[PSUBS-MAILIST] gasket test results

Wed Jul 8 13:38:25 EDT 2015

Rick,
The manufacturer will supply torque rates for installation. Once you get a feel for it, you'll probably find that it's somewhere in the region of finger tight + a slight graunch with a box wrench to snug it up enough to hold, but no more. Smooth surfaces and proper lubrication will take care of the o-ring. These things are designed to be used that way, remember. As to backing nuts, we liked them because you don't have to worry about moisture in the threads and, more importantly, you don't have to twist wires to install or remove them. The full tilt commercial thru-hulls are built long enough for this, and make them worth the money. If you've got the money, that is. Those puppies are pricey these days.
Vance

-----Original Message-----
From: Rick Patton via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Sent: Wed, Jul 8, 2015 1:25 pm
Subject: Re: [PSUBS-MAILIST] gasket test results

Good luck on your upcoming test Hank. How are you launching your barge once it gets there to the dive spot?  
While on the subject of gaskets and 0 rings, I have some subcon and blueglobe threw hulls. Sub Subcons of course have an O ring that sits in a groove and is screwed into a threaded ss plug that is welded into the hull. I have two concerns,1) how do I know when to stop tightening it as it won't be able to compress with depth and 2) I would think that the O ring might distort with the screwing motion as it snugs down. My preference would be to drill out the ss threw hull plug so that the threaded shaft of the Subcon would just pass threw and then put a backing nut on the inside to compress it but then the hull plug would have to be in my mind too thin to be able to get a nut on it. On the Blueglobes, how do you know when it is snugged enough without doing any damage to the fitting?  

Rick  

On Wed, Jul 8, 2015 at 2:15 AM, hank pronk via Personal_Submersibles    <personal_submersibles at psubs.org> wrote:   

I did my testing this morning and found some scary results.  I bonded EPDM gasket material to my port test chamber and tested a port to 500 psi.  The gasket extruded about 1/16 of an inch.  When I greased the surface of the gasket and pressured it to 500 psi, the gasket extruded 1/2 inch.  When the pressure is released the gasket returns to its original position.    
 When the same test is done without bonding, I get the same result.    

 My next test will be with the bearing surface machined to create tiny ridges for traction.    
 Hank    
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