RE: Unmanned test dives

["Morrisson, Richard D" <Richard.Morrisson@PSS.Boeing.com>]

See comments inserted into body of text below

> ----------
> From: 	Jonathan Wallace[SMTP:jon@zk3.dec.com]
> Sent: 	Monday, March 01, 1999 1:38 PM
> To: 	personal_submersibles@psubs.org
> Subject: 	Re: Unmanned test dives
> 
> "Morrisson, Richard D" wrote:
> 
> > For the viewports I would suggest facing the port into a pipe with a cap on the end and a machined flange on the other similar to your sub's port receiving hole.  The pipe can then be flooded and pressurized to the depth you want to test to.  Pressure cycling and/or long term exposure is then very trivial, it could even be automatic with a little ingenuity.  In addition, a dial indicator can be positioned on the port to measure deflections.  This may help predict failures or show non-elastic deformations.  A 3000psi scuba cylinder with a regulator can provide the pressure for an air over water charge line to the pressure vessel good to any depth up to 6000'.  Using a small orifice can prevent most of the explosive problems with this setup.  Make sure your pipe and the flanges have the capacity for the pressure you will be using.  You can even make this double ended to allow testing of two ports at the same time.
> 
> I'm not familiar with "air over water" charge lines, but this sounds like a feasible
> alternative to field testing the viewing ports.  Is a piston needed to separate the
> air from the water to prevent dissipation of the air into the water (to provide an
> evenly distributed PSI over the entire view port)?  
>no piston is needed, but a bladder or piston arangement like in an accumulator (hydraulic style) could be used if you want.  The pressure distribution is not affected by the air, but the air should be bled out of the system to reduce the explosive potential (compressed gas stores a lot of energy compared to water).  
> Could you provide more details
>The air over water charge system I referred to could be simply a short piece of pipe (say 1" by 12" long) with caps and fittings on each end arranged vertically and filled with water.  Use an orifice or needle valve at the bottom to greatly restrict the flow and connect it with tubing to the test chamber (the large pipe with flanges for the ports).  A valve on a threaded port on the chamber would be used to fill the chamber with water (from garden hose or equivalent) and then isolate it.  To bleed, the water should be flowing into the test chamber and on out the charge line until no bubbles show.  After shutting off the water and closing the isolation valve, the "charge" connection from a regulated source could be added (i.e. "air over water").  Add a gage port to the charge line to monitor pressure (depth).  14.7 psig will equal 33' of seawater.  When arranging the ports, remember, the bubble to be bled is going to rise to the highest point in the chamber.
> about the design of such a unit or provide a reference where I can view a similar
> device?
> 
If you need more detail than this, perhaps you could (should) enlist the direct help of an engineer when setting it up.  This will be less expensive than "dunking" your whole sub, most likely, but it will still incur some costs to do it right.
I hope this helped.

> Jon
>