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.
Supervised Autonomy Bridges the Gap in ROV Inspections
ROVs dominate the world of subsea inspections, maintenance, and repair, but as operators work in a post-downturn economy, autonomous systems have become more in demand. Autonomous inspections are possible today, but how can they help with light and heavy intervention?
Kreuz, Seamec Mobilize Vessel for ONGC Offshore Project
As part of a 2-year deal, the Kreuz Glorious will help with the inspection of offshore jackets in the Arabian Sea. Kreuz will also provide personnel for project management and offshore construction.
C-Innovation Opens New Dock Facility for Subsea Work
The Port Fourchon, Louisiana, facility will serve as the base for the company’s operations in the area. Its subsea services group has performed multiple hydrate remediation projects in the US Gulf of Mexico since its formation.
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.
29 November 2018
27 November 2018
19 November 2018
05 December 2018
20 November 2018