Dust Extractors

[DarrylF]

I have a standard 1hp 500cfm taiwanese unit fitted with a Carbatec felt top bag. It has worked OK for 18 months or so, but it has a couple of problems. Doesn't have quite the suction I'd like for the ducted setup I've got, a little noisy, tends to heat up the workshop and lately it's started tripping the circuit breaker when switched on again after running for a while.

With the lathe in the workshop now getting quite a hammering, dust is becoming a real problem. With the extractor running while turning it's a lot better - but then I get hot as hell in there, and the extractor doesn't deal with it very well. I'd like to be running an extractor with lathe hoods whilever I'm turning - especially for sanding.

From a bit of hunting around seems the Jet dust extractors are nice units. Anyone have one? How does it deal with long periods running? Quiet enough?

I've seen recently the cartidge type filters - anyone used these? Seem like a damn good idea - especially with the cleaning setup, damn sight easier than vacuuming a bag out.

There was a new model offered with a combo of a Jet 2hp extractor & cartridge filter for $975 I think. More than I would prefer to spend of course, but if it's going to do the job it's hopefully something I wont want to be replacing in 6 months from now. Anyone bought this combo? Any comments?

BTW - in addition to the lathe I have basically a full workshop - 12" table saw, 12" thicknesser, bandsaw, various sanders etc in a double garage workshop. I've ducted the major gear with 4" PVC & blast gates. I'm only a weekend warrior, but reasonably serious about my toys http://ubb.ubeaut.com.au/ubb/smile.gif

[DPB]

Darryl, perhaps this is too obvious, but when you state that your dust extractor is not working like it used to, it reminds me of my experience.

When I first purchased my extractor it would suck up anything - even a 500mm 4x2 http://ubb.ubeaut.com.au/ubb/wink.gif. But as time went on, it became less efficient.

My first thought was to empty the lower bag and clean the upper bag. But this did not seem to help much. So the next step was take the ducting apart.

Well, what a surprise! Jammed up against the grid at the in port of the extractor was all sorts of junk - finishing rags, rubber gloves, and about 100mm of wood dust and chips. It's a wonder the extractor had any suck left at all, and that I didn't burn out the motor.

And that wasn't the end of it. The ductwork I used was the flexible kind sold by Carba-Tec for that purpose. Wherever the ducting ran horizontally, the "ribs" in the flexible hose trapped the small chips and dust. When I held these sections vertically, heaps of crap fell out.

When you think about it, this kind of ducting, although simple to install is counter-intuitive. It can't do anything but impede the flow of the waste. So my next shop improvement project is to replace any of the horizontal ducting with sheet metal ducting.

Does anyone know where this can be obtained?

[Eastie]

I agree - check your ducting. I run a similar unit a while ago and had none of the problems you've experieinced. This also fits the build for your overheating problem.
I'd also look to see if you can't run the last section of duct outside your workshop and setup the extractor outdoors to reduce noise, heat and fine dust inside.
In a previous job we bought a number of Jet units and had no problem with them in semi-perminant use. We also retrofitted air-con hepa filter cartridges which improved them dramatically - probably similar in nature to the commercial ones now available.

DPB - pvc would be easier and suits this purpose. Before someone pipes up on dust explosions I ask you to prepare your case extremely well.

Cheers,
Mark

[DarrylF]

I use PVC ducting, which tends not to clog too much at all. The flexible sections are regularly shaken out and the blast gates get a regular blast of compressed air. So basically the problem isn't that - it's just that I'm asking more of it than I used to, and it was really only marginal to start with.

You can get a good range of hoses, blast gates, metal ducting etc from http://www.speedlock.com.au - just discovered their site, so haven't been to see them yet.

[mikmaz1]

hi all,
hey eastie could you do a post on the pros and cons of pvc ducting.
i have been thinking of using pvc but worried about static build up.
thankyou
seeyasoon mik.
(have done a search ,came up 0)

[This message has been edited by mikmaz1 (edited 18 December 2002).]

[Red neck]

By PVC I assume you chaps are referring to the standard PVC sewage pipe of 100-mm diameter, yes? The reason I ask is because I plan on ducting my shed and being a bit tight with a quid don’t propose to spend good $db’s on galvanised ducting.

The problem with PVC seems to be the possibility of static electricity causing a spark to jump across a dust laden air stream. If one considers the natural oils in timber, that spark could lead to an explosion or fire. In my day job I work with static electricity and find that proper bonding is the clue. In other words maintain a constant electrical potential across all components and ground to a suitable earth. Heavy gauge copper wire running through the ducts and earthed to the equipment at each end should meet this requirement. The equipment, of course, should be properly grounded. At junctions where the wire could create a sawdust trap, simply drill a hole and run the wire outside the pipe until past the junction and renter the through another hole. Silastic should seal the holes.

The other problem with PVC sewage pipe is the metric tube size that will require connection to imperial size blast gates, machine ports and dust extractors. I have experimented by creating short stubs of accurate diameter that will bridge that gap. By cutting a short piece of PVC longitudinally, and removing just the right amount of the circumference, the component can be glued with PVC cement to make a suitable adapter. Just requires a bit of simple math to determine the difference in circumferences. I’d be interested to gather any thoughts you may have on such issues.

On the subject of dust extractors I have a 2hp Carba-tec with an induction motor. I am severely impressed with the performance of this machine. I also have a smaller 1 hp Delta. Both are fitted with induction motors and are relatively quiet for the job. My only complaint with the Delta machine is the metal grate on the inlet side of the plenum chamber. This acts as an effective block for larger pieces of debris resulting in a need to dismantle the hose to clear it. I use this machine on the CMS, router and lathe and find it very effective when sanding. It is marginally quieter than the 2hp unit. If you have suction problems, check the ducts, ports, blast gates and give the outlet bag a good clean. It is surprising how the latter can improve operation of the extractor.

RN

[soundman]

There has been some discussion in the past concerning dust extractors.

Firstly concerning dangers of static caused dust explosion. There have been several substantial discussions by learned types & the opinion is that it is most unlikely to occur. I have never heard of a dust extractor exploding!!!!????.

secondly there are three main causes for loss of suction.
1. blockages (obvious)
2. bunged up bag (I bang mine out on a tree once in a while & very ocasionaly hand was it)
3. DUCTING The losses in ducting are frequently underestimated and can be huge.
It is reasonable to state that a 2hp extractor with 4 metres of hose will suck about as much as a 1 hp extractor with 1 metre of hose.

A 1hp extractor with 4 metres of flexible hose will be just about useless, particularly if it is connected to a planer or such.

The flexible stuff is very lossy. 4inch pvc is a bit better but if you expect any sort of efficiency 6 inch is a minimum then the metal stuff is looking more competitive.

corners bends and size changing adaptors cause huge losses.

I read some articles did some tests of my own & resolved to buy a biger extractor for my saw bench and drag the old 1hp arround as required.

I've had a 1.5hp delta for about 12 months now & have found it good. it flows about the same as most of the 2hp units probably because the design is a little more streamlined.

Thinking about felt bags. Filtration fabrics will make to order any size.

The big paper filters liook good but they ain't cheap.

cheers

[DarrylF]

Re the static question: I've also read a lot of discussions on the topic and one in particular by an expert on the topic (one of the US sites, can't remember which). The conclusion seems to be that it's simply an old wives tale - the amount of static is simply not large enough, the explosive potential of wood dusts not high enough to cause any sort of a problem. Nobody I've seen discussing it has ever pointed to an actual incident in a home shop, and the commerical incidents have all been with much more hazardous materials - flour being one of them. A flour explosion in a bakery is supposed to have caused the great fire of London.

So yeah, I use 100mm ungrounded PVC sewer piping and sleep fine at night. There is a problem with blast gate sizes of course, so I made my own. Took the correct size PVC pipe joiners, sliced them down the middle with the bandsaw, expoxied to either side of a sandwich of two pieces of 5mm ply with holes the inside diameter of the PVC cut in them. The 2 ply pieces are joined around 3 edges with 10mm wide pieces of ply, and a third piece of ply slides in between them to seal it. When I want the gate open I slide the center piece out and drop in a 1" piece to seal the top opening. Works very well - certainly seals better than the cheap plastic blast gates. Flex hose fits right inside a PVC joiner nicely - used duct tape to seal, but it barely needs it.

I know there are losses involved with using ducting, so I kept lengths & bends to a minimum. Not using ducting is just not practical in my situation.

The key problems I want to solve are that the dust extractor I have generates lots of heat, does not like running for extended periods, and while the felt bag filters pretty well it's a total pain in the ass to clean. Suction is mostly OK, but could definitely be better - can't run more than 1 intake for instance.

So basically I'm looking for the ideal extractor - something that's quiet, good quality, doesn't heat up too much, filters as well as possible, is easy to clean, and has the suction to run 2 open ports on the lathe for instance. A 1.5-2hp unit with a cartidge filter seems the ideal choice these days - and hopefully spending the extra bucks means I won't be back here in another 18 months asking about the next upgrade http://ubb.ubeaut.com.au/ubb/smile.gif

[John G]

Darryl,
Is the problem with your current machine is that is has always run noisy and hot? Or it has only just started running noisy and hot?
All the replies so far seem to assume the second - that something has gone wrong. Could it be that it's just always been that way, and you've only noticed the heat because summer is now with us? Therefore all the advice about checking your ducting and bags is irrelevent?

In other words, is something broken, or it is just the machine? If you think something is broken, what happens if you run the machine with ducting and bags disconnected? Just run it for a few hours and see if it's still getting hot. If so, it's a problem with the motor and not your ducting.

[DarrylF]

I've noticed the problem recently because I only bought a lathe 5 weeks ago. Dust is nowhere near as bad when I run the extractor while turning, and that means running it for extended periods, something I very rarely do when making a piece of furniture etc. The heat problem is of course only a problem on a hot day, and only rears it's head after running for a while. While running the extractor on the lathe I only run maybe 2m of duct & flex hose, so I don't think that's an issue.

So basically turning is showing the problems with the machine that already existed.

I think I'm sold on the Jet 1.5 or 2hp + cartidge filter, but I'd love to hear from anyone who's used one, owns one, or knows of a viable alternative quality machine.

[Tim the Timber Turner]

A couple of points come to mind.

1: The overheating problem is most likly in the motor. If the motor size is matched to the impeller then you can't overload the unit. Blocking off the inlet to the extractor will result in the amperage dropping not unlike freewheeling. A vacuum cleaner works opposite and will load up if you block off the inlet.

2: You must match ducting diameter with extractor output and partical size. For example if you use 6" ducting and a one HP unit, any heavy particals such as chips will settle in the ducting and may well block it.
So the larger the partical size the smaller the duct size = higher velocity to keep everything moving.

3: The biggest single difference I made to my 2HP Woodfast was to increase the filter area by a factor of 3. This was done by installing 9 small dia bags in place of the original bag at a cost of under $200 plus a half day to fit.

4: I wouldn't use a paper filter while turning wet wood unless the filter was washable and I don't know if they are.


I run 14 mtrs of 6" sewer pipe with 7 drops. The best part of the system in the 8 meters of 3" flexible hose used to vacuum the machines and windows ect.

I also run a copper wire for the static. I didn't like the boots I got when I touched the ducting.

My 2 bobs worth.

Cheers and merry Christmas.


Tim

[DarrylF]

Yeah, I think the overheating is a motor problem - mostly likely just poor quality bearings I think.

I read a fair bit about duct sizes etc before I put the current ducting in - expecting to do some redesign if I go to a 2hp unit of course.

I want to avoid cloth bags, mostly because I despise cleaning them so much http://ubb.ubeaut.com.au/ubb/smile.gif The cartidge filters are usually polyester rather than paper - last longer and aren't so affected by moisture. I wouldn't expect to be using it when turning wet wood anyway - don't mind cleaning up shavings, it's just the dust I hate.

To fill in a little more of the picture here, my workshop is a double garage at the front of the house with an internal door. My wife is asthmatic, and I have a 2 year old daughter. My wife has problems with the fine dust, and I definitely don't want to affect my daughter.

The door between the workshop and the house is well sealed, but of course every time I wander inside for a drink etc I let fine dust into the house.

I could buy an airflow helmet and deal with cleaning up the dust, but that doesn't protect my family. If spending extra bucks helps, along with fixing the other problems, I won't think twice about it.

[soundman]

As for your heating problem check 3 things.
1/ the cooling airflow is not impeded & the cooling impeller hasn't come to grief.
2/ the start /run circuit is operation correctly and the start & run capacitor/s are within tolerance (common failure)(may be ask an electrician )
3/ bearins may be a problem, easy to check.

I've had a generic 1hp mackine for years & it has never run hot.

I think you have a problem.


Cheers.

OH one more thing.
make sure that you don't have a foreign body loged in the main impeller

All of the above may cause the problems you discribe

[This message has been edited by soundman (edited 19 December 2002).]

[Iain]

I was thinking of the cooling impeller, mine sucked up a bag off the floor once and it stuck in the tube under the unit, didn't notice it for a while.
Also make sure that the cooling impeller is on the right way round.
Is there clearance under the unit where the air comes in?

[BrianR]

I know there has been a lot of talk about PVC pipe, sparks and dust, but I have a 2hp dust extractor with 100mm PVC and sometimes I add a flex hose to it.
What does happen is that I get humungus static electricity sparks from the hose to the metal frame of my lathe and sometimes from me to grounded metal. I haven't calculated the energy level in the spark yet but intuitively it seems large enough to cause ignition of dust. I have added some protection in the form of grounded metal rings just prior to the vacuum machine to hopefully keep sparks out of the vacuum bag.

Also 100mm pipe is too small as someone else said.

[Mick4412]

Darryl,
I have read this post with interest. Like you, my workshop is half of a double garage, with direct access to the house.
I have a 2HP dust extractor from Carba-tec. I use a 15" thicknesser and a 8" Joiner regularly -both of these are directly connected to the dust extractor. I have a table saw, router table,biscuit joiner, and a CMSS, plus the usual range of sanders and a lathe.
The router table and biscuit joiner currently are connected to a household vacuum cleaner.
I finish a lot of my work by French Polishing, but, having no dedicated sealed area for polishing, I have an inherant problem with dust. I cover my "polishing work" fully with sheets, but irrespective of what combinations of dust extraction I use eg the mitre saw is now directly connected to a vacuum cleaner, and the unit is inside a box arrangement connected to the 2Hp extractor, when I lift the sheets from the pieces to be polished, a fine layer of dust is evident.
Short of buying a new home , with workshop, and dedicated, sealed areas for polishing, I don't think there is ann easy answer, especially if there is a problem with asthma in the family,
Given that, what you have said in your posts, if there is no problem with blockages etc in the unit or ducting, perhaps your unit is too small, or the lengths of yor ducting too long, for your current setup to work efficiently.
regrds
mick

[DarrylF]

Mick,

As you say, short of a separate sealed area for finishing, it's tough to avoid that fine dust being a problem for finishing. I do find the Jet air filter helps - if I clean up completely and leave the filter on high for a while it solves most of the problem.

My old 500cfm unit with the Jet air filter running was basically OK with most of my machines - 12" table saw, disc/belt sander, bandsaw, router table. It struggled a bit with the 12" thicknesser, and it's bloody hard getting decent pickup from the CMS.

The problem really came with the lathe - just didn't move enough air to pick up properly, and couldn't deal with running for long periods. After turning for a while the dust would be bad enough to affect even me badly - in other words, bloody awful.

Anyway, looks like the problem is solved. I picked up a Jet 1200cfm extractor with the Jet cartidge filter yesterday from Major Woodworking Machinery in Sydney. It's a nice machine - well made, went together nicely. The only noise is from a hell of a lot of air moving very quickly - with the cartidge filter it sounds almost as if it has no filter fitted. I've not run it very much yet, but I'll let you know how it goes.

Next job is a redesign of the ducting and the workshop layout. The layout has kinda grown like topsy, and I'm sure it can work a lot better than it does. I gotta build a decent lathe stand too, and dust hoods for it.

Thanks for your help guys.

[Vonrek]

Dear Darryl
Hope your new extractor is working well. As a matter of interest there was an article in Australian Wood Review No. 30 by Richard Raffan on designing effective extraction systems for different kinds of turning, sanding etc. Might be a good idea to get a hold of the article before you start your redesign of the ducting.

Merry Christmas

Tim

[sandman]

Hi Daryl, If you're on the subject of dust extraction, there is a terrific book available from most woodies shops/mail order cat's, it's titled "dust extraction in the workshop" costs about $28-$30 & is VERY informative! Get a copy as it is money well spent if you're going to the trouble of doing it, do it right the first time!
Regards,
Rich.