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Thread: Cyclone static pressure filter gauge

  1. #1
    Join Date
    Oct 2005
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    Cyclone static pressure filter gauge

    So I got my CV max repaired and it’s running great again. I figured I should get the static pressure gauge setup I bought since the filters are still pretty much new. My understanding was all I needed to do was put a connection into the side of the filter transition and hook that up to the gauge. I tried that as I am actually getting negative air pressure due to what I guess is limited back pressure on the new filters and with how fast the air is going by. Looking Oneida’s install guide for their gauge they use a brass static pressure tube aimed into the airflow. Do I need that or am I installing the hookup in the wrong area of the filter? Thanks

    https://www.oneida-air.com/amfile/fi...oduct_id/1596/
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  2. #2
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    A pressure port in the side of a duct needs to be absolutely flush with the inside wall of the duct. If it protrudes even a little bit into the duct the air speeds up going over it dropping the pressure.

    That elbow is a difficult spot for a pressure port. You might have better luck on the flange that the filter is mounted to. That should be a stagnant area so less error from velocity.
    Beranek's Law:

    It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.
    L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

  3. #3
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    I looked to see how much Oneida wanted for the gauge and parts and was shocked. I bought a used Magnehelic gauge and probe on eBay for a small fraction of the Oneida price.

  4. #4
    I have the Oneida kit because I couldn't find any vendors or eBay sellers who would ship to Germany. The Oneida kit comes with a pitot tube and the Magnehelic gauge. I installed mine in the filter plenum at the point of entry from the blower output. I was limited in my choice of mounting options because of the corner I painted myself into when I built the system. I'll do better when I upgrade cyclones later this year and build a new filter plenum.




    The pitot tube must be in the air stream, but if you use a simple manometer, you can use a flush port. As David states, the end of the tube must be flush with the inside surface of the duct.

  5. #5
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    I wanted a gauge to tell me when the cartridge filter on my dust collector was getting plugged. I have a Wynn filter and needed to make a plywood adapter for it. I fixed an elbow into the plywood and attached a loop of clear vinyl tubing about 4' long. I don't have a picture of the gauge but it's just colored water in the loop. With the DC off the water is at the same level in both sides of the loop. If there's not much back pressure the water is still pretty much level in both sides. As the filter becomes plugged, the difference in the height of the water in the loops will increase as back pressure pushes one column down. Simple and no moving parts.
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    Last edited by Curt Harms; 07-12-2020 at 9:41 AM.

  6. #6
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    Just in case, for those not away, you can build your own Oneida Filter Efficiency Gauge using the exact same components for a fraction of the cost. See here: LINK
    If at first you don't succeed, redefine success!

  7. #7
    Join Date
    Dec 2006
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    Toronto Ontario
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    I use a tube type manometer on my Oneida.

    I use a curved piece of 1/4” copper tube in the filter airstream.

    Absolute accuracy isn’t important, mine normally is just below 1” WC, I clean the filter when it’s between 2 and 3” WC.........Rod

  8. #8
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    Making your own tube manometer with colored water is a great and cheap way to do it.

    When I did measurements on my system, I found the filter pressure varied with cfm the system was pulling. At high flow rates, the filter pressure went up and low flow rates it went down.

  9. #9
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    Quote Originally Posted by Larry Frank View Post
    Making your own tube manometer with colored water is a great and cheap way to do it.

    When I did measurements on my system, I found the filter pressure varied with cfm the system was pulling. At high flow rates, the filter pressure went up and low flow rates it went down.
    Yes, my “standard” condition is the overhead and cabinet blast gates open on my table saw. That allows for a consistent reading....Rod

  10. #10
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    Finally got some tone to play with things this afternoon. I had a Dwyer pitot tube I bought and I installed that and got negative pressure no mater what. I tried turning it 360 degrees and no luck. Next I tried installing it away from the elbow but in the top of the filter mount. I still got a negative pressure. Finally I installed a longer vinyl tube and installed it on the bottom of the filter and now I am getting about 0.4”. It seems like there is barely any back pressure and due to that I cannot get a positive pressure up higher on the filter stack. I appreciate the help
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  11. #11
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    Feb 2003
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    Having barely any back pressure hardly seems like something to complain about. That would indicate to me that you have enough filter capacity. I imagine that if you processed a bunch of MDF or something equally fine, eventually you'd see some back pressure as the filters become clogged.

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