ASME BPVC 2023 Section I

Condition: New product

PG-35 COMPENSATION REQUIRED FOR
OPENINGS IN FLAT UNSTAYED HEADS AND
FLAT STAYED PLATES
PG-35.1 General. The rules in this paragraph apply to
all openings other than small openings covered by
PG-32.1.4b.
PG-35.2 Flat unstayed heads that have an opening
with a diameter that does not exceed one-half of the
head diameter or shortest span, as defined in PG-31,
shall have a total cross-sectional area of compensation
not less than 0.5 times the required area specified in
PG-33.2.
As an alternative, the thickness may be increased to
provide the necessary openings compensation as specified
in PG-35.2.1 and PG-35.2.2
PG-35.2.1 By using 2C or 0.75 in place of C, whichever
is less, in PG-31.3.2, eq. 1, or PG-31.3.3, eq. 3 for
calculating head thickness in PG-31.3 or
PG-35.2.2 In PG-31.3.2, eq. 2, or PG-31.3.3, eq. 5
by doubling the quantity under the square root sign.
PG-35.3 Flat unstayed heads that have an opening
with a diameter that exceeds one-half of the head diameter
or shortest span, as defined in PG-31.3, shall be designed
as provided in PG-16.1.
PG-35.4 Openings in flat stayed plates such as waterlegs
and tubesheets of firetube boilers shall have a total
cross-sectional area of compensation not less than 0.5
times the area specified in PG-33.2.
Compensation is not required for furnace connections
or door openings in stayed plates meeting the requirements
of PFT-20.6 or PFT-40.
PG-36 LIMITS OF METAL AVAILABLE FOR
COMPENSATION
PG-36.1 The boundaries of the cross-sectional area in
any plane normal to the vessel wall and passing through
the center of the opening within which area metal must be
located in order to have value as compensation are designated
as the limits of compensation for that plane see
Figure PG-33.1.
PG-36.2 The limits of compensation, measured
parallel to the vessel wall, shall be at a distance, on
each side of the axis of the opening, equal to the
greater of the following:
PG-36.2.1 The diameter of the finished opening.
PG-36.2.2 The radius of the finished opening plus
the thickness of the vessel wall, plus the thickness of the
nozzle wall.
PG-36.3 The limits of compensation, measured
normal to the vessel wall, shall conform to the contour
of the surface at a distance from each surface equal to

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the smaller of the following:
PG-36.3.1 212 times the nominal shell thickness.
PG-36.3.2 212 times the nozzle-wall thickness plus
the thickness of any added compensation, exclusive of
weld metal on the side of the shell under consideration.
PG-36.4 Metal within the limits of reinforcement that
may be considered to have reinforcing value shall include
the following:
PG-36.4.1 Metal in the vessel wall over and above
the thickness required to resist pressure. The area of the
vessel wall available as compensation is the larger of the
v a l u e s o f A1 g i v e n b y t h e e q u a t i o n s s h o w n i n
Figure PG-33.1.
PG-36.4.2 Metal over and above the thickness
required to resist pressure in that part of a nozzle wall
extending outside the vessel wall. The maximum area
in the nozzle wall available as compensation is the
smaller of the values of A2 given by the equations
shown in Figure PG-33.1.
All metal in the nozzle wall extending inward from the
outer surface of the vessel wall may be included. No allowance
shall be taken for the fact that a differential pressure
on an inwardly extending nozzle may cause opposing
stress to that of the stress in the shell around the opening.
PG-36.4.3 Metal added as compensation continuously
about the nozzle when welded to both the vessel
and nozzle, and metal provided in attachment welds.
PG-36.5 Typical examples of the application of the
above rules are presented in A-65 through A-69.
PG-37 STRENGTH OF COMPENSATION
PG-37.1 Material used for compensation shall have an
allowable stress value equal to or greater than that of the
material in the vessel wall, except that material of lower
strength may be used provided the area of compensation
is increased in inverse proportion to the ratio of the allowable
stress values of the two materials to compensate for
the lower allowable stress value of the compensation. No
credit may be taken for the additional strength of any
compensation having a higher allowable stress value
than that of the vessel wall. Deposited weld metal
outside of either the vessel wall or any reinforcing pad
used as reinforcement shall be credited with an allowable
stress value equivalent to the weaker of the materials
connected by the weld. Vessel-to-nozzle or pad-tonozzle
attachment weld metal within the vessel wall or
within the pad may be credited with a stress value
equal to that of the vessel wall or pad, respectively.
ASME BPVC.I-2023
36