[Beowulf] Swimming in oil..

[Robert G. Brown]

On Mon, 11 Feb 2019, Lux, Jim (337K) via Beowulf wrote:

> Stu reports swimming, but perhaps he was really more wading.

A beautiful summary below.  I should keep it to use with my students
when we cover Archimedes' Principle and buoyancy.  I hadn't even thought
about this danger from dealing with large tanks of low density fluid,
but it makes sense -- you can drown in CO2 if you go down in a crater
full of CO2 because you don't float to the top and surely can't swim to
the top...

OTOH, in the Dead Sea or the Great Salt Lake (or even just the
Mediterranean) the density is greater than that of fresh water, and it
is correspondingly easier to tread water or swim, harder to drown.  I
don't think you could "drown" in a well-ventilated vat of mercury unless
you deliberately rolled face down on it, although breathing in the
mercury vapor over its surface would certainly be a problem.

Very nice!

    rgb

> 
> 
> A significant problem with large vats of liquid, whether used for cooling
> electronic equipment, or just storage, is that if the density is
> significantly less than that of water, you don?t float. Humans are just
> slightly positively buoyant in water (with full lungs). Change that to oil
> or corn syrup or scotch whisky with a density of 0.9, and it?s like having
> 5-10 kg of weight on you, and that takes a lot of work to stay on the
> surface.
> 
> This is a well known hazard in the petroleum processing industry (aside from
> the fact that the air above the tank?s liquid surface is probably full of all
> manner of unhealthy things and not oxygen) ? you fall in the big tank, you
> die.
> 
> 
> Diala AX (a HV insulating oil I?ve used) has a specific gravity of 0.885, and
> is somewhat more viscous than water (not a lot) ? if you fell into it, and
> couldn?t support yourself by standing on the bottom or equipment within the
> tank, you?d need to be rescued pretty quickly. The increased viscosity would
> also mean that it?s more work to keep ?treading oil? to stay above the surface.
> 
> 
> USP white mineral oil is about 0.85 g/cc. We had a thousand gallon tank of
> this where I used to work, and there was a whole discussion about safety ? it
> was a wide flat tank, so in theory, if you fell in, you could stand up
> (except that the tank was polyethylene and it *is* oil.. there were
> questions about whether you could stand up on the slippery surface)
> 
> 
> Of course, you can get oil in all densities ? the stuff they use for road
> surfacing is quite dense.
> 
> 
> 
> Fluorinert FC-40 (which I?ve also used) is quite dense ? 1.85 g/cc ? you?d float
> well above the surface like a cork. A quick glance at the line card for Novec?
> shows they?re all pretty dense - 1.4g/cc is the least dense.
> 
> 
> --
> 
> 
> 
>

Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu