Construction Begins
Entry posted by Swede
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I start with the Collection Chamber, the CC. The sheer quantity of material needed to pull off the "T-Cell" is greater than one might think. Over the last week or two, I have been doing drawings, conceptualizing, and making a list of materials needed, because once I start, I hate having to pause in the middle of the process and order some forgotten component.
The first major component is a good pump for circulation of the electrolyte. This is a peristaltic pump on steroids from Cole Palmer, capable of liters per minute, and fully controllable:
eBay was the source, and the whole setup was NIB. This particular pump head requires an exact tubing dimension to function best. Using the chemical compatibilities charts available at Saint Grobain Plastics, I selected a Tygon formulation. Tygon tube will often run about $4 per foot. This gigantic roll was $49, or 50 cents per foot.
I found out why it was so cheap... It was probably stolen from the Coca-Cola bottling company! The formulation is B-44-4X.
The CC construction was based upon a stack of 12" X 12" type I PVC sheet. I ordered 1/4", 1/2" and 3/4" thicknesses. Unfortunately, these are cut from larger sheets, and while the cuts were good, the sheets did vary slightly, and did NOT simply lend themselves to being glued together into a box without considerable work. A good table saw is necessary to complete the job, fitted preferably with a laminate or plastics blade. Just like Pyro, a table saw will bite you real bad if you are careless. Today, I had a strong kickback of a full 1 square foot piece of PVC. It was thrown at high velocity directly into my stomach. The first moments after this happened, I thought "I'm dead. That thing just ruptured my internal organs." That's how hard it hit. On the ground, in agony, I look at my stomach... the skin was hardly broken, but it was like getting punched by Mike Tyson. Right now theres a huge, angry purple welt, and a lot of pain.
Anyway, a lot of mental fiddling on the bench took place before I even opened the glue. Not trusting just a basic box shape to contain 5 gallons of electrolyte, I decided to reinforce the bottom with strips, and further reinforce the vertical seams with doublers.
Since it's easier to drill just a sheet, rather than a box, I drilled and tapped two holes 3/8" NPT in the sheets on opposing sides for the PVDF plastic hose barbs that would allow intake and exhaust ports for pumping. 3/8" pipe is a standard tapered pipe thread which seals well, and will accept a number of different fittings. Finally satisfied that the pieces would properly fit together, the gluing process began. The gluing was incredibly tedious, messy, and unpleasant. Standard woodworking clamps, gloves, tape, razor blades, weights, all were used.
Be Warned!
DO NOT attempt such a vessel unless you are a real masochist. Frankly it was a bitch to do well, and took far longer than I had anticipated. Each and every joint requires cleaning, heavy priming, cement, and accurate clamping. The components tend to move relative to each other, and the carefully planned doublers and such did not fit properly once gluing began. There is a better answer... U.S. Plastics sells prefabricated PVC tanks in a variety of sizes. They are not cheap, and will still require some work, but please trust me on this, this was a total pain in the ass, and I wish I had ordered one of the prefab tanks instead of making this a DIY project. If this tank doesn't work well, or if I want to upgrade to 10 or 15 gallons, I WILL order a tank rather than do this again! Be afraid, be very afraid.
One option for a simpler, cheaper tank would be a short section of PVC or CPVC round cemented onto a flat sheet, and I will be doing something similar to that for the EC, the Electrode Cell. But there is no reason one couldn't make a great tank from a 12" diameter, 18" tall section of schedule 80 PVC pipe.
With the basic tank shape complete, I worried about the seams in the corners. I decided to make some PVC corner strips that would seal and strengthen the joints:
Primer, glue, everywhere. Messy, NOT FUN.
The tank at 90% complete...
All that remains is to engineer a lid. One of my remaining 1/2" PVC sheets will do the honor. I will first have to smooth out and perhaps flame polish or otherwise clean up the tank rim to ensure a good seal. The lid will have a groove milled into it to accept either viton or PTFE cord to act as a seal, and it will, of course, have ports for accessories, ventilation, and such.
I'll say it again, making this tank was not easy. I'd estimate the cost in materials (from this company) (PVC sheets, glue, primer) to be close to $100... note that I can buy a TEN gallon, prefabricated PVC tank, professionally built, for $137. Stupid, stupid. Of course, I overbuilt it. 3/8" thick sheet would have been adequate. I went with 3/4" thick. The lousy tank probably weighs 25 lb.
I am going to let it dry overnight. Tomorrow, I will install hose barbs, and create a test loop using the big Masterflex peristaltic pump, as well as begin the lid. Ideally, the lid will make use of quick-acting clamps rather than two dozen stainless steel studs... it will all depend upon how much gas is evolved in this cool collection chamber, rather than in the hot electrode chamber.
NEXT DAY, Added: I haven't tested the cell for water tightness yet. Reflecting upon the hassle of construction, and realizing that off the shelf items can be altered for use, I pondered a bit about this whole concept. I still have to make an EC, an Electrode Chamber, out of CPVC. That won't be too hard.
Browsing eBay as usual, I was looking for pool chlorinator electrodes, and came across a lowly trickle chlorinator, made by Hayward and other companies. These are tall, heavy "filter" units that have a screw-top, inlet and outlet ports for the water, and usually a plastic dial metering system that trickles water over 3" chlorine tablets. Here's a typical unit:
http://www.aquanet.net/images/haycl200.jpg
I'd put the picture up but the blog controls only allow a certain number of images, no more. Moderators, can you bup that up by four or five? It'd help me, as I like posting a lot of images. Thank you!
Anyway, looking at these chlorinators made me think of the electrode cell. This just might be perfect! Obviously it will need to be heavily modified, but I'll bet a pound of perc that the cell is made of CPVC, not just plain PVC. Those chlorine tabs are wicked, and CPVC is more chemically resistant than PVC type I, so it would make sense that these units are CPVC. The O-ring would have to be very resistant chemically, probably viton. The manufacturers have done 80% of the work for us, for those that want a two-chamber system. I'll try to pick one up off eBay and see if it can be modded!
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