Nadia Strikovski Staff Systems Architect, CAESAR II Development Part 1: Load Case Template Usage for the Expansion Stress Range
A typical piping system is subject to various internal and external loading. For proper design of the piping system, two different distinct failure criteria need to be considered—one for primary loads where even a single application may lead to catastrophic failure, and one for secondary loads which lead to fatigue failure.
Primary loads are usually force-driven and include system weight, pressure, and spring forces. Secondary loads are usually displacement-driven, almost always self-limiting and cyclic in nature, and typically include thermal expansion, imposed anchor movements, and vibration. Most piping codes recognize this distinction and recommend evaluating the sustained (SUS) stresses (caused by primary loads) and expansion (EXP) stress ranges (caused by secondary loads), and provide guidance for calculating the stresses and the corresponding allowable stresses for each failure criteria.
Let’s concentrate on the expansion (EXP) stress range and how to set up the appropriate load cases in CAESAR II. Note that the expansion stress range considers the temperature change between two states of the system, where a state is the physical position of the system (with regards to nonlinear restraints and presence of other loads) under the temperature.
One of the most powerful features of the CAESAR II Static Output Processor lies in the ability to filter your output reports. Filtering lets you customize output to just the information you want to see. You can also set filters to catch “issues” such as support lift off. For more information on this, review CAESAR II documentation.