[PSUBS-MAILIST] add penetrator

[hank pronk via Personal_Submersibles]

Hi Sean,Thank you,I intend on using a .5 inch strait fine thread penetrator with o-ring seal.  That is the reason for going through the hatch land.  The hatch land was machined flat on the top and will accommodate the penetrator with no machining because the penetrator has the recess in it for the o-ring.  Also the land is very beefy.  It may be better to just buy a new penetrator with more connections.  I am one wire short.   As always  you are big help!Hank 

    On Monday, March 14, 2016 7:22 PM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
 

 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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