TABLE OF CONTENTS Some equations and design concepts are presented in this section to give the evaluator who is not already familiar with pipeline design methods a feel for some of the commonly used formulas. This section is not intended to replace a design manual or design methodology. Used with the corresponding risk evaluation sections, this appendix can assist the nonengineer in understanding design aspects of the pipeline being examined.
Minimum pipeline wall thicknesses are determined based on the amount of stress that the pipe must withstand. Design stresses are determined by careful consideration of all loadings to which the pipeline will be subjected. Loadings are not limited to physical weights such as soil and traffic over the line. A typical analysis of anticipated loads for a buried pipeline would include allowances for:
Internal pressure
Surge pressures
Soil loadings (including soil movements)
Traffic loadings.
Additional criteria are considered for special installation circumstances such as drilled crossing and overhead spans. These criteria include
Bending Stresses (Overhead crossings and Drilled Crossings)
Tensile Loads (Drilled Crossings)
Bouyancy.
For each of these loadings, failure must be defined and all failure modes must be identified. Failure is often defined as permanent deformation of the pipe. After permanent deformation, the pipe may no longer be suitable for the service intended. Permanent deformation occurs through failure modes such as bending, buckling, crushing, rupture, bulging, and tearing. In engineering terms, these relate to stresses of shear, compression, torsion, and tension. These stresses are...
