Pipe stress analysis is an analytical method to determine how a piping system behaves based on its material, pressure, temperature, fluid, and support. Pipe stress analysis is not an accurate depiction of the piping behavior, but it is a good approximation.
The analytical method can be by inspection, simple to complex hand calculations, or a computer model. The computer models can vary from 1-D beam elements to complex, finite element models. For instance, if it is a water system with no outside forces applied to the piping system, inspection or hand calculations are usually sufficient. If it is a high-pressure, high-temperature, hazardous-fluids system, and/or large outside forces are applied to the piping system, a computer-aided model may be required.
Understanding pipe stress analysis software does not make for a solid foundation of pipe stress analysis. It’s important to understand the various types of pipe stresses, the process, and other items related to pipe stress analysis for best practices in performing a pipe stress analysis.
There are many piping codes and standards that could be used during a pipe stress analysis depending on the application (power, process chemical, gas distribution) and location (country or local jurisdiction). However, to keep things simple, this discussion is based on American Society of Mechanical Engineers (ASME) B31.1 Power Piping. The physics of pipe stress analysis does not change with piping code.
Pipe stress analysis should be done primarily to provide safety to the public, whether you are designing a building heating system or a high-pressure gas line in a refinery. Public safety is paramount. The National Society of Professional Engineers (NSPE) Code of Ethics’ first cannon is: “Hold paramount the safety, health, and welfare of the public.”On a good day, a pipe failure is only a broken support that the owner does not call the designer/engineer about. On a bad day, the owner requires the designer/engineer to pay for the damage and the engineer to provide a solution for free. On a horrible day, someone is killed.
Another reason a pipe stress analysis is performed is to increase the life of piping. Most engineers won’t consider a piece of pipe to be equipment, but it is no different than a pump. Both have moving parts and must be designed and maintained properly to ensure a proper life. Pipe stress analysis also is used to protect equipment, because a pipe is nothing more than a big lever arm connected to a delicate piece of equipment. If not properly supported and designed, it can have devastating effects on that equipment.