[PSUBS-MAILIST] add penetrator

[Sean T. Stevenson via Personal_Submersibles]

Can you sketch or otherwise provide a picture of your idea with the hatch land? I can't quite visualize what you mean. There are some potential pitfalls, but I need to see what you're talking about.

As far as penetrators in the hull shell, the  ASME Boiler and Pressure Vessel Code, Section 8, Division 2 (addressing PVHOs) refers to so-called "insignificant" penetrations as follows:

Openings of 3½  inches or smaller are considered  insignificant if they are made in plate of  3/8  inch or less in thickness and their finishing connections  are welded.  The opening must not exceed 2-3/8 inches if  the  plate is greater than  3/8  inch thick.  Threaded, studded, or expanded connections may not exceed 2-3/8  inches regardless of plate thickness.  To qualify,  the openings must be normal orientation. Two adjacent openings not exceeding the sizes listed above must have a minimum center to center distance equal to the sum of their diameters in order to remain insignificant. 

Furthermore, two openings of diameters d1 and d2, in a group of three or more, must have a minimum  center distance equal to 2.5 (d1  +  d2) when in spherical shells or heads or (1 + 1.5 cos  θ)(d1  +  d2) when in cylinders or cones, θ being the angle from the longitudinal axis of the shell.

That said, I am personally hesitant to use any tapered thread (I.e. NPT) fitting in a hull shell, and would instead recommend either a welded fitting or an O-ring sealed straight thread fitting. The latter, of course, requires a pad lest the required spot face to seat the fitting reduce the local shell thickness, so your options are limited.

Sean


On March 14, 2016 3:14:38 PM MDT, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Hi Sean,I would like to add one more electrical penetrator to my new
>sub and I don't want to weld in a reinforcement  for the penetrator.  I
>am thinking of drilling and threading into the edge of my hatch land .
> I am thinking it will not bother the strength of the hatch because it
>is two inches thick.  Gamma has four holes drilled and threaded in the
>bare hull with no bushing or anything.  That was certified to 1,000
>feet so I figure I can do that through the 2 inch material.  What do
>you think?Hank
>
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