CAN/CSA-Z662 Piping Code Calculations

Note: Please see the following AutoPIPE help section: 

Help > Contents> Contents Tab> Reference Information> Code Compliance Calculations> select a piping code to see the calculations performed by AutoPIPE.

General notes:

Combination name: Equiv1

1. AutoPIPE calculates the Equivalent Tensile stress 1 (CSA Z662-07 clause 4.7.1 Combined hoop and longitudinal stresses) meant for restrained portions of a pipeline (exclude bending, torsion and shear stresses)

2. In order to obtain consistent results for Equivalent Tensile 1 , a pressure extension analysis should be performed (enable the pressure extension analysis option on the Analysis Set dialog for the analysis set). This type of static analysis insures that the axial pressure forces, which can be substantial in axially restrained system, is included in the stress calculations.

3. AutoPIPE uses the built-in category maximum case (EXP) which instructs the program to use the forces and moments from the expansion case with maximum temperature (which generally will result in maximum forces and moments) in an analysis set.

4. Longitudinal pressure calculations always use P*AP/AS formula, and the pressure area term AP always used corroded inside diameter (where AP  =  Pressure area of pipe, AS = Cross sectional area of pipe, P = Design internal pressure).

5. Internally, AutoPIPE uses Tresca criterion with no bending, shear or torsional stress to calculate Equivalent Tensile 1 stresses.

6. AutoPIPE considers compressive axial pipe force as negative, for example if the axial pipe forces due to gravity and expansion are compressive, then the stresses due to gravity and expansion will be added to the Longitudinal Pressure stress (causing compressive axial pipe force). Otherwise, if the axial stress due to gravity and expansion forces is tensile in nature, then this stress will be subtracted from the Longitudinal Pressure Stress.

6. When pressure extension analysis is performed, AutoPIPE will subtract the stress due to axial pressure force from the longitudinal pressure stress

Comments, Questions, and Answers on CAN/CSA-Z662 Piping Code Calculations

Item #1: When reviewing the code equation Equiv1, appears that the value is exactly the same as Hoop. Why is AutoPipe not considering the longitudinal term of the equation in 4.7.1?

Item #2: The longitudinal stress calculated following the program documentation does not match the results, why not?

Item #3: Does Equiv2 or Tensile 2 which captures the compliance to CSA Z662 Clause only capturing the bending stresses due to thermal expansion?

Item #4: What is the reasoning for taking only gravity and thermal expansion bending moments into account for Equiv2 and not pressure?

Item #5: Why are the CSA-Z662 Longitudinal stress calculation on the intermediate soil points over-stress in  results?

Item #6: Is it possible to break the stresses down into a longitudinal component and a bending component and get the results for each per CSA Z662 piping codes?

Item #7: Restrained Piping - Internal Pressure Effects

See Also

Piping Code Calculations

Bentley AutoPIPE