Re: [PSUBS-MAILIST] how to calculate pressure on sub

["Adam Lawrence" <adteleka@in-tch.com>]

You don't need to add the 14.7 psia because you set it as the reference
point. That's why your depth gage reads zero at the surface.

Its like saying that a 1 atm sub that is just setting on the sea
shore is experiencing 14.7 psi, it's not, because that force is cancelled. Delta P = 0.

One good way of reasoning through the pressure on your sub is to just say
that salt water weighs 64 lb. per cubic foot and freshwater weighs 62.4
lb. per cubic foot (At 50 F). So now we need to know what a 1 in. by 1 in. by 12 in.
column of water weighs which will give psi per foot or water. Knowing this
then allows you to merely multiply this factor by your depth and you have
the pressure at that depth.

 

(64 lb / ft^3)x(1 ft /12 in)x(1 ft / 12 in) = 0.444444 lb / in^2 *ft.

Which is psi per foot of  saltwater.

Divide by 12 again and you have 0.037037037 psi per in.

 

So now you can multiply your depth by 0.44444 and you'll have the pressure.

 

Or you can divide your pressure by 0.44444 and you get your depth.

 

Water density changes with temperature, as the temperature decreases density
increases. If your really wanting to know what your exact depth is you can account for this too.

All you need is a thermometer and you can interpolate off of a table.

 

Adam

----- Original Message -----

From: Roger June

To: personal_submersibles@psubs.org

Sent: Tuesday, September 30, 2003 1:15 PM

Subject: Re: [PSUBS-MAILIST] how to calculate pressure on sub

33 feet of sea water = 1 ATM = 14.7 psi
34 feet of fresh water = 1 ATM = 14.7 psi

therfore;

depth of sub in feet / 33 feet of sea water = pressure in ATM's from the sea water

pressure in ATM's from the sea water + 1 atm (pressure from air) = total number of ATM's

total number of ATM's x 14.7 psi = total psi

So;

((100 ft/33 ft)+1 atm)*14.7 psi = 59.24 psi
((200 ft/33 ft)+1 atm)*14.7 psi = 103.79 psi
((300 ft/33 ft)+1 atm)*14.7 psi = 148.34 psi

If you want the depth for fresh water use 34 ft inplace of 33 ft




>
> From: bruno masse <rodin4@videotron.ca>
> Date: 2003/09/29 Mon PM 04:05:46 EDT
> To: personal_submersibles@psubs.org
> Subject: [PSUBS-MAILIST] how to calculate pressure on sub
>
> hi every body,
>
> i,d like to know how to calculate the water pressure on the sub
> when you go down at 100,200,300 feets
> in pound inch.
> thank you
>
>

Roger June
REJ and Company
513-300-1189
rjune@fuse.net


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---

hi every body,

 

i,d like to know how to calculate the water pressure on the sub

when you go down at 100,200,300 feets

in pound inch.

thank you