramatically.

So here's my take on a DIY pressure relief valve which automatically re-sets itself to the closed position as soon as a vac hose blockage is cleared:

It's based on a plastic rainwater goods 75mm/50mm reducer, in the centre of which is mounted a moving valve stem and seal arrangement. The valve seats against the inner (sloping) walls of the reducer, and with the thin expanded PVC packaging material that I used on the ply valve head it seals very well.

The valve is retained in the closed position by a combination of a rare earth magnet and a compression spring. The magnet acts against the bottom of a 15mm square steel tube which also acts as the centre bearing support for the valve head itself and the valve stem. The compression spring acts against the top of that same tube.

The support tube is retained by a plastic ring with an internal rubber "O" ring, which was cut from a plastic rainwater pipe with integral in-line joiner. This plastic retainer also acts as a "lock" to hold the main body of the valve tight against the underside of the dustbin lid.

When a hose blockage occurs the force of the suction overcomes the power of both the magnet and the spring, so opening the system to atmosphere through the holes drilled into the main valve body below the level of the dustbin lid. This prevents the "implosion" of the weakest link in the chain - as above, in my case it's the metal dustbin.

But as soon as the hose is unblocked again the power of the compression spring overcomes the pressure of the air passing through the valve body. This closes the valve again and it's then held closed by the power of the magnet against the support tube until the next time the hose gets blocked.

The pix below illustrate it well I hope. BTW, the holes shown drilled into the lower valve support and into the main body in the pix are shown before I tested the hose blocked-valve open action. As shown in the pix these holes are too small to allow the valve function fully. But the over-elaborate coloured sketch (well, I had nothing better to do except think about back ache!!!!) does show the holes as I later enlarged them to allow the valve to open fully.

I hope this may be of interest.



















































Now here's the sketch (coloured so it will hopefully be clearer at this small size).

Sorry, I've just read that the max number of attachments are 10 so I'll finish off this post with the sketch and its Legend in a moment.

AES


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## MattRoberts (11 Nov 2016)

That's a nice neat solution, thanks for sharing. 

You do realise in that last pic you have the vac attached to the wrong port on the cyclone though right?


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## AES (11 Nov 2016)

Thanks Matt, yes, I did realise I'd connected it up wrong - AFTER I took the pic, naturally.

Don't know why the 1st part of my post appears twice, sorry. * NOW EDITED TO REMOVE ERONEOUS POST.
Neither do I know where the drawing & Legend has gone either - I thought I'd just posted it.

Here we go (again)!


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## pike (11 Nov 2016)

Very impressive AES! I am going to ignore this whole valve thing.. probably until something implodes...

Matt I'm certain he was just checking we were paying attention ;-)


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## AES (11 Nov 2016)

Now here's the Legend for the sketch:

A - Dark Green	- Main Body(Geberit black plastic 75mm/50mm dia. rain water pipe reducer; 4 x
15+mm dia. equi-spaced holes in lower sides)
B - Yellow - Valve Stem, upper & lower (8mm nom. dia. Brass, drilled & tapped 6BA)
C - Brown - Valve Stem Bearing/Guide (15mm Sq. MS tube, approx. 3mm wall thickness)
D - Orange - Internal Seal Seat Disc (3mm ply, 50mm nom. dia.)
E - Purple - Rare Earth Magnet (8mm nom. dia; 3mm centre through hole)
F - Dark Blue	- Valve Seal Seat Disc (3mm MS, 25mm nom. dia.)
G - Dotted - Valve Seal (approx. 3mm thick expanded PVC sheet packing material)
H - Light Green	- Valve Head (19mm ply, 50mm nom. dia; coned to suit taper of inner Main Body)
J - Red - Lower Valve Guide (3mm hardboard, 50mm nom. dia; 4 x 15+mm dia equi-spaced
holes)
K - Light Blue	- Manual Reset Knob (plastic or wooden disc to suit - spares box!)
L - Grey/Black	- Valve Spring (8mm nom. ID x 6tpi, free length to suit)
M - Dashed/Grey	- Upper & lower retaining bolts (6BA Brass)
N - Heavy Blue	- Approx. line of dust bin lid on installation (NOTE: Body Retaining Ring omitted for
clarity)

Yes, I DO know I've broken all the basic rules of "Tech Drawing" ("Sorry, Mr. Johnstone, Sir"), but my excuse is that A) I was trying to make it clear at the small size we have for attachments, and B) I had nothing else better to do than think about bloody back ache!).

I stress that this sort of stuff is NOT my speciality, this was all "empirical" but it does work fine (now I've enlarged those holes in the body).

If anyone has any Q's I'll be pleased to help if I can.

AES


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## pike (11 Nov 2016)

Would a quick fix for the lazy be to make a inch wide hole and put some tape on it?


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## MattRoberts (12 Nov 2016)

Have updated my first post to highlight your alternative solution AES


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## sunnybob (12 Nov 2016)

if you arent clever enough to build that, its a spring loaded check valve fitted into swimming pool pipe line to prevent syphoning.

http://www.ebay.co.uk/itm/SWIMMING-POOL ... SwbqpTtyaC


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## AES (12 Nov 2016)

Thanks for the interest everyone.

@MattRoberts:

Thanks mate.

@sunnybob:

Yeah, looks like a possible solution. And if you added the "value" of my time making that valve, then mine probably cost a lot more than the 25 quid your swimming pool valve costs. Not so much "fun" though!  

@pike:

You'd have to try the tape idea to see if it works OK (i.e. doesn't break the tape under normal ("unblocked") suction operation, but does break the tape when a hose gets blocked).

But just a point - I THINK that if your hole is one inch dia, that's roughly 3+ sq ins of unsupported tape surface area ("py" - 3.142 x 1 inch) times nominal sea level atmospheric pressure (14.7 psi), equals roughly 45 lbs force on the tape in normal operation. Seems to me the tape would need to be pretty thick/have good adhesion to stay in place when in normal operation. And of course when a blockage does occur and the tape did break/come unstuck, then the broken bits of tape would disappear into the dustbin. So you'd have to find another similar bit of tape and stick that on again after clearing the hose blockage.

But give it a go. Certainly quicker a cheaper than messing about with a valve like mine (even if it was good fun). Let us know if tape works please. I wouldn't be at all surprised if it does work ("KISS" and all that).

Cheers

AES


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## pike (12 Nov 2016)

AES, your valve is quality. I'm just thinking if there was a basic solution of hole and tape it might avoid implosions for people who haven't yet made one. Assuming the hole could be reused for the valve.


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## AES (17 Nov 2016)

"Quality", pike. Thanks for that, I like it.  

I posted it because I thought that maybe someone else may like to do something similar, and as it does work OK now, and as the dimensions are all based on junk found in my various "scrap boxes" (apart from the valve body which I had to buy), it's pretty easy to adjust sizes to the contents of one's own "might come in useful one day" box/es.

BTW, when commenting on your idea for sticky tape over a 1 inch hole (above), I accidentally used py x dia for the area of the circle of unsupported tape. That's rot of course, (py x dia is for the circumference of a circle), I should have said py x rad squared. Makes a difference too, of course - instead of the 45 odd psi I posted, the proper number is nearer 11.5 psi. Sorry.

Have you tried the tape idea yet?

AES


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## Graeme48 (4 Jun 2018)

Good morning all.
As a newbie, please forgive me for bumping an old post, but this is a subject of great confusion to me at the moment.

After a period of nearly 15 years with little to no woodworking, I am now at a stage where I can resurrect my primary interest of woodturning. Times have moved on since I last did this and health aspects are now more of a concern. Using a double garage as a workshop, I already have a wall mounted Fercell Fly chip extractor which still seems to work well and I will be using a powered respirator when I replace my now obsolete Racal.

I am thinking of installing a cyclone into the chip extraction system, to further reduce the fine particle dust that seeps through the filter on the chip extractor and have several 'silly' questions, which hours of Google time cannot answer simply.

1. Am I correct that the ducting goes from machine to cyclone to chip extractor?
2. Do the 'heavier' chips pass through the cyclone?
3. The existing ducting on the chip extractor is 100mm, so this obviously needs reducing down to the fitting on the cyclone - if I then use smaller diameter ducting between the cyclone and each machine (lathe, bandsaw, sander) will this reduce the efficiency?
4. Is there a practical limit to the extent of ducting between each machine and the cyclone/extractor setup - my workshop is approx 5m wide with machines on opposite walls, which also implies running ducting at ceiling level.

Thanks for any advice offered


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## AES (4 Jun 2018)

Hullo Graeme,

I'm by no means an expert on all this stuff, but like many here I'm dabbling - sometimes with some success!  

I can't do better than direct you to an excellent "sticky" in this Forum by member siggy 7. Here's the link:

a-guide-to-dust-extraction-by-member-siggy-7-t102025.html

And if you want/need to go deeper than that (I found the above thread a GREAT help) then there's what seems to be the bible for wood workers, namely Bill Pentz's info, here:

http://billpentz.com/woodworking/cyclone/index.cfm

When you've got through that lot, you'll find lots of youtube videos on the practical aspects of making individual items like blast gates and cyclones, etc. Just use the youtube search function and look up "Dust Extraction".

I'm not a turner myself, but from the little I've seen, as a turner you have several concerns - "lightweight"/airborne dust - long spirals of shavings - smaller "chips n chunks". All need handling a bit differently.

HTH


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## sunnybob (4 Jun 2018)

Theres 10 years worth of reading on this subject, and at least a 100 different opinions, but to answer your questions as briefly as possible;
1. Am I correct that the ducting goes from machine to cyclone to chip extractor?
Yes, the flow is from the lathe to the side of the cyclone, then out the top of the cyclone to the extractor unit.

2. Do the 'heavier' chips pass through the cyclone?
Yes, and no. Normally, the chips will fall down the cyclone into the collector, but sometimes, if there are a LOT of chips, as in a thicknesser machine, sometimes they will go through the cyclone.


3. The existing ducting on the chip extractor is 100mm, so this obviously needs reducing down to the fitting on the cyclone - if I then use smaller diameter ducting between the cyclone and each machine (lathe, bandsaw, sander) will this reduce the efficiency?
Yes, and no, again. Depends on the bore of the cyclone pipe. If youre thinking of one of those 50 mm dust deputy things, then youre wasting your time and money because the 100 mm pipe will just suck everything straight through the cyclone. Dont ask how I know this, but I do have a 50 mm dust deputy for sale.
I now have a 62 mm cyclone made from an old 3/4 size traffic cone, and all my ducting and blast valves are 62 mm, and its quite acceptable performance when running one machine at a time. But I would like a bigger cyclone in the future.

4. Is there a practical limit to the extent of ducting between each machine and the cyclone/extractor setup - my workshop is approx 5m wide with machines on opposite walls, which also implies running ducting at ceiling level.
Yes. the further the pipework travels, the less flow you get. Every metre, every fitting and every turn slows the flow. Work out the most direct route across the workshop, even if that is a diagonal. Use as few elbows as possible, preferably long sweeping bends. Dont use T joins, they are the worst for restricting flow. If you have to, use Y branches and put a blast gate as close as poss to each machine.


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## Graeme48 (5 Jun 2018)

Thanks to SunnyBob and AES for the replies, it looks like I have more reading to do  but some excellent source material to start with.


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## dtecting (20 Jul 2018)

Hello First time with pictures Hope it works.
Have used this valve on my cyclone with no problems
https://www.dropbox.com/sh/peqm83fes5w7pg6/AABG96fkZar_2sJU8aIsrbsCa?dl=0


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## sunnybob (20 Jul 2018)

I'm not completely convinced about release valves on smaller systems.

If the pipework blocks, the noise change is so dramatic (even with the extractor in an enclosure) that you hear it straight away.
Unless you are completely isolated with music headphones of course, which i really dont like and wont use. But it would need a big extractor to collapse any pipework, and the pipe would have to be blocked for a fair old time before the motor got too hot and gave up.

I made a slight modification to my 63 mm plastic blast gates that actually help stop a problem like this. I cut the very corners off at the end of the slide housing for a completely different reason. The blast gates kept getting jammed with dust forced into the slide runner every time the slide was opened and closed till in the end the blade would not fully close and it was a real pig to clear them out. I cut the corners off so that the slide now just pushes the dust all the way out the ends instead of blocking. An unexpected extra bonus of this was when the pipe did block, the valves all gave out with a piercing whistle which nobody could ignore.


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## AES (20 Jul 2018)

The only reason I made my "auto valve" is because I found out in testing that there was enough suction to start collapsing the wall of a SS dustbin bought especially as a collector - admittedly only a cheapo from the local DIY place though.

By the time I reacted to the changed noise (sunnybob is quite right, it's easy to hear the changed note) the wall of the dustbin had already started to fold up. OK, not a serious problem, and easy to get (most!) of the denting out of the wall, but still!

Also my "extractor" (it's a Kaercher wet/dry shop vac) also has an auto valve built in, but as said, during testing, I found the dustbin wall started to collapse before the valve on the vac released the pressure from me deliberately blocking the pipe.

Perhaps I should add that my "system" is very simple, no blast gates or fixed piping such as sunnybob describes. Just the fleX hose that came with the vac, some "solid" PVC pipe between the vac and the single cyclone, and only 1 tool in use on DE at a time. So I thought making a valve worth it. But that's just me.


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## sunnybob (20 Jul 2018)

are you sure that dustbin was steel, and not aluminium foil? :shock:   

were you doing destruction testing? I cant think of a situation that would completely block the pipe to that extent.
Last week while using the hose to vacuum the floor and bench of the workshop I accidentally sucked up a pair of black vinyl disposable gloves. They made a huge whooshing noise and I could hear them go down the hose, through the blast gate, turn right at the T, and all the way round the cyclone, before I could get to the wall mounted off switch. I found them past the cyclone inside the extractor bin when I cleaned out. But even that didnt block the pipe completely.


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## AES (20 Jul 2018)

Well the bin isn't ali foil, and the label in the shop said it's SS, but it IS rather thin I grant you (like most such things, the "strength" comes from the wire "hoop" at the top and the corrugated sides - plus the bottom of course). But my simple test was simply to put my hand over the end of the flex hose - within a second or 2 of being covered the sides of the bin started to fold inwards.

From that I concluded a "safety valve" was necessary, so I made one and fitted it.


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## MattRoberts (21 Jul 2018)

You're more likely to get a bin collapse from an LVHP system (shop vac) than an HVLP system (chip extractor).

I have a thick walled plastic 30L container under my LVHP cyclone system, and it collapses easily without a pressure relief valve.


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