[PSUBS-MAILIST] air compensation

[Alan via Personal_Submersibles]

Hank,
you will have the internal space of your actuator to equalise, which
shouldn't be a problem as this will be slowly equalised as you descend.
Then you have the piston going out during manipulator use, & there will be air going
in to fill that void. If you are running either off a 1st stage regulator or a relieving
regulator like Cliff's, the air will be kept at ambient & it will only be that small
flow in to the space the piston has vacated. 
You could estimate the internal volume change by using an on line cylinder volume calculator & plugging in the piston diameter & the difference in length it changes 
as it protrudes.
If the actuators full stroke takes (as an example) 4 seconds at full speed, &
the volume is 100ml, you could then run air through your intended hose at your supply pressure (130 psi for scuba regulator) in to a small crushed plastic bag, & see if it can
at least fill the bag with 100ml of air in 4 seconds. 
Have done similar for rough estimates.
Or just blow through the hose in to a plastic bag ( like lots of people do at Christmas
time) & you might think yep this will do with 130psi behind it.
BTW on A relieving regulator the orifice is pretty small & in Cliff's case it is venting
the internal volume of his 4 thrusters in the last 30ft of ascent.
Cheers Alan

Sent from my iPad

> On 9/12/2017, at 4:37 PM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Hi All,
> I am new to air compensating so I need to know if the air line size to each of my actuators is critical.  To save money I want to recycle  the high pressure nylon tubing that is used for hydraulic lines on my hydraulic arm.  The nylon air lines  are a bit over .125 ID
> thanks'
> Hank 
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