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03-28-2003, 12:20 PM
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#1
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Shark
Join Date: Jun 2001
Location: St. Petersburg, FL
Posts: 1,588
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Mixing eductor-driven fractionation
As per Doug's request on the eductor thread: we actually build mixing eductors as the air pullers on the protein skimmers at the lab. Originally, I was asked to revamp older DIY downdraft skimmers that weren't keeping up well due to new flow constraints, and this is what I came up with. Blows away downdraft, venturi, Beckett, etc. Think Beckett, then supercharge it, and you have a mixing eductor-based skimmer. And the entire educting unit is built out of stock and minorly modified PVC, and its self contained like a beckett housing.
Exploded view of the eductor
The tee is a 2" PVC tee. The 2" x 3/4" reducer bushings on the end of the tee have the 3/4 retainers ground flush with a dremel tool, so that the 3/4" pipe can pass all the way through. On one side of the tee, the 3/4" pipe is passed through and on the inside ends with a 3/4" slip x slip coupling. On the outside is a 3/4" union. On the other side of the tee, the 3/4" is passed through the reducer bushing and ends with a 3/4" coupling. Inside this 3/4" coupling is a 3/4" x 1/2" reducer bushing (slip x FIPT on the 1/2" side). In the female pipe threads of the 1/2" side, screw in a 1/2" hose barb that has most of the length trimmed off. The actual "t" branch of the tee is use to suck air. In the eductor shown, this branch is covered with a 2" x 1" slip x slip reducer bushing and a 1" street ell pointing up. This helps eliminate splashback. The unions allow removal of the eductor from the skimmer for easy rinsing of any salt creep that forms.
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"The cultured might call him heathenish, This man of few words, because his one care is not to interfere but to let nature renew The sense of direction men undo." Lao Tzu
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03-28-2003, 12:22 PM
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#2
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Shark
Join Date: Jun 2001
Location: St. Petersburg, FL
Posts: 1,588
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View inside assembled eductor through the t branch (sans splashguard)
__________________
"The cultured might call him heathenish, This man of few words, because his one care is not to interfere but to let nature renew The sense of direction men undo." Lao Tzu
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03-28-2003, 12:31 PM
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#3
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Shark
Join Date: Jun 2001
Location: St. Petersburg, FL
Posts: 1,588
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Eductor attached to skimmer.
Note, the after the 2" 90 that attaches to the 4" x 2" reducer bushing, the 2' pipe goes through the 4' x 2" reducer bushing, as it is ground flush with the dremel. On the inside of the 4" tee, the two inch pipe ends in a 2" 90 ell that points up (shown in next post). This makes the bottom of the skimmer act as a clarifying chamber to help with microbubbles and to keep contacted bubbles from being flushed to the sump instead of caught. The return on the skimmer is plumbed with a Hartford loop (will be shown later) to maintain constant water level in the contact chamber. The water in the mixing chamber should be as close to possible as the height of the bottom of the eductor. This allows for finer bubbles.
Another note. The four inch riser that ends in the 4 x 2 reducer coupling was not tall enough. Even with 5' of 2" pipe on top, The skimmer was blasting foam five feet above it. This skimmer is powered by an Iwaki 55.
__________________
"The cultured might call him heathenish, This man of few words, because his one care is not to interfere but to let nature renew The sense of direction men undo." Lao Tzu
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03-28-2003, 12:32 PM
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#4
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Shark
Join Date: Jun 2001
Location: St. Petersburg, FL
Posts: 1,588
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Aforementioned upturned 2" elbow in the 4" tee.
__________________
"The cultured might call him heathenish, This man of few words, because his one care is not to interfere but to let nature renew The sense of direction men undo." Lao Tzu
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03-28-2003, 12:33 PM
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#5
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Shark
Join Date: Jun 2001
Location: St. Petersburg, FL
Posts: 1,588
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__________________
"The cultured might call him heathenish, This man of few words, because his one care is not to interfere but to let nature renew The sense of direction men undo." Lao Tzu
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03-28-2003, 12:38 PM
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#6
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A goof
Join Date: Jan 2000
Location: Plymouth, MN USA
Posts: 2,923
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how tall is the whole skimmer?
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03-28-2003, 12:48 PM
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#7
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Shark
Join Date: Jun 2001
Location: St. Petersburg, FL
Posts: 1,588
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Dunno at the moment. Have to go make it about a foot and a half taller in 5 minutes anyway. For reference, the clear PVC is 4".
__________________
"The cultured might call him heathenish, This man of few words, because his one care is not to interfere but to let nature renew The sense of direction men undo." Lao Tzu
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03-28-2003, 03:02 PM
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#8
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Shark
Join Date: Jun 2001
Location: St. Petersburg, FL
Posts: 1,588
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After significant lengthening of the riser, here is the skimmer in operation.
__________________
"The cultured might call him heathenish, This man of few words, because his one care is not to interfere but to let nature renew The sense of direction men undo." Lao Tzu
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03-28-2003, 03:03 PM
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#9
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Shark
Join Date: Jun 2001
Location: St. Petersburg, FL
Posts: 1,588
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foam in riser
__________________
"The cultured might call him heathenish, This man of few words, because his one care is not to interfere but to let nature renew The sense of direction men undo." Lao Tzu
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03-28-2003, 03:05 PM
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#10
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Shark
Join Date: Jun 2001
Location: St. Petersburg, FL
Posts: 1,588
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from above
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"The cultured might call him heathenish, This man of few words, because his one care is not to interfere but to let nature renew The sense of direction men undo." Lao Tzu
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03-28-2003, 03:06 PM
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#11
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Shark
Join Date: Jun 2001
Location: St. Petersburg, FL
Posts: 1,588
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BTW, this is with the pump throttled down by about 50%.
__________________
"The cultured might call him heathenish, This man of few words, because his one care is not to interfere but to let nature renew The sense of direction men undo." Lao Tzu
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03-28-2003, 04:22 PM
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#12
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Shark
Join Date: Jun 2001
Location: St. Petersburg, FL
Posts: 1,588
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Jon: 4' 11"
__________________
"The cultured might call him heathenish, This man of few words, because his one care is not to interfere but to let nature renew The sense of direction men undo." Lao Tzu
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03-28-2003, 07:25 PM
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#13
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A goof
Join Date: Jan 2000
Location: Plymouth, MN USA
Posts: 2,923
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A few questions, It looks like you increased the clear riser a lot, then you have the collection area on top of that? it looks like a large U tube with output on top, does the foam go up that then collects in the other smaller verticle tube? can you describe our show the Hartford loop?
I don't think I will make one for my current tank, I like to keep things clean and inside the stand for now, but I will probably make one when we move.
Jon
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03-28-2003, 08:35 PM
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#14
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Shark
Join Date: Jun 2001
Location: St. Petersburg, FL
Posts: 1,588
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I'm working on an entire schematic to show the Hartford loop, as I couldn't photograph it between the tanks. The riser tube doesn't need to be that long. The easiest way to let it be shorter is either by throttling down the pump (beware: this will reduce the positive pressure in the eductor and may make large bubbles), or by putting a ball valve on the splashguard to control the air entry into the eductor.
__________________
"The cultured might call him heathenish, This man of few words, because his one care is not to interfere but to let nature renew The sense of direction men undo." Lao Tzu
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03-28-2003, 09:52 PM
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#15
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Shark
Join Date: Jun 2001
Location: St. Petersburg, FL
Posts: 1,588
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Schematic.
Post if you have any questions about the design. Yes there is a way to make it sit flat on the floor. I just haven't drawn that version yet. Bear with me. 
__________________
"The cultured might call him heathenish, This man of few words, because his one care is not to interfere but to let nature renew The sense of direction men undo." Lao Tzu
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