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Dust Collection Air Flow Probes

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Blog entry by BlankMan posted 748 days ago 1724 reads 0 times favorited 6 comments Add to Favorites Watch

Well with all the talk about dust collection going on I got the itch to measure my system again. I didn’t have my new hood for the chop saw built so that wasn’t measured and I’d like to know how it fairs. Also, last time I measured everything I had trouble reading Velocity Pressure, that reading was bouncing around so I averaged the low and high. I think that was in part due to where I placed the Pitot Tube, it was probably encountering too much air turbulence. So this time instead of using a Pitot Tube I thought I’d try using a Total Pressure Probe and Static Pressure Probe, which is what a Pitot Tube is combined into one.

I looked around and could not find a 3” Total Pressure Probe so I decided to make one myself. Below are pictures of the construction process.

Here’s the raw materials I picked up to make the probes. 3/16” barbed couplings, 3/16” brass tubing, 3/16” solid brass rod, 3/8”-16×3/4” brass screws & jam nuts, and rubber washers.

Here’s the materials after machining.

And here’s the probes completed. Two views of the Total Pressure Probe on the left and the Static Pressure port on the right.

And that Total Pressure Probe is exactly a 90° bend, the camera lens is distorting the angle.

Now I just have to install them in the duct. Which won’t be as easy as making them…

-- -Curt, Milwaukee, WI



6 comments so far

View patron's profile

patron

12844 posts in 1843 days


#1 posted 748 days ago

well blank
the pictures aren’t loading for me
(it’s my slow server)

but from the text
i’m betting that this works
and you know what you are doing

but not knowing anything about this

i’m drawing a blank blank

i’ll check back when i get my new satellite receiver

-- david - only thru kindness can this world be whole . If we don't succeed we run the risk of failure. Dan Quayle

View TopamaxSurvivor's profile

TopamaxSurvivor

14402 posts in 2177 days


#2 posted 747 days ago

Now you need a few of those spendy Magnahelics to read them ;-) What are you expecting to learn? Isn’ the dust moving through the duct?

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View BlankMan's profile

BlankMan

1487 posts in 1855 days


#3 posted 747 days ago

I have a Dwyer Series Mark II Molded Plastic Manometer and a Series 475 Mark III Handheld Digital Manometer.

I want to know Air Velocity and CFM. As a side note I’ll also know Static Pressure. More curiosity then anything else.

-- -Curt, Milwaukee, WI

View BlankMan's profile

BlankMan

1487 posts in 1855 days


#4 posted 747 days ago

Well, I didn’t really think this would happen but it did. The Static Pressure probe I had in my main duct turned out to be a good chip catcher. I took the cone off the cyclone so I could get at the duct leading to the cyclone’s inlet so I could install the Total Pressure Probe. When I had it In place I used my Milwaukee Inspection Camera to check that I had it straight. That’s when I caught sight of this.

It’s been in there for years so I guess it isn’t too bad. Took that picture blind because all I could do was reach up inside the cyclone body and point the camera out the inlet.

So I took that probe out and installed the Static Pressure Port I made. This one shouldn’t catch any chips I would hope.

-- -Curt, Milwaukee, WI

View TopamaxSurvivor's profile

TopamaxSurvivor

14402 posts in 2177 days


#5 posted 747 days ago

That should work. I have installed a lot of them with just a short piece of tubing poke into HVAC ducts.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View BlankMan's profile

BlankMan

1487 posts in 1855 days


#6 posted 746 days ago

Well I think I’ve pretty much given up trying to accurately measure Velocity Pressure so I can calculate Air Velocity and CFM. The readings I get are are just too unstable, Velocity Pressure is just constantly bouncing around on the digital manometer. Too much air turbulence in the air flow I’m guessing.

It’s probably due to were the probes are placed. In those two picture above of the duct work you can see two takeoff branches, one down one up, and that crimp on the pipe at the bottom of the pictures is the inlet to the cyclone. To get accurate readings the probes need to be placed in the duct with 8-1/2 diameters of pipe downstream and 1-1/2 diameters of pipe upstream with nothing to disrupt the air flow, no branches, ports, etc. and I surely do not have that. But that is the only place I could measure what is being drawn into the cyclone.

But as the pictures show the duct is very clean. The little bit of sawdust by the new static port tap is what was knocked off the old static pressure probe when I took it out.

-- -Curt, Milwaukee, WI

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