<html><head></head><body><p dir="ltr">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.</p>
<p dir="ltr">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:</p>
<p dir="ltr">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. </p>
<p dir="ltr">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.</p>
<p dir="ltr">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.</p>
<p dir="ltr">Sean<br>
</p>
<br><br><div class="gmail_quote">On March 14, 2016 3:14:38 PM MDT, hank pronk via Personal_Submersibles <personal_submersibles@psubs.org> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px"><div id="yui_3_16_0_1_1457989721783_2466">Hi Sean,</div><div id="yui_3_16_0_1_1457989721783_2466" dir="ltr">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?</div><div id="yui_3_16_0_1_1457989721783_2466" dir="ltr">Hank</div></div><p style="margin-top: 2.5em; margin-bottom: 1em; border-bottom: 1px solid #000"></p><pre class="k9mail"><hr /><br />Personal_Submersibles
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