Dust extraction sucks!

[Chris_belgium]

My dust extraction sucks!

Been working on a dust box thingie, after doing some testing I'm very dissapointed with the performance. Problem is I have no clue at to what the problem is.

This is the extractor I'm using, it has a 120mm outlet wich is 'plugged' straigth into the dust box

Problem is I have no clue as to what 'performance' this extractor has, maybe someone with a similar extractor (impeller size, motor hp) could offer some info.

Impeller is 19cm diam.
Wich way should the impeller turn clockwise or counterclockwise? And should the motor be wired up in the delta or in the star configuration?

Motor is 1,5hp

So the 120mm outlet of the extractor goes directly into the box, then there are 2 100mm outlets, one of the outlets is connected to my p/t with a 100mm flexi hose, the other outlet has a reductor in it from 100mm to 32 mm wich has my 4m long vacuum hose connected to it. Performance is very very weak.

My main question is, would a motor like this be sufficient for a system like this or do I need to buy a bigger motor?

Another thing is there seems to be a lot of room around the impeller inside the housing, I am not sure if this is a home or factory built housing around the impeller, so it could be that the dimensions of the housing are all wrong and that is my problem.

Anyone have a idea as to where the problem lies, any help as usual is greatly appreciated,

Chris.

 

[Modernist]

If you are sucking in line with the shaft and outputting via the horis. pipe then the rotor goes clockwise. Blower looks more thatn adequate physically. No idea about the motor

 

[PeterBassett]

The impeller in your picture should be running clockwise.

It uses centrifugal (centripetal, don't start) force to spin the air to the outside of the casing and from there out of the port at the top-right. This creates a vacuum in the middle, which sucks in more air. etc etc etc.

I can't tell from your picture, where is the input for the dust box?

Pete

 

[Chris_belgium]

The inlets are just underneath the motor, hidden on the picture by the gussets under the extractor table.

 

[woodbloke]

Mine 'sucked' too...the box is now residing in a landfill somewhere - Rob

 

[PeterBassett]

I would have thought that just the size of the box would have been enough to have the dust drop out.

It seems to be a fairly circuitous route that the air has to take, all of this is robbing the air of energy and thus loosing efficiency.

If I were to have a box that big I'd just try reling on it's size and the Bernoulli principle.

That black grid is a solid board. It is just to stop the air taking the short route to the exit.

It might not work, but it doesn't work now, so what have you got to loose?

Pete

 

[Chris_belgium]

I would have thought that just the size of the box would have been enough to have the dust drop out.

It seems to be a fairly circuitous route that the air has to take, all of this is robbing the air of energy and thus loosing efficiency.

If I were to have a box that big I'd just try reling on it's size and the Bernoulli principle.

That black grid is a solid board. It is just to stop the air taking the short route to the exit.

It might not work, but it doesn't work now, so what have you got to loose?

Pete

Valid point, I'll remove one of the baffles (there's 2) and see if there is an improvement, if it does I'll play around a bit with different setups, will keep you guys updated!

 

[Digit]

It's a big box! Is it air tight?

Roy.

 

[matthewwh]

I'm not a huge expert on extraction so I stand to be corrected. However, two things strike me as unusual about your system.

First you are running an HVLP (high volume, low pressure) setup with narrow pipes. Normally narrow tubes are associated with high pressure systems, so 4" pipework as far upstream as you can go may improve the results.

Second, the extractor is blowing directly against the back wall of the can which may be causing back pressure and reducing the efficiency of the impeller, in most setups I have seen there is either a bag installed directly in line with the outlet (not ideal) or a feeder pipe to the can which allows the exhaust more room to expend its pressure in the direction of flow rather than working against it.

Best of luck.

 

[would not]

Maybe a daft question but is it wired up right as with 3 phase - wire it wrong and they will run backwards.

 

[matthewwh]

Correction on the exhaust can, I'm looking at the first picture rather than the second one - try running it with a length of 4" hose with nothing on the outlet port and see how much suck you get?

 

[PeterBassett]

It's a big box! Is it air tight?

Roy.

That's a very good point too.

 

[Chris_belgium]

It's a big box! Is it air tight?

Roy.

I've put generous amounts of silicone inbetween the boards and also inbetween the plexi and the box, so it should be airtight, i've checked for leaks and couldn't find any.

 

[Chris_belgium]

Maybe a daft question but is it wired up right as with 3 phase - wire it wrong and they will run backwards.

I've tried it in both directions in star and delta configuration and the results we're ranging from poor to very poor now it's wired to run clockwise and in the delta configuration wich is I hope correct.

 

[Chris_belgium]

Correction on the exhaust can, I'm looking at the first picture rather than the second one - try running it with a length of 4" hose with nothing on the outlet port and see how much suck you get?

Will first run it without the baffles in the box, if the results are still dissapointing I will try this idea.

 

[Mike.C]

Mine 'sucked' too...the box is now residing in a landfill somewhere - Rob

Snap. I tried to get help by asking about my 3 extractors on the drop box thread but no one could help me.

The thing is dust is my pet hate and yet my system never seems to get any better

Cheers

Mike

 

[WellsWood]

My thoughts are exactly as per Mattew's first comment; you're using the wrong type of extractor to achieve much with a "drop box".

HVLP extractors make a relatively low vacuum, but they do shift a lot of air very quickly, and rely on this high flow rate to shift debris. The downside to this is they are pretty intolerant of interfering with the airflow - any reduction of the bore or extended lengths of hose for example and their efficiency drops off alarmingly. This is why cyclone systems are preferable with HVLP sources, they allow the seperation of particles from the air whilst maintaining the flow rate - getting this balance right is also why good one's are tricky to build.

If you have any kind of vacuum extractor available try connecting it to your box, you'll be amazed at the difference. It'll also show up any leaks in the box much more readily, which the HVLP on won't.

 

[Chris_belgium]

What's the main difference with the hvlp and the vacuum type extractors, probably just a different kind of impeller/housing? Can these be bought seperately?

 

[9fingers]

If you have a 3 phase supply from the leccy board, it will be 440v and so your motor should be star connected.

I'm surprised it ran in delta with out letting out the smoke.

If you are running from an inverter powered from single phase 240v then you need to wire in delta.

My extractor has a 14" impeller and has a 3hp motor. Your 1.5 cheveaux seems very underpowered for a 19" impeller.

From memory, Bill Pentz suggests about 5hp for a 14/15" blower. www.billpentz.com

Bob

 

[Chris_belgium]

If you have a 3 phase supply from the leccy board, it will be 440v and so your motor should be star connected.

I'm surprised it ran in delta with out letting out the smoke.

If you are running from an inverter powered from single phase 240v then you need to wire in delta.

My extractor has a 14" impeller and has a 3hp motor. Your 1.5 cheveaux seems very underpowered for a 19" impeller.

From memory, Bill Pentz suggests about 5hp for a 14/15" blower. www.billpentz.com

Bob

I've got 3phase 220 supply, altough I have no way to measure how much rpm the motor actually does, it does sound very 'healthy', no struggling in any way so i'm guessing it is strong enough for this impeller.