Re: HO Tank Car Lid


There are formulas in ASME Section VIII of the Boiler and Pressure Vessel Code that will allow you to calculate, or at least read off a set of curves, the expected maximum external pressure a steel fabricated vessel (say, a tank car) can withstand without collapsing.  Suffice it to say that the maximum possible external pressure a vessel in free air can see is 14.7 psi absolute (psia).  This would be less, say, if you assume this tank car is on Tennessee Pass or somewhere like that.

Some of the factors in the calculation are the ratio of the wall thickness to the diameter, and any reinforcement and the distance between reinforcements.  The tank heads count.  

I think the most common way you can get a vessel like a tank car to collapse is to fill it with steam and then close the vents while it's hot.  These guys who sucked a vacuum in one with a vacuum truck were probably doing this demonstration for the purposes of showing what could happen if you didn't have a vent open, and I'd say this is not surprising, that it would collapse at -7 psig or so (about 7 or so psia).  Notice that, in the video, they taped all the couplings on their hose to prevent air from leaking inward.  My best guess is that, if you did start to drain a tank car full of oil without opening a vent, a lot of it would run out by gravity but at some point it probably would collapse before it was fully drained.

A riveted 8k or 10 tank during the period of this list could have been slightly stiffer than a modern welded one, but probably not by much.  Or maybe not.

Ron Merrick

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