Re: [PSUBS-MAILIST] Question about pressure compensation

[MerlinSub@t-online.de (Carsten Standfuss)]

Dear Alec..- even Sgt.Peppers has air compensate Motors and batteries
without problems - But I was never real deep with it. 

A fire need : Temperation or a spark, oxygen, and something can burn.. 
Remove one of the three itms from the list and nothing will happen. 

regards Carsten

Alec Smyth schrieb:
> 
> Carsten,
> 
> What worries me is pressure compensation of trolling motors with air
> (something I am doing on both my boats). It's a popular solution, and
> has been used for decades. Yet those motors must have tremendous
> sparking around the brushes. I saw Carl Stanley's new sub on television
> the other day and it appears to have air compensated trolling motors...
> and he's diving to thousands of feet. How do you reconcile this?
> 
> Thanks,
> 
> Alec
> 
> -----Original Message-----
> From: Carsten Standfuss [mailto:MerlinSub@t-online.de]
> Sent: Wednesday, January 19, 2005 11:52 AM
> To: personal_submersibles@psubs.org
> Subject: Re: [PSUBS-MAILIST] Question about pressure compensation
> 
> Hi Thijs - imagine that in your (in this sample) very small battery box
> are just 100 O2 atoms at 1 atms and 21 % PPO2 equal to 0,21. Imagine a
> spark inside.. Nothing will happens.
> 
> Now you dive and pressure compansate the box to a pressure equal to the
> deep with air as compensation gas. Say 10 atmosphers with a P02 of 2,1
> atmos. How many atoms 02 you have now close to the spark ? Right = 1000
> atoms.
> 
> The o2 Partial pressure in the Apollo-capsul which catch fire was below
> 1,0 atm.
> 
> Thats is also the reason that in manned decompression chambers the
> equipment is nonflammbale and everything which can create sparks is
> strickly forbitten.
> 
> Use argon or Co2 to compress the battery-compartment an it will be fine.
> On the other side normaly you have no sparks in your battery
> compartment...
> 
> On a manned dry ambient boat this can create a real risk.
> At a deep of about 47 meters you have a PO2 equal to the same boat on
> the surface filed with pure oxygen ! (The same amount of o2 atoms in the
> cabin..)
> 
> Another problem. A Po2 of 1,6 or more in the loop is a great risk for
> rebreather divers ! To much oxygen (to much o2 atoms per square inch)
> damage your lungs and body. This pressure is equal to 1,6/0,21 or 7,6
> times 1 bar equal to a dive deep of 66 meter or 216 feet.
> 
> If you want to ge deeper with the ambient boat you have to lower the
> oxygen percent in the gas mix.. But thi gas mix has a to low PO2 on the
> surface..
> 
> For that reason we will go in our diver lock out chamber with heliox gas
> mixes with reduce PO2 mix if we go for greater deeps. And we chang the
> po2 if we go higher or deeper.
> 
> regards Carsten
> 
> > Thijs Struijs schrieb:
> >
> > Bill and the rest,
> >
> > Pressure compensation of battery pods and trusters with air seems the
> > most simple and clean way to do it i think. It also has the advantage
> > that you don't have to put a square battery in a bulky round box. But
> > in a discussion on this subject a view years ago Michael Wludarczyk
> > wrote that at higher pressure (300 psi / 200 mtr.)  the partial
> > pressure of the oxygen (PPO2) becomes so high that there is a
> > substantial fire risk. This is of course a lethal depth for an ambient
> > sub but i want to go to 100 mtr. in an 1 atm. sub. Eigther i missed
> > something during my schooldays or i simply forgot but PPO2 doesn't
> > mean anything to me.  Is there someone on the list who can say
> > something sensible about this?
> >
> > Thanks,
> >
> > Thijs Struijs
> > The Netherlands
> 
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