[PSUBS-MAILIST] Acrylic temperature rating

[Alan James]

Just something interesting I found in G.L. with regard to depth
rating of acrylic hemispheres.
A dome rated for 990 ft (30 bar) in 10C water temperature is only 
rated to 495 ft  (15 bar) in 38C. 
According to this simple sea temperature at depth profiler 
http://www.windows2universe.org/earth/Water/temp.html
at 600 ft most water is under 10C. So you would never expose the dome to
overly high pressures at high temperatures.
I am not sure how G.L. deal with this issue & whether with deeper diving submarines
you would just claim to operate in low temperatures & go for the largest depth
rating for that dome.
To add another dimension to this, I guess you would need to factor in the cabin 
temperature, because that would be effecting the inside of the acrylic.
Also the acrylic having high thermal insulation properties would be slow to cool
down & would remain at a higher temperature than the surrounding water for a
time, especially if diving quickly.
On the plus side there is something like a 5x safety factor in there.
Vance did you ever strike relatively warm temperatures at depth?

Regards Alan
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