The theory of stress on the piping system is development of the theory of stress that has developed in mechanics. Definitions that are used as force, moment, stress, strain, and others are same with the definitions used in mechanics. Stress that occurs in piping system can be caused by internal pressure, external pressure, weight of pipe itself, and thermal expansion load in the piping system because of temperature differences. At both pipe stress analysis and mechanics, some terms of stress had been known based on direction as follow:
- Longitudinal stress, the stress along the axis parallel to the direction of the pipe.
- Circumferential stress or hoop stress, the stress with circular direction and direct with circular wall pipe.
- Radial stress, the stress with a direction parallel to the straight line that runs to the axis of pipe and out through the wall pipe.
Stresses that occur in piping system will be totaled and analyzed to take the largest and dominant value of stress to be used as input for stress analysis on piping system. Based on stress equation, from the three type stress above, radial stress has relatively small value, so sometimes that value can be ignored. Longitudinal stress has the largest and dominant value of stress than others so it can be included as an input for the stress analysis. Stress analysis is performed at all points along the pipeline to generate distribution of stress value along the pipeline.