Putting in the simplest form, analysis is just the simplification of real world to an engineer, with a measure of how much assumption is put in the analysis process. Lesser the assumptions; more accurate and close is the result to real world situation. However, stress analysis, in actual practices and from technical perspective isn’t just as easy as it is to write. It involves several complex calculations, consideration of different boundary conditions and many other parameters in order to be able to apply Finite Element Analysis – FEA tools for safer designs according to internationally accepted standards.
A call for safety in pipe designs
There have been instances such as that of Alexander L. Kielland, a submersible oil rig platform in Norwegian North Sea, the worst incident in the area since World War II. One of the causes was higher stress in a certain D6 bracings due to winds and waves, as compared to other horizontal bracings on the platform which led to this catastrophic accident. Although the bracing’s fatigue life was estimated to be about 0.7 to 5 years, the failure occurred since only a little attention was given to installation of hydrophone in the bracing and fatigue cracks propagated from two separate initiation sites. All this was because of lack of inspection of the bracing prior to installation in field.
The reasons originate from the seeds of lack of ability of engineers to study the actual conditions prior to setting of equipment in field. Bridging this gap of analysis in ideal conditions and in real world conditions is critical. Fortunately, today’s best stress analysis engineers, who once started with the drawing boards and umpteen calculations, have adopted modern means of analysis of stress and stress concentration results through computational FEA approach.
Safety according to ASME standards
In spite of knowing and having all the design data, designers often find it challenging to handle large data sets and perform analysis for each of them. Owing to such reasons, stress analyst engineers focus and insist on following the ASME – American Society of Mechanical Engineers standards, internationally accepted and a base of safer designs, in conjugation with FEA tools. Specified rules, standards and regulations for pipe designs such as stress concentration factor, safety factors, considerations for critical sections attracting failure etc. can be found under ASME B31.3. B31.3 that covers pipe stresses for industrial and related applications and borrows heavily from B31.1, which has guidelines for power generation plants. In terms of philosophy and details about the stress analysis, both these codes are quite similar, however, contains minute specifications pertaining to specific applications.
These codes abide by the safety of environment, human operators, and particularly, they avoid large economical losses. It focuses upon the main challenges for designers to be able to understand the real life situation of the component under analysis when clubbed with modern computational FEA tools in software such as ANSYS. The simulation and analysis results lying in the capabilities of the software, essentially closes the gap of real and ideal world to land upon error free design decisions. More than this, engineers are empowered to test several design parameters through parameter based optimization approach within lesser time and eliminates the need to manually select the best design input (for analysis) from a large data set.
Conclusion
Today, engineers are of the opinion that abiding by safety standards and by the means of modern technology tools and software, design analysis process has become simpler, safer and quicker. FEA tools deliver design analysis that is consistent with internationally accepted standards such as ASME. It essentially allows the designer to have an idea of ‘what is happening in real world’ and not only prepare the designs through an ideal software interface.
