Plastic welding

[Rob Martin]

Does anyone do any plastic welding? One of our primary fermenter lids has a crack that I'm hoping can be repaired.

[Joe Yoder]

super glue?

[Rob Martin]

I was a bit concerned about using a glue that would come in occassional contact with fermenting wort. I have read some articles about actual plastic welding.

If I can't find a plastic welder, I thought about just trying to melt the crack shut with a torch or something.

[Bill]

A soldering iron using the flat blade/bit should do it. Or you can go with your torch idea and a piece of metal. I wouldn't suggest you put flame directly to the plastic for fear of burning it. I've sealed plastic parts using a soldering iron before with different levels of success. You may want to practice on another piece of plastic to get a feel for it.

[fergmeister]

If you were old enough to have rabbit ears on your tv you may remember a cool toy called a spin welder. I found one for you http://cgi.ebay.com/1974-Mattel-SPINWEL ... dZViewItem I bet this would work well on the Sake Kegs.
C

[sam]

I have extensive plastic welding experience with commercial equipment. I don't personally own any, just what I used at a food plant a few years back. I spoke with a guy the other day about this and he indicated that he had some success with a soldering iron and compatible plastic for a filler. I will check with him and get back to you.

[Rob Martin]

Today I got around to working on this cracked lid. It is a plastic lid for the rice wine / sanke that some use for fermeters. Basically I used held a piece of sheet metal to the lid and torched it with a propane soldering torch. It melted the crack shut. I don't think it will have a lot of structural strength and probably would crack again if the lid was cranked on hard, but with a gentle turn, I'm satisfied enough to start using it again for the primary where there is enough CO2 positive pressure being created.

[Jdl973]

Rob,

A good dose of silicone sealer and fine fiber mesh on the top of the lid would not hurt to add a bit of re-enforcement to the lid.

Just an idea


Jason

[fergmeister]

Neither would be Kevlar, high strength polymer, fiber reinforced rubber adhesive, but!!! Is this the inner lid you are trying to fix? What about just a a bit of cling wrap over this cover and ligtly screwing the over lid on??????
Hmm

[Rob Martin]

Naw, it was the top, outer lid.

[brick]

I have a couple of lids like that, with the split on the side of the lid. I just use them as is with no problems since nothing can get in. The things we need to keep out are all airborne and won't get in the wort unless it falls in. They will not crawl in the crack on the side of the lid. The only issue is doing pressure transfers and those still work that even with the crack. It is almost open fermentation since you don't build up much pressure during fermentation but you have the added protection from falling contamination.

[Rob Martin]

Thanks for the assurance Brick. The crack is just like you describe, a circular crack along the edge. I took a piece of sheet metal to protect the plastic and applied indirect heat. From the inside, you cannot tell anything occured - no fissures, dimples, deformed plastic. On the top is marred, but that is on the outside. I'll keep this lid for ales where fermentation is relatively quick and there is a positive pressure pushing out. For lagering, where the pressure is not as high, I'll keep using the one good lid I have.