Optimizing Analysis Methodology for HPHT Equipment

The American Petroleum Institute (API) is continuing to develop technical reports, guidelines and standards for the construction of high-pressure, high-temperature (HPHT) equipment for offshore oil and gas exploration and production. HPHT is considered to be equipment with a pressure rating greater than 103 MPa (15,000 psi) and/or a temperature rating greater than 177°C (350°F). One alternative in the evolving API standards is to use the analysis methodology in ASME Section VIII, Division 3, including fracture mechanics, for determination of the static pressure rating and the design fatigue life. However, detailed requirements for finite element analysis (FEA) parameters such as element type and mesh density are not specified. In addition, specific requirements for fracture mechanics analysis are not provided. This paper explores the effect of variations in those parameters on the calculated static pressure rating and the design fatigue life and gives recommendations for optimizing the parameters of the design itself (e.g. blend radii at transitions) and the analysis considering the required accuracy of the result, analysis time and cost.