Effect of Thermal Aging on Strain Capacity of X80 SAW Pipes

Application of API X80 grade line pipes has been promoted to increase the operating pressure. It is generally known that the deformability of submerged arc welding (SAW) pipes is decreased by increasing strength of the pipes. The assessment of the strain capacity of X80 SAW pipes is required for strain-based design (SBD). In the assessment of the strain capacity, one of the important issues is the effect of thermal aging during the anti-corrosion coating on the yielding phenomenon. In this study, full-scale pipe bending tests of X80 SAW pipes produced by UOE process were performed to evaluate the effect of thermal aging on the strain capacity.

Multi-Tier Tensile Strain Models for Strain-Based Design: Part 2 — Development and Formulation of Tensile Strain Capacity Models

This is the second paper in a three-paper series related to the development of tensile strain models. The fundamental basis of the models [1] and evaluation of the models against experiment data [2] are presented in two companion papers. This paper presents the structure and formulation of the models. The philosophy and development of the multi-tier tensile strain models are described. The tensile strain models are applicable for linepipe grades from X65 to X100 and two welding processes, i.e., mechanized GMAW and FCAW/SMAW. The tensile strain capacity (TSC) is given as a function of key material properties and weld and flaw geometric parameters, including pipe wall thickness, girth weld high-low misalignment, pipe strain hardening (Y/T ratio), weld strength mismatch, girth weld flaw size, toughness, and internal pressure. Two essential parts of the tensile strain models are the crack driving force and material’s toughness. This paper covers principally the crack driving force. The significance and determination of material’s toughness are covered in the companion papers [1,2].

Simulation of the Response of Buried Pipelines to Slope Movement Using 3D Continuum Modeling

Pipeline integrity is affected by the action of external soil loads in addition to internal fluid pressure. External soil loads can be generated by landslides or at sites subject to ground subsidence, heave or seismic effects. Under these varied conditions of ground movement potential pipeline safety involves constraints on design and operations. The design processes includes developing an understanding of strains that could be imposed on the pipe (strain demand) and strain limits that the pipe can withstand without failure. The ability to predict the pipeline load, stress or strains state in the presence of soil restraint and/or soil displacement induced loading is not well described in design standards or codes of practice. This paper describes the ongoing work involved in a study investigating the mechanical behavior of buried pipelines interacting with active landslides. Detailed pipe-soil interaction analyses were completed with a 3D continuum SPH method. This paper describes the LS-DYNA numerical modeling process, previously developed by the authors, which was refined and applied to site-specific conditions. To illustrate the performance of the modeling process to consider a translational slide, additional numerical model validation was completed and is described in this paper. These comparisons illustrate that good agreement was observed between the modeling results and experimental full scale trial results. Sample results of the application of the validated 3D continuum modeling process are presented. These results are being used to develop generalized trends in pipeline response to slope movements. The paper describes both the progress achieved to date and the future potential for simplified engineering design tools to assess the load or deformation capacity requirements of buried pipelines exposed to different types of slope movement.

Applying the Quantitative Risk Assessment (QRA) to Improve Safety Management of Oil and Gas Pipeline Stations in China

The oil and gas pipeline companies in China are facing unprecedented opportunities and challenges because of China’s increasing demand for oil and gas energy that is attributed to rapid economic and social development. Limitation of land resource and the fast urbanization lead to a determinate result that many pipelines have to go through or be adjacent to highly populated areas such as cities or towns. The increasing Chinese government regulation, and public concerns about industrial safety and environmental protection push the pipeline companies to enhance the safety, health and environmental protection management. In recent years, PetroChina Pipeline Company (PPC) pays a lot of attention and effort to improve employees and public safety around the pipeline facilities. A comprehensive, integrated HSE management system is continuously improved and effectively implemented in PPC. PPC conducts hazard identification, risk assessment, risk control and mitigation, risk monitoring. For the oil and gas stations in highly populated area or with numerous employees, PPC carries out quantitative risk assessment (QRA) to evaluate and manage the population risk. To make the assessment, “Guidelines for quantitative risk assessments” (purple book) published by Committee for the Prevention of Disasters of Netherlands is used along with a software package. The basic principles, process, and methods of QRA technology are introduced in this article. The process is to identify the station hazards, determinate the failure scenarios of the facilities, estimate the possibilities of leakage failures, calculate the consequences of failures and damages to population, demonstrate the individual risk and social risk, and evaluate whether the risk is acceptable. The process may involve the mathematical modeling of fluid and gas spill, dispersion, fire and explosion. One QRA case in an oil pipeline station is described in this article to illustrate the application process and discuss several key issues in the assessment. Using QRA technique, about 20 stations have been evaluated in PPC. On the basis of the results, managers have taken prevention and mitigation plans to control the risk. QRAs in the pipeline station can provide a quantitative basis and valuable reference for the company’s decision-making and land use planning. Also, QRA can play a role to make a better relationship between the pipeline companies and the local regulator and public. Finally, this article delivers limitations of QRA in Chinese pipeline stations and discusses issues of the solutions.

Emerging Technology: Remote Controlled Hot Tap System for Subsea Pipelines

Subsea hot tapping of pipelines is performed for a variety of reasons, including tie-ins, pipeline repair, insertion of instrumentation, facilitating chemical injection or providing access for temporary isolation tools. The full hot tap process — that is, installing the hot tap assembly, performing the tap and recovering the hot tap machine — is normally conducted with diver assistance. After bolting the assembly of the machine, isolation valve and fitting to the pipeline (or machine and isolation valve to a pre-installed flanged membrane on the pipeline), the divers then operate the machine to perform the tap, under instructions from — and supervision — by hot tap technicians located on deck of the diving support vessel (DSV). Subsequent unbolting and removal of the hot tap machine is also carried out by the divers. The demands of deep water have necessitated development of a totally diver-less, remote-controlled system. Diver operations are limited to a maximum of 300 meters of water depth, whereas a significant portion of existing subsea field infrastructure, as well as projected future developments, are in deeper waters in depths up to 3,000 meters. In addition, diver safety concerns in shallow water, as well as impaired diver efficiency in difficult environmental conditions such as wave breaking zones, prompts the call for a reduction of diver exposure or complete elimination of diver assistance. The recent completion of a remote-controlled hot tap machine (Subsea 1200RC) is an important step toward developing a totally diver-less system. The installation of the hot tap assembly and subsequent removal of the machine still require diver assistance, but the performance of the tap itself is remotely controlled by a hot tap technician from the deck of the DSV. The concept is a topside-driven hot tap machine with “passive Remotely Operated Vehicle (ROV) interface”, which means a stationary ROV with its hydraulics and control system is attached to the hot tap machine and operated from an onboard laptop. This results in a light weight hot tap frame and total direct control of the cutting process. The machine has been designed, built, tested and successfully deployed on a recent subsea tap for a pipeline operator in Asia. This technology promotes the “separation of man and machine” proposition. It reduces risk by reducing diver exposure, enhances safety, provides direct control and visibility from a laptop and facilitates fast and accurate execution. Ultimately, the concept may be extended toward onshore hot tap applications in risky environments calling for remotely operated systems. Diverless tapping is now also qualified and offered by others.

An Update to the UKOPA Pipeline Damage Distributions

The United Kingdom Onshore Pipeline Operators Association (UKOPA) was formed by UK pipeline operators to provide a common forum for representing operators interests in the safe management of pipelines. This includes providing historical failure statistics for use in pipeline quantitative risk assessment and UKOPA maintain a database to record this data. The UKOPA database holds data on product loss failures of UK major accident hazard pipelines from 1962 onwards and currently has a total length of 22,370 km of pipelines reporting. Overall exposure from 1952 to 2010 is of over 785,000 km years of operating experience with a total of 184 product loss incidents during this period. The low number of failures means that the historical failure rate for pipelines of some specific diameters, wall thicknesses and material grades is zero or statistically insignificant. It is unreasonable to assume that the failure rate for these pipelines is actually zero. However, unlike the European Gas Incident data Group (EGIG) database, which also includes the UK gas transmission pipeline data, the UKOPA database contains extensive data on measured part wall damage that did not cause product loss. The data on damage to pipelines caused by external interference can be assessed to derive statistical distribution parameters describing the expected gouge length, gouge depth and dent depth resulting from an incident. Overall 3rd party interference incident rates for different class locations can also be determined. These distributions and incident rates can be used in structural reliability based techniques to predict the failure frequency due to 3rd party damage for a given set of pipeline parameters. The UKOPA recommended methodology for the assessment of pipeline failure frequency due to 3rd party damage is implemented in the FFREQ software. The distributions of 3rd party damage currently used in FFREQ date from the mid-1990s. This paper describes the work involved in updating the analysis of the damage database and presents the updated distribution parameters. A comparison of predictions using the old and new distributions is also presented.

Meeting the New Regulatory Requirements for Pipeline Control Room Management

The U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA) has amended the U.S. pipeline safety regulations to prescribe safety requirements for controllers, control rooms, and Supervisory Control and Data Acquisition (SCADA) systems used to remotely monitor and control pipeline operations. The objective of Control Room Management (CRM) is to help assure the controllers will continue to be successful in maintaining pipeline integrity and safety, and help reduce the number and consequences of shortfalls in control room management practices and operator errors when remotely monitoring and controlling pipelines and responding to abnormal and emergency conditions. CRM helps to address this by prescribing safety requirements intended to verify that procedures, systems, and equipment are well thought out and function as intended. CRM also intends to help assure that pipeline operators are addressing human fatigue risks and other human factors inside the control room that could inhibit a controller’s ability to carry out the roles and responsibilities the operator has defined for the safe operation of the pipeline. This paper will go over the background and elements of the rule, additional guidance and resources that have been provided publically, and lessons learned through the development and roll out of the new requirements.

Pressure Correction Factor for Strain Capacity Predictions Based on Curved Wide Plate Testing

Strain-based girth weld defect assessment procedures are essentially based on large scale testing. Ever since the 1980’s curved wide plate testing has been widely applied to determine the tensile strain capacity of flawed girth welds. However, the effect of internal pressure is not captured in curved wide plate testing. Accordingly, unconservative predictions of strain capacity occur when straightforwardly transferred to pressurized pipes. To address this anomaly, this paper presents results of finite element simulations incorporating ductile crack growth. Simulations on homogeneous and girth welded specimens indicate that a correction factor of 0.5 allows to conservatively predict the strain capacity of a pressurized pipe through wide plate testing under the considered conditions.

A Practical Approach to Pipeline System Materials Verification

The Pipeline and Hazardous Material Safety Administration (PHSMA) has increased emphasis on records that are “traceable, verifiable, and complete.” Organizing records into a document structure that is traceable, verifiable, and complete can be a daunting task. Through work with operators, Det Norske Veritas (U.S.A.) Inc. (DNV) identified a methodology to efficiently search and organize material property data and records into a structure that is fit for regulatory audit. The methodology consists of four steps: (1) Search/Organize Documentation. (2) Digitally Capture Paper Documents. (3) Determine Document Precedence. (4) Create a Reference-able Listing. The first step reviews all files and records and identifies records that are pertinent to properties verification. The search is conducted at an operator’s office(s) by a team of personnel familiar with pipeline construction and maintenance documentation. Once records have been identified, they are digitally captured (scanned) making them easy to reference. This requires a set of metadata and unique name for each document. The metadata consists of project number, document type (maintenance form, drawing, etc…), pipeline name, and information location. Document precedence is used to identify documents most likely to contain correct material information. Document precedence is determined with operator employees that can identify document(s) that have been historically given high reliability. Finally, a listing tabulates material properties along with the unique document name(s) for the specific records. The listing contains pipe (by segment or joint), fittings (valves, prefabricated elbows, etc…), and other components that may affect Maximum (Allowable) Operating Pressures. Typically the listing uses linear pipeline stationing as the main reference. Implementation of the methodology yields a listing of material properties specifically linked to a digital document database — i.e., a records system that is “traceable, verifiable, and complete.” In addition to material properties, this methodology has also been applied to risk-related information (e.g. cathodic protection, crossings, coating information, etc…). The listing can then be used to identify any information gaps and potentially prioritize them based on reliability.

Experimental Study on Blockage of Gas Hydrate Slurry in a Flow Loop

Hydrate formation and blockage in long deepwater pipelines has long been a trouble for offshore petroleum production. Consequently, understandings of the procedures as well as influencing factors of hydrate blockage are key points to make reasonable flow assurance strategies. Thus two series of experiments have been conducted in a high-pressure hydrate flow loop newly constructed by multi-phase flow research group in China University of Petroleum (Beijing). One of the systems consists of water and CO2, while the other one includes water, diesel oil and natural gas. The relative time of hydrate blockage has been studied by varying pressure and flow rate for both two systems. The dimensions of hydrate particles in fluid during plugging are also investigated. The results indicate that the influencing factor exerts a similar effect on the relative time for the different systems. Besides, the sizes of particles in the fluid would change significantly due to hydrate formation.