Life time extension of offshore pipelines
INTRODUCTION - LIFE TIME EXTENSION OF OFFSHORE PIPELINES
The Mining Act (Mijnbouwwet) in the Netherlands requires that an offshore pipeline may only be used if certified by a competent assessment institute. A life expectancy is included in the initial design of the pipeline. If the age of the tube has exceeded this expectation, it should no longer be used. A Lifetime Extension Assessment (LTE) can prove that the pipe can still be used safely for some years. Bureau Veritas has more than 30 years of experience in conducting LTE assessments on flexible and rigid pipelines.
The steps of the Life Time Extension Assessment are similar to those of design review for a new pipeline. A customer LTE study must show how many years the pipeline can still remain in use, safe for humans and the environment. In this study, the customer must include the following aspects:
a. Inventory and study of existing data:
- Basis of the initial pipeline design
- Data on the position of the pipeline during its lifetime, including corners in the pipeline (static load), and relevant data on water depth, flow, soil and seawater
- Adjustments or repairs during service life
- Cathodic protection or other corrosion protection systems
- All inspection documents of the pipelines, including conducted undersea inspections, NDT inspections, hydrostatic tests and visual inspection
- Operational conditions during its lifetime, including the presence of H2S and CO2 in the transported medium, working pressure, chemicals used and temperature.
- Reviews of the Pipeline Integrity Management System
b. Sometimes there are insufficient data to do the study. Then additional tests are needed, for example strength tests, material tests or intelligent pig runs.
c. After this, the organisation provides an assumption report on the assumption of the remaining life of the pipeline. Bureau Veritas will review and test this report and its study against the relevant standards in the field of LTE studies.
After successfully completing the above steps, Bureau Veritas issues two documents, the Fitness For Purpose Assessment Report of the Pipeline and the Declaration of Lifetime Extension of the Pipeline