Pipeline Corrosion Integrity Management by Direct Assessment

Integrity management of pipelines is a systematic, comprehensive and integrated approach to proactively counter the threats to pipeline integrity. Pressure testing, in-line inspection and direct assessment methods are used to verify the integrity of a buried pipeline. The Paper Discuses Direct Assessment Methodologies for Hydrocarbon Non Piggable Pipelines. Advantages and Disadvantages of Direct Assessment methodology and DA Protocols. The DA process accomplishes this by utilizing and integrating condition monitoring, effective mitigation, meticulous documentation and timely structured reporting processes. DA is a structured, iterative integrity assessment process through which an operator may be able to assess and evaluate the integrity of a pipeline segment. TIME DEPENDENT THREATS INEVITABLY LED TO NUMEROUS FAILURES WITH A COMMON DEFINING MECHANISM OR SOURCE – CORROSION. This Paper will focus on internal, external and stress corrosion cracking direct assessment along with pre and post assessment, quality assurance, data analysis and integration, and remediation and mitigation activities. This paper will discuss some of the regulatory requirements for Pipeline Integrity Management System.

Deepwater Pipeline Challenges

With the ever-increasing demand of energy in the country, the Indian exploration and production is now compelled to move into deepwater frontiers. The country’s energy reserve is getting exhausted with drying shallow water assets and the mainland is already overwhelmed with the pressure of sustaining the world’s second largest population. Therefore, “the upstream oil and gas fraternity of the country” has to now enter “less explored” Indian deepwater block which has already started with the launch of the NELP block by the government. Although, the world has moved into deepwater long back, the Indian industry is still developing the ways and means to tackle the challenges involved in deep water. This paper presents the insights into design and installation of deepwater pipelines along with case study of Middle East to India Deepwater Pipeline (MEIDP) of M/s SAGE, which shall be laid at a maximum water depth of 3450 m. This paper broadly elucidates the challenges in designing the deepwater pipelines such as requirement of thick-walled line pipes to sustain collapse due to external over-pressure and tensile stresses generated due to installation forces, pipeline route selection and optimization, geo-hazard assessment & mitigation, design against fault line crossings/ seismic design, free span, repair systems, seabed intervention etc. It also covers the additional manufacturing & testing requirements including tighter tolerances for line pipes suitable for deepwater installations. It also highlights the deepwater installation capabilities of Pipe lay Barges for the laying of pipeline in the deepwater to ultra-deep waters along with new evolving testing and commissioning philosophies. This paper intends to bring awareness among the “oil and gas fraternity” regarding challenges involved in deep water pipelines with respect to design, installation etc.

Analyzing Effects of Soil Parameters on Buried Pipe Behavior and Deciding Governing Parameter Using Statistical Approach

One of the most common and practical difficulties a pipeline engineer faces at the initial stage of the project is the lack of Soil survey data. Hence, various soil parameters like soil type, density, friction angle, cohesive pressure, depth of cover, pipe coating etc. are needed to be assumed. The critical designs like anchor block requirement, pipe route changes, support loads which involve a huge cost are required to be ‘Issued for Construction’ based on assumed data. This paper briefly illustrates and compares the results obtained from the two most common buried pipe stress analysis methods viz. ‘American Lifeline Alliance - Appendix B’ (1) and ‘Stress Analysis Methods for Underground Pipelines’ (2) and shows their effects graphically on the various Stress Analysis results like pipe movement, end force, active length (virtual anchor length) and bending stress generated in the buried pipeline. Further, this paper comes up with an unique application of ANOVA, a Statistical method, to find out the most significant soil parameter affecting the said results. The paper explains this method with a solved example. These results are useful for a pipeline engineer to determine the governing soil parameter in the design and thus provide a useful tool to make optimum assumptions in absence of soil data so as to minimize the changes in future design and helps saving the cost of the project due to rework.

The Influence of Diffusible Hydrogen in Weld Metal and Moisture Content Levels in Flux Related With Weld Metal Mechanical Properties in Submerged Arc Welding Process for Line Pipe Manufacturing

The mechanical properties of welding material is correlative with the diffusible hydrogen content in weld metal and level of moisture content in flux. Minitab16program to predict mechanical properties correlated to diffusible hydrogen content in weld metal and level of moisture content in flux, such as yield strength, tensile strength, elongation and average Charpy impact toughness of welding material is established by using submerged arc welding process in line pipe manufacturing. The present paper aims to experiment and investigate the line pipe SAW Flux used for offshore/onshore applications. Flux moisture content has been studied under Karl Fischer Coulometer method. Subsequently, flux was then used to make weld to analysis for ‘diffusible hydrogen content in weld metal’ through mercury displacement method. This detailed study envisages and explains the correlations between the mechanical properties and micro structures of weldments. Evaluating the variance of moisture level in flux and diffusible hydrogen content in weld metal proves the advantage of restricting the moisture content along with good practices to accomplish better weld quality.

Self Directed Integrity Assessment of Non-Piggable Pipelines

The responsibility for managing an asset safely, efficiently and to optimize productivity lies solely with the pipeline operators. To achieve these objectives, operators are implementing comprehensive pipeline integrity management programs. These programs may be driven by a country’s pipeline regulator or in many cases may be “self-directed” by the pipeline operator especially in countries where pipeline regulators do not exist. A critical aspect of an operator’s Integrity Management Plan (IMP) is to evaluate the history, limitations and the key threats for each pipeline and accordingly select the most appropriate integrity tool. The guidelines for assessing piggable lines has been well documented but until recently there was not much awareness for assessment of non-piggable pipelines. A lot of these non-piggable pipelines transverse through high consequence areas and usually minimal historic records are available for these lines. To add to the risk factor, usually these lines also lack any baseline assessment. The US regulators, that is Office of Pipeline Safety had recognized the need for establishment of codes and standards for integrity assessment of all pipelines more than a decade ago. This led to comprehensive mandatory rules, standards and codes for the US pipeline operators to follow regardless of the line being piggable or non-piggable. In India the story has been a bit different. In the past few years, our governing body for development of self-regulatory standards for the Indian oil and gas industry that is Oil Industry Safety Directorate (OISD) recognized a need for development of a standard specifically for integrity assessment of non-piggable pipelines. The standard was formalized and accepted by the Indian Ministry of Petroleum in September 2013 as OISD 233. OISD 233 standard is based on assessing the time dependent threats of External Corrosion (EC) and Internal Corrosion (IC) through applying the non-intrusive techniques of “Direct Assessment”. The four-step, iterative DA (ECDA, ICDA and SCCDA) process requires the integration of data from available line histories, multiple indirect field surveys, direct examination and the subsequent post assessment of the documented results. This paper presents the case study where the Indian pipeline operators took a self-initiative and implemented DA programs for prioritizing the integrity assessment of their most critical non-piggable pipelines even before the OISD 233 standard was established. The paper also looks into the relevance of the standard to the events and other case studies following the release of OISD 233.

Internal Corrosion Monitoring System Selection for Cross Country Natural Gas Pipeline: A Case Study of SHPPL

Reliance Gas Pipelines Limited (RGPL) is currently implementing a gas pipeline project from Shahdol, Madhya Pradesh to Phulpur, Uttar Pradesh for evacuation of gas produced from Coal Bed Methane (CBM) blocks owned by Reliance Industries Ltd. This pipeline will be hooked up with GAIL’s HVJ Pipeline at Phulpur. Over all Pipeline system includes 312 km (approx.) long trunk line, and associated facilities such as Compressor Station at Shahdol, Intermediate Pigging facilities, Metering & Regulating facilities at Phulpur and 12 No. Mainline valve stations. Gas produced from CBM blocks will be dehydrated within Gas Gathering Station facilities of CBM Project located upstream of pipeline Compressor station at Shahdol. Gas received at pipeline battery limit is dry and non-corrosive gas in nature, Internal corrosion is not expected in normal course of operation, however internal corrosion of the natural gas pipeline can occur when the pipe wall is exposed to moisture and other contaminants either under process upset conditions or under particular operating conditions. Even though internal corrosion is not expected during normal course of operations, to take care of any eventuality, it is proposed to implement Internal Corrosion Monitoring (ICMS) system in this project. ICMS will provide an efficient and reliable means of continuous monitoring internal corrosion. Internal Corrosion Monitoring (ICMS) system is used as a part of overall integrity management framework; to achieve two objectives viz., verify the corrosive behaviour of gas and to verify the efficacy of applied preventive actions. Philosophy involved in evaluating a suitable CM technique would include : • Applicable corrosion damage mechanisms, anticipated corrosion rates and probable locations. • Suitable CM technique and location based on process condition, system corrosivity, water content, pigging facilities, available corrosion allowance, design life, maintenance etc., • Measurement frequency. Some of the Corrosion Monitoring techniques used for pipeline and of relevance are: • Weight-loss Corrosion Coupons (CC), • Electrical Resistance probes (ER), • Linear Polarization Resistance Probe (LPR) • Ultrasonic Thickness Measurement (UT) • Sampling Points (SP) This paper discusses the merits / demerits of these corrosion monitoring techniques, considerations for selecting a specific technique for the Shahdol – Phulpur Gas Pipeline Project and highlights the implementation of the internal corrosion monitoring system.

AC Interference Effect on NG Pipeline and its Mitigation Techniques

All gas pipeline system operators should produce and demonstrate compliance with operational and maintenance philosophies, which include integrity management policies, procedures and safe systems of work throughout their operational life. They should identify all hazards that may impact the system integrity with respect to tolerable individual and societal risk. Risk assessment should be undertaken, mitigation measures established and any residual risk associated with the management of each risk mitigation strategy must be defined and risk ownership established. A credible integrity risk is associated with Alternating Current (AC) induced corrosion of underground steel pipelines that are routed in close proximity to high voltage overhead electrical power systems. This document provides information about AC interference effect on pipeline and demonstrates credible risk mitigation techniques with integrity management. It also describes safety measures and new mitigation technique to avoid electromagnetic interference generated by electric line on underground natural gas pipeline during installation and operational life where the pipeline is laid in common ROU. It shall be emphasised that the owner/operator bears responsibility for the safe operation and maintenance of pipeline system and implement required means and methods to assure integrity of system throughout the design life of the pipeline system.

Double Block and Bleed Pipeline Isolations: Improving Safety/Decreasing Maintenance Costs

Safety is always the number one focus of the pipeline industry. This paper will discuss how Double Block & Bleed (DB&B) maximizes safety during a pipeline isolation. In addition to safety, DB&B also maximizes project efficiency, which results in minimizing project and maintenance costs. The goal of DB&B for both safety and efficiency is to approach 100 percent success in achieving a seal with no detectable seepage. Pipeline isolations are frequently utilized for maintenance such as replacement of leaking block valves, cut out and repair of third party damage, and cut out and replacement of imperfections identified during inline inspection runs. This paper will begin with a review of laboratory testing and calculation of DB&B efficiency, followed by one or more field case studies.

Integrity Management: II — Pipeline Operation and Maintenance

Oil & Gas pipeline industry has experience external corrosion and damage impacting its structural integrity for decades. Over 30 years, composite technology has been implemented to strengthen pipelines back to its design condition. The composite application is very common for pipelines of all sizes having operating temperatures from ambient to 60 deg. C. ONGC – Uran plant is a major facility to process crude oil with associated gas and condensate received from Mumbai High through Subsea pipeline. Regeneration Column was designed for 50 PSI with Design Temperature of 130 Deg. C. and insulated skin. Weather and humidity was accelerating external corrosion around stiffener rings to the point that, it warranted a shutdown to replace either a section or full tower, thereby impacting the production throughput of ONGC-Uran facility. ONGC hired M/s. EIL as a consulting company to map out extent of corrosion and to identify area needed attention to rehabilitate. Consultant recommended to go for weld build up in identified LML areas (Local Metal Loss) through a planned shutdown of the column. We were aware about composite technology and further investigation helped to find the right combination of Carbon and High Temperature Epoxy system meeting our requirement through online repair and rehabilitation avoiding shutdown of Regeneration Column. We selected Carbon with high temperature epoxy based composite system designed for 130 deg. C and installation between 90 to 110 deg. C. Composite application system was designed accordingly and a third party inspection agency was hired to witness prototype tests and composite application techniques. Bonding of Carbon Composite to the Carbon Steel pipe of equivalent grade was successfully tested in the lab. After infield application, the thickness and hardness of composite system were measured throughout the repaired area during and after the process by TPI. Project was completed by T.D. Williamson in end 2012.