advice on building a fluid tank

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Im thinking about building a drilling mud sand separation system and was wondering about building a tank. I was thinking about building a 4' high 8 ' wide and 16' long tank about 3500 gallons. It would have an external skeleton of 2" by 3/8" flat bar on 16" centers on edge and I was wondering if 10 gauge plate would be heavy enough to keep from bowing between centers or how thick of plate do I need to go? it will have a King cobra scalper and  8 6" desilters sitting on top of it eventually. This is for water wells so the lighter the better. any advice would be appreciated.
Reply:For that much weight, Id go not less than 1/4" and my extarnal frame work would be out of channel not flatbar. Just my take on the project.Youre looking at roughly 26250 psi on those side walls.
Reply:thanks man. how did you figure the side wall pressure? the bottom will be setting on the ground. I have been trying to find a formula for that and did not know were to look. one more question are you talking 2" channel or something taller than than that?.
Reply:Well for the water youre looking at just about 7.5 psi for a cubic of water. And A36 plate steel has a strength of 36 ksi (kilo-pound per sq inch) You could run a higher strength alloy like A572-40 or A572-50 which are more for vessals like water tanks like large. It just welds a little harder. If you go with the 572 steel, Id run an 80 series rod. Oh the 572 series plate carries a 45 and 50 ksi
Reply:put a v-bottom in tank plus  a man hole in one end for ez-clean out
Reply:the flat bar on end dosent work well on tanks for belly bands.    3" angle iron works much better.  leave a leg sticking out like you would with the flat bar and radius the ends so their not as dangerous.Vantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.
Reply:Originally Posted by idacalIm thinking about building a drilling mud sand separation system and was wondering about building a tank. I was thinking about building a 4' high 8 ' wide and 16' long tank about 3500 gallons. It would have an external skeleton of 2" by 3/8" flat bar on 16" centers on edge and I was wondering if 10 gauge plate would be heavy enough to keep from bowing between centers or how thick of plate do I need to go? it will have a King cobra scalper and  8 6" desilters sitting on top of it eventually. This is for water wells so the lighter the better. any advice would be appreciated.
Reply:thanks for the advice, angle iron and channel doesnt seem as clean of a build more of a homemade look. but with 3" 1/4"angle It would be close to the same price I need to sit down and refigure everything again. It is going to have sloped sides and a big manhole is a very good idea nothing like shoveling muck out and over the top of the tank.
Reply:Originally Posted by Magnetic Mechanic1.7 lbs/square inch according to my chart
Reply:Head Pressure has nothing to do with volume (cubic feet).A column  of water four feet high (deep) produces a pressure of 1.7 lbs/sq. in. at the bottom.  That is simply the weight of a 4 ft deep inch square column of water.  Being a fluid, this pressure is in all directions. It makes no difference how  wide or what shape the column is.I believe you are reading the chart wrong.a head of 10 feet = 4.3 lbs/sq.11 feet = 4.8 lbs/sq. 12 feet = 5.2 lbs/sq. Attached ImagesA butterfly without wings, is just an ugly bug
Reply:I don't know where you got 7.5.multiply inches of head by .036127 to get head in lbs/ sq. in. Attached ImagesA butterfly without wings, is just an ugly bug
Reply:the tank if 4x8x16 will be 512 cubic feet. A cubic foot is about 7 gallons of water . so 512cf x7gal/cf  x8 pounds per gallon=28627 pounds of water, The height of 4 feet equates to 1.7 pounds of pressure at the bottom of the tank.
Reply:Originally Posted by Magnetic MechanicHead Pressure has nothing to do with volume (cubic feet).A column  of water four feet high (deep) produces a pressure of 1.7 lbs/sq. in. at the bottom.  That is simply the weight of a 4 ft deep inch square column of water.  Being a fluid, this pressure is in all directions. It makes no difference how  wide or what shape the column is.I believe you are reading the chart wrong.a head of 10 feet = 4.3 lbs/sq.11 feet = 4.8 lbs/sq. 12 feet = 5.2 lbs/sq.
Reply:well we have been building tanks like that under my company name since 1952.   The average size is 4' X 8' x 4' deep usually 3/16" plate. The largest single tanks that I can recall we built were 12' x 30' x 8' deep and that was 1/2" plate.  Also some stainless tanks, some steel tanks with stainless liners, some with poly liners.   Back when we actually made things here in America 90% of our business was related to plating and support of plating, tanks, baskets, turn key plants, piping, overhead conveyors, spin dryers and engineering. The problem with the flat bar for stiffeners is its to narrow to be effective at containing the bulge.  the material will just bulge around it.   Look at 99% of the professionally manufactured tanks out their and you will see the same thing.we still do about 30 a year but nothing like the volumes we used to see.Honestly I think I have over 10,000 stainless plating baskets under my belt when I was younger.   They rapidly became my least favorite thing on earth right behind drilling holes.Vantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.
Reply:Originally Posted by Magnetic MechanicI don't know where you got 7.5.multiply inches of head by .036127 to get head in lbs/ sq. in.
Reply:That would require a change in atmosphere such as would be caused by diving.
Reply:Originally Posted by flatbustedbrokeThat would require a change in atmosphere such as would be caused by diving.
Reply:Originally Posted by HammerBut water has mass, so why wouldnt it increase its psi as it increases in mass? If you stack cinder blocks, as it gets higher, it gets heavier. Should be the same principle.
Reply:Originally Posted by HammerThe 7.5 psi is the pressure a cubic foot of water creates. I made a mistake in this number though. When I divided the cubic foot of pressure of 61.92 on a scratch pad I divided it by 9 as if it were a cubic yard. Thats was the weight. But the psi should increase every bit as much as it would for divers. If say fresh water has a psi of .43 per foot then why wouldnt it increase to 4.3 at 10'?
Reply:Originally Posted by flatbustedbrokeYour prior post said that it should increase just as it would for a diver and pressure increases on divers as they change altitude.The Red Devil would be better able to explain this.
Reply:Originally Posted by HammerThe 7.5 psi is the pressure a cubic foot of water creates. I made a mistake in this number though. When I divided the cubic foot of pressure of 61.92 on a scratch pad I divided it by 9 as if it were a cubic yard. Thats was the weight. But the psi should increase every bit as much as it would for divers. If say fresh water has a psi of .43 per foot then why wouldnt it increase to 4.3 at 10'?
Reply:as far as i know the mass ( or density )of water is always 1At STP (standard temperature and pressure), which is 1 atmosphere and 25 degrees celcius (sometimes listed at 20, or others).Last edited by rat4spd; 12-21-2008 at 12:49 AM.
Reply:the pressure depends on the height of the water  ( or the shape of the container.) if we agree that one  cubic foot of water = 7.5 gallons...       --- then a (flat)  12' x 1' tray 1" high = one  cubic foot, and the 1" of height will create .43 psi/foot x 1/12 foot = 0.03 psi at the bottom       ---then a 12" x 12" x 12" box =   one cubic foot, the the 12" of height will create  .43 psi at the bottom      ---then a 1" diameter vertical pipe ( area of 1" pipe =0.78 sq in., volume of  (1) linear foot  of 1" pipe =0.78 sq in  x 12 in  = 9.36 cubic  in., which divided by 144 cu in / cu ft  =0.06 gallons)  will need to be 7.5 gal divide by 0.06 gal/foot or 125 feet tall...and will have a pressure at the bottom of 125 x .43= 53.75 psi ..
Reply:Originally Posted by HammerBut water has mass, so why wouldnt it increase its psi as it increases in mass? If you stack cinder blocks, as it gets higher, it gets heavier. Should be the same principle.
Reply:"Design of Welded Structures", by Omar Blodgett and available (cheap) thru the "James F. Lincoln Arc Welding Foundation", adresses this problem very specifically in section 6.5.Giving you all info needed to properly calculate plate thickness and stiffener size/location. Get it, you won't regret it.The book will also help you on a million other aspects of design.Mr. Blodgett is the greatest mind to ever have set pen to paper on welding related engineering. He also has a large amount of common sense and seems to be a very nice guy.JTMcC.DuaneRight on!A butterfly without wings, is just an ugly bug
Reply:this tank is for a water well drilling rig is it going to drill with just water or will it use drilling mud if they use mud i would think the weight would be more
Reply:We have tanks goin' up and down the road every day here.  Salt water, mud, water,.....I'll try to take some pics and talk to the guys.I have a sneaking suspicion you're going to have to do baffles, or pass thru bulkheads inside the tank.  I don't know."Any day above ground is a good day"http://www.farmersamm.com/
Reply:its going to have two compartments in it, clean and dirty mud but it will always be transported empty.