Sorry, I have not been on here much due to not feeling well.
Your diagram looks good. I suggest you make slotted inserts for the sides and bottom, as I do, so that you do not weaken the cell walls themselves with the slots. The inserts do add some rigidity to the structure, without risking compromizing the case along the slots. If you build up the walls out of a couple of layers with overlapping joints, it really makes the corners stronger with less risk of leaks. I will try to work up a mechanical drawing to show what I mean by this.
In order to save money, since you are starting out fresh and do not already have an investment in tooling like we do, go with the thinnest plates that you can get away with that will remain rigid in use. We already have the tooling for cutting slots properly sized for 16 guage 316, but that may change soon for us as well. Retooling for thinner 316 is less expensive in the long run, than to continue using what we have just so we don't waste stainless plates we already have cut.
Anti-slosh plates do not work nearly as well as anti-slosh matting. Try to find some compatible plastic woven mesh similar to what is used for washable air conditioner filters. Just make sure it is not fiberglass if you intend to use it with KOH. Some poor grade glass fibers are not chemically inert like lab glass, and will react to KOH, causing fire or explosion.
If the unit is just a testing prototype, I will just use thread tape for the seal and install the ports directly. If the unit is going to be used in a long-term application, I use the following procedure;
When I put any ports through the plastic top. I drill and tap the plastic with a hole larger than I need (1 1/4" NPT for 1" NPT). I undercut the outside with an O-ring groove right up against the threads. I cut an o-ring seat into a 1 1/4" X 1" 316 or 304 hex bushing and insert an o-ring onto the bushing. I add thread tape, then thread the bushing snugly into the hole. If the fitting is expected to have any mechanical stress on it, I will install a 1 1/4" 316 or 304 hex nut onto the inside. The reason for the bushing is to spread the fitting stresses over a larger area, and prevent damaging the relatively fragile plastic threads through repeated connect and disconnect cycles that may occur during maintenance.
I used to be able to source o-ringed 316 bulkhead fittings from marine supply outlets, cannot seem to find any nowadays. It seems everyone is going with brass or plastic. Plastic may be ok, but I have seen some plastics get brittle and crack when exposed to the vapor of the wrong electrolyte for a long time.
BobStatistics: Posted by Bob Boyce — Sun Aug 20, 2006 12:00 pm
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