ASME pressure vessel calculations

The ASME pressure vessel rupture stress formula is applied to calculate a vessel stress is S = P(R+0.6t)Et Where ... 

Hechmer and Hollinger have proposed ten guidelines on the evaluation of stresses in pressure vessels calculated by finite-element method in the spirit of the ASME Boiler and Pressure Vessel Code. ... 

The ASME pressure vessel stress formula to calculate the applied vessel stress is ... 

There are many opinions regarding the use of Division 1 versus Division 2, but the bottom line is economics. In the article ASME Pressure-Vessel Code Which Division to Choose , the authors have listed a number of factors for consideration. Division 1 uses approximate formulas, charts, and graphs in simple calculations. Division 2, on the other hand, uses a complex method of formulas, charts, and design-by-analysis which must be described in a stress report. Sometimes so many additional requirements are added to (he minimum specifications of a Division 1 vessel that it might be more economical to supply a Division 2 vessel and take advantage of the higher allowalilc stresses. 

Venter, A.M., Troiano, E Hyland, E.J., and Parker, A.P. (2007) Hill stress calculations for autofrettaged tubes compared with neutron diffraction residual stresses and measured yield pressure and fatigue life. ASME Pressure Vessel and Piping Division Conference, July 22-26, 2007, San Antonio, TX, Paper No. PVP 2007-26617. 

The coefficient of discharge method (Kj = 0.62) was specified to calculate the capacity of the rupture disc device. However, the validity of this method is limited to a disc mounted close to the pressure vessel and the discharging to atmosphere. The ASME Code provides guidance for the limited use of this method ... 

Maximum Allowable Working Pressure (MAWP) the maximum pressure pounds per square inch gauge permissible at the top of a completed vessel in its operating position for a specific designated temperature corresponding to the MAWP pressure. This pressure is calculated in accordance with the ASME code (Par. UG-98) [1] for all parts or elements of the vessel using closest next larger to calculated value nominal thickness (closest standard for steel... 

A new ASME code for calculating high pressure vessels (Sect VIII Div. 3) is based on the formulae to determine the internal pressure pcompi-pi for complete plastic yielding through the full wall with some assumptions, e.g. perfectly elastic-plastic material behavior and the GE-hypothesis [2]. 

ASME Section I SRVs are devices designed to protect power boilers during an overpressure event. Only the U.S. code addresses this sizing separately. PED, on the other hand, makes no distinction between fired and unftred pressure vessels and the method as per Section 8.3 can be used. Here we give the calculation only in metric units. 

This was a chemical plant that only purchased high quality ASME-coded pressure vessels and had a staff of engineers who could easily calculate maximum allowable design pressures. Chemical plant supervisors must be clear on instructions and be vigilant about craftsmen changing the scope of the job, especially during the off-shifts, when supervision may be very limited. 

When an estimator costs pressure vessels such as reactors and distillation columns, care must be taken to ensure that the wall thickness is adequate. The default method in IPE calculates the wall thickness required based on the ASME Boiler and Pressure Vessel Code Section VIII Division 1 method for the case where the wall thickness is governed by containment of internal pressure (see Chapter 13 for details of this method). If other loads govern the design, then the IPE software can significantly underestimate the vessel cost. This is particularly important for vessels that operate at pressures below 5 bara, where the required wall thickness is likely to be influenced by dead weight loads and bending moments from the vessel supports, and for tall vessels such as distillation columns and large packed-bed reactors, where wind loads may... 

Proof stress is the stress to cause a specified permanent extension, usually 0.1%. The maximum allowable stress specified by the ASME Boiler and Pressure Vessel (BPV) Code is calculated from these and other material properties at the design temperature, and allows for suitable safety factors. The basis for establishing maximum allowable stress values is discussed in Chapter 13 and is described in detail in the ASME BPV Code Section 11 Part D, Mandatory Appendix 1. 

Pressure vessels are subjected to other loads in addition to pressure (see Section 13.4.7) and must be designed to withstand the worst combination of loading without failure. It is not practical to give an explicit relationship for the vessel thickness to resist combined loads. A trial thickness must be assumed (based on that calculated for pressure alone) and the resultant stress from all loads determined to ensure that the maximum allowable stress intensity is not exceeded at any point. When combined loads are analyzed, the maximum compressive stress must be considered as well as the maximum tensile stress. The maximum allowable stress in compression is different from the maximum allowable stress in tension and is determined using the method given in ASME BPV Code Sec. VIII D.l Part UG-23. 

The national pressure vessel codes and standards require that all pressure vessels be subjected to a pressure test to prove the integrity of the finished vessel (ASME BPV Code Sec. VIIID. 1 Part UG-99). A hydraulic test is normally carried out, but a pneumatic test can be substituted under circumstances where the use of a liquid for testing is not practical. Hydraulic tests are safer because only a small amoimt of energy is stored in the compressed liquid. A standard pressure test is used when the required thickness of the vessel parts can be calculated in accordance with the particular code or standard. The vessel is tested at a pressure 30% above the design pressure. The test pressure is adjusted to allow for the difference in strength of the vessel material at the test temperature compared with the design temperature, and for any corrosion allowance. 

The structure of this formula can quickly be related to the thin-walled pressure vessel cylinder equation. Using the equation that calculates the stress at the center of the vessel wall, ux = P R + 0.5t)/t, and rearranging to solve for the thickness, results m. t = PR/ ux — 0.5P. The addition of the weld joint efficiency, E, and changing the coefficient before P to 0.6 results in the ASME code formula, t = PR/ SE — 0.6P), which they feel best represents the minimum wall thickness required to contain an internal pressure, P, in a cylindrical vessel having a radius, R, and made of a material with an allowable stress, S. 

A comparison of the equations developed above is shown in Fig. 1. Each of the four formulas, referred to as Thin-1, Thin-2, ASME, and Thick-walled, were used to evaluate the stress on the walls of the same hypothetical pressure vessel (with a radius of 2 in. and a pressure of 1000 psi) at various wall thicknesses between 1/8 and 7/8 in. The resultant stresses for the first three formulas were then normalized to the calculated thick-walled vessel stress and plotted to demonstrate the relative accuracy of the various methods. 

Standard calculation forms can save considerable time in pressure vessel design. These forms also systematize the mechanical design procedure to insure that nothing is omitted. Most engineering contractors have developed their own vessel calculation forms. Basically, all are alike in that they correlate, in easy-to-use fashion, the design rules set forth in Section VIII of the ASME Boiler and Pressure Vessel Code for Unfired Pressure Vessels. They also include design considerations not covered by the code, such as wind loading for tall vessels. (Text continues on p. 139.)... 

This calculation leaves out the extra allowance for corrosion, etc., but illustrates the basic approach used in designing pipelines and pressure vessels for internal pressures of as much as 3000 psig (design for external pressures or vacuums is more complicated). For more details see the ASME code [2]. 

The comparisons shown on Charts 1 and 2 are based on the 1956 Revision of Section 8 of the ASME Code for unfired pressure vessels. The clad-steel stress values used are based on the use of the full thickness of the composite plate as permitted by this Code. A factor of safety of 4 is used in all calculations. 

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