Pressure vessel

[mlh77]

Hi,

I'm designing a tank that will operate at a pressure of 15 PSIG with an over pressure relief valve at 30 PSI. The design will be a rolled 14 ga. A36 sheet with a welded seam to create a 36" diameter tube and welded end caps. First of all, I make the assumption that 14 ga. is thick enough? I have looked at elliptical end caps and they are too pricy so, I would like to use flat end caps in the proper thickness. How thick should the end caps to withstand 30 PSI?

Thanks,

Mike

 

[fegenbush]

The design of such items is strictly controlled by design codes. Which design code is based on your jurisdiction (Country, State/Province, City, etc.). I recommend consulting with an engineer experienced in pressure vessel design in your area to determine a safe design.

 

[Duwe6]

fegenbush is giving good advice. What you are describing - 30 psig - will probably be required to meet ASME Section VIII pressure vessel criteria. And the resolution of that 'probably' will reside with the "Authority having Jurisdiction" - typically the state Boiler & Pressure Vessel Board.

Even if your vessel - drum - does not fall under a jurisdiction, an experienced vessel engineer is mandatory. [generic MechE's & CivE's need not apply] So are the services of a pressure vessel-grade fitter and welder, along with NDE and a hydro. Unless you like indavertant BOOM's and other mayhem.

 

[JStephen]

I don't know that you can actually get A36 in 14 gauge. Also, check with whoever is going to be welding this and see what they'd consider a minimum in order to weld it.
ASME B&PV Code Section VIII includes design of flat plate end caps. For general reference in the design of flat plates, refer to the formulas in Roark's Formulas For Stress and Strain. A conical shape might also work. You can very easily wind up using $200 worth of calculations to save $100 worth of material on little stuff like this.
There are various exemptions in the ASME code, you might check if your vessel fits any of them. You might be able to tweak the pressure some to fit.
If the vessel actually does need to meet ASME, just shop around for local ASME shops and let them design it for most economical design.
Normally, light weight is not a consideration, and a shop might use 1/4" shell just because that's what they had on hand.
If you can adjust dimensions, it might be cheaper to make it smaller diameter and use pipe instead of rolled plate.
If you can find ready-made mass-produced compressed air tanks that will work, they may be a lot cheaper than having anything custom-built.

 

[GenB]

Can you tell what's the use. Water, air, other.