Pentz Cyclone vs. Thien Separator

[Negative_Zero [OP]]

Does anyone know of any reasonable authority as to which imposes greater drag on static pressure between a Pentz Cyclone and a well-made "top hat" Thien separator?

What I mean by top hat separator is one that is installed on top of a collection barrel with a direct connection to the impeller and motor and the input running into the size of the separator so there is no elbow (I posted a photo of one in the thread regarding the Harbor Freight DC here).

Is there a practical way to measure or even estimate static pressure without exotic tools? I have read some on the Pentz site and it makes me dizzy (and scared), so I am hoping someone else has already done the brain damage to think about this.

Thanks,

-Will

[Buster2000]

Re: Pentz Cyclone vs. Thien Separator

I fi understand your question: You're asking what causes the increase in static pressure between the two?

Air friction. The Pentz design (and most current comercial models) try to smooth out any areas of turbulence whithin the cycone. Improvements like the air ramp and square opening are designed to smooth the transition from each part fo the cyclone. Further the geometry of the cyclone itself causes particles to separate out.

Typically in a trash can separator air comes the volume of the cannister allows the air speed to drop, causing large particles to drop out. The Thein seems to attempt to smooth out the airflow a little bit. But realistically, it's still air blowing around a rough cyclinder.

Pentz has his Cyclone system at 2.25", and the Wood Magazine Cylone at 4.5" both without filter. He has a trashcan separator as adding 4.5" (that's on top of the collectors and filter pressure).

Thein changes the configuration of the collector to essentially imitate a really rough cyclone, but even with an improved lid on the colector I suspect that the separator is on the high side... As a whole system he's got to be above the Wood Magazine cyclone. As an conservative guess I suspect he's be around 6" of pressure, keep in mind it's very difficult to estimate, since it depends on how the whole system is set up, not just the lid.

Keep in mind what you're trying to do. Collect as much dust at the source, and not reintroduce it into your shop (filter it). To do that you need enough airflow at the tool to collect that dust, and a good way to separate dust from air (a separator and filter).

Finally Don't let the Pentz site keep you down, anything is better than nothing. Perfect dust collection is a bit of a pipe dream. There are so many tools that just will not be hooked up to DC, or will have poor collection points. The best thing you can do is try to collect as much as possible, and get a cross flow of fresh air in your shop.

[Chris in Saskatoon]

Re: Pentz Cyclone vs. Thien Separator

Does anyone know of any reasonable authority as to which imposes greater drag on static pressure between a Pentz Cyclone and a well-made "top hat" Thien separator?

Is there a practical way to measure or even estimate static pressure without exotic tools? I have read some on the Pentz site and it makes me dizzy (and scared), so I am hoping someone else has already done the brain damage to think about this.

I'm not aware of anyone doing any tests as to relative static pressure. The top-hat style is interesting because the airflow is going to be different than the normal cyclone lids.

Static pressure would normally be measured using a magnehelic through the side of the duct. This device measures pressure difference, so typically you would connect before and after the component being measured and read the drop across the device. There's some information on the process here.

[Don Burch]

Re: Pentz Cyclone vs. Thien Separator

Using SP loss as the criteria for comparing the two devices makes little sense.
A properly functioning cyclone, regardless of manufacturer, provides very effective particle separation from the air stream and effectively channels particulate matter to a separate waste bin. Unless the waste backs up into the cone, the efficiency of the cyclone remains constant.

The Thien separator is not a cyclone. It is a slight improvement on the trash can separator designed to keep as much particulate as possible in the trash can for ease of disposal and is not based on any real science. It is not a bad device, just not a cyclone in the true sense.
The cone is not engineered, there is no waste outlet.
The waste in this device is constantly in the airstream. As more waste accumulates, the "cone" area becomes reduced. The Thein baffle introduces enough change in the flow to allow more heavy waste to be contained in the trash can, but the fine dust carries on.

A proper cyclone can be built very inexpensively using the plans provided by Bill Pentz. This design can be scaled as required. Oneida have the Dust Deputy, Clear Vue have the Mini CV. They will both out perform any trash can concept on the planet, as will any cyclone built according to these plans. The cost of the sheet metal is low, any competent sheet metal shop can cut the pieces for you. The major expense is the blower assembly and the exhaust filters.


Don

[Negative_Zero [OP]]

Re: Pentz Cyclone vs. Thien Separator

Thanks for your thoughts, Don.

I accept your assertion that a Thien Baffle Separator will likely not remove as much of the dust from the air as would a cyclone but, respectfully, I disagree that there is no reason to consider it as a more easily achieved alternative to the cyclone, if its drag on suction is comparable.

I see five reasons to consider a Thien Baffle Separator: (1) it has significantly lower costs, and in many cases can be made largely from materials that woodworkers will have on hand, (2) it can be made with woodworking skills, without needing to learn how to weld or otherwise fabricate sheet metal (or pay someone else to do that); (3) it takes up much less space, particularly height, which may make a cyclone impractical for some shops; (3) having even separation of only the heavier dust and chips will allow modifications to be made to a DC inlet to remove grills that protect the impeller, increasing suction; (4) removal of some of the dust and chips will reduce the frequency at which the filter needs to be cleaned and increases the time when suction is at or near its maximum; and (5) the removal of separated dust and chips is easier than removing the bag from a single stage DC.

I have a single stage DC (so the cost of motor, blower and filtering is already covered) so I am considering what I can do to reduce the waste going to the catch bag and clogging the filter bag. Moreover, my DC is poorly designed in that there is flexible pipe between the blower and the filter-catch bag unit and had an inlet that is smaller than optimal, so I am already thinking about relocating the blower and motor to improve the suction. However, if adding a Thien Baffle Separator connected to the blower will reduce the suction to the degree that my DC no longer has sufficient suction for my needs this will be wasted effort. While, many people who have made well designed Thien Baffle Separators report that they are seeing about 5% of the waste that previously went to the catch bag continuing to go through (which would be sufficient for my purposes), there is very little information about how much suction is reduced. The common report that there is virtually no reduction of suction seems incredible.

It is also not certain in my mind that the drag on suction in a Baffle separator is greater than a cyclone, because part of the way that the baffle changes the dynamics of the typical lid separator is that the area in which the air circulates is (largely) reduced to the area above the baffle, which is also much smaller than the circulation area of a cyclone. I wonder if this could not result in less drag on suction.

I suppose I am wondering if a Thien Baffle Separator would be good enough, making it a viable option for some who still want a significant reduction in the dangers of dust in our wood shops.

A little more information about my set-up. I am working in a single-car separated garage in the mild climate of Vancouver (not worried about source of replacement air), that I have to share with other uses (all tools have to roll and be stowed when not being used). As a result, I am planning to have the filtering outside (not worried that a bag will not filter enough) and run a single 6" non-flex collection line to a central location to which I will roll and connect each tool for use.

Thanks for all replies and consideration of my question.

-Will

[Buster2000]

Re: Pentz Cyclone vs. Thien Separator

It is also not certain in my mind that the drag on suction in a Baffle separator is greater than a cyclone, because part of the way that the baffle changes the dynamics of the typical lid separator is that the area in which the air circulates is (largely) reduced to the area above the baffle, which is also much smaller than the circulation area of a cyclone. I wonder if this could not result in less drag on suction.

Will

I think your fooling yourself here. That small space would be a very turbulent place for the air. This is probably an improvment over a trash can separator, but I don't suspect by much.

Phil's website describes this as having the separating power of the cyclone... but I don't buy it. I understand the basics of cyclones, and this isn't the same. I see no reason to think smaller particles are being separated any differently than in a regular trash can separator. Which means all teh dust is going through to your filter.

Here is my take on the system, any gains you make in removing the screen and the flexible pipe will be more than cancelled out by the trash can collector. You'll may see a small incremental gain in suction base on a cleaner filter. In the end however the fine dust will just pass through to the filters as before...

[Claude in Kitchener]

Re: Pentz Cyclone vs. Thien Separator

Will, that is a well presented argument in favor of the Thien Separator.

Maybe you should direct your question to Phil himself! Here is the contact info:

phil@cgallery.com
When E-Mailing, please include the word "SkipSpamFilter" in the body of your message to avoid our dreaded spam filter.

If you find out any useful info from him please share it with us.


I don't agree with Buster2000. I think a Thien separator is a worthwhile incremental improvement over a standard trash can separator. I wouldn't expect cyclone performance but much better performance than the standard trash can separator units. Trash can separators merely send the "dirty air" in along the edge of the can and suck "clean air" from the center with little happening in between to separate the dirt from the air. They count on the 180 degree turn in the air flow to separate the particles from the air stream. This works modestly well until the can fills above the 50% mark and then you get a much less separation.

The thien baffle does not send the air stream towards the bottom of the can but along the circumference of the can. There is much greater opportunity for separation to occur and the baffle stops the scrubbing action so the container can be used nearly to it's capacity.

The elimination of the flex hose, increasing the inlet size and the addition of a pleated filter (or direct venting outside without a filter) will go a long way toward overcoming the SP loss created by the thien separator.

I have recently acquired a Delta 50-760 DC and plan to add a Thien separator. I have some ideas to improve the performance of the separator but my schedule is such that this will not happen until late summer or fall. If anyone is interested I will post the process and the results.

[Buster2000]

Re: Pentz Cyclone vs. Thien Separator

Claude,

I agree will makes a great case why he should use the Thein separator. In his situation this is a very good solution. He will have very little ducting from the separator to any machine. So SP drop from ducting will be very small.

What I’m trying to impress upon him is that the Thein separator is not a cyclone. He seems to be under the impression that he will see no SP increase by introducing the separator, further he seems to believe that the Thein separator has a similar separating capacity as a cyclone.

I think bill Pentz provides us with some pretty good boundaries for our expected SP. A trash can separator is at 4.5”, and a true Pentz cyclone is at 2.25”. Here is the basic Thein separator I’ve been looking at: http://www.cgallery.com/jpthien/cy.htm The Thein separator attempts to keep the air speed up by limiting the air flow to the top of the can, in a sense using a bit of cyclone separation (large particle will hit the wall, lose speed, and drop). But note, the act of turning the air and blasting it against the wall (even at a low angle) will introduce considerable amount of air friction. As well the area above the baffle is still open, another huge source of friction. Finally the air still has to take a 90 degree turn out of the lid. The Pentz cyclone on the other hand goes to pretty great lengths to reduce these types of air friction. So given this where do you think the SP will fall? Even it is half way between you’re still look at around 3.25”+ of SP from the separator alone, and in my opinion you’re going to be closer to 4” than to 3”.

I would also like to point out the elimination of the flex hose (which for replacing 3’ of 6” flex with solid pipe is only 0.26” of SP), increasing the inlet size, and moving to a pleated filter are all things that can be done independent of the Thein separator. The advantage in my opinion is the reduction of larger particles reaching the filters. So it will take longer for us to see the effects of the filter plugging, and the reduction in air flow associated with that. Further, the convenience associated with it may outweigh any drop in air flow…

As for separation, this is basic. It’s the tapered section of the cyclone that selects out finer and finer particles. Smaller particles have no other reason to settle out of a fast air flow.

Buster

[Claude in Kitchener]

Re: Pentz Cyclone vs. Thien Separator

As for separation, this is basic. It’s the tapered section of the cyclone that selects out finer and finer particles. Smaller particles have no other reason to settle out of a fast air flow.

Buster

I don't think the tapered section is solely responsible for the fine particle separation. Otherwise, why have the straight section so big? And why have the opening to the outlet pipe positioned above the tapered section? Particle separation, large and small, occurs throughout the straight section. The length of the straight section allows several revolutions of the airflow before reaching the center outlet. This allows time for all the particles to slow down, from friction against the side of the cyclone, and fall out of the airstream. The tapered section's primary function is to funnel the particles into the waste container. Once the air stream turns to go out the outlet pipe no further significant separation occurs.

The thien separator mimics this but is limited to a little less than one revolution of the container so, certainly, some small particles get to the outlet. The benefit is simple cheap construction and performance somewhere between a separator lid and a true cyclone.

The OP original question is about SP loss and it's a valid and important question. If the loss is 4" and the improvement in the DC can make up for 1-2" of that loss then he is likely to end up with a system that works to his satisfaction.

[Negative_Zero [OP]]

Re: Pentz Cyclone vs. Thien Separator

Buster said:

He seems to be under the impression that he will see no SP increase by introducing the separator, further he seems to believe that the Thein separator has a similar separating capacity as a cyclone.

Actually, the main point of creating this thread was to try to quantify how much SP increase the most efficient Thien separator would introduce, and not to assume it was either zero or infinite.

What Phil Thien has shown is that the options are not limited to cyclone vs. trash can, if the people using Thien separators are to be believed (and they seem to have no economic interest in deception). Typical reports seem to report separation of at least 80% and up to 95% of the dust and chips. That achieves most of what a cyclone does and probably enough for my needs.

I should have posted a link to a "top hat" separator, as it represents a signicant improvement to reduce the SP increase of a Thien separator. What I am thinking of can be seen here and here. These modifications combine many of the attributes of the cyclone with the Thien baffle, and I think are likely to introduce much less SP increase, but I was hoping to get beyond mere guessing.

I know how to measure separation efficiency (how much is in the barrel vs. how much there was to start). It seems that there is no simpleton's method to measure SP, so I am out of luck. This is perhaps why I could not find more reliable information to make the comparison.

Thanks for everyone's thoughts,

-Will

[Chris in Saskatoon]

Re: Pentz Cyclone vs. Thien Separator

The tapered section's primary function is to funnel the particles into the waste container. Once the air stream turns to go out the outlet pipe no further significant separation occurs.

I think there's a bit more to it than that, otherwise the slope of the tapered section wouldn't matter.

If you look at the videos of the Clearvue cyclones in operation you'll see distinct streams of dust right down to the bottom of the tapered section, which makes me think that the air doesn't turn around right away.

Lastly, check out the wikipedia link on cyclonic separation. From there:

Air flows in a spiral pattern, beginning at the top (wide end) of the cyclone and ending at the bottom (narrow) end before exiting the cyclone in a straight stream through the center of the cyclone and out the top.

[Rod Sheridan]

Re: Pentz Cyclone vs. Thien Separator

Buster said:





It seems that there is no simpleton's method to measure SP, so I am out of luck. This is perhaps why I could not find more reliable information to make the comparison.

Thanks for everyone's thoughts,

-Will

I guess you're not a simpleton like me.

Get a bucket of water, a length of clear plastic tubing and and a tape measure.

Mount the tubing in a straight vertical column with one end in the bucket of water, the other end connected to what you want to measure.

Use the tape measure to measure how many inches of water column you have. (Note this works for vacuum, for pressure it just blows bubbles).

Regards, Rod.

[NTM]

Re: Pentz Cyclone vs. Thien Separator

While thinking about setting up my DC I went through thr conical versus cylindrical debate (Pentz vs. Thien). In reviewing these I came to certain conclusions:

"The cylindrical unit is a good chip separator but may not be as good a dust collector as the conical version."

Without some sort of mechanism to reduce the rotational radius of the airstream there may not be an opportunity to remove the smaller particles. As the airstream spirals down it encounters an ever diminishing cross section in the cone. The airstream changes in direction at an increasing rate; resulting in a decreasing cut point and smaller particles spin out of the airstream. I noticed this when I started using a Veritas® Cyclone Lid with my shop vacuum. Although the debris tank on the vacuum did not fill as fast, the cake on the filter built up at a similar rate as when the cyclone lid was not used.

"The main benefit of the Thien design is to create a larger usable volume in the debris tank".

Any debris which falls below the lower baffle through the drop slot cannot re-enter the air stream. The vortex is contained between the lower baffle and the lid. I have noticed with my Veritas® Cyclone Lid the vortex can scour and carry away material for over a foot into
the debris tank.

"The Thein unit is an effective and inexpensive method of turning a single stage dust collector into a dual stage collector."

A dual stage system has the innate attribute of protecting the impeller from large and heavy debris particles. They drop into the debris tank before the airstream reaches the impeller. I think this is a good idea when one is going to use the dust collection system to vacuum the shop floor.

My system is a network of 4" ppiping with blast gates connected 1200 CFM single stage collector. Between the network and collector I have a chip seperator consisting of a 45 gal. drum topped with a cylindrical cyclone chamber. It is Thienlike with a drop slot but the intake on mine enters horizontally rather than vetically through elbows. To mitigate or improve the cut size issue I replaced the filter bag with a pleated paper cylindrical filter canister. This cannister has an internal flapper to knock the cake into a disposal bag. It woks well for me. I don't have any reservations that its performance would be enhanced by a more expensive conical chip seperator.

[Negative_Zero [OP]]

Re: Pentz Cyclone vs. Thien Separator

Hi NTM,

Thanks for sharing your experience. Can you post a photo of your separator? It sounds interesting.

-Will

[Don Burch]

Re: Pentz Cyclone vs. Thien Separator

Buster said:

Actually, the main point of creating this thread was to try to quantify how much SP increase the most efficient Thien separator would introduce, and not to assume it was either zero or infinite.

What Phil Thien has shown is that the options are not limited to cyclone vs. trash can, if the people using Thien separators are to be believed (and they seem to have no economic interest in deception). Typical reports seem to report separation of at least 80% and up to 95% of the dust and chips. That achieves most of what a cyclone does and probably enough for my needs.

I should have posted a link to a "top hat" separator, as it represents a signicant improvement to reduce the SP increase of a Thien separator. What I am thinking of can be seen here and here. These modifications combine many of the attributes of the cyclone with the Thien baffle, and I think are likely to introduce much less SP increase, but I was hoping to get beyond mere guessing.

I know how to measure separation efficiency (how much is in the barrel vs. how much there was to start). It seems that there is no simpleton's method to measure SP, so I am out of luck. This is perhaps why I could not find more reliable information to make the comparison.

Thanks for everyone's thoughts,

-Will

Will,
I went back to the net to look some more. I apologize for not reading more carefully in your original post.
Your original example involves hacking up the traditional single stage unit to basically salvage the blower to place in a new assembly - a barrel or what ever.

None of the discussions talk about what the single stage DC is really capable of. We know the manufacturer rates the machine based on what? So in Pentz's calculator, there is no adder for the basic single stage collector.
So, is it reasonable to assume that a top hat design with baffle would not be any worse than a conventional single stage unit with respect to SP loss. And likely better because the barrel is rigid so any turbulence in the lower container due to bag movement is eliminated.

So in light of no information to the contrary, I would have to say that the top hat design does not introduce any additional SP loss unless the order of flow has any relevance - single stage DC pushes stream to the separation chamber, top hat and cyclone suck the stream through the separation chamber. A stand alone knock out device, regardless of design, will add losses.

In my opinion there remain weaknesses in this approach.
1. the efficiency decreases as the drum fills. The solution offered for this is to know when to empty the drum.
2. the design is not engineered.

• to address particle separation. If you experience excessive carryover the solution offered for this problem is to simply add another knock out drum.
• proper blower capacity for a given drum size is unknown
• criteria for optimal blower performance are not considered. The fan manufacturers have some basic design considerations to minimize turbulence in the fan itself.

For me, effective dust collection is a health issue, not simply house keeping. I am in good health but recognize the hazards of this hidden natural carcinogen. Total cost of ownership is my focus.

Don