Re: [PSUBS-MAILIST] Isn't 'Mini book review.' anymore--pressure test

[AndrePevestorf@aol.com]

In einer eMail vom 11.04.2002 07:24:40 (MEZ) - Mitteleurop. Sommerze schreibt jonnie@scarymonsters.net:


> I'm less concerned with generating the pressure on a vessel filled with
> water, actually, and more concerned with sealing a big tank with a door in it.
> Maybe there's some advice to be gleaned on the subject?
>
>                     Thanks for the interesing dialogue!
>
>                             John


Yes, the sealing problem is more interesting and not so easy to realize.

A bajonet hatch is much expensive as I have learned from Carsten and his CSSX diver hatch design. 
The "two-outer-flange-bolted-together-design" as Thijs Struijs advise sounds more easy and less expensive too. The formulars for the dimensions of the flanges are the same as for any other pipe flanges. 
Iīm agree that it would be the best to order such a test chamber completely from a boiler firm. Including the design and dimensions. Carstenīs CSSX hull is just build by such a high skilled boiler company and itīs not so expensive as I feared.

To relieve the load on the seal it could be an advantage to use other posibilitys then a flat seal between the flanges but to manufacture a groove in a flange with such a large diameter needs very expensive machines and makes only sense AFTER welding. The width of sheet metal can be rolled by the rolling machines depends on the manufacture and the terms of delivery for sheet metals. CSSX is made from 3m sections.

Ring stiffeners increase the building costs but can reduce the over all weight and so the material costs.

If the sub is not filled with water its necessary to avoid the huge bouyancy of the emty pressure hull.

Maybe we should ask Carsten if itīs possible to use CSSX as a test chamber until the machine is installed. :-))

A considerably more interesting question is:  Is it possible to tune the deep dive capability of a pressure hull by means of initial pre-stressing with internal pressure? If the internal pressure causes a yielding in the structure then there should be remaining "Eigenspannungen"  -- self stresses?? internal stresses?  engineers will know what I want to express..

This remaining tensile stresses have to be compensated by the pressure stresses due to the external pressure during a later dive. So the resistance behavior of the hull will be improved. 
The problem is that a sufficient internal pressure to reach yielding stress in the hull must be much more higher then the crush deep pressure. 

A.