Jon, What is also not
evident is whether the pi/2n is taken as radians or just in degrees. When
I see pi I think radians. Hugh
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org] On Behalf Of Jon Wallace
Sent: Tuesday, 2 November 2010 6:32 a.m.
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] ASME PVHO
Sean,
Context is "maximum plus/minus deviation from true circular form"
measured radially either inside or outside the shell. The formula is used
to determine the chord length for the template used to perform the
measurement. The PVHO document states that this section is a replacement
of UG-80(b)(2).
Lc = 2R sin (pi/2n)
c = 2.28(R/t)^0.54 is-less-than-or-equal-to 2.80
Sorry can't do subscripts and stuff with this
mailer. The "^" character in "c" formula is
"raised to power".
Hugh,
The only way I was able to get a number less than 2.8 was to use "1"
as the radius and ".9" as the thickness. For any reasonable
dimensions of a manned vessel, R/t will never equate to a number smaller than
or equal to 2.8.
Jon
On 11/1/2010 1:26 AM, Hugh Fulton wrote:
Hi Jon,
I think that we should have the
Q.A. part tied up for P-subs as well so that the home builders appreciate the
requirement for roundness. I am afraid I am lacking in the understanding
and math behind getting the answers and I think that Cliff, Sean, and you would
come to some agreement as to a formula.
I cant believe that it is a
misprint in ASME. I am missing something somewhere but I don’t know
what. Chs, Hugh
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