Det Norske Veritas - Germanischer Lloyd

Corroded pipelines
 N DNV-RP-F101

Annotation

Introduction

This Recommended Practice (RP) document provides recommendations for assessing pipelines containing corrosion defects subjected to:

- Internal pressure loading only.

- Internal pressure loading combined with longitudinal compressive stresses.

Two alternative approaches to perform the assessment of corrosion defects are described, 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 Sec.3 (Part A), includes calibrated safety factors taking into account the natural spread in material properties, 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 the determination of the pressure resistance (capacity). This part of the recommended practice is also a supplement to DNV-OS-F101. Probabilistically calibrated equations (with partial safety factors) for the determination of the pressure resistance of a corroded pipeline are given.

- The second approach, given in Sec.4 (Part B), is based on the Allowable Stress Design (ASD) 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.