Dust collector "upgrade" and CFM readings

[Don Kondra]

Greetings,

Edit > It appears I have entered square inches instead of square feet on my meter > .196 vs .134

The correct numbers are in red..

To recap...

I started with a two bagger, 2 HP no name dust collector with an 11" impeller. For years, I've been hauling around 20' of 4" hose and it worked well enough

The purchase of an edge sander plus getting tired of tripping over the hose prompted this upgrade.

I did a lot of research on different brands/models and decided, for a one man shop using one tool at a time, I really didn't Need a larger system but I did want better control over fine dust And a better/easier way to dispose of the shavings. Dragging out the canvas bag to empty and finessing the clamp back on was one of my least looked forward to tasks, sigh...

The addition of a canister filter did eliminate the "puff of dust at start up" but there was still a slow accumulation of fine dust everywhere.

Using the motor/impeller I added an Oneida Super Dust Deputy, their 35-gallon dust bin, a Wynn filter and a remote control.

Old set up.

1 - old system.jpg

New set up.

Cyclone install done.jpg

Overall shot with 5" spiral runs and 5" flex hose at collection ports.

16 - final set up.jpg

Close up of band saw.

15 - band saw hook up.jpg

Close up of thickness planer.

14 - planer hook up.jpg

The new system has been up and running for about a month now and I've been very pleased.

Especially with the total cost of about $2200 which is a fraction of a larger systems cost and didn't require any new wiring.

Although the dust bin is only slightly more than half full, the clean out box on the Wynn filter has less dust in it than what is on my coffee table

Too early to tell but I'm hoping I won't experience any of the filter cleaning problems I've read about, the cyclone appears to very efficient.

The majority of what is in there is fine dust from the SCMS, band saw and stroke sander. Maybe an 8' board of jointing/planing for jigs and testing.

I purchased an anemometer for $50 Cdn from eBay and it finally arrived > http://www.ebay.com/itm/261486368012....N36.S1.R1.TR2

All readings were taken with the fan of the meter in the middle of the 5" hose/collector port opening.

My straightest run is to the band saw with about a short 30 degree turn at collection. CFM is 462, velocity is 3400. I have enlarged the opening for the blade at the top of the bottom door and flared the edges outward. This allows for more intake air..

The run to the jointer has 10' of clear flex hose and a gentle 180 degree turn, readings were 422/3100. Less of a loss than I was expecting using that much flex hose compared to the band saw's run.

The run to the thickness planer has a short 160 (?) degree turn but still read 435/3200. If the readings are taken with the meter on the inside of the curve they were 503/3700.

The run to the stroke sander is reasonably straight and read 476/3500.

This is where it gets interesting !

I had some 6" hose left over from hooking up the dust bin and thought I would use it on the SCMS since it is a gentle 180 degree turn of 6'. The reasoning was maybe the larger diameter of the hose would overcome the curves static pressure loss ? Not so, readings were 340/2500.

I redid the run with 5" hose and the readings went up to 448/3300.

This makes me question suggestions of increasing the main trunk to 6" from the SDD's 5" inlet.

I'm used to using the hose as a "vacuum cleaner" on the floor so I hooked up 6' of 4" hose to the thickness planer run. The 4" hose is much easier to manipulate than the 5"...

Readings were 340/2500, the same as the 6" hose on the SCMS.

This also reaffirmed my decision to change over all my machines dust port openings to 5".

Please note, if anyone is considering this "upgrade" with a lesser motor/impeller such as mine, running with two dust ports opened at the same time reduced the CFM to roughly half at each port.

Cheers, Don

[Rod Sheridan]

Don, I'm wondering if you have a measurement error using the anemometer.

I normally add a length of straight pipe and make 5 or 6 velocity readings distributed around the pipe diameter.

I then average these and calculate the airflow manually from that.

Try that method out and see if it changes your results.........Regards, Rod.

[peter gagliardi]

Increasing a pipes diameter bigger than the collectors inlet size will lower your velocity. Wood dust and chip velocity is ideal at 4000-4500. Won't make a difference on your short runs , but bigger chips will fall out of suspension on long runs, where it's easy to lose velocity, and build up in the pipe.
I got some years ago, a dust collection slide rule from the Murphy-Rogers booth at a woodworking show that has proven quite handy over the years

[David Kumm]

I think the math might be the problem. A 5" hose calc would be 2.5X2.5X3.14/144XVelocity. So 2.5x2.5x3.14=19.625. 19.625/144=.1362847 X 3500 = 477 cfm. Measuring in the center also gives a high reading as the edges are often lower and there is more sq inch at the perimeter. If you redo the math you will find that the 5" and 6" come out about the same. Dave

[Don Kondra]

Don, I'm wondering if you have a measurement error using the anemometer.

I normally add a length of straight pipe and make 5 or 6 velocity readings distributed around the pipe diameter.

I then average these and calculate the airflow manually from that.

Try that method out and see if it changes your results.........Regards, Rod.

Not sure how adding a straight piece of pipe would be of any benefit Rod, I am more interested in an in situ reading.

I did perform a quick test for you though using the thickness planer run

In situ, the inside measurement was 436, the middle 402 and the outside of the curve 360 for an average of 400. Pretty darn close to the inside measurement !

If I "straighten" the flex hose the reading in the middle goes to 429 and there isn't as much variance on the outsides, roughly 20 CFM.

I was as careful as possible to position the meter in the same spot for testing the various runs but I am seeing a variance of about 20 CFM between yesterday's readings and today's ?

For my purposes, the numbers themselves aren't as important as the relationship between the different lengths and curves of each run compared to the others.

This is how I positioned the meter to take my measurements.

Measuring.jpg

I think the math might be the problem. A 5" hose calc would be 2.5X2.5X3.14/144XVelocity. So 2.5x2.5x3.14=19.625. 19.625/144=.1362847 X 3500 = 477 cfm. Measuring in the center also gives a high reading as the edges are often lower and there is more sq inch at the perimeter. If you redo the math you will find that the 5" and 6" come out about the same. Dave

So you are assuming the velocity reading is the "correct" one ? And you were right

I am seeing more of a difference in readings between the inside and outside on the runs with bends compared to straight connections.

For comparison purposes, I have chosen to use the middle testing numbers...

Cheers, Don

[David Kumm]

Don, I tend to trust the velocity readings and do my own conversion. 600 cfm with an 11" impeller and 5" pipe doesn't sound right. Usually a 5" pipe with a cyclone in front and a 14-15" impeller will get you in the 600+ range but diameter makes a big difference. The 5" and 6" comparison should end up pretty close in cfm. The anemometer will be too inaccurate at those speeds to really tell. I agree that the relationship is more important than the actual numbers. The turbulence created in the runs with bends might be causing the variation in those readings. Dave

[Michael W. Clark]

Hi Don,
How is your anemometer accounting for the different duct areas? You said you re-measured in the 5" hose and the readings were "630/3300". I assume this is 630 CFM and 3300 FPM. This flow and velocity combination does not agree with the area of a 5" hose/duct.

Also, If you are disconnecting the hood to take the flow, you are not seeing the true flow. In some cases the hood may actually help your flow by lowering your entry losses, or it could go the other way depending on the tool. The best way is to read the flow in the duct with the tool running so any fan effect from the cutter is also accounted for.

A pitot tube is one of the best tools for this because you can take readings anywhere in the duct by drilling a small hole to insert the tube. Your anemometer is good for measuring HVAC registers and hood face velocities (don't do this on your ww tools as you will be too close to moving parts).

Mike

Edit: Just saw David's post and I agree also that the relative improvement is important. I would be curious as to the improvement in flow by getting away from the flex hose and going all duct. Then, I would be curious how much hit you take in flow due to the cyclone. It will have more pressure drop than your old setup.
Mike

[Don Kondra]

Thanks guys !

All of my measurement are taken AT the entrance to the port or hood, etc..

In order to get repeatable results I cut a hole in a section of 5" spiral pipe and measured with the pipe straight and then in the normal working configuration.

Testing the thickness planer hook up.

For the straight the numbers are 395/3000.

Straight measure.jpg

For the curve the numbers are 381/2850.

Curve measure.jpg

In both orientations the CFM readings fluctuated by about 10 and the velocity by about 50 ?

Cheers, Don

[David Kumm]

Don, I like your methodology but the conversion is still off. A 5" round duct with a velocity of 2850 fpm = 388 cfm, 3000 fpm = 409 cfm. Dave

[Wade Lippman]

I am a little lost in this discussion.
I would think you have to measure the velocity, and then use a formula to determine the CFM.
So when he measured the velocity of the 5 and 6" pipes, the drop in velocity was to be expected, but the CFM should have gone up. Yes?

[Michael W. Clark]

I am a little lost in this discussion.
I would think you have to measure the velocity, and then use a formula to determine the CFM.
So when he measured the velocity of the 5 and 6" pipes, the drop in velocity was to be expected, but the CFM should have gone up. Yes?

Yes, this is what is expected, assuming no other changes were made to the system.

[David Kumm]

Formula for those who didn't follow. Radius squared X Pi- divided by 144 X velocity ( fpm ) = CFM. 2.5 x 2.5 x 3.14 = 19.625/144 = .1362847 x 3500 fpm = 477 cfm. Dave

[Don Kondra]

When all else fails, read the manual

In very fine print it says enter the square feet of the circle.

I had entered the square inches of the circle, NOT the sq ft.

Now my meter reads 2800 fpm @ 380 cfm.

2.5" x 2.5" x 3.14 = 19.6/144 = 0.136 sq. ft.

My bad, my apologies, sigh....

For my penance, I have corrected the above CFM numbers in red.

Cheers, Don

[Michael W. Clark]

Hi Don,
2500 FPM in a 6" duct is 495 CFM, not 340 CFM. You are moving more air in the 6" as compared to the 5" at 448 CFM.
Mike

[Don Kondra]

Hi Don,
2500 FPM in a 6" duct is 495 CFM, not 340 CFM. You are moving more air in the 6" as compared to the 5" at 448 CFM.
Mike

Ah, but the air is going slower

Would not the velocity of 3350 vs 2500 be more important ?

Cheers, Don