Offshore oil and gas wells are being drilled into formations that have pressures up to 200 MPa (30,000 psi) and temperatures over 175°C (350°F). Most of the existing API Standards for pressure equipment, such as valves and blow out preventers (BOPs), are limited to pressures of about 100 MPa (15,000 psi). The design requirements in ASME Section VIII Division 3, Alternative Rules for Construction of High Pressure Vessels (Div. 3), can be adapted for the design of this equipment with some modifications. Since the strength of the materials used in these applications is limited due to environmental cracking concerns, it is necessary to accept some local yielding in areas of stress concentrations. Therefore, it is particularly important to apply the elastic-plastic analysis requirements in Div. 3 with appropriate limits on local strain as well as the robust fracture mechanics based fatigue analysis requirements.
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