CASE

2260
CASES OF ASME BOILER AND PRESSURE VESSEL CODE

Approval Date: May 20, 1998

See Numeric Index for expiration
and any reaffirmation dates.

Case 2260 TABLE 1

Alternative Rules for Design of Ellipsoidal and M for
Torispherical Formed Heads M for M for M for 0.08 < r/D
Section VIII, Division 1 t/L r/D p 0.06 r/D p 0.07 r/D p 0.08 0.2
0.002 1.00 1.00 1.00 1.00
0.004 1.00 1.00 1.00 1.00
Inquiry: For Section VIII, Division 1 vessels, may 0.006 1.28 1.00 1.00 1.00
ellipsoidal and torispherical formed heads subjected to 0.008 1.41 1.20 1.00 1.00
0.010 1.41 1.26 1.10 1.00
internal pressure be designed to rules other than those 0.012 1.38 1.25 1.13 1.00
given in UG-32(d), 1-4(c) and UG-32(e), 1-4(d) respec- 0.016 1.31 1.21 1.12 1.00
tively? 0.020 1.25 1.17 1.08 1.00
0.030 1.14 1.08 1.01 1.00
0.040 1.07 1.01 1.00 1.00
0.060 1.00 1.00 1.00 1.00
Reply: It is the opinion of the Committee that Section
VIII, Division 1 vessel ellipsoidal and torispherical
formed heads subjected to internal pressure may be
designed using the following rules in lieu of those given
in UG-32(d), 1-4(c), and UG-32(e), 1-4(d) respectively.
(a) Nomenclature head skirt divided by twice the inside height of
ERTp Modulus of elasticity at 70F, psi. The value of the head.
ERT for ferrous materials shall be taken from See UG-32(c) for other nomenclature.
Table UF-27. For nonferrous materials except (b) Torispherical Heads. The minimum required
zirconium, the value of ERT shall be taken from thickness of a torispherical head having 0.002 t / L
Section II, Part D, Tables TM-2, TM-3, TM-4, 0.06 shall be larger of the thicknesses calculated by
or TM-5. For zirconium, the value of ERT shall the following formulas (1) and (2).
be taken from Section II, Part D, Figures NFZ-
1 and NFZ-2. PLM
tp (1)
ETp Modulus of elasticity at maximum design tem- 2SE 0.2P
perature, psi. The value of ET for ferrous materi-
als shall be taken from Table UF-27. For nonfer-
3PLKERT
rous materials except zirconium, the value of tp (2)
4SaET
ET shall be taken from Section II, Part D, Tables
TM-2, TM-3, TM-4, or TM-5. For zirconium,
the value of ET shall be taken from Section The value of Sa shall be 115,000 psi for all ferrous
II, Part D, Figures NFZ-1 and NFZ-2. If the and nonferrous materials except for aluminum, alumi-
maximum design temperature is greater than num alloys, copper, copper alloys, titanium and zirco-
that shown in the above tables or figures, then nium, for which the value of Sa shall be calculated by
use the value of ET corresponding to the maxi- the following formula (3).
mum temperature given in the above tables or
figures. 115,000 ERT
Sa p (3)
hp one-half of the length of the inside minor axis 30 106
of the ellipsoidal head, or the inside depth of
the ellipsoidal head measured from the tangent The value of M shall be obtained from Table 1.
line (head-bend line), in. Interpolation may be used for r / D values which fall
D/2hp ratio of the major to the minor axis of ellipsoidal within the range of the tabulated values. No extrapola-
heads, which equals the inside diameter of the tion of the values is permitted.

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 CASE (continued)

2260
CASES OF ASME BOILER AND PRESSURE VESSEL CODE

TABLE 2 TABLE 3
MAXIMUM METAL TEMPERATURE
K for K for K for K for K for K for
r/D p r/D p r/D p r/D p r/D p r/D p Table in Which
t/L 0.06 0.08 0.10 0.14 0.17 0.20 Material is Listed Temperature, F
0.002 7.87 6.29 5.24 3.95 3.31 2.81 UCS-23 700
0.004 6.77 5.60 4.69 3.49 2.93 2.50 UNF-23.1 300
0.006 6.04 5.14 4.38 3.27 2.73 2.33 UNF-23.2 150
0.008 5.51 4.78 4.14 3.13 2.60 2.21 UNF-23.3 900
0.010 5.11 4.49 3.93 3.02 2.51 2.13 UNF-23.4 600
0.012 4.79 4.25 3.76 2.93 2.44 2.06 UNF-23.5 600
0.016 4.31 3.87 3.47 2.77 2.33 1.97 UHA-23 800
0.020 3.96 3.58 3.24 2.63 2.24 1.91 UHT-23 700
0.030 3.48 3.10 2.84 2.37 2.07 1.79
0.040 3.32 2.97 2.69 2.23 1.95 1.72
0.060 3.12 2.80 2.56 2.17 1.92 1.71

outside a circle whose center coincides with the center

of the head and whose diameter is equal to 80% of
the head inside diameter.
The value of K shall be obtained from Table 2. (f) This Case has been developed for fatigue life
Interpolation may be used for r / D values which fall of 400 full pressure range cycles with nonintegral
within the range of the tabulated values. No extrapola- attachments and 1000 full pressure range cycles with
tion of the values is permitted. integral attachments. See U-2(g) for design of heads
For designs where t / L > 0.06, the rules of UG-32(f) exceeding the above fatigue life.
or 1-3 shall be used. In 1-3 formulas (1) and (2), R (g) The rules of this Code Case may result in rela-
shall be replaced with L . tively high local strains in the knuckle. The effect of
(c) Ellipsoidal Heads. The minimum required thick- these high strains in areas where structural attachments
ness of an ellipsoidal head with D /2h ratio less than are located shall be considered. See U-2(g).
or equal to 2.0 shall be established as an equivalent (h) This Case shall not be used for Part UCI and
torispherical head using the rules given in (b) above. Part UCD heads.
An acceptable approximation of a 2:1 ellipsoidal head (i) The maximum design temperature shall not ex-
is one with a knuckle radius of 0.17D and a spherical ceed the maximum temperature limit specified in Ta-
radius of 0.9D . ble 3.
(d) The requirement of UHT-32 does not apply. (j) All other applicable Code requirements including
(e) Size of the finished openings in the knuckle area those of UG-32 shall be met.
shall not exceed the lesser of 238 in. or 0.5 r. For an (k) This Case number shall be shown on the Manufac-
ellipsoidal head, the knuckle area is the area located turers Data Report.

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