Another aluminum tank burst test

This week, I burst this 5 gallon aluminum air tank. I like this tank because it comes with five NPT ports and two brackets welded to it.

It failed at 46.5 bar (674 psi) in the heat affected zone of the longitudinal weld, basically the same location as the aluminum Harbor Freight tank.

5galbursttest

I bought a 1000 psi (69 bar) pressure transducer on eBay for $35. I recorded the pressure with an Arduino Uno and SD card shield. pressureplot5galburst

Dry mass = 3.2 kg (7.0 lbs).

OD = 8.196” (20.819 cm)

t = 0.098” (2.489 mm)

UTS = 27,512 psi (189.69 MPa)

According to the manufacturer, the tank material is 5086 – H116. From what I’ve read, the strength of the welded material is no less than the –O condition, but my UTS is less than all of the published 5086 UTS I’ve seen. I think the difference can be attributed to local thinning at the burst location.

I want to mount the tank using the brackets that come welded to it. I ran a quick analysis to see if one bracket is strong enough to hold a tank full of LOX (they appear sturdy). The weight of the tank and 5 gallons of LOX is 243 N (54.7 lbf). fea1 fea2Based on the UTS I calculated from the burst test, I have a factor of safety of 22.9 at the bracket/tank weld.

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