pressure vessel help

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Hello and thank you for helping me out on this one.so i am trying to figure out how to make a pressure tank with materials i already have and i am worried about the endcaps. I have 20" OD stainless steel 316 with .125 wall cylinder. i also have two .125 316 flat plates that i wanted to weld on for endcaps. my working pressure would be around 100psi with a temperature around 90F. i have been looking around the interweb for the calculations for flat endcaps and cant seem to find what i need. any help would be great! Thank you for your time.
Reply:Flat caps on pressure tanks are not common, in my opinion anyway.Except hydraulic cylinders, they are flat bottom.Actually, if you thought of your tank with a moveable end, like a cylinder, there would be about 30,620 lbs of force against the end cap.Last edited by MinnesotaDave; 05-12-2014 at 05:57 PM.Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:Start with 1.3 Theories of Failurehttp://books.google.com/books?id=OWM...ations&f=falseDave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:you aren't even starting with what you need to make a pressure vessel with a 100 psi working pressure (not even close).  Flat end caps out of that material with that diameter and thickness aren't even in the ball park from a stress standpoint.  Simply put.. UNSAFE!!!!!  And that's just the end caps, you haven't even considered the moment carrying capacity of joint between the endcap and cylinder among many other things that you would need to consider to do what you want to do safely.  If you do decide to do this (and I am suggesting you don't), don't pressurize it with anybody else around and you should get behind a concrete wall or very far away and not do it around anything you don't want severely damaged.
Reply:This is a very big No No IMO. If you don't have an engineered spec to build by including a weld procedure and material specs then thats where you need to start. 100psi of anything especially air or gas is not a good thing to have fail.
Reply:I am no engineer but I do build pressure vessels for a living. This project seems like a bad idea to me. The vessels i have built with flat end caps generally have plate twice the thickness of the shell pipe, so .125 seems way too thin. But hey... What's the worst that could happen?IAMAW Local 330Airco 300 AC/DC HeliwelderAirco Dip-Pak 200 with Profax spool gunPowr-Kraft AC225Everlast PowerArc 200stBuffalo Forge No.21 drill pressSpeedglas 9100xxAirco, Oxweld, Purox, Victor torchesLincoln Ranger 8
Reply:[QUOTE=wnywelder;4170421What's the worst that could happen?[/QUOTE]Can you spell "KABOOM?"Many moons and a career or two ago, we had some irrigation manifolds make like that.  Flat plate on the end of some 30" or so pipe.   Kept blowing the ends off, no matter how much concrete was poured on the ends.  We had a brainstorming session to come up with a solution.  Smart mouth me suggested domed ends like on propane tanks.   So I was the one that got to lay upside down in the mudhole and install them.    I think they worked.TimLast edited by pin2hot; 05-12-2014 at 07:46 PM.
Reply:Originally Posted by MinnesotaDaveStart with 1.3 Theories of Failurehttp://books.google.com/books?id=OWM...ations&f=false
Reply:Originally Posted by geezerbillWow, that is some exciting stuff....wish I had time to read it all!
Reply:Flat heads are complicated, but they are detailed in ASME section 8.  Unstayed flat heads used in pressure vessel construction depend on the type of attachment to the cylinder, among other things.  IAW: The minimum required thickness of flat unstayed circular heads, covers and blind flanges shall be calculated by the following formula:t = d√(CP / SE)t= minimum thicknessd= diameterC= a factor depending upon the method of attachmentof head, shell dimensions, and other items as listedin (d) below, dimensionless. The factors forwelded covers also include a factor of 0.667 thateffectively increases the allowable stress for suchconstructions to 1.5S.P= internal design pressureS= maximum allowable stress value in tension fromapplicable table of stress values referenced byUG-23.E= joint efficiency, from Table UW-12, of any CategoryA weld as defined in UW-3(a).Basically, 1/8" endcaps aren't even close to minimum required thickness for an unstayed flat head.
Reply:What the pros want you to use is the "Orange Peel" method of capping a pressure vessel.Always ALWAYS test at 5 (five) PSI underwater to find leaks.I am not a pro for pressure vessel building but I have TIG welded .024 stainless bellows for Locomotive exhaust that were tested to 220 PSI for 20 minutes.Proceed as you choose.
Reply:Originally Posted by calilabsHello and thank you for helping me out on this one. I have 20" OD stainless steel 316 with .125 wall cylinder. i also have two .125 316 flat plates that i wanted to weld on for endcaps. Thank you for your time.
Reply:Probably cheaper to pick up a used 200lb propane tank and purge it, use that for an air tank they are rated for working pressure of at least 250psi. Can be found cheap if you look around.What your looking at building is basically an air bomb, I wouldn't want to even test it unless it was filled with water and I had a remote fill valve. Go on youtube and look up what compressor explosions can do, whole buildings get demolished when a 100gal tank blows at operating pressure.