Re: [PSUBS-MAILIST] Hydraulic Drive Unit

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

Sean T. Stevenson schrieb:
> 
> Carsten - one thing you mentioned didn't quite make sense:
> 
> Quoting Carsten Standfuss <MerlinSub@t-online.de>:
> 
> > Also the lip-bearing
> > of the cylinders and motors are normally designed for inside pressure
> > higher than outside..
> 
> If I understand you correctly - do you mean to say that you anticipated having
> higher ambient pressure than the pressure within your cylinders and motors?
> 
> This situation is avoided entirely by pressure compensating your hydraulic
> reservior to a bias above ambient.  The pump would create a (ideally) constant
> differential pressure above ambient.
> 
> Or do I misunderstand you?
> 
> -Sean

No you are right - pressure compensating over ambient will help..

.. but imagine what happens when the unit is out of order (no pressure
in the pipes.. or if you have to open the system to refit/replace
something - I mean underwater - Euronaut is designed to stay one week 
at 800 feet. The other thing is that hydraulic motors have normally 
a third wire/pipe for the leak-oil they allways produce a little
during running - and this pipe is pressure less .. 

But ask Gary - I am not a expert on hydraulics.. 

                 ___________________
	             \___
Outside    ======================= Inside 
           ======================= 
                     ----
         flow =>    / Seal    
                 -------------------

best regards - Carsten