Design Method Combining API and ASME Codes for Subsea Equipment for HP/HT Conditions up to 25,000-psi Pressure and 400°F Temperature
A current challenge in the offshore industry is the design of subsea equipment for pressures exceeding 15,000 psi and temperatures exceeding 250°F. This combination of pressure and temperature has been fairly accepted as the start of the high-pressure/high-temperature (HP/HT) region. The current American Petroleum Institute (API) standard for designing subsea equipment, API Specification (SPEC) 17D (2011), is limited to a working pressure of 15,000 psi and provides little guidance on temperature conditions exceeding 250°F. This paper demonstrates a design methodology that combines the API and American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessels Code (BPVC) for designing an example subsea pressure containing component for HP/HT conditions greater than 15,000 psi and 250°F.
This paper shows the evaluation of a combined load-capacity chart for an API SPEC 17D flange flow-loop [API SPEC 6A (2010), 4 in., 20 ksi] for a design pressure of 20,000 psi and a temperature of 350°F with external tension and bending loads. Both the linear elastic and elastic plastic methods for protection against plastic collapse are used to determine the structural capacity of the flange body. These methods combine the API material and design allowables and ASME design methods. Stress classification and linearization are used for the evaluation of design capacities with linear methods. Modified load-resistance design factors are used both to evaluate design capacities and to account for the difference in ASME and API hydrostatic-test pressures with elastic plastic methods. The structural capacity is combined with thermal analysis to determine the effects of high temperature on the flange capacity. To assess the cyclic-loading capacity of the flange, stress-based fatigue analysis and fracture-mechanics analysis are also compared.
The results obtained are comparable to existing API Technical Report (TR) 6AF1 (1998) charts. This work has been performed to demonstrate both the acceptance of existing methods for HP/HT conditions and to introduce the advanced ASME design methods for designing API SPEC 17D subsea equipment. The methods presented are acceptable for designing equipment for working pressures up to 25,000 psi and temperatures up to 400°F.
Equinor Awards Milestone Wireless Subsea Drone Contract
The $43-million deal with Saipem will utilize a wireless underwater intervention drone and an ROV for intervention work on the Njord field in the Norwegian North Sea. Equinor said the contract is the first ever from an operator for advanced wireless drone services.
Equinor Installs Templates for Troll, Other North Sea Fields
After seeing a significant increase in the price level for subsea equipment, Equinor says it is realizing the ways in which standardized subsea templates help build financial competitiveness. The new standard allowed for the installation of 14 templates in one month.
Subsea Pipelines, Umbilicals Installed for Nova Field
The completion of the subsea installation marks another major step for one of several projects scheduled to tie back to the Gjøa platform in the Norwegian North Sea. Production for the Wintershall Dea-operated project is expected to start up in 2021.
Don't miss out on the latest technology delivered to your email every two weeks. Sign up for the OGF newsletter. If you are not logged in, you will receive a confirmation email that you will need to click on to confirm you want to receive the newsletter.
03 October 2019
08 October 2019
03 October 2019
02 October 2019