Filter pressure gauge

B

bababrown

Member
I just added a home brew filter pressure gauge to my CV-1800. I used 1/4" clear tubing with Marvel Mystery Oil such that it won't freeze and hopefully won't evaporate too rapidly. I made a scale on my computer in 0.1" increments of H2O increased in size by 1/.0876 to account for the 0.876 specific gravity of the oil. This gives a little better resolution on the readings.I covered the scale with lexan to protect it. I tapped into the transition by drilling a 3/32" hole in the MDF and overlaying that with a PVC piece tapped for a 1/4" MIP to barb adapter. I'm adding the pictures in the gallery section. It's reading about 0.35" of H2O.
bababrown
 
Update on filter pressure gauge

Update on filter pressure gauge

I've run the filter pressure gauge over a year now. It read 0.35" WC at 969 CFM when first installed with nearly clean filters. It has crept up to 0.5" WC now. I blew down the filters several times yesterday and exhausted the dust out thru a 20 ft long section of 4" pipe. Very fine dust came out but I doubt there was a cup. I used both the leaf blower and an air hose to blow the filters down. Each time I get a short blast of dust so there is more tin the filters. The reading stayed at 0.5". The mystery oil has not evaporated. So the gauge appears to work.
bababrown
 
Filter Pressure Gauge

Filter Pressure Gauge

I use a Dwyer 167-6 Pitot tube with a homemade U-tube manometer filled with colored water. I measure peak velocity pressure at the center of the pipe from which I calculate peak velocity. I then use 90% of peak velocity as effective or average velocity with pipe cross sectional area to calculate airflow. I have a straight section of pipe near the cyclone at which I can measure the airflow from most of my machines. See the photo section (Richard L Brown) for details. It costs about $100 for the Pitot tube and manometer although you can cut some by building your own manometer. It is a lot of money for a few numbers but where do you go if you don't know where you are?
bababrown
 
Filter Pressure Gauge

Filter Pressure Gauge

Dan,
A very good question. So this AM I remeasured and got 980 CFM, or 1/16" higher velocity pressure than before! So something else has changed to give me more airflow than the filter has reduced it. The amount is small. Anything, like a different fitting on the lathe hood or other blast gates leaking a bit could make that difference. If I go to my prediction curves near 970 CFM I see that 1" head loss increase should give me 75 CFM less airflow, so 0.15" should give me 11 CFM less. Not much. This thing really sucks!
bababrown
 
Help with filter performance tracking

Help with filter performance tracking

I am about to finish installing my cyclone and have taken my initial SP and Velocity measurements. I will be installing the clean-out under the filters soon and would like to take a measurement that I can compare to at a later time to track filter loading and flow through. I have a differential manometer and pitot tube with a static pressure tube also. If anyone could help with what measurement I can take once the new filters are installed and where those measurements should be taken would be great.
 
Help with filter performance tracking

Help with filter performance tracking

mshimick,
I would recommend a static pressure reading taken thru the side of the blower to filter transition. You want the air to blow straight across a tiny hole in the MDF. That way you get static pressure uncorrupted by velocity pressure. See the photos in the gallery section (Richard L Brown). I tapped a barb fitting into a piece of PVC and screwed that onto the side of the transition. But I drilled thru the MDF with a 3/64 drill so the hole is tiny. I run a vinyl hose to one side of a U-tube manometer and leave the other side open to atmosphere. I used Marvel Mystery Oil in my home built manometer so it doesn't evaporate or freeze in the cold. Because mystery oil is 0.876 times as dense as water I stretched an inch scale on the computer and printer by 1/0.876= 1.14 times. The approach works fine. I've had no problems with dust clogging it, or freezing, or evaporation. And the reading is always there when the cyclone is running. The pressure has climbed from about 0.35 to 0.5 inches in a couple of years.
I would not recommend airflow measurement at the filters. Measure on the inlet side instead. Also, don't use the pitot tube in dusty air. I have a straight section of pipe not far from the inlet to the cyclone in which the air flows from most of my machines. I make the measurements at that point and I depend on the blast gates doing a good job of controlling airflow (i.e. not leaking). You can periodically measure airflow with the pitot tube and manometer in clean air. I just drilled and tapped a hole in the side of the SDR35 pipe and I plug it with a 12-24 screw when I'm done. Hope this helps.
bababrown
 
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