scope:

Introduction

This document provides recommended practice for assessing pipelines containing corrosion. Recommendations are given for assessing corrosion defects subjected to:

1) Internal pressure loading only.

2) Internal pressure loading combined with longitudinal compressive stresses.

This Recommended Practice (RP) document describes two alternative approaches to the assessment of corrosion, and the document is divided into two parts. The main difference between the two approaches is in their safety philosophy:

The first approach, given in Part A, includes calibrated safety factors taking into account the natural spread in material properties and wall thickness and internal pressure variations. Uncertainties associated with the sizing of the defect and the specification of the material properties are specifically considered in determination of the allowable operating pressure. This part of the RP is also a supplement to DNV-OS-F101. Probabilistic calibrated equations (with partial safety factors) for the determination of the allowable operating pressure of a corroded pipeline are given.

The second approach, given in Part B, is based on the ASD (Allowable Stress Design) format. The failure pressure (capacity) of the corrosion defect is calculated, and this failure pressure is multiplied by a single usage factor based on the original design factor. Consideration of the uncertainties associated with the sizing of the corrosion defect is left to the judgement of the user.