Re: [PSUBS-MAILIST] Caisson Gauge

[MerlinSub@t-online.de]

Thats the way we made it allready in the Euronaut. A Altimeter from a old russian MIG 17. Run the diesel with close air inlet up you reach a high of 6000 feet. Than stop the diesel and wait and look to the gauge..  By the way we reach 16000 feet in 3 minutes.. 

vbr Carsten



<JimToddPsub@aol.com> schrieb:
> James,
>  
> I'm planning to install an aircraft altimeter for the same  purpose.  An 
> altimeter is simply a barometer with a wide range, so you  could use that 
> instead.  It has the sealed air chamber (aneroid) which  expands or contracts in 
> response to changes in external pressure.
>  
> With the hatch closed and latched you can pump air out with an  external 
> vacuum pump, turn the pump off, close the valve, take a reading on  the 
> altimeter, wait a few minutes, then take another reading to see if any air  leaked 
> back into the sub.  This can even be done with the sub unoccupied as  long 
> as the altimeter is positioned where you can read it through a  viewport.
>  
> In most cases you can use the adjustment knob to set the altimeter to 0 for 
>  the first reading.  I plan to run the vacuum pump until the gauge  reads 
> 5,000 ft. altitude, shut the valve, and wait 5 minutes.  If the  altimeter 
> reading drops to 3,000 feet for example, I know a seal is leaking  inwardly.  
> One caution:  If the sub is sitting in strong sunlight, you  could get some 
> increase in internal air pressure just from heat build-up.
>  
> This test is on my pre-dive checklist on every dive.  During a  dive the 
> pressure reading should change very little if your scrubber and O2  inlet are 
> in balance.
>   
> 
>  
> (http://upload.wikimedia.org/wikipedia/commons/c/c3/Sens_alt_components.PNG)  
> 
> Comments and criticisms are most welcome.
>  
> Jim
>  
>  
>  
> In a message dated 3/27/2012 7:36:00 A.M. Central Daylight Time,  
> jamesf@guernseysubmarine.com writes:
> 
> Hi All,
>  
> Mr Numpty here.  
>  
> I kind of know the answer to this already, but i thought someone may be  
> able to clarify my mistake.
>  
> I was very pleased when i spotted just the sort of gauge i was after  
> mounted on the back of a sewage tanker.   A pressure gauge but one  that reads a 
> negative pressure as well as a positive.   So it starts  at 0 and can go to 
> -1 or +1 bar.  Idea was that it would go inside the  cabin to monitor 
> internal pressure.  (I'd like it to be able to measure a  negative pressure as 
> well as i intend to drop the internal pressure to  test for penetrator seal 
> leaks).
>  
> _http://www.tankerspares.co.uk/product/100mm_dia._30-0-30_Bottom_Mounted_Vac
> uum_Pressure_Gauge_30-0-301-4_ 
> (http://www.tankerspares.co.uk/product/100mm_dia._30-0-30_Bottom_Mounted_Vacuum_Pressure_Gauge_30-0-301-4) 
>  
> I was just thinking about mounting it up and ive suddenly realised that  
> its not going to work is it?  It must measure the port pressure relative  to 
> the ambient pressure, which if i just mount it on a bulkhead will  always be 
> the same no matter what the pressure actually is.
>  
> I suppose i'd have to make a pressure proof box sealed at  surface pressure 
> and pipe the port to the inside of the  hull?   So its kind of like a 
> caisson gauge.
>  
> Just thinking aloud really.
>  
> James
>  
> 
> 




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