What Do Pipelines and Airplanes Have in Common?
Authors: Limon Sergio , Hoeppner David W. , Clark Paul N. , Komorowski Jerzy 
Published: November 2016

In 1958, General Curtis E. LeMay established the structural integrity program for the United States Air Force (USAF). Since then, the USAF has been honing the requirements for extending the service life, durability, and safety of aircraft. These requirements have evolved to include Damage Tolerance principles that encompass the design and the management of aircraft with the objective of reducing maintenance burdens and ensure structural integrity for airworthiness, safety, and mission capability. Recently, requirements of some agencies and companies include Holistic Life Structural Integrity Process (HOLSIP) and concepts aimed at improving the early prediction and detection of structural discontinuities that can pose a safety concern. HOLSIP is intended to reduce the inspection & maintenance cycle while identifying prevention and mitigative measures to be employed. This holistic methodology addresses the total life of components and related issues. It is a physics based approach that incorporates the interaction of known possible degradation mechanisms and their potential failure modes. It provides the basis for analytical, experimental and procedural methods to make structural integrity predictions of components from the design, manufacturing, commissioning, maintenance and inspection intervals that would meet the desired level of safety and reliability. Non-destructive evaluation methods are incorporated in this approach as well. As part of continuing to ensure the safety and reliability of pipelines systems, the energy pipeline industry performs periodic risk assessments and maintenance activities and can enhance current integrity management programs by adopting HOLSIP principles and framework.

In the early 2000s, pipeline industry associations and government regulators published a risk assessment based process for prioritizing pipeline segments for inspection and remediation. These processes have been formally integrated into an Integrity Management Program (IMP). By incorporating risk assessments and periodic inspections as part of the IMP, energy pipeline operators have achieved great success in removing damage that can pose an immediate or short-term safety concern to the public, environment and piping facilities. However, in-service pipeline failures continue to occur suggesting that the treatment of integrity threats, degradation mechanisms and failure modes is still fragmented. There needs to be a strong sense of wholeness in the approach to managing pipeline integrity. The absence of this can lead to unnecessary inspections and assessments, early pipeline retirements, over conservative assumptions or worse, further in-service accidents.

As energy pipelines around the world continue to age and their safe performance is expected to increase, the need for HOLSIP becomes more apparent. This paper provides an overview of the fundamental principles and concepts of a holistic approach developed for maintaining aircraft fleets and how they apply to structural integrity engineering assessments for pipelines. A comparison with the current pipeline integrity management practices and regulations is highlighted.