[PSUBS-MAILIST] oil compensation

[hank pronk via Personal_Submersibles]

 Alan,I am compensating two thrusters from one air cylinder filled with oil.  It seems to be working terrific, but maybe best to just leave it alone.  Why fix it if it aint broke.Hank
    On Wednesday, September 13, 2017, 10:05:19 PM MDT, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  
 
 Hank,are you oil compensating your thruster?If so you would need to calculate the volume of air in the cylinder & air lineleading to it. I am not sure what depth you are taking the sub to, but at300ft the air will compress to 1/12th it's original volume.If you oil filled the compensator it would be a better back up for any oilthat will leak out of your thruster.You could always go with one of those accumulator bladders Scott mentionedor Cliff's relieving regulator. ( Hugh's idea)Alan

Sent from my iPad
On 14/09/2017, at 12:31 PM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:


Hi All,Thank you Greg, just sent them a request.
I have tested my air cylinder compensator for my thrusters both in the pressure test and a couple days ago to 100 feet.   The set up seems to work with no water intrusion into the motors.  I have the cylinder mounted below the motors witch causes a small air pocket in the hydraulic fitting on top of the motor.  I am not worried about the small amount of air except the potential of oil being forced up past the air pocket.  This makes me think the compensating cylinder should be above the motors.  Then I wonder why does the compensating cylinder need oil in it at all.  As long as the bore in the cylinder has enough volume so the piston is not bottomed out at max depth.  I also have a small spring pushing the cylinder rod to create a small internal pressure above ambient.  Is my logic flawed?  it would be very convenient to eliminate the oil in the cylinder and would make the compensator  faster to react to pressure change say in a fast ascent.  Hank

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