The FAD and Primary Stress
Primary stresses are those stresses required to satisfy the laws of static equilibrium. They are not self limiting, that is they are not relieved by local yielding or by limits to thermal growth. When performing crack assessments, primary stress affects both the Kr and LPr values from the FAD. As a result, changing primary stress affects the placement of results on both the X and Y axis on the FAD.
INSPECT includes the COMPRESS ASME calculation engine. One benefit of this is that primary stresses are determined using the equipment’s Original Code of Construction. INSPECT contains a database of Older Codes to help evaluate older equipment as well.
INSPECT offers a selection of methods for including primary stress in a Level 2 assessment. Engineers can choose from Automatic Stress Determination as well as user defined Linear, Uniform, Weight (Numerical Integration) and Polynomial stress distributions.
INSPECT automatically determines supplemental loads for cracks orientated in the circumferential direction. Engineers may also override this and specify their own supplemental loading. This is also beneficial for cases where a simple component is modeled and external loads such as Wind or Seismic need to be considered.