polycarbonate tank

[free75degrees]

I'm wodering if polycarbonate sheet would work as a tank liner. I am thinking I could use 1/16" sheets. To join 2 flat sheets together in a plane I would use a strip about 2 inches wide to overlap the 2 larger sheets and use solvent cement to weld them together. At the corners I would use square rod at the inside of the corner to cement the sheets together. The structure of the tank would come from an exterior wood frame.

I have worked with acrylic before and I think it is fairly similar to polycorbonate as far as how it is glued. With acrylic, the solvent cement works really great. I have had joints where the break occurred in the material near the joint rather than the joint itself. There is a similar cement for polycarbonate that I think works the same. Polycarbonate is rated to 180* continuous with spikes up to 250* so it would be good for tanks temps. A 4'x8' sheet can be had for about $80 at usplastic.com.

Any thoughts on this? Has anybody worked with polycarbonate sheet? Would this work?

 

[Nofossil]

Dunno about polycarbonate, but many plastics are not able to withstand high temperatures for extended periods. You'd want to get clearance from a plastics engineer.

 

[WoodNotOil]

I think you also have to take into account the temp the glue joints can withstand. Definitely talk to an engineer about it first, but sounds promising.

 

[slowzuki]

Hmm the glass transition is about 150 C so well above boiling. You'd want quite careful designing a tank with 1/16", you'd need quite a frame to hold the water in.

 

[Jackpine Savage]

I hate to be skeptical, but I would be concerned about the lack of flexibility and brittleness. If the polycarbonate wasn't perfectly fitted to the wood frame the lack of stretch would surely cause a failure somewhere. The wood is also going to flex some when the water is added. Then you also have heat expansion to contend with. But I'm no engineer, so I could be completely off base.

 

[free75degrees]

Hmm the glass transition is about 150 C so well above boiling. You'd want quite careful designing a tank with 1/16", you'd need quite a frame to hold the water in.

I have a homemade epdm lined tank now, so it would be a replacement for the epdm which obviously provide none of the structure now.

 

[free75degrees]

I hate to be skeptical, but I would be concerned about the lack of flexibility and brittleness. If the polycarbonate wasn't perfectly fitted to the wood frame the lack of stretch would surely cause a failure somewhere. The wood is also going to flex some when the water is added. Then you also have heat expansion to contend with. But I'm no engineer, so I could be completely off base.

Skeptical is good, I'd hate to do something like this and have it fail.

I think polycarbonate is fairly flexible, especially at 1/16". Part of the reason it is great for safety glasses, etc. is that it can absorb a lot of energy before breaking. Expansion is certainly an issue that would require some research.

 

[free75degrees]

Dunno about polycarbonate, but many plastics are not able to withstand high temperatures for extended periods. You'd want to get clearance from a plastics engineer.

Yes, talking to an engineer would be a must. Where do you find a plastics engineer?

 

[free75degrees]

Tom From Maine - are you there? I know you have done a lot of pvc research, did you ever look into polycarbonate? The reason I am looking into polycarbonate over pvc is that I have the ability to make joints with solvent cement, whereas i know nothing about welding plastic.

 

[Blevesque]

Free75 would this work for you it says working temp to 210 and the price seems good.

(broken link removed to http://www.usplastic.com/catalog/product.asp?catalog_name=USPlastic&category;_name=9122&product;_id=10400)

 

[tom in maine]

Hi,
Polycarbonate is a no go. It will pick up water over time and weaken and crack.
Polypropylene (PP) will work fine, if you support it. One can certainly weld up a "liner" out of rigid PP sheet and have it inside a structural shell.
Stand alone PP tanks will stress crack over time. Have sold replacement liners for them in years gone by. When used as a structural liner, there should be
no problem, if you weld it properly. Since you are welding it, I don't think you want to go with anything too thin as a liner.

 

[pybyr]

What about cross-linked polyethylene sheet like Tu-Tuf- sort of like a big flat equivalent to PEX tubing- which can obviously take temperature and pressure?

 

[tom in maine]

It has to have some thickness. TuTuf is rather thin, as I recall. Thickness must be over 30 mils or permeation takes place. Also thinner materials
offer little margin for shipping and handling problems.

There are suprisingly few materials that fit the application and are not stupidly expensive and relatively easy to work with.
Tom

 

[Medman]

I think that cost is the issue here. PP sheeting in the required sizes for a 1000 gal. tank, plus the cost of welding, is higher than the cost of used propane tanks for pressurized storage. It sounds like a great idea, but unless pressurized storage is a no-go I think it would be cost prohibitive.

 

[tom in maine]

I agree.
That is why we make the tanks we make.
They are simple to install and easy to get into tight places.
Cost/value is subjective. We keep the cost as low as we can.