Thread: How much extractor do we need?

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DRAFT: FAQ - Dust Extraction (Practical Aspects)
In your case you probably should add how many people are on average likely to be making dust at the same time.

1) The number of hours you spend a week actually making dust in your shed - not just sitting or doing non-dust making activities in your shed. Varies, but 25-30hrs per week is probably average
2) The size of the shed you work in, not the size of the area in the shed you utilise, but the total size of the shed. Floor space is about 400 sqm I think, ceiling height is about 7m
3) The type and size/power of dust making machinery you use in the shed. List below
4) The types of wood you work with Mainly US hardwoods (Ash, Oak, Cherry, Walnut) as well as Vic Ash and pine, MDF, chipboard, plywood
5) Size and location of openings like doors and windows that you can keep open without annoying the neighbours and irrespective of the weather. If the weather is good, roller door at the front big enough to drive a semi through and a normal door at the back. If the weather is bad, normal sized door at the front.
6) Number of people making dust at once Honestly hard to say; could be 1, could be 5

Current extraction list:
CNC router- 10" manifold, 8" at router head, closed when not in use
1350mm 2-head wide belt sander - 2x 8" closed when not in use
Spindle moulder - 4" normally open. Would like to bump up to 6"
14" docking saw - 4" always open
Twin drum/linisher - 2x 3" with bellmouth. We know it's useless, want to bump up to 2x 6" Always open
24" helical thicknesser - 6" always open unless sander, CNC or rip saw is in use
16" helical buzzer - 4" always open
2x bandsaws - 4" each always open, rarely used
Edgebander - 4" closed when not in use
16" rip saw - 6" + 4" closed when not in use
Panel saw - 8", split to 6" + 3" always open, want to change to 4" on top
Floor sweep - 6" closed when not in use

I think that's it. Worst case scenario, we need to run wide belt, CNC, thicknesser and panel saw at the same time.

Current extractor is 15kw Micronair VC8 on a 3 cu.m bin, located outside

Thanks for the info.

You appear to have clearly identified a large elephant in the corner.

Before you purchase a new DC I would recommend upgrading most of those 4" outlets to 6" and at least 6" ducting all the way back to the DC after that.
Do the machines have enough air flow into cabinets to allow for enough air to flow so fine dust can be scavenged up?
How do you ensure the blast gates are open?

It can be waste of time to try and extract more and more air only from the cabinet (even using 6" ports).
If fine dust escapes above a work table its more effective to add a scavenging port above the machine itself as close as possible to the dust source.

Use of Bell Mouth hoods on make ducts will pick up an extra 10-15% more air.

CNC router- 10" manifold, 8" at router head, closed when not in use
1350mm 2-head wide belt sander - 2x 8" closed when not in use (should be OK)
Spindle moulder - 4" normally open. Would like to bump up to 6" (Yep do it - maybe 2 x 6" with one above the moulder itself)
14" docking saw - 4" always open (at least a 6" Bell mouth hood)
Twin drum/linisher - 2x 3" with bellmouth. We know it's useless, want to bump up to 2x 6" Always open (YEP definitely a problem)
24" helical thicknesser - 6" always open unless sander, CNC or rip saw is in use (probably should close it when not in use)
16" helical buzzer - 4" always open (6" needed)
2x bandsaws - 4" each always open, rarely used ( should have 3 x 4") but low priority as low usage
Edgebander - 4" closed when not in use (some photos needed as to where the dust port is located)
16" rip saw - 6" + 4" closed when not in use (consider using and extra 6" scavenger on top)
Panel saw - 8", split to 6" + 3" always open, want to change to 4" on top (yep)
Floor sweep - 6" closed when not in use

While I agree with the need to upgrade the 4" to 6", aside from the moulder it's not going to be feasible without redoing the entire main line due to how everything is arranged in the factory, the moulder is near the entry point and under the main line, all the other 4"s are further down and off to the side. The edgebander maybe runs once every 2 months and splits internally to 2x 2" anyway, so I don't think 6" will do much good there.

I should note that the thicknesser is a 6" line that opens to 8" on the machine and the buzzer and moulder are 4" opening to 6"

I'm counting myself lucky that they'll talk about a new machine (after quite a few years of effort), an entirely new ducting system is going to blow the limited budget way out.

The CNC sorts its own blast gate out, the rest are manual and it just becomes habit.

Originally Posted by elanjacobs

While I agree with the need to upgrade the 4" to 6", aside from the moulder it's not going to be feasible without redoing the entire main line due to how everything is arranged in the factory, the moulder is near the entry point and under the main line, all the other 4"s are further down and off to the side. The edgebander maybe runs once every 2 months and splits internally to 2x 2" anyway, so I don't think 6" will do much good there.

I should note that the thicknesser is a 6" line that opens to 8" on the machine and the buzzer and moulder are 4" opening to 6"

Doesn't help much and it sounds like teh machines are probably not breathing all that well (air inlet path) either.

I'm counting myself lucky that they'll talk about a new machine (after quite a few years of effort), an entirely new ducting system is going to blow the limited budget way out.

Well unfortunately you just have to tell the boss that a bigger machine is a waste of money because while bigger DCs have bigger impellers they move more air ONLY because they can make use of bigger ducting.
Unless the vacuum/pressure of the DC is increased (and they nearly ALL run at the same vacuum/pressure) you simply won't get more flow if you use the same ducting.
It's not your DC but the ducting that is limiting the flow. Some DCs will have maybe 20% more pressure/vacuum and you might get 10-15% more flow in small ducts from this, but that is it.
Provided the machines can breathe properly, upgrading from a 4" to 6" TRIPLES the flow making a really significant difference to fine dust management.

A side issue is if you do just go for an increased pressure/vacuum system you will generate a lot more noise. This is a major reason why they just don't crank the pressure up on DCs.
To generate double the flow through a 4" duct will make it scream like a jet engine and while it might not sound as loud as a WW machine it will be in a much more irritating and damaging frequency range. Unlike machines that make most of their noise while cutting wood the DC noise is generated all the time the gate is open.

The CNC sorts its own blast gate out, the rest are manual and it just becomes habit.

A worker that works for even a short period on a machine (ie so they don't notice dust build up) may forget to open the gate and this all adds to general shed contamination. Our vacuum switch lockouts on machine operation (unless the gates are open) at the mens shed are working really well and is being adopted by a number of other mens sheds. This is a $3 part and is well worth it.

If the small 4" lines are being maxed out now on flow then putting in a new DE will not sort out the issues you currently have as 4" lines simply aren't big enough no matter how you slice it. I am looking at a similar problem in a factory unit now with exactly the same issues and while it is most probably the hardest thing to change it must be done. Why throw many thousands of dollars at a system when the result won't match the money spent and the accountant gets P'd off with the result. Cry once? Fix the ducting and see what happens.

If you want to boost the vacuum in your existing system the easiest way would be to install a VFD and run the impeller at 60Hz.
This will give you a 20% boost in vacuum but it won't help that much in the 4" ducting.

15kW VFDs start at about $1500 but the sparky bill could be similar, still a lot cheaper than a new DC and most likely better performance than a new one running at 50Hz.

The main thing that's not breathing properly is the DC itself, the vibration clean just can't clear out all the fine sander and CNC dust from the pleated filters. When they're clean there's suction galore, but 3 months later they're packed up again, that's why I want to go reverse pulse.

I'll see what I can do about ducting, but I'm not keeping my hopes up. We know someone at A.G.Coombs, maybe he can get us a deal

Originally Posted by elanjacobs

The main thing that's not breathing properly is the DC itself, the vibration clean just can't clear out all the fine sander and CNC dust from the pleated filters. When they're clean there's suction galore, but 3 months later they're packed up again, that's why I want to go reverse pulse.

It sounds like you maybe should consider putting the CNC and Sander on their own cyclone?

Quite possibly, but there's no space for that. The DC is already on common land without permission, we can't take up any more space outside and there isn't space to take inside.

Unfortunately, the ideal solution isn't going to be affordable or practical, so I have to find the least bad alternative

So, assuming the ideal size ductwork to everything, roughly how much air do we need to move? The units we're looking at are roughly 12,000 cu.m/hr @3000 pa, will that be enough?

I am not qualified to tell you what duct sizes and impeller you need but I can tell you that when a cartridge pulsing system is working they sound like small cannon shots being fired as each filter is pulsed all through the cycle and may need to be banging all day long. Very irritating for everyone including office staff if they are close to the filter house. Even with the pulsing the filters may still clog up to the point of needing replacement or sending out to a filter leaning company. A much cheaper option than tossing them. They can be cleaned 3 to 4 times before needing to be replaced. The plant I worked in had downdraft tables and sanding booths for edge breaking and polishing of large aircraft parts. They sent out half the filters every 3 months for cleaning while a new set was installed. When the filters come back they went into the machine in the next round of cleaning took place. That way they only needed to have half a set of the 24 filters in waiting. Your desire for a different cleaning system may work longer but eventually they will need to be cleaned/replaced at some point. Salesmen will pitch whatever they have rather than what is the best. Why are you filtering the air rather than exhausting outside?

Pete

Originally Posted by QC Inspector

Why are you filtering the air rather than exhausting outside?

We're doing both. The entire unit is outside, but I'm pretty sure it's not legal to exhaust with no filter at all, especially since we're only a few hundred metres from a residential area. I wasn't around when the current DC was bought, so I don't know why pleated filters were chosen over felt bags.

We got nearly 10 years from the first set of filters with very little maintenance, but our work load is changing and we're now creating monstrous amounts of dust, rather than the larger chips from planers and moulders of 10 years ago.

Originally Posted by elanjacobs

So, assuming the ideal size ductwork to everything, roughly how much air do we need to move? The units we're looking at are roughly 12,000 cu.m/hr @3000 pa, will that be enough?

3000 Pa is pretty standard for larger DCs so nothing special in that regard.
Manufacturers will usually state this figure for the fan only, ie no ducting or machines (this is fair and reasonable given they don't know what you are going to connect it to) and no filters.
Sometimes this does include brand new filters and it would be useful to know if it does even though it won't change much.
Even if it does include filters this will be for clean filters, so then the pressure with drop off as they clog up.

12,000 m^2/hr is a lot of air and in theory enough for your machines but it's kind of meaningless.
It will be what the impeller can move when unrestricted and not what ends up flowing through ducting and clogged filters.
The traffic cops on air flow in any DC system are the filters, ducting and machine port sizes and machine breathability.
Unless these are issues are attended to you will end up with the same flows as you already have.

None of this is that relevant if as you say when the filter is clean you reckon you have enough flow, although unless you have performed a particle count you will never know what is really going on.

I keep thinking that a large cyclone might be a better option? I'm not familiar with very large cyclones and it is my understanding that they use a very large (20") impeller and suitably sized motor and while they have plenty of suck that is not the only KPI required. The other aspect is fine dust removal by the cyclone itself (ie pre any final filter) which reduces the amount of very fine dust filtration required. This comes down to the ability of the cyclone not only to separate chips from air, but fine dust from air. Only cyclones designed in a special way like the Clearvue can do this. Clearvues are so efficient that they emit only a very small fraction of the very finest invisible dust so that they can be used without filters if they vent outside. The problem with a Clearvue is it will not be able to provide the flow required to service several of your larger machines at the same time.

It may be worth looking at a large industrial cyclone that still uses a final filter.
If the cyclone itself pulls out enough fine dust out of the air streams this may reduce or simplify the need for any final filter cleaning.