TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractDrilling industry technology is advancing rapidly. Drillers are encountering downhole pressures over 20,000 psi and temperatures over 450°F. These high pressure high temperature (HPHT) conditions require drilling and completion equipment that is beyond the scope of today's API specifications.API specifications 6A 1 , 16A 2 , 16C 3 , and 17D 4 address the design and design verification methods for drilling equipment. These specifications currently reference the ASME Boiler and Pressure Vessel Code, Section VIII, Division 2 5 (ASME VIII-2) as one of the primary design verification methodologies. API specifications first referenced ASME VIII-2 as a design verification methodology nearly 20 years ago, because it was the best available at that time. This is called the "ASME Method".The ASME Section VIII, Division 3 6 (ASME VIII-3) was developed to give the requirements for the construction of high pressure vessels. ASME VIII-3 was first issued in 1997 and is intended to be used in place of ASME VIII-2 for high pressure vessels, generally in excess of 10,000 psi.The design of drilling and completion equipment should be done using first principles. The authors propose that the designs for 15,000 psi or higher service should be verified using the rules from ASME VIII-3. A significant difference between the two design verification methods is that the user specifies the loading criteria for the performance-based ASME VIII-3. ASME VIII-3 requires cyclic load (fatigue or fracture mechanics) analysis and has limitations in materials, fabrication and inspections, and testing requirements that specifically apply to thick-walled pressure vessels. This paper discusses how the performance-based code methods of ASME VIII-3 can be integrated into API specifications for HPHT drilling and completion equipment.
With advances in computational modeling techniques, limit load methods are gaining wider acceptance as a tool for determining the structural integrity of pressure vessels. The objective of a limit load analysis is to size a vessel or structure considering nonlinear methods such as elastic-plastic material properties and non-linear strain-displacement relations. Case studies are presented in this paper that feature external pressures, gravity, and wind loads. The technique applies an appropriate initial magnitude for each load type and uses the analysis model to increase the load until a lower bound is calculated. The lower bound value is determined by incrementally increasing the load until convergence is not possible then the results are extracted. This paper presents how limit load techniques were used to address the structural integrity of four engineered systems including the structural stability of a corroded tower under wind and vacuum loads, determining the pressure capacity of a pressure vessel, analysis of a subsea vessel under high external pressures, and the remaining buckling resistance of a dented subsea flowline. The paper highlights the application of limit load techniques using criteria detailed in WRC 464.
In this paper, a load factor for use in a limit-load analysis of a pipeline and its components is established. The load factor is based on the ASME pipeline Code’s design margin for the service and location of the installation [1, 2]. These Codes are recognized by 49 CRF192 [3]. A load factor for internal pressure loads can be derived analytically based on the equations of determining design pressure and wall thickness in the ASME B31 piping Codes. Once the load factor is established, the limit-load methodology may be used in a Finite Element Analysis (FEA) of pipelines and related components. Two application examples are presented showing analyses done with Abaqus [4], a commercial, general purpose FEA software package. The first example calculates the design pressure of an X65 pipe given the pipe dimensions (outer diameter and wall thickness). Second example deals with the re-certification of a Y-connector. This paper is not intended to revise or replace any provision of ASME B31.4 and/or B31.8 [1, 2]. Instead, it provides a limit-load approach for assessment with same design margin as the ASME B31 Codes for use in a detailed FEA of pipelines and the associated components.
Stress Engineering Services, Inc. performed a series of analyses for Brown Fintube to determine the mechanical behavior of its high performance 46-inch reactor feed/effluent exchanger. Initial efforts focused on the global behavior of the exchanger subjected to pressure and thermal loads, while the ultimate objective addressed potential leakage in the main body flange. Using finite element analyses incorporating shell, solid, and continuum models, Stress Engineering was able to demonstrate that the sealing load of the flanges could be maintained even with elevated bolt temperatures up to 400°F. Using the methods permitted by the ASME Boiler & Pressure Vessel Code, Section VIII, Division 2, linearized stresses were calculated. All calculated stress intensities were less than the Division 2 allowable stresses. Based upon the results of the analyses, the design of the main body flange also met the stress design criteria per Division 1 of the Code. This project was a clear demonstration on how analysis methods can be used to solve complex engineering problems that include a wide range of variables and operating conditions. The conservative calculation techniques of Division 1 of the Code were also confirmed in this work.
In this paper, a rational stress limit based on the von Mises equivalent stress is established for pipelines subjected to internal pressure. This stress limit is based on the ASME pipeline Code’s design margin for the service and location of the installation [1, 2]. These Codes are recognized by 49 CRF192 [5]. Both capped-end and open end conditions are considered. The single value of stress limits can be derived by classical hand calculations for use in assessing the results of a finite element analysis (FEA). Two application examples are presented showing studies done with the ABAQUS [3], a commercial (FEA) software. A stress limit was first found using classical hand calculations and verified by a simple finite element model. The linearized stresses at some critical locations were then compared to the established stress limit, and multiples, for the assessments of membrane, membrane plus bending, etc. stresses. This paper is not intended to revise or replace any provision of ASME B31.8 [2]. Instead, it provides a rational stress limit that may be used in the assessment of detailed FEA analyses of pipelines and the associated components.
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