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PASS/NOZZLE-FEM 3.5. Program Manual | |
The code is used only to calculate allowable membrane stress as per [1]. It is defined by tables 1A and 1B as per [1]. Table 1A provides allowable stresses for ferrous materials for Section VIII, Division 1 construction. Table 1B provides allowable stresses for nonferrous materials for Section VIII, Division 1 construction. When tables 1A and 1B are provided value of allowable stress the program applies it:
$$ S = S_{tab}. $$If user materials are not provided by tables 1A and 1B as per [1] then allowable membrane stress is assumed according to table 1-100 of Mandatory Appendix 1 [1] that shown in table 5.9 below.
| Table 5.9. Criteria for Establishing Allowable Stress Values for Tables 1A and 1B | ||||||
| Product/Material | Room Temperature and Below | Above Room Temperature | ||||
| Tensile Strength | Yield Strength | Tensile Strength | Yield Strength | Stress Rupture | Creep Rate | |
| Wrought or cast ferrous and nonferrous | $\displaystyle\frac{S_T}{3.5}$ | $\displaystyle\frac{S_Y}{1.5}$ | $\displaystyle\min\left\{\frac{S_T}{3.5}; \frac{1.1}{3.5}S_T S_T\right\}$ | $\displaystyle\min\left\{\frac{S_Y}{1.5}; \frac{S_Y R_Y}{1.5}\quad or\quad 0.9S_Y R_Y\right\}$ [Note (1)] | $\min\left(F_{avg}S_{R avg}, 0.8S_{R min}\right)$ | $1.0 S_{C}$ |
| Welded pipe or tube, ferrous and nonferrous | $\displaystyle\frac{0.85 S_T}{3.5}$ | $\displaystyle\frac{0.85 S_Y}{1.5}$ | $\displaystyle 0.85\min\left\{\frac{S_T}{3.5}; \frac{1.1}{3.5}S_T S_T\right\}$ | $\displaystyle 0.85\min\left\{\frac{S_Y}{1.5}; \frac{S_Y R_Y}{1.5}\quad or\quad 0.9S_Y R_Y\right\}$ [Note (1)] | $\displaystyle 0.85\min\left(F_{avg}S_{R avg}, 0.8S_{R min}\right)$ | $0.85 S_{C}$ |
| NOTE (1): Two sets of allowable stress values may be provided for austenitic stainless steels in Table 1A; and nickel alloys, copper alloys, and cobalt alloys in Table 1B; having an SY/ST ratio less than 0.625. The lower values are not specifically identified by a footnote. These lower values do not exceed two-thirds of the yield strength at temperature. The higher alternative allowable stresses are identified by a footnote. These higher stresses may exceed two-thirds but do not exceed 90% of the yield strength at temperature. The higher values should be used only where slightly higher deformation is not in itself objectionable. These higher stresses are not recommended for the design of flanges or for other strain-sensitive applications. | ||||||
Nomenclature for this table 5.9 is as follows:
| 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 time-to-rupture versus log stress plot at 100 000 h such that log [Favg]=1/n, but Favg may not exceed 0.67. |
| n | = | a negative number equal to Δlog time-to-rupture divided by Δlog stress at 100 000 h |
| 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. |
| SR avg | = | average stress to cause rupture at the end of 100 000 h. |
| SR min | = | minimum stress to cause rupture at the end of 100 000 h. |
| ST | = | specified minimum tensile strength at room temperature. |
| Sy | = | specified minimum yield strength at room temperature. |
Other allowable stresses and strength assessment are provided in according to ASME BPVC VIII.2 [4].
PASS/NOZZLE-FEM 3.5. Program Manual
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