Dust extraction idea

[MattRoberts]

My current dust extraction setup looks like this:

It consists of a 2hp extractor sitting on top of a thien baffle. It works just fine, however it's only connected to the tablesaw, so it's not under much pressure. I'm looking to plumb in proper piping and have it connected to multiple machines.

The issue is that my extractor has a 5" port which I'm reducing to 4" in order to connect it to my thien baffle. Now I know that using any dust separator will naturally reduce the airflow. By also restricting its 5" capability down to 4", I'm further impacting the airflow. I would like to use 5" pipe around my shop, with 4" runs to the various machines. I also have another extractor, a 1hp with a 4" port.

So I had what will either be a brainwave, or a completely moronic idea.

If I have the 2hp extractor do all the leg work using 5" pipe before getting to the thien, it will have maximum efficiency. I then use the 1hp extractor on the other side of the thien simply to pull the air out. I have previously read that you can run extractors in serial without impeding the airflow

Have I missed something blindingly obvious? Let me know your thoughts!

 

[MattRoberts]

Do I take it it's a bad idea, or is it more a case that we won't know until we try it?

 

[MikeK]

A 2HP blower should be good enough for a small shop. Since the restriction is at your Thien Baffle, why not make another baffle, or enlarge the opening of the existing baffle, with a 5-inch port? The first thing I would do would be trying the 2HP blower without any reductions to baseline the performance. You might be surprised if it works well enough.

From all I've read about two-stage extractors, either a Thien Baffle or a Cyclone, one benefit is the blower is after the extractor and the swarf never touches the impeller blades. In your proposal, all swarf will impact the 2HP impeller blades before being pushed to the Thien Baffle. It might work, but I would never attempt if if I had the opportunity to keep the blower after the extractor.

If you do try it, please let us know. Who knows...you might be correct!

 

[Myfordman]

Somebody here did do experiments with combining multiple blowers but I cant recall the results.
I do seem to recall it was counter intuitive and the incorrect combination caused one blower to starve the other.

A good search though the forum should find the write up.

Sorry I can't be more help.

 

[Myfordman]

After a bit of a search, this extract from the Rotron website puts the situation quite succinctly.

Using Multiple Fans

When applying more than one fan in a system:

"n" fans in series will increase pressure "n" times at a given flow rate, with no additional free delivery flow. Fans in series can be useful in high resistance systems.
"n" fans in parallel will increase flow "n" times at a given pressure level, with no additional shutoff pressure generated. Fans in parallel can be useful in low resistance systems.

 

[sunnybob]

I think that you are over thinking it.

If your present system works with one machine. It will work with any other machine any where else.
Unless you are planning to run 2 or more dust producing machines at the same time, there is no problem to solve.

 

[MattRoberts]

Thanks for the thoughts gents.

Myfordman - with a thien and the addition of ducting runs, you could argue that I will have a high resistance system, no?

Sunnybob - it's a fair point, and I will be using only one machine at a time. I'm just concerned that by adding 4" instead of 5" ducting, my extractor might not be as super sucky as I want it to be or as it could be!

 

[sunnybob]

My dust extractor is 4" (100 mm) inlet.
But that immediately is reduced to 63 mm for the entire pipe run including blast gates.
I can run a 12" bench top thicknesser without problems, and thats connected to the main pipe through 5 metres of 63 mm ridged flexible hose.

Just how much mess are you making?

 

[MattRoberts]

I guess my biggest concern is for the mitre saw shroud. I want enough volume of air to be shifted to capture that dust - it's the biggest source of dust in my shop

 

[siggy_7]

Fans in series give you increased pressure drop, fans in parallel increase flow rate. Unless you have a very restrictive ducting set-up (and if you do, I would advise sorting that first) I would suggest it better to connect two blowers after the Thien baffle in parallel, thus increasing your flow rate.

From your description I believe you want to replace some 4" ducting with 5" to improve flow losses - what length of ducting are we talking about here? And what sort of flow rate do you reckon you're getting from the extractor? Do you know the impeller diameter on the extractor, or can you measure the casing (to give an idea of max. pressure)?

 

[MattRoberts]

It's all theoretical at the moment Siggy - I'm refurbishing my workshop and finally installing duct work. I have an airflow measurement tool (anenemoter?), so will be doing some tests to check the best results and will report back!

 

[sunnybob]

I hope you can read this, it will keep you going for a couple hours
http://www.routerforums.com/tools-woodw ... ments.html

 

[MattRoberts]

Thanks Bob, will have a gander!