1. Stresses in Piping System
Sustained Stress and Expansion Stress are widely used terms in piping stress analysis. The calculated sustained and expansion stresses has to be kept below allowable stress provided in code for all the piping system which needs analysis.
2. Sustained Stress
One of the principal stress caused by weight(pipe weight, insulation weight, fluid weight etc.) and pressure(internal and external) is sustained stress. Sustained stress is crucial and to be kept below the allowable values, reason being it exist throughout the operating cycle. ASME B31 codes provide equations and allowable values to calculate and compare sustained stress.
3. Expansion Stress
Displacement driven ancillary stress in piping system as a result of temperature change or thermal differential from the installed to operating temperature is expansion stress. If free expansion or contraction of system owing to change in temperature from one value to another is restricted, thermal stress will be generated. ASME B31 codes provide equations and allowable values to calculate and compare expansion stress.