ASME BPVC 2023 Section II part D (metric)

MANDATORY APPENDIX 1
BASIS FOR ESTABLISHING STRESS VALUES IN TABLES 1A AND 1B
1-100 DERIVATION OF ALLOWABLE STRESS
VALUES
The values in Tables 1A and 1B are established by the
Committee only. In the determination of allowable stress
values for materials, the Committee is guided by successful
experience in service, insofar as evidence of satisfactory
performance is available. Such evidence is considered
equivalent to test data where operating conditions are
known with reasonable certainty. In the evaluation of
new materials, the Committee is guided to a certain extent
by the comparison of test information with available data
on successful applications of similar materials.
Nomenclature:
Favg = multiplier applied to average stress for rupture
in 100 000 h. At 815°C and below, Favg = 0.67.
Above 815°C, it is determined from the slope
of the log timetorupture versus log stress plot
at 100 000 h such that log Favg = 1/n, but it
may not exceed 0.67.
RT = ratio of the average temperature dependent
trend curve value of tensile strength to the
room temperature tensile strength
RY = ratio of the average temperature dependent
trend curve value of yield strength to the room
temperature yield strength
SC = average stress to produce a creep rate of
0.01/1 000 h
SRavg = average stress to cause rupture at the end of
100 000 h
SRmin = minimum stress to cause rupture at the end of
100 000 h
ST = specified minimum tensile strength at room
temperature, MPa
SY = specified minimum yield strength at room temperature,
MPa
n = a negative number equal to log timeto
rupture divided by log stress at 100 000 h
NA = not applicable
The maximum allowable stress shall be the lowest value
obtained from the criteria in Table 1-100 . The mechanical
properties considered, and the factors applied
to establish the maximum allowable stresses, are as given
below.
a At temperatures below the range where creep and
stress rupture strength govern the selection of stresses,
the maximum allowable stress value is the lowest of the
following:
1 the specified minimum tensile strength at room