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

I just finished working on a Sunshine NC&StL 36' rebuilt boxcar.  When decaling the yellow stripes, the Sunshine decals fell apart.  I decided to order the K4 decals for the 40' NC&StL boxcar to try to use the yellow stripes on the Sunshine model.  This was my first experience with K4 and I found them easy to use and they did a nice job covering the Youngstown doors.  I used the kit's lettering to finish the car. 

I have not seen much discussion of the K4 decals.  Have others used them and what has been your experience?

Thanks

Chuck Cover
Santa Fe, NM

Claus Schlund wrote:

What Ed is trying to say is that normal atmospheric pressure is about 14.7 PSI.

Thus a PERFECT VACUUM would read at -14.7 PSI (note the minus sign).

Therefore, a "vacuum at -27psi" is not possible under any circumstance on earth

They pulled a higher vacuum with a vacuum truck. Those are usually used for sucking out clogged sewer pipes and the like and obviously exceed “full” vacuum (14.5 psig). I don’t know HOW it works, tho.

Tony Thompson

tony@...