Water Tank Platform

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Hello all,I am considering welding a small tower/platform (about 5' tall) for a 1500 gal. poly water tank. The tank is around 8' in diameter and around 5' tall. The tank full of water should weigh somewhere around 12500 lbs. I would like to build a majority of the frame out oilfield pipe maybe 2 7/8" or larger if need be. The posts could be 2 7/8" on a 4' with girder like cross pieces made of i-beams with purlins placed on top of the i-beam spaced maybe 12' O.C. and sucker rod x-type bracing. How many posts would y'all recommend and what are your thoughts on the the rest of the design and what sizes would you recommend for the i-beams and the purlins?Thanks,Kelly
Reply:Hi,Here is a quick drawing I made to give everyone a better idea of what I'm talking about. I hope you can read my writing.Thanks,Kelly
Reply:thats alot of weight to guess on a structure..I would have it engineered or get specks on one already built..I dont know much about oil field pipe but many comments on the forum say its not very weldable, and lateral support is needed so the whole platform doesnt twist or sway..so trying to weld those angle supports could pose a problem..Of all the things I lost I miss my mind the most...I know just enough about everything to be dangerous......You cant cure stupid..only kill it...
Reply:My calculations show an 8ftx5ft cylinder full of water to weigh closer to 15600lbs, not including the weight of the cylinder itself (at least a couple hundred pounds) and brackets/supports to keep it in place.  I think you're underestimating the weight to be carried.
Reply:viper522,I am guessing at the size of the tank, however that tank is a 1500 gal. tank. I understand water weighs 8.34 lbs./gal, so 1,500x8.34=12,510 lbs+ let's say 400lbs for the tank = 12,910lbs. So it should weigh around 13,000lbs.Thanks,Kelly
Reply:Agrarian, myself and another welder made one almost identical to your drawing for a hunting camp a few years back, but we put it on a skid and we used 4" sch 40 pipe for everything and it was 8ft. tall. For the floor for the tank to sit on, we used galvanized grating. If it was me I would go with 4" instead of the 2 7/8".
Reply:cajun welder:So you recommend 4" instead of 2 7/8", that's probably a good idea. With nine legs, each leg ought to support about 1,444lbs! I think I can get some 4" oilfield pipe. How many posts did you use on the one you built.Mick120:I didn't mention this in my previous posts, but I was planning on putting down at least 3/4" plywood or maybe some sheet or plate steel. How many posts did you use and what size pipe did you use on the one you built?Thanks,KellyAgrarianWelder
Reply:We have one that has 6 4" sch 40 posts arranged in a circle with 4" c channel between posts and for cross members with 3/4 teated plywood for tank to sit on.  3/8 flat  on floor. Been on there 16 years no probsMillermatic 252millermatic 175miller 300 Thunderboltlincoln ranger 250smith torcheslots of bfh'sIf it dont fit get a bigger hammer
Reply:Agrarian, I used 8. If I don't have to work this weekend I'll try to go take some pictures and post them for you to see.
Reply:I installed 2 10,000 gallon tanks that hold sucrose and they stand at 100,000lbs full + tank + frame. The frame that came with them are only 10 - 4" sch 80 pipes, 2' tall with 3x3x1/4" angle connecting them all, sitting on 8x8x3/8" base plates. I put on a 3/8" plate over the entire thing to keep the tank from sinking.The biggest thing is making sure your concrete footing will support the weight especially under windy, hurricane, tornado, or whatever/wherever you are conditions. I wouldn't see why a 9 post 4" sch pipe wouldn't hold it in your drawling. 5' seems a little high for 2 7/8". I like putting a full sheet of steel underneath the tank, you know that won't wear out. Remember to make brackets to strap the tank down.
Reply:im not one to eliminate a welding project..but seems to me you could form an 8 x 8 x 5 foot block and pour  12 yards of concrete in it easier than this platform is turning out to be...
Reply:Country Metals,Thanks for the info on your huge sucrose tank project. Do you think I could possibly back down to six posts based on your project?Here is a drawing of the proposed tower on SketchUp. Should I use 2x6" 14 ga. RHS or C-Purlins or should I use something heavier, like 11 ga. ? Do y'all think that 16" O.C. is adequate or should I make it 12" O.C? In the text in the picture I put 1/8" for the sheet metal, do y'all think the  heavy expanded steel would hold up, or should I use a heavier plate steel?Weldbead,I ought to just bring in enough dirt to bring the ground up 5'. What do you think, 20-20 yards of dirt and gravel?Thanks,Kelly
Reply:i think 3/4 rod aint worth schhit in compression.hold it in your lap for all i care.
Reply:Weldbead the rods are tension members in that drawing.AgrarianWelder I was looking at some litt the other day about how fast the new ACQ treated wood eats standard galvanized and untreated hangers.  In some cases you can get serious corrosion in as little as 90 days after instalation.The newer PT wood's are especially agressive in promoting corrosion of steel even galvanized steel. Most have to be specially treated or you need to use copper or stainless to prevent corrosion. Alum, the traditional flashing for PT, is specifically not recomended because of how fast it will corrode.With both 1/8" steel or plywood, I'd have concerns about rain getting under the tank and then sitting and starting rot/rust. If you choose to go this route, I'd caulk that seam well with a top quality urethane caulk after filling the tank. A open design like bridge grate might be a better choice..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:[QUOTE=DSW;532787]Weldbead the rods are tension members in that drawing.until it starts to lean..then half are in compression and dont do any bracing...