So I have gone ahead and made a whole heap of these little suckers.
There is a rule of thumb I found getting around the interweb, probably pulled from someones ass years ago, that says;
- Diameter of SPP = 1/10th - 1/12th of column diameter
- Length of SPP = Diameter of SPP
- Wire diameter = 1/10th of SPP diameter
I also found;
- a couple of people who said they thought that the SPP length was probably better off being 1.5 x SPP diameter
- the biggest problem most people had with this stuff (aside from the prohibitive cost) is column flooding, normally this is using small sized SPP.
Bearing all of this in mind I've made mine 8mm in diameter using 0.8mm SS MIG wire and cut them to roughly 12mm long.
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It took a little bit of stuffing about to get the shape and size of the tang right, but not too much, I only ended up making the one.
I went with the rectangular shape because it seems to give a more open spiral. The tang has to be a fair bit smaller than I first thought it would.
It is made from an old drill bit and as you can (kind of) see from the wear on it, you probably wouldn't have a lot of luck with anything much softer.
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I had the roll of wire mounted in a vise on a stand (just out of the shot) and kept the tension by hand (too little or too much and it would lose traction and spring off the tang), I also had my knee millimetres from the E-Stop at all times but found that it was quite stable while running and didn't really have any probs.
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I made 4l all up, enough to fill a 500mm x 4" packed section. Roughly 5500 of the little suckers.
It took a couple of hours to get set up, and another couple to wind it all out (could probably run faster, but safety first right).
I cut it with side cutters sitting on the lounge watching the telly over a couple of nights, about 5hrs all up.
It took 4.5 Kgs of wire, around $100ish if you were to buy it, so still not exactly cheap!
One last thing I found was a chart that supposedly seemed to show theoretical HETP of different sizes of SPP in different sized columns.
- 2.5mm SPP = 60-70 plates/meter in 50mm column
- 5mm SPP = 20-30 plates/meter in 50mm column
- 8mm SPP = 10-11 plates/meter in 82mm column
This like all the other info I have found may be complete BS, but trying to use the small stuff and get ridiculously low HETP in larger columns with high flows is definitely going to lead you up the flooding path.
According to the chart my 8mm stuff should put me in the ball park of scrubbers, which I will be happy with (considering it should be easier to pack and clean), and who knows it might end up better and shouldn't cause any flooding issues.
So is this stuff the miracle packing some would have you believe??? Is it going to be a better option for those of us using packed sections on bubblers???...
Probably not.
Tune in in a couple of months when I'm ready to run it to find out 8-}
Cheers
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