ASME BPVC 2023 Section I

Condition: New product

same material, outside diameter, and the maximum allowable
working pressure of the head.
PG-32.1.5.3 For full-hemispherical heads, the
maximum allowable opening diameter shall not exceed
that permitted in PG-32.1.4 using K = K2 for an equivalent
shell constructed of the same material, outside diameter,
and the maximum allowable working pressure of the head.
PG-32.2 Shape of Openings.10
PG-32.2.1 Openings in cylindrical portions of
vessels or in formed heads shall preferably be circular,
elliptical, or obround.11
When the long dimension of an elliptical or obround
opening exceeds twice the short dimension, the compensation
across the short dimension shall be increased as
necessary to provide against excessive distortion due
to twisting moment.
PG-32.2.2 Openings may be of other shapes than
those given in PG-32.2.1, and all corners shall be provided
with a suitable radius. When the openings are of such
proportions that their strength cannot be computed
with assurance of accuracy, or when doubt exists as to
the safety of a vessel with such openings, the part of
the vessel affected shall meet the requirements of PG-16.1.
PG-32.3 Size of Openings.
PG-32.3.1 Properly reinforced openings in cylindrical
and spherical shells are not limited as to size
and shall comply with the provisions that follow, and
with the additional provisions given under PG-32.3.2.
PG-32.3.2 The rules given herein for compensation
apply to openings not exceeding the following dimensions:
a for vessels 60 in. 1 500 mm inside diameter and
less, one-half the vessel inside diameter but not over 20 in.
500 mm
b for vessels over 60 in. 1 500 mm inside diameter,
one-third the vessel inside diameter but not over 40 in.
1 000 mm
PG-32.3.3 Larger openings should be given special
attention and may be provided with compensation in any
suitable manner that complies with the intent of the Code
rules. It is recommended that the compensation provided
be distributed close to the opening. A provision of about
two-thirds of the required compensation within a distance
of three-fourths times the limit established in PG-36.2 on
each side of the opening as measured from the center of
the opening is suggested. Special consideration should be
given to the fabrication details used and the inspection
employed on critical openings; compensation often
may be advantageously obtained by use of a thicker
shell plate for a vessel course or inserted locally
around the opening; welds may be ground to concave

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contour and the inside corners of the opening rounded
to a generous radius to reduce stress concentrations.
In extreme cases of large openings approaching full
vessel diameter, openings of unusual shape, etc., the requirements
of PG-16.1 may be advisable.
PG-33 COMPENSATION REQUIRED FOR
OPENINGS IN SHELLS AND DISHED HEADS
PG-33.1 General. The rules in this subparagraph apply
to all openings other than flanged-in openings in dished
heads covered by PG-29.3, PG-29.7, and PG-29.12; openings
in flat heads covered by PG-35; and openings covered
within PG-32.1.2, PG-32.1.4, and PG-32.1.5.
When required, compensation shall be provided in such
amount and distribution that the requirements for area of
compensation are satisfied for all planes through the
center of the opening and normal to the vessel surface.
For a circular opening in a cylindrical shell, the plane
containing the axis of the shell is the plane of greatest
loading due to pressure.
PG-33.2 Area Required. The total cross-sectional area
of compensation required in any given plane for a vessel
under internal pressure shall be not less than A, as defined
in Figure PG-33.1.
PG-33.3 The notation used in this paragraph is defined
as follows:
d = diameter in the plane under consideration of the
finished opening see Figure PG-33.2. For nozzles
that penetrate partially or fully through the shell, d
= the nozzle inside diameter. For set-on nozzles, d
= the diameter of the opening in the shell.
x = the maximum diameter of the threads, in the plane
under consideration, in the finished opening, for
inside tapped NPT fittings
Dp = outside diameter of reinforcing element The
actual size of reinforcing element may exceed
the limits of reinforcement established by
PG-36; however, credit cannot be taken for any
material outside these limits.
F = factor from PG-33 and Figure PG-33.3, which
compensates for the variation in pressure stresses
on different planes with respect to the longitudinal
axis of a cylindrical shell. F = 1.0 for formed or flat
heads.
fr = strength reduction factor, not greater than 1.0 see
Figure PG-33.1
fr1 = Sn/Sv
fr2 = lesser of Sn or Sp/Sv
fr3 = SP/Sv
h = distance nozzle projects inward from the outer
surface of the vessel wall Extension of the