Quote:
Originally posted by g.l.amour
about the spills in plexi cathar
i'm having similar problems with the tops or jet-middle pieces i make. first leaktest's give no leaks whatsoever. but after a few weeks small leaks start to form. not like in that picture but enough to color the copper. no damage because apparently evaporates too fast.
1) micro cracks after a while because of the pressure
2) bad sealant
i tend to think that it is caused by nr1. because its not high grade stuff i use; maybe lexan is better than cheap-ass plexi...
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I'm almost positive in my case that it's not #1. The polycarb used is extremely difficult to crack. It just flexes around pressure points and it's almost "gummy" in a plastic sense.
A number of times I've cranked down the barbs super-tight just to see what would happen. Instead of cracking the thread eventually strips, but this takes a LOT of effort. On middle plates that were rejected due to machining faults I've been able to bend the tubes 90 degrees and bend them back again, and they look almost as good as new, which is an indication of how pliable the polycarb is to pressure situations.
I personally feel it's due to a bad sealant application or bad sealant curing. I apply the sealant by hand and do my best to ensure that there's no dry points, but I guess one or two might slip past me occasionally. Failing that, while it still hasnt fully cured (and therefore shrunk back into its final shape) the sealant was probably sealing, but after a week it will have cured, possibly revealing any small leaks then.
Acrylic/Plexi has poor stress resiliance compared to polycarb. If you're having problems with stress fractures, I recommend switching to polycarb.