Re: [PSUBS-MAILIST] ASME PVHO

[Jon Wallace <jonw@psubs.org>]

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