ASME VIII Stress Analysis of a Gas Control Valve
Wilde have carried out rigorous design analysis and assessment procedures on a number of critical gas control valves for offshore applications. For each load case, the valves were assessed to the requirements of ASME VIII Division 2 Pressure vessel code, including fatigue calculations.
Equipment operating in the arduous North Sea environment must be designed and manufactured to the most stringent standards possible with two major factors in mind:
- Safety – of critical importance.
- Reliability – Loss of oil and gas production in the North Sea due to structural failures is expensive.
Wilde carried out rigorous design analysis and assessment procedures on a number of critical gas control valves destined for operation in the TROLL Phase 1 Development. This is located offshore of Bergen, Norway. The valves ranged up to 40 inches in port diameter, operate with pressures up to 255 bar and weigh up to 60 Tonnes.
The largest and most complex finite element model was that of the valve body. This comprised a three dimensional model, using solid 20 node brick elements. Each valve, including internals, was subjected to 40-50 load case to predict the behaviour under all postulated operating and fault conditions.
For each load case, the valves were assessed to the requirements of ASME VIII Division 2 Pressure vessel code, including fatigue calculations. This required stress linearization through sections to obtain the necessary membrane and bending stress components required for the code assessment. In addition, contact studies were undertaken to predict the interaction between the valve body and its internal components.
As a result of this work, several design changes were made and checked using FEA. These changes improved the design safety margins of the valves and hence improved confidence in the design. Test programs were subsequently completed successfully, justifying the confidence made possible through the FEA studies
February 1997
