J. Phil Thien's Projects

Alan -
Were you ever able to test your theory? 
Did placing any 'vanes' below the separator have any effect? (Good or bad)
Quite curious in the results...
- Jim

Alan -
Thanks for the suggestions - all good ideas that will help. 
Unfortunately, the last suggestion is the only one I cannot feasibly implement...  It is a precision sander (designed to take off 1/2 the last coat of sealer/finish you applied) so the abrasive wear on a porous MDF sheet would always have to be compensated for during use. 

The machine is designed to create dust, so that is to be expected.  However, anything I can trap in the separator will be much easier to dispose of than from the bag! 

One question I have though is about the diameter.  Theoretically, the larger the diameter, the slower the rotation.  When I think of a tetherball (do kids still play that?) as the ball winds the rope around the pole, the linear velocity of the ball does not change, but the angular velocity increases.  The total energy (less gravity and air resistance) remains the same, but the 'effect' on the ball appears more dramatic. 

What allows for greater separation?  Does the lowered velocity of the air permit the fines to drop out?  Or does the rapid spinning of the air drive the fines to the outside wall? 

Is that the design philosophy of traditional tapered cyclones?  The larger diameter at the top allows the particulates to drop out and the narrowing diameter keeps them 'spun' against the sides?  I will look forward to the discussion and knowledge that will ensue!

Thanks!
Jim

Alan -
The wide belt of the sander is a vacuum hold-down.  It can securely hold large sheets of thin veneer very flat for sanding between finish coats.  The perforated belt travels over a perforated bed with a sealed box underneath.  The box is ducted to the intake of a blower capable of several inches of suction.  The 5"output of the blower currently goes to a large filter bag. 

My plan is to place the separator after the blower because of the difficulties in re-routing the ductwork and modifying the machine.  I'll still keep the bag after the separator to trap the 'very fines'. 

My assumption is that the separation will still happen in a positive or negative pressure.  I just don't know if the diameter is better increased or decreased from the common sizes that people are building since I am running a larger airflow than common DC units. 

Thanks for the inquiry, I'll look forward to any recommendations you may have.
- Jim

Guswah -
You have come to the right place.  Search these posts for lots of great ideas and success stories of converting all types of DC units. 

As far as your inside/outside issues go.  When in operation, the air moves too fast to be affected by the differences inside/outside.  What may be more significant is the uninsulated duct as a permanent opening through your walls.   Depending on the climate you live in, the differential may be a greater consideration.  I would be certain that your openings are sealed and moisture protected per your local building codes and climate considerations. 

Check out what other people have done and I am sure you will be pleased with your results.
- Jim

We have a wide belt sander with a vacuum hold down under the belt. 
Needless to say, the vacuum sucks a significant portion of the dust fines being generated. 
It has a large filter bag attached, but it needs a separator in the system. 

The vacuum has a 5" duct (120mm).  Velocity is good: 4500fpm when fully covered, to ~6500fpm when open.    The specs on the vacuum rate it at >800cfm which seems about right. 

Question #1 is: Is there an optimal diameter for the separator? 
Since it is a sander, it only has fines, no chips. 
I am planning on at least a 2x Top Hat with a bell mouth port. 

Due to the configuration of the machinery, it is quite practical to place the separator after the blower. 
So, Question #2: Are the other considerations for having a 'positive pressure separator vs. the conventional negative pressure designs? 

I'll look forward to any suggestions the 'collective wisdom' can provide.

Thanks!
Jim

Quote from: deancrozon on February 12, 2017, 11:44:40 AM
Can this be scaled up to 48 inch diameter with a twenty inch inlet, and still work ok?

Dean -
I can't imagine why you haven't had many responses to your request!  ;)
If you browse through the posts about building a Separator, you will find that a 5hp system is huge among our builders.   :o
I have a very large one ahead of a 20hp bag house.  But it has a 14" duct and should have been scaled smaller to be more effective.  I can't calculate how much horsepower you would need to drive such an enormous air mass at a speed fast enough to create the centripedal force to pull clean air out without debris. 

If you have a system that is that big, I have two suggestions:  8) You need a professional engineer to get the benefit out of such a large system; Or, you need to make smaller subsystems closer to the source of your debris generation. 

Otherwise,  Good Luck!  :D

DB & JGarner -
If you are fortunate to live in a climate where you can work in your shop most of the year without heating or cooling, you are tempted to discharge outdoors.  Our primary task in dust collection/filtration is to keep the particles out of our lungs.  Overall environmental cleaning is a noble idea, but idealistic if not unreasonable.  Releasing 1 micron particles into the atmosphere is not considered by regulating agencies because its dispersal is so great that it becomes irrelevant.   We would be better off trying to regulate pollen and hay-fever sources because they are much more harmful to human lungs. 

However, dust concentrated within an indoor space, is extremely important - which is why our dialogue on this website continues. 

Since my primary concern is to keep those dust particles out of my (and my co-oworkers) lungs.  I am sometimes in situations where I cannot collect the dust and chips and fumes into my DC.  At those few times, I simply place a HEPA filter over a box fan and blow it from behind us across the dust source(s).  This keeps a supply of clean air for us to breather while the particultes are blown away.  Once the dust settles, we can remove our filter masks.  Later, we suck it up into a shop vac with a Thien separator installed.  All clean!

Allen -
     Phil's discussion about a curved side entry is scroll-like.  However, in the Thien Separator, the air needs to make a few rotations before the fines (as many as possible) are dropped out.  A scroll would have to get it all within its single path. 
     In reality, a tapered cyclone cone mimics a scroll design.  As the air path moves down, it gets an increasingly smaller radius increasingly forcing the fines to the exterior.  Think of it as a 'vertical scroll'. 
     Clear as mud?
     - Jim

T-Man,
Famous Last Words from a Red-Neck:  "Hey Y'all, ...wonder what this will do..." 
After your shop burns down, having a separate shop vac, will be a lot less than your deductible. 
We all have to live within a comfort zone of the risks we take - you have to be comfortable with yours... 

As for me, I don't EVER worry about static sparks igniting my dust collector - I believe it is an urban legend.  There are documented studies where engineers TRIED to ignite the moving dust flow and failed.  However, dust explosions from other sources of ignition are real - and disastrous. 

On our grinder, we have a cloth bag that will not ignite, but will support combustion - like almost every other cloth bag on dust collectors around the world.  We don't have ANY evidence that a grinding spark, can come close to following the duct, going through the blower, swirling through the cyclone and maintaining anything close to the heat needed for combustion. 

When dust fires DO occur, they seem to be doubly tragic because they typically smolder for hours before turning into flames.  It doesn't ignite while you are working nearby and could easily extinguish it.  It always seems to wait until it is unattended and can spread significantly before being detected. 

A good smoke detector should sniff that out before it bursts into flames - a good idea in any shop. 

I would consider the risk to be QUITE minimal, but they thought the same thing about the Hindenberg! 

Hope this helps!
Jim

Adam -
Most of the time we want to make the diameter as large as our container to create a much centrifugal force as possible to remove the debris from the airstream.   Most of the containers available to us are still small enough to get their air rotating inside the separator. 

You can mount a smaller diameter Separator on top of a large cannister.  I have put a "Shop-Vac-sized" unit on top of a 33gal Brute.  The Separator is just that - it separates the swirling air above from the still air below.  But I have found that a short ring (2-3") below the separator helps with small diameters on top of large containers. 

For what it's worth...
- Jim

T-man, 
Yes and No.  (How is that for a 'definitive maybe'?) 

The separator will separate the 'grind dust' from your bench grinder.  Since the metals you are grinding are a higher molecular weight, they are easier to remove from the air stream than the lighter wood dust. 

There are two potential complications.  The first is that the metal debris is much sharper and irregular than wood dust.  While wood dust likes to 'bridge' across openings and pile up in corners, it doesn't 'grab' real well.  However, metal fines are able to imbed and latch onto each other with greater tenacity.  You will find that the metal particles will find more nooks and crannies to imbed themselves and cling much harder than with wood dust. 

The second issue is with metal by-products.  When wood working, you should not expect to find bits of your blades and bits in the dustbin.  The debris collected from grinding is a conglomeration of wheel debris, and the different metals, plating, paints and other assorted items that go through your grinder. 

My bench grinder has a squirrel cage blower mounted behind the grinder that went into a ~15cu ft reusable fabric bag.  The bag gets clogged with fines and starves the airflow.  Cleaning the bag is a 'hazmat experience' .  I started to use a Thein separator to drop out as much debris as possible.  But when I saw how contaminated the separator was becoming, I couldn't bear to see my wonderful separator being defiled. 

So I bought a $30 (on sale) DD and mounted it to a plastic bucket.  I don't care how disgusting the little cyclone gets.  I can wipe out the bucket several times before I have to clean the bag again.  It is a filthy system that works well enough not to have to share it with anything else. 

That has been my experience - I hope it helps!
- Jim

Wuf' -
You aren't the first to have this problem... 
Past solutions have been shared:
http://www.jpthien.com/smf/index.php?topic=461.msg2426#msg2426
http://www.jpthien.com/smf/index.php?topic=198.msg2435#msg2435 

Search 'relief valve' for more comments and ideas... 

Hope this helps!
Jim

JGT -
Don't give up on the 20gallon Brute just yet... 
We started with 55 gallon drums, then dropped to 32g Brutes.  Now, we use 20g Brutes and even smaller. 

Why?  With the large containers, anyone/everyone procrastinates until it is ready to overflow and it takes 2 guys and a forklift to dump it.  Now, if someone works for 2 hours, they can dump the small container by themselves at break or lunchtime.  Every individual is responsible for cleaning up their own messes.

So I would take a look at how much debris you generate at any onetime and decide if it will fit into a 20g and make life easier. 

Hope this helps!
Jim

Gordo -
I have both Dust Deputy and Separator units in operation at my shop. 
If your primary objective is to extend the interval between cleaning you DC filter bags, both will accomplish that.  Spending $39 on a Dust Deputy is cheap and quick and will dump the vast majority of debris into a bucket ahead of your ShopVac. 

Since you have mentioned air quality, the equation changes.  Most of these readers started with a DC that has a cloth bag.  If you replace that with a Wynn filter, you will make a huge improvement to your air quality regardless of what device is ahead of the DC.  But... you are using a ShopVac.  All of these generic devices have higher suction, but lower CFM.  You need to maintain as much CFM as possible in order for your vacuum to draw your debris into its collection and not escape into the 'cloud' around you and your tool. 

If you build one of the many 'Top Hats' shown by users on top of a 5 gallon bucket, you will find that it will present less of a load on your vacuum than the Dust Deputy.  Here is your empirical measurement:  Connect a DD to your vacuum and note the pitch drop when it is connected.  This shows you the load the little cyclone places on your vacuum (without picking up anything).  Then, connect a Separator.  Almost every design listed in this web-site will present less of a pitch drop - hence, less of a load to your vacuum.  This means that more air is flowing thorugh the Separator, which means that more air is sucked in at your tool - which means that less debris is floating in the 'cloud' that you are breathing... 

Depending on the tools you are using:  Saw vs. Router vs. Sander - you can tweak the size and design of your Separator to optimize the performance.  Since you will be limited to using a 'HEPA'-type bag on your vacuum, it will present its own load, all by itself.  Therefore, using a Separator that will present less of a load will be important to you. 

I hope my verbosity helps you maintain a cleaner, healthier shop!
- Jim

Gordo -
Searching through the posts, you will find that the separator works extremely well with most sawdust.  Many readers have added HEPA filters to trap the remaining fines.   Search for "Wynn Filter" and you will see how many readers have improved their common DC units. 

The more attention you spend on your details in construction, the greater achievements can be made with those last few fractions of efficiency. 

Certainly, your health risks are greatly minimized by using the Separator ahead of your ShopVac.  In order to get the air quality down to safe levels, you have to take more steps.   Even if you can't remove ALL fines, here is a poor man's way to breather cleaner air while working... 
Put a good filter onto a common box fan; aim the small stream of 'clean air' where you breathe while working; save money for a better system...
http://www.jpthien.com/smf/index.php?topic=270.msg1566#msg1566
http://www.jpthien.com/smf/index.php?topic=408.msg2287#msg2287

Hope this helps!
Jim