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API STD 530-2004 pdf free download

API STD 530-2004 pdf free download.Calculation of Heater-Tube Thickness in Petroleum Refineries.
3.6 elastic allowable stress time-independent allowable stress σ el Allowable stress for the elastic range. See 6.2. 3.7 elastic design pressure p el Maximum pressure that the heater coil can sustain for short periods of time. NOTE This pressure is usually related to relief-valve settings, pump shut-in pressures, etc. 3.8 equivalent tube metal temperature T eq Calculated constant metal temperature that in a specified period of time produces the same creep damage as does a changing metal temperature. NOTE The equivalent tube metal temperature concept is described in more detail in 5.8. It provides a procedure to calculate the equivalent tube metal temperature based on a linear change of tube metal temperature from start-of-run to end-of-run. 3.9 inside diameter Inside diameter of a tube with the corrosion allowance removed; used in the design calculations. NOTE The inside diameter of an as-cast tube is the inside diameter of the tube with the porosity and corrosion allowances removed. 3.10 minimum thickness δ min Minimum required thickness of a new tube, taking into account all appropriate allowances. NOTE See 5.4, Equation (5). 3.11 outside diameter D o Outside diameter of a new tube. 3.12 rupture allowable stress time-dependent allowable stress σ r Allowable stress for the creep-rupture range. See 5.4.
3.13 rupture design pressure p r Maximum operating pressure that the coil section can sustain during normal operation. 3.14 rupture exponent n Parameter used for design in the creep-rupture range. NOTE See Figures E.2 through E.65 and Tables E.1 through E.22 (and Figures F.2 through F.65 and Tables F.1 through F.22). 3.15 stress thickness δ σ Thickness, excluding all thickness allowances, calculated from an equation that uses an allowable stress. 3.16 temperature allowance T A Part of the design metal temperature that is included for process- or flue-gas mal-distribution, operating unknowns, and design inaccuracies. NOTE The temperature allowance is added to the calculated maximum tube metal temperature or to the equivalent tube metal temperature to obtain the design metal temperature (see 3.5). 4 General Design Information 4.1 Information Required The design parameters (design pressures, design fluid temperature, corrosion allowance, and tube material) shall be defined. In addition, the following information shall be furnished: a) design life of the heater tube; b) whether the equivalent-temperature concept is to be applied and, if so, the operating conditions at the start and at the end of the run; c) temperature allowance (see ANSI/API 560), if any; d) corrosion fraction (if different from that shown in Figure 1); e) whether elastic-range thermal-stress limits are to be applied. If any of items a) to e) are not furnished, use the following applicable parameters: ⎯ design life equal to 100,000 hours; ⎯ design metal temperature based on the maximum metal temperature (the equivalent-temperature concept shall not apply); ⎯ temperature allowance equal to 15 °C (25 °F);⎯ corrosion fraction given in Figure 1; ⎯ elastic-range thermal-stress limits. 4.2 Limitations for Design Procedures 4.2.1 The allowable stresses are based on a consideration of yield strength and rupture strength only; plastic or creep strain has not been considered. Using these allowable stresses can result in small permanent strains in some applications; however, these small strains do not affect the safety or operability of heater tubes. 4.2.2 No considerations are included for adverse environmental effects, such as graphitization, carburization or hydrogen attack. Limitations imposed by hydrogen attack may be developed from the Nelson curves in API 941 [4] . 4.2.3 These design procedures have been developed for seamless tubes. They are not applicable to tubes that have a longitudinal weld. ANSI/API 560 allows only seamless tubes. 4.2.4 These design procedures have been developed for thin tubes (tubes with a thickness-to-outside- diameter ratio, δ min /D o , of less than 0.15). Additional considerations can apply to the design of thicker tubes. 4.2.5 No considerations are included for the effects of cyclic pressure or cyclic thermal loading. 4.2.6 Limits for thermal stresses are provided in Annex C. Stresses imposed by tube/fluid weight, supports, end connections, and so forth are not discussed in this standard. 4.2.7 The relationship between temperature, stress, and time to failure (taken here to mean test, service, or design life) is represented by the Larson-Miller Parameter (LMP) as explained 6.6 and in H.5. The limiting design metal temperature ranges for each material for which the LMP applies are shown in Table 5. 4.2.8 The procedures in this standard have been developed for systems in which the heater tubes are subject to an internal pressure that exceeds the external pressure. There are some cases in which a heater tube can be subject to a greater external pressure than the internal pressure.

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