A Probabilistic Margin Assessment of the ASME Section III, Division 5 Primary Load Design Rules for Class A Components

This work presents a comprehensive probabilistic margin assessment of the ASME BPVC primary load design rules for Class A components in Section III Division 5. This work evaluates the design margin of several of the Class A materials for a simple, but representative, component geometry across the entire Division 5 elevated temperature range. The margin assessment applies a probabilistic life prediction methodology developed in previous work that accounts for the variability in material strength and deformation. A Gaussian process fit captures the the strength variability, and a Monte Carlo approach accounts for the variability of steady-state creep deformation parameters leading to variability in the stresses developed in a component. A very efficient method based on the analogy between very viscous Stokes flow to steady-state creeping solid determines the steady-state stress distribution under primary load for the Monte Carlo approach. This work is therefore capable of efficiently evaluating the design margin of several materials across a wide range of temperatures. The probabilistic margin assessment presented in this work gives an insight into the design margin in the currently deterministic ASME Section III, Division 5 primary load design rules for high temperature nuclear components.

Numerical Simulation for Flow of Rolling Piston Type of Rotary Compressor

In this numerical study, the temperature, pressure and flow structure inside the rotary compressor are obtained to analyze the work consumption and efficiency. The geometry of the compressor such as volume, inlet angle, and mass of reed valve are varied to look for optimal performance and design margin as the suggestions for manufacturing. The work done on refrigerant increases proportionally with the volume of the compressor. However, there is an optimal volume for efficiency. The design margin for inlet angle is determined. The best efficiency exists in a specific inlet angle. Larger mass of reed valve leads to the increase of input power due to the additional resistance from greater inertia, which causes a decrease of efficiency. The flow visualization by simulation diagnoses the potential factors, which may cause noise problem.

Discussion of the Background of the Design Margins in API 17TR8 HPHT Design Referencing ASME VIII Division 3

There has been a significant amount of discussion of the appropriateness of the design margins from ASME Boiler and Pressure Vessel Code Section VIII Division 3 being applied to the design of HPHT equipment. A technical report has been issued with a first revision which references the use of ASME Section VIII Division 2 and Section VIII Division 3 for design of HPHT equipment above 15 ksi. Additionally, there has been recent pressure testing which attempted to validate the margins used in ASME Section VIII Division 3 and API 17TR8. There has also been a significant amount of discussion that the equipment in HPHT service may be very different from the pressure equipment which utilizes ASME Section VIII Division 3 and the design methods discussed in the standards. This paper will discuss the background of ASME Section VIII Division 3, including an overview of how the standard began, and the types of equipment which were being considered when the document was first drafted. It will also discuss the background of the design margin used in ASME Section VIII Division 3 over the years and how the current margin came into play. It will also discuss the margins used in addition to the margins on the structural capacity of a piece of equipment and how the margins interrelate within the Code. This paper will demonstrate the robust nature of ASME Section VIII Division 3, and its applicability to the design of HPHT equipment.

A General Comparison of the Design Margins and Design Rules for ASME Section VIII, Divisions 1 and 2

Beginning with the 2017 Edition of the ASME Boiler and Pressure Vessel Code, vessels designed according to the rules of Section VIII, Division 2 shall be designated as either Class 1 or Class 2. One of the key differences between Class 1 and Class 2 is the applicable Design Margin of 3.0 and 2.4 against the Ultimate Tensile Strength of the material, respectively. Vessels designed in accordance to Section VIII, Division 1 have a Design Margin of 3.5 against the Ultimate Tensile Strength of the material. Code Case 2695 allows the vessel designer to utilize the design rules of Section VIII, Division 2 for a Section VIII, Division 1 vessel while maintaining the tensile strength Design Margin of 3.5. However, Design Margins against the Ultimate Tensile Strength of the material are not the only applicable margins that must be considered. This paper reviews the procedure for deriving the allowable stresses of materials under tensile loading based on the required Design Margins for each Division and Class with some historical background provided. Discussion and comparisons of some of the relevant differences between the design rules of Section VIII, Division 1 and 2 and how the differing Design Margins affect the component design is presented. Carbon Steel with joint efficiencies of 1.0 are used for simplicity.