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Is EPDM for tank liner a catch-22?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by Rory, Jan 13, 2009.

  1. tom in maine

    tom in maine Minister of Fire

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    DaveBP,
    Both excellent points. If you were using the skim coat, you should not be using plates, they would be extraneous.

    EPDM has a lot of variants out there. I hate to think that much of it comes from overseas, but have found that is the case with a lot
    of polymers that we have researched.ARGH.
    I am very skeptical of this type of material that is produced overseas. Quality is questionable and engineering support is not immediate.
    I am still waiting to hear back from a company that responded to my initial query in November 2008. They needed to confirm something with the engineers in Formosa.
    I don't think we will be doing business!

    Fortunately there are still some manufacturers of these product here in the US and we can reach the right people with a simple phone call and speak English to them.

    My experience with Solaroll, was not good. It was pulled off the market, for good reason. Entran was a different case, but spoke to the issue of formulations and additives.

    All that being said. EPDM does work. I am certain that there are better quality versions of it. Who that is and where they are, I am not sure.
    Tom

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  2. pybyr

    pybyr Minister of Fire

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    Here are some leads I found - this product looks as if it is similar to Tu-Tuf, only a lot thicker.

    If it is up to lining landfills, which it apparently is, then it ought to be up to the use for a heat tank
    http://www.geocheminc.com/hdpealloy.htm
    and they’ll apparently fabricate it into a pre-shaped-to-dimensions tank liner:
    http://www.geocheminc.com/tank.htm
    looks hard to beat unless the cost is insanely high- which I tend to think it actually may not be if people are using it for the applications that they describe.

    If I did not already have some gorgeous already-fabricated stainless steel that is worth about as much as a roadworthy used car in the cellar, I’d be pursuing this membrane like wildfire- and I think that the “homemade tankage” thread from "Smee" in Maine represents the most elegantly simple DIY membrane support structure that I have seen yet- just that I would not use either EPDM or PVC
  3. tom in maine

    tom in maine Minister of Fire

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    When it comes to plastic liners, you need to be over 20 mils thick. Anything under that is too permeable and water will migrate across the plastic. Add heat into that equation and it becomes more pronounced.

    HDPE will not take the temperature. Polypropylene will, but it is rather stiff. These are both usually used as geomembranes and are used for large tanks, landfill or lagoon applications, which stiffness is a plus and handling is simpler than trying to do a small (500-1,000g) tank.

    There are some options out there. They all have limitations. And unless you have used them for a very long time, you cannot necessarily believe everything that a salesman tells you! I am afraid I know that all too well.

    At this time, even though there are some limitations, high temp PVC and some alloys utilizing it and EPDM are the ones that work well for this application.

    As a DIY project, one can certainly site weld thicker PP sheeting for a liner.
    I am intrigued but leery of truck bed liners. They could take the temp, but being sprayed on a tank and then exposed to the temps could cause differential expansion failures between the adhered liner and the shell.
  4. Fred61

    Fred61 Minister of Fire

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    Well I'm going to be the guinea pig. I located a two part epoxy called water insensitive coating and if I can believe the sales person, it has been used on tanks at IBM and other industrial locations. It's rated for 320* wet. Check out the link below. This isn't the stuff I'm using but is interesting. I had a couple more links but I screwed something up when I posted them.

    www.armorshieldlining.com/hot_water_tank.html
  5. NHFarmer

    NHFarmer Feeling the Heat

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    Looks interesting,any ideas on cost and is it a DIY project?Keep us posted
  6. Fred61

    Fred61 Minister of Fire

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    It is a DIY project. Of course it will be some time before we know whether it works or not (hopefully). I was in the adhesives and coatings buisness up until 1999 and have a lot of faith in the chemistry. What I did is cut one end of a 500 gallon fuel oil tank and, at present, am preparing the surface to accept the epoxy layer. I will be using the tappings for probe wells, and return water to my flat plate HX. The guy I spoke with at the supply house felt that poly urea (like some bedliners, not Rhino and Bullhide) would work because the operating temp. is about 230* but I decided to go for the epoxy, which has a working temp. almost 100* higher for that extra margin of safety. It isn't cheap. About $250.00 for a 2 gallon kit. I felt a little vindicated on my choice after finding a couple hot water tank manufacturers online that offered epoxy coated liners.


    http://www.hotwater.com/lit/spec/storage/AOSTT35200.pdf
  7. Der Fuirmeister

    Der Fuirmeister Member

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    pybyr, you used 409 SS. How is it working for you? Did you price other SS sheet such as 304 or 316?

    After a year of researching, looking for the perfect answer to the tank liner question, I've decided to use SS. I'm gettin' too old to fool around with replacing EPDM in 5-10 years. Long story - short, I'm using SS because a 1100 gal. SS tank will only run $900 more than EPDM. And when it's done I will leak before it will. I also plan to run at 190-200* on a regular basis. This translates into getting ~30% more usable btu storage for the same size tank using SS vs. EPDM.

    Your input or others would be appreciated.
  8. pybyr

    pybyr Minister of Fire

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    When I went to have the tank fabricated, 409 was substantially less costly than 304 or 316, and it apparently discolors but does not corrode, which is OK for this application. My tank has water in it but has not really been put into use yet by actually being fully heated- need to finish some of the controls, and keep getting sidetracked with other projects. Truth be told, if I were starting afresh and couldn't use a propane tank (which'd be my first choice) I would probably go with an American Solartechnics tank.
  9. Der Fuirmeister

    Der Fuirmeister Member

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    Thanks for your input. I can't use a propane tank in the area I have. I've also looked at the American Solartechnics tank, but would like a larger tank. 900-1100 gal. would be the size. Since I'm off work I can fabricate a tank for roughly $1200-$1400. I'm looking at a grade 201 SS which is 15-20% cheaper than 304 (201 is $1.70 / lb in 12 ga. sheet), but have read some things about stress corrosion cracking above 60*C (140*F). I've also just found a geomembrane product designed for high temps. If that doesn't pan out I'll end up with SS.

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