Ducting system questions?

[Rob Cheetham]

Hey. Im wanting to make a ducting system through my small shop to save having to have trailing hoses. Its only a small shop 5.5m x 3.2m

I have a few questions that I would like to know as I dont fully understand all things air flow etc. My questions are:

* What is the best material to use for ducting? Galvanised steel, pvc, stainless steel etc?
* Is it best to put two 45 bends together to make a 90 to reduce sharp bends in system?
* With an estimated run of about 12m how much does air flow reduce over certain distances?

I plan on doing a drop down to my table saw, P/T, band saw and router table each with a 90 bend consiting of two 45 connectors to reduce the sharpness of the bend. All drop downs to a tool will have blast gates installed also.

My extractor is the axminster ap154ceh cyclone and has an airflow spec of 941 cfm at 150mm or 778 cfm at 100mm. It has a 150mm adapter which breaks down to two 100mm outlets. I really only want to be using 100mm pipe so will use the 150mm - 100mm adpater.

My table saw requires min 550cfm
My PT requires min 588cfm
Unsure on my band saw and router table but I would think it would be about the same.
Table saw is a laguna fusion 3, pt is a axminster ap260spt spiral block, band saw is record power bs400 and my router table is the axminster ujk table set up with axminster router box underneath housing a trend router.


Any help on all this would be greatly apprciated. Also any links to websites or youtube videos with good info would be great too. Thanks for reading and look forward to any information you can chuck my way.

TIA

 

[Inspector]

Claims of flow by most sellers are roughly double what you will get in a system. They test with just the impeller, no ducts or filters, in the centre of the airstream where it is highest.

Duct sizes limit the flow. 4" being roughly 450 CFM max, 5" being roughly 800 CFM and 6" being roughly 1250 CFM max. It is the wall surface area to duct diameter that limits it. Flex hose has roughly 3 times as much drag as smooth pipe. Keep it to a minimum if you can.

Some intense reading that will take a long time to read and digest. Dust Collection Research - Home

A calculator that will help do what if calculations to your configuration and show the looses. Duct Friction Loss

Information starting at page 54 show losses of different fittings etc. You'll see a pair of 45º fittings has more drag than a single long radius 90º fitting. http://www.lorencook.com/PDFs/Catalogs/Cookbook_Catalog.pdf

Pete

 

[ian33a]

It's easy to get bogged down with calculations and to lose sight of the main intention. Your workshop isn't massive and, if you are not careful, you will feel like you are part of an air-conditioning experiment.

Over the years I've tried a variety of things and have settled upon two discrete systems: an HVLP system based upon 100mm and a LVHP system based upon 63mm pipe. Both systems are plastic, and both use Axminster products. Nothing has 90 degree bends.

With the 100mm system, I keep the extractor really close to the machinery and work everything through 45 degree elbows, Y sections and blast gates. Each section can be shut off, almost right at the Y section and it seems to pull a decent enough flow for what I need. I also keep flexible ducting down to a minimum. This drives my sanders, bandsaw and can drive my planer/thicknesser and router table, albeit, the latter two with flexible pipe.

For all of the smaller power tools and the mitre saw I use the 63mm system. This has a cyclone and the output connects to a pair of dust ports, each can be isolated using blast gates. One dust port goes to the mitre saw and there are a few spares which can have Festool flexible pipes connected to the router table or anything else in that section of the workshop. The other dust port is used exclusively for the MFT. I have flexible hoses of various sizes for things like the track saw, the domino and routers. All of the dust port inlets have blast gates.

At one stage I had grounding everywhere. We moved recently and I haven't bothered as much this time. In Devon, we aren't exactly in the middle of a climatic desert so static building up is far less than in very dry conditions.

As an engineer I could have sat down for ages and done the maths. I couldn't be bothered to be honest. I worked on the principle of retaining flexibility in coupling things up while minimising each individual port length (within reason) and keeping them all isolated from one another as much as possible. As a hobbyist, I'm not paid by the minute and can afford to plug and unplug hoses, within reason. I appreciate, however, that if it's your time and money it may be a different matter for you.

 

[clogs]

once decided on pipe runs, I think plastic drain pipe would be cheapest, smooth insides and easy for the end and corner fittings...
the more educated will know...
but I was always worried about static elec build up in what ever material u use for the trunking....
obv metal trunking would be self grounding....
I maybe worried for nothing....>

 

[Inspector]

Static explosions in home systems don't happen. Too small to make a spark big and hot enough, plus you need to generate way more dust than a small shop can produce to get to explosion levels. You are more likely to have a fire from cutting metal, picking some up and hitting the impeller or dull cutter making embers.



Pete

 

[Daniel2]

Think simple....Don't over complicate it.
For the home workshop, standard PVC pipe and
fittings are more than sufficient. Plug and play...!!

 

[Robbo3]

Static explosions in home systems don't happen. Too small to make a spark big and hot enough, plus you need to generate way more dust than a small shop can produce to get to explosion levels. You are more likely to have a fire from cutting metal, picking some up and hitting the impeller or dull cutter making embers.
Pete

Hooray for a sensible answer.
There is a UK fire service report (which I can't find) that states there are no known fires started by static in a domestic workshop in the UK.
Industrial is different. The Birds (custard/coffee) factory in Banbury has had 3 fires over the years.

 

[Rob Cheetham]

Duct sizes limit the flow. 4" being roughly 450 CFM max, 5" being roughly 800 CFM and 6" being roughly 1250 CFM max. It is the wall surface area to duct diameter that limits it. Flex hose has roughly 3 times as much drag as smooth pipe. Keep it to a minimum if you can.

Thanks for the information. Do you reckon it would still be worth doing then and just making sure to keep to as much smooth pipe as possible?

 

[Rob Cheetham]

With the 100mm system, I keep the extractor really close to the machinery and work everything through 45 degree elbows, Y sections and blast gates. Each section can be shut off, almost right at the Y section and it seems to pull a decent enough flow for what I need. I also keep flexible ducting down to a minimum. This drives my sanders, bandsaw and can drive my planer/thicknesser and router table, albeit, the latter two with flexible pipe.

Thanks for the input. Yes this system will be mainly for my bigger machines. Like you I have festool extractor for my kapex saw and other small power tools.

You say you have 45 degree elbows. Would joining two 45 to make 90 work as well do you reckon?

 

[Rob Cheetham]

I think plastic drain pipe would be cheapest, smooth insides and easy for the end and corner fittings...

This is a nice idea. Im just wondering if if you could find standard 100mm to fit wood working machinery. Thanks for the advice

 

[Rob Cheetham]

Static explosions in home systems don't happen

This is good to know. I was wondering about this and did think the same tbh. But thanks for clarifying this

 

[Rob Cheetham]

Think simple....Don't over complicate it.
For the home workshop, standard PVC pipe and
fittings are more than sufficient. Plug and play...!!

Thanks for the input. Any good sources you know off for pvc pipe and fittings? Thanks

 

[ian33a]

Thanks for the input. Yes this system will be mainly for my bigger machines. Like you I have festool extractor for my kapex saw and other small power tools.

You say you have 45 degree elbows. Would joining two 45 to make 90 work as well do you reckon?

It does work but it's better to do a sweeping bend, so a 45, as bit of straight pipe and another 45. Otherwise, the bend is abrupt and may be just as bad or even worse than a single 90.

By no means definitive aero, but here's part of mine

 

[daftdog]

Plastic ducting would be best dont glue it then when it gets blocked because you get fall out of dust in horizontal sections you can take it apart to clean it.The smaller the duct the faster the air speed the better it carries the dust long, sweep bends are best, angled penetrations from vertical to horizontal reduce friction saving velocity if you have more than one pick up point fit a stop valve in each branch so you only vac one tool at a time,make branches removable for cleaning purposes. Dust will accumulate in your system. Best of luck.