Homemade cyclone dust collector collapsing

[sometimewoodworker]

I've only just set mine up and decided to go for three buckets after reading too many accounts of the blue barrels collapsing.
No problems so far but still early days.

View attachment 107574

Once you’ve happy with the function I recommend using as short a pipe as possible between the vac and cyclone also from the cyclone to the tool.

 

[harryc]

Just because someone is selling a product doesn’t make it good or sensible to use it, nor does it change the fact that a correctly built and or resourced bin will function without one and adding one reduces the efficiency of the cyclone allowing dust to bypass it

There are a lot of products that are solving problems in the wrong way

So you think it’s sensible having a bin explode oh dear!

 

[shed9]

Post away in any and all subjects Pete , some people may not like your style and thats up to them, i for one like your answers to most queastions and enjoy seeing you're posts

What he said ^

 

[Tenacity]

I think the valve idea is good, occasionally swopping hose connection I let the hose grab a surface and bucket collapses, with a valve fitted this wouldn't happen and no extra strain will be put on the dust extractor motor. I've got to rig up an in line relief valve for my small sander to stop the vac red warning light coming on, finding the right adaptor sizes is always a pain at present The problem is connecting a 4 inch through a cyclone with 2 inch port and so the vacuum collapses the bin because of 2 inch reduced flow. Eventually a 4 inch system to the lathe would be good, not checked if there is a 4 inch diy cyclone available. Good luck or should that be good suck

 

[LJM]

So you think it’s sensible having a bin explode oh dear!

That is not what he said. Oh dear!

 

[harryc]

That is not what he said. Oh dear!

Sure........you just carry on.

 

[shed9]

So you think it’s sensible having a bin explode oh dear!

How's it going to explode? It's a negative pressure.

 

[Robbo3]

Yes, yes, and collection barrel is not strong enough.
For a lathe you need maximum airflow and you have reduced the flow in (1,963.5)to ¼ of the suck out (490.9) and that doesn’t allow for the reduction in suck (mass of air moved) of the cyclone.

as mentioned above;
use a 50 mm hose to the lathe
use the shortest hoses possible
if that isn’t enough, strengthen the barrel

Note a pressure relief valve in the barrel will reduce the cyclone efficiency.

Also almost all flexible hose has a bad effect on suck (reduction in mass of air moved due to turbulence created by concertina pipe wall) so use the shortest length possible. There are semi flexible hoses with a smooth interior that are far better, but much more expensive, than the hoses you are using

How can a Pressure Relief Valve reduce efficiency? It's a sealed unit mounted on the catchment container. It only opens when the vacuum becomes enough to overcome the force of the spring.
Please cite a reliable source for your statement .

As I've said previously, if you have a balanced flow of air through the system there is no need to strengthen the container if you add a PRV which is there just in case the inlet hose gets blocked or restricted.

The OP didn't say he was using the cyclone on the lathe but in case he is, catching shavings from turning can be quite difficult, even frustrating, especially with the smaller diameter hoses that these cyclones use.
I only use extraction whilst sanding on the lathe as it wouldn't cope with being waste high in shavings. These are swept into garden waste bags to be either disposed of or burnt.

 

[sometimewoodworker]

So you think it’s sensible having a bin explode oh dear!

Wrong language, wrong idea, wrong concept.

This probably explains why you are completely confused.

The bins in badly designed systems are collapsing from too low pressure from imbalance in in and out flow. Nobody is experiencing over pressure in the bin.

 

[sometimewoodworker]

How can a Pressure Relief Valve reduce efficiency?

The air going into the bin (through a PRV) in an HPLV system disrupts the dust dropping into the bin and permits bypassing the bin and diverting a percentage into the dust extractor.

It's a sealed unit mounted on the catchment container. It only opens when the vacuum becomes enough to overcome the force of the spring.

If it’s a sealed unit or not (many/most are not, and what do you mean by that anyway?) is irrelevant, and I am well aware of how they are designed to work.
The problem is that the free fall of dust into the bin is disrupted by air from outside being forced out of the bin taking dust/shavings with it into the extractor.

Please cite a reliable source for your statement .

practical experience with a sealed unit giving zero bypass dust (virtually 100% in the bin). Later a a unit that had a bypass fitted allowing around 20+% of dust into the same extractor.

The OP didn't say he was using the cyclone on the lathe

Please go back to the first post and explain why “The cyclone then feeds out to a 50mm 2.5m flexible hose which is then positioned near my lathe.” Doesn’t mean that the cyclone is being used on the lathe?

but in case he is, catching shavings from turning can be quite difficult, even frustrating,

I don’t say anything about what it’s being used for is a good idea or not, certainly a HVLP system is far more appropriate and will give better, probably not great, collection. But reduction of pressure in a HPLV system will always provide less good collection and in the wrong place (on the bin) poor dust control.

If you want to provide bypass air to the vacuum put the pressure relief valve in the correct place, between the vacuum and cyclone, then you don’t screw up the airflow. Yes it’s more difficult to put it there but it is the correct place.

 

[Britman]

I had the same problem - I just made a box about 40cm cube from OSB with a cased lid that had the cyclone mounted on it - all the joints sealed with caulk, draught excluder on the lid and over-centre clamps. Works a treat.
View attachment 107518

Snap, had the same issue as OP but quickly did what you have.
Works a treat.

 

[Tanglefoot20]

Hi there.... m e is the same setup as in the picture above.....however I used a blue barrel with no issues at all.....you have to make sure you get the thicker style barrel with metal clamp..
Amazon sell them for around £20

 

[TFWS]

as a newbie and having already committed to a barrel, cyclone and hoses and having no clue about any of this other than forums and youtube, i had the collapsing barrel issue too.

i researched this and aside from changing components it seemed to me that the easiest fix was to re-enforce the barrel so i built a timber cage around it and fixed the barrel sides to the frame.

 

[TheTiddles]

as a newbie and having already committed to a barrel, cyclone and hoses and having no clue about any of this other than forums and youtube, i had the collapsing barrel issue too.

i researched this and aside from changing components it seemed to me that the easiest fix was to re-enforce the barrel so i built a timber cage around it and fixed the barrel sides to the frame.

Yep, it’s that simple.

 

[WannabeeCarpenter]

There seems to be a competition going as to who can make the most wordy explanation for something very simple

This made me properly laugh!!!

 

[Spectric]

How can a Pressure Relief Valve reduce efficiency? It's a sealed unit mounted on the catchment container. It only opens when the vacuum becomes enough to overcome the force of the spring.

Easy way to visualise this is to get your or the missus's hoover out and get a feel for how well it can work and then make a hole in the hose and notice the difference. Some hoovers actually provide a slide device on the handle for this very purpose so that you can reduce the suction by basically creating a leak.

For extraction you want airflow and to increase the airflow just increase the hose sizes where possible which will reduce the pressure.

 

[Davey44]

I've only just set mine up and decided to go for three buckets after reading too many accounts of the blue barrels collapsing.
No problems so far but still early days.

View attachment 107574

I had a similar challenge when I installed a cyclone on a 'blue-barrel' using a vacuum from Aldi/Lidl. It was obvious that there was too great a vacuum being generated , although this did not in any way compromise the effectiveness of the cyclone. I constructed and installed a vacuum relief valve of about 3cm sq with weak spring, but it was too strong for the purpose. I went on to make a significantly larger valve (approx 7cm sq) with an even weaker spring, but this too didnlt solve the problem. I shall, when I am able, find a source of a 25 litre steel drum and install that in place of the blue plastic version.

 

[Terry - Somerset]

Simplistically the barrel collapses because there is too much "suck" - this is a waste of energy. There are three solutions:

• reduce the "suck" - the motor has too much power. May be both costly and a pain as you already have the motor!
• increase airflow so the "suck" does what is intended - collect max of dust etc. Limited by size of inlet connection on cyclones.
• install PRV between the cyclone and "sucker". Stops barrel collapse, is cheap, but essentially a bodge to fix an unbalanced system.

 

[Robbo3]

The air going into the bin (through a PRV) in an HPLV system disrupts the dust dropping into the bin and permits bypassing the bin and diverting a percentage into the dust extractor.

The air does NOT go through the PRV. The PRV is nowhere near the hoses or cyclone. The PRV is an addition to the catchment container. It is a safety device that only opens if the vacuum is great enough to overcome the force of the spring holding it closed.

The problem is that the free fall of dust into the bin is disrupted by air from outside being forced out of the bin taking dust/shavings with it into the extractor.

Only if the PRV opens.
In normal use that shouldn't happen. If it does there is something wrong with the system design or the container is full.

If you want to provide bypass air to the vacuum put the pressure relief valve in the correct place, between the vacuum and cyclone, then you don’t screw up the airflow. Yes it’s more difficult to put it there but it is the correct place.

That defeats your advice that strengthening the catchment container is the way to go.

 

[sometimewoodworker]

The air does NOT go through the PRV.

Then take it out or don’t put one in.

The PRV is nowhere near the hoses or cyclone.

In the majority of systems the hoses attach to the cyclone then the cyclone attaches to the collection container, so of course a PRV isn't near the hoses.

The PRV is an addition to the catchment container. It is a safety device that only opens if the vacuum is great enough to overcome the force of the spring holding it closed.

So then air DOES go through the PRV so that point and the air that is going into the container through the PRV must leave to the suck device disrupting the cyclone function taking dust with it.

You clearly have a poor (no) understanding of fluid dynamics if you imagine that air introduced into the collection container (through the PRV)
doesn't disrupt a HPLV cyclone function causing dust to travel into the suck device hose and into the suck device

That defeats your advice that strengthening the catchment container is the way to go.

I never said it’s the only way.

I said that putting a PRV to stop container collapse is a bad cludge, poor design, bad choice, and shows that who ever puts one in is badly advised or incompetent.

putting in a PRV to stop a suck device
getting damaged from too low/no airflow is a completely different situation and an appropriate use of a PRV but placement of a PRV in the catchment bin is wrong and those advocating that are either uneducated or lazy. Correct placement, if you have a need to add a PRV, is upstream of the cyclone.

Note LPHV systems are completely different and nothing to do with the present topic (sure the both suck dust)