Piping Stress Types

Piping code stress types
With regard to stresses, there are three main types of stresses that a designer must check for:

Primary stresses resulting from primary loads (sustained)

• From external loading
• Not self-limiting and cause distortion
• Limit these loads to prevent plastic deformation

Examples of loads: Internal-pressure, Weight.
Sustained stresses must be less than sustained allowable stresses.

Secondary stresses resulting from secondary loads (expansion):

• By displacements constraints
• Self-limiting and cause no distortion
• Limit these loads to prevent fatigue failure

Examples of loads: Thermal load, Transient, Support-movement, Vibration.
Expansion stresses must be less than the thermal allowable stress range.

Peak stresses resulting from occasional loads (occasional)

• Cause the highest stresses but cause no distortion
• Limit these loads to prevent fatigue crack initiation

Examples of loads: Wind, Earthquake, Impact, Fluid-hammers.
Occasional stresses must be less than the occasional allowable stresses.