Stresses in a Piping System Axial Stress, Hoop Stress, Radial Stress, Torsional Stress, Shear Stress, Bending Stress. Sources for the generation of
Stresses in a Piping System
Types of Stress in Pipe stress analysis considers various types of stress, including:
- Axial Stress: Along the length of the pipe.
- Hoop Stress: Circumferential stress due to internal pressure.
- Radial Stress: Stress perpendicular to the longitudinal axis.
- Torsional Stress: Twisting or rotational stress.
- Shear Stress: Stress parallel to the pipe’s cross-section.
- Bending Stress: Stress due to curvature.
Sources for the generation of stress in a Piping System:
- Weight
- Internal/External Pressure
- Temperature change
- Occasional Loads due to the wind, seismic disturbances, PSV discharge, etc.
- Forces due to Vibration.
Sustained Stresses in Piping System
Sustained Stresses are the stresses generated by sustained loads. (e.g. Pressure, Weight). These loads are present continuously throughout plant life. Resistive force arising out of sustained stresses balances the external forces keeping the system in equilibrium. Exceeding sustained allowable stress value causes catastrophic failure of the system.
As per ASME B 31.3, (clause 302.3.5) “ The sum of the longitudinal stresses, SL, in any component in a piping system, due to sustained loads such as pressure and weight, shall not exceed “Sh“. Where Sh=Basic allowable stress at the metal temperature for the operating condition being considered.
Pressure Stresses are taken care of by calculating and selecting the proper pipe thickness. The pressure thickness (t) of a straight pipe can be obtained as per ASME B31.3 from the equation (Clause 304.1.2) mentioned below:
