During WWII most surface naval vessels had aboard a barometer, usually in the captain's cabin. Its purpose was in weather tracking. American Submarines carried a barometer on the bridge. Why? There was no weather below 50 feet.
As far as I know the WW2 era subs used to install two of such instruments having a bit different scale to measure two types of pressure. May be I'm wrong but I think so! A manometer-barometer installed on the conning tower/deck to measure the barometric p and the other one which installed in commander's cabin, used to show the sub's inside p, which is very important. Prior to the Great War, surface ships/liners used to keep three m compasses, installed in three different locations of a ship, to get correct reading/position etc. I think the WW2 subs too, certainly had different aspects of this instrument, that I never read before, from the technical point of view.
Thank you for the responce. But you fail to explain WHY these barometeric readings important. I found the reason in a WWII submariner's memior but I am curious if anyone else knows this simple secret.
According to "Take Her Deep", the memior of a former commander of the USS HALIBUT, just prior to diving high pressure air was bled into the hull of an American SS as SOP. The bridge barometer was then monitored to witness if the air-pressure was steady or if it dropped. Droping was a sign that somewhere there was a leak, steady meant there was hull-integity and it was safe to dive. This was a low-tech solution to the problem of having to manually checking all possible leaking values. As I recall the USS SQUALUS sank in 1939 in an test-dive in the Long Island Sound due to an open value and the use of a barometer check was a solution to the question of hull-integrity.
Nicely explained. Thank you. Though the process looks like a low-tech one, but directly involved with ultimate safety measures for the personnels onboard!
There was also the use of a barometer to monitor sub internal air pressure as a health factor for the submariners. In the course of operations and enduring depth-charge attacks sometimes leaks would spring. One counter-measure would be to bleed high-pressure air from the reserve tanks into the hull as an attempt to equalize in part the internal pressure with the external sea-pressure. This was a losing proposition, but it was done to slow the leaks, buying time. But too much internal pressure is harmful to the humans. Still, its better than a quick drowning.
Here I may recall one important thing may be you've noted too, that the typical US/UK subs of WW2 have a severe drawback when it used to dive into water. During the process these subs vent out the pressurised air through vent valve of the ballast tank, gushed out in such a way that could be seen from a great distance (as like whales at sea) and not a 'safe' process to hide from the enemy; though corrected the tech afterwards.
