Reliability and Maintainability of In-Service Pipelines

Mojtaba Mahmoodian

• Publisher: Gulf Professional Publishing
• Year: 2018
• Print ISBN: 9780128135785
• eBook ISBN: 9780128135792
• Topic: Physical Sciences
• Subtopic: Energy

Reliability and Maintainability of In-Service Pipelines helps engineers understand the best structural analysis methods and more accurately predict the life of their pipeline assets. Expanded to cover real case studies from oil and gas, sewer and water pipes, this reference also explains inline inspection and how the practice influences reliability analysis, along with various reliability models beyond the well-known Monte Carlo method. Encompassing both numerical and analytical methods in structural reliability analysis, this book gives engineers a stronger point of reference covering both pipeline maintenance and monitoring techniques in a single resource.- Provides tactics on cost-effective pipeline integrity management decisions and strategy for a variety of different pipes- Presents readers with rational tools for strengthening and rehabing existing pipelines- Teaches how to optimize materials selection and design parameters for designing future pipelines with a longer service life

Chapter 1

Introduction

Abstract

This chapter introduces the most common type of pipelines used in industry. Pipes categorized based on their material type and their areas of usage as well as their overall characteristics are mentioned.

At the first step of reliability analysis and service life prediction of pipelines, it is necessary to gain knowledge about the design principles and loads affecting buried pipes. The performance criteria for in-service loads are introduced in this chapter as ultimate limit state and serviceability limit state. Flexural and shear failures are the two main ultimate limit states that are considered in design and assessment. Serviceability limit states may be measured by cracking condition. These criteria should be met for a pipeline to be safe and in-service. This chapter reviews the loads and stresses acting on pipelines. The stress formulations will be used later on in reliability analysis, where the limit state function (failure mode) is checked.

Material deterioration is the most common form of pipeline deterioration and is a matter of concern for both the strength and durability functions. How to incorporate the effect of corrosion in the structural analysis of a pipeline is of practical importance. This chapter outlines the corrosion formulation for different pipe types. This knowledge will be used in Chapter 2 for suggesting efficient methods for inspection and maintenance of in-service pipelines as well as in Chapter 4 for formulation of failure function(s) in time-dependent reliability analysis methods.

Keywords

Pipe material; pipe design; loading on pipes; pipe deterioration; reinforcement corrosion; steel corrosion

Chapter Outline

• 1.1 Background 2
• 1.2 Scopes of Pipeline Reliability Analysis 4
• 1.3 Types of Pipelines 5
  • 1.3.1 Metallic Pipelines 8
  • 1.3.2 Nonmetallic Pipes 11
• 1.4 Design of Buried Pipelines 15
• 1.5 Loads and Stresses on Pipelines 22
  • 1.5.1 Loads on Pipelines 22
  • 1.5.2 Stress in Buried Pipelines 25
• 1.6 Deterioration of Pipes 28
  • 1.6.1 Deterioration of Concrete Pipes 29
  • 1.6.2 Deterioration of Ferrous Pipes 36
  • 1.6.3 Deterioration of Plastic Pipes 42
  • 1.6.4 Deterioration of Other Types of Pipes 44
• References 45
• Further Reading 48

1.1 Background

Pipelines are widely used engineering structures for the collection, conveyance, and distribution of fluid in different areas from rural and urban regions to marine areas. Most of the time, pipelines are placed underground, surcharged by soil weight and traffic loads. Evidently, underground pipelines are required to resist the influence of the external loads (soil and traffic), internal fluid pressure, as well as environmental loads. Buried pipelines are subject to chemical and mechanical loading in their environment of service and these stresses cause failure that is costly to repair.

In many cases underground pipelines are required to withstand particular environmental hazards. Corrosion of pipe material is the most common form of pipeline deterioration and should be considered in both strength and serviceability analysis of buried pipes (Ahammed and Melchers, 1997; Sharma et al., 2008).

According to “The World Factbook” (2010), the United States has approximately 800,000 km and Russia has 252,000 km of pipes transporting products like crude oil, natural gas, and petroleum products. The statistics for the United Kingdom and Australia are 20,000 and 32,000 km, respectively. More than half of the US oil and gas pipeline network is over 40 years old and corrosion has caused 23% and 39% of failures of oil and gas pipelines, respectively (Anon, 2002).

Twenty percent of Russia’s oil and gas system is almost at the end of its design life and it is expected that in 15 years time, 50% of their pipelines will be at the end of their design life (Mahmoodian and Li, 2017).

In Canada, there are 34,000 km of oil pipelines and 26,000 km of gas pipelines where the prevention of corrosion-related failures at reasonable costs is also the main concern (Sinha and Pandey, 2002).

“The Water Infrastructure Network” reported the annual cost for maintenance and operation of the US national drinking water system at US$38.5 billion per year, which includes corrosion costs of US$19.25 billion (WIN, 2000). A study undertaken by The Water Services Association of Australia reveals that aggregated annual corrosion cost to the Australian urban water industry is approximately US$736 million (WSAA, 2009).

In the United Kingdom there are approximately 310,000 km of sewer pipes with an estimated total asset value of £110 billion (OFWAT, 2002). The investment for repair and maintenance of this infrastructure is approximately £40 billion for the period of 1990–2015 (The Urban Waste Water Treatment Directive, 91/271/EEC, 2012). It has been known that sewer collapses are predominantly caused by the deterioration of the pipes. For cementitious sewers, sulfide corrosion is the primary cause of these collapses (Pomeroy, 1976; ASCE (69), 2007).

In Los Angeles, USA, approximately 10% of the sewer pipes are subject to significant sulfide corrosion, and the costs for the rehabilitation of these pipelines are roughly estimated at £325 million (Zhang et al., 2008). As an example of a European country, in Belgium, the cost of sulfide corrosion of sewers is estimated at £4 million per year, representing about 10% of total cost for wastewater collection and treatment systems (Vincke, 2002).

These statistics indicate that pipeline networks are faced with high emergency repair and renewal costs, and frequent charges arising from increasing rates of deterioration worldwide. On the other hand, budget limitations are significantly restricting pipeline networks and reducing their capabilities in terms of addressing these needs. Large investments are required for building new pipelines networks. It is unlikely to be able to replace the existing pipe infrastructure completely over a short period of time. There...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Dedication
• Acknowledgements
• Chapter 1. Introduction
• Chapter 2. Pipeline Inspection and Maintenance
• Chapter 3. Methods for Structural Reliability Analysis
• Chapter 4. Time-Dependent Reliability Analysis
• Chapter 5. Case Studies on the Application of Structural Reliability Analysis Methods
• Index