WHAT IS PIPELINE MATERIAL VERIFICATION?
Pipeline material verification is the process of confirming or re-establishing a robust knowledge of the different material properties and attributes within a particular pipeline segment where data may be incomplete or inadequately documented. The end result is to establish records of material properties and attributes that are traceable, verifiable and complete (TVC).
Uncertainties or gaps in records can originate as early as pipeline construction if documentation is not kept or traceability is lost. The quality or completeness of records may also degrade over time due to asset sales, office moves, lost paper records, staff retirement, and so on.
The term material verification encompasses the properties and attributes that are essential for safe operation and to support integrity management programs and assessments.
Specifically, it refers to one or more of the following:
Diameter is generally well known for the main pipeline segment. However, a large number of laterals, fittings and appurtenances may be present on the pipeline for which the diameter is not well documented, such as station piping, offtakes, service taps, blow-offs, and so on. Although diameter is easily measured when access is available, verifying the diameter of buried components is more challenging.
Pipe Wall Thickness
Wall thickness is a direct determinant of safe operating pressure as one of the parameters within the design equation (for example, under 49 CFR 192.619 in the USA). Even more critical is the accuracy of wall thickness data when used to assess defects through remaining strength, predicted failure pressure, or remaining fatigue life calculations. On one hand, inaccurate data may lead to unsafe defects remaining in the pipeline or, on the other hand, over-conservatism may result in unnecessary repairs or reduced operating pressures.
Pipe Type or Seam Type
Identifying seamless or welded pipes is fundamental for a robust integrity management program. Once the ‘pipe type’ is known to be welded, further differentiation may be required with respect to the numerous different seam welding processes that have been used historically. These different weld types have different propensities to certain resident defect types or reduced resistance to fracture initiation and propagation, in particular vintage seam types such as low-frequency ERW, flash-welded and lap-welded pipe.
Pipe grade is a direct determinant of safe operating pressure as one of the parameters within the design equation (for example, under 49 CFR 192.619 in the USA).
Pipe grades are determined based on measurement of Yield Strength (YS) and Ultimate Tensile Strength (UTS) values. These values are critical inputs to remaining strength assessments and Predicted Failure Pressure (PFP) for metal loss and crack-like features respectively.
Toughness as a general term refers to a material’s tolerance to the presence of flaws. More specifically, fracture toughness is the material’s resistance to fracture propagation. Materials with a high fracture toughness can tolerate more severe cracks or crack-like defects at a given operating pressure without propagation of the feature.
For pipelines that contain or may be susceptible to cracks or crack-like features, accurate knowledge of the fracture toughness or Charpy data is critical since it can vary across a very wide range, from 1 Joule (or ft-lb) to several hundred Joules (ft-lbs). Additionally, operators must consider that toughness of the pipe body may be significantly different to that in the seam weld.
Toughness must be measured using destructive testing, for which the difficulty and cost of obtaining samples makes the process challenging. By implementing a clear and holistic strategy for Pipeline Material Verification, operators can minimize the cost and uncertainty involved in achieving complete and accurate data.
WHY IS MATERIAL VERIFICATION REQUIRED?
A robust knowledge of pipeline material properties and attributes is essential to support a safe operating pressure, as well as to underpin critical integrity management processes such as fitness for service, remaining strength or predicted failure pressure assessments.
When evaluating a pipeline’s suitability for service in hydrogen, or blended hydrogen, a fundamental step is to identify the different materials and pipe grades present to ensure compliance with codes, and to ensure that integrity management takes account of accurate material property inputs in the context of hydrogen-assisted degradation mechanisms.
For piggable pipelines, in-line inspection (ILI) technologies now permit operators to collect actual material property and attribute data from every pipe for up to 100% data completeness. The measurement principle for these ILI systems must now be well understood. Each system must provide discrete information on each pipe joint. For unpiggable pipelines, novel non-destructive techniques have made it feasible to measure pipe grade without removing pipes from service.
Operators can now take advantage of these technological and process-driven developments to achieve a step-change in the completeness and quality of the following data used within their integrity management programs.
US Gas Transmission Pipelines – 49 CFR 192
In 2020, new regulations came into effect in the USA under 49 CFR 192 for gas transmission pipelines that mandate operators to implement a material verification program to support a safe maximum allowable operating pressure (MAOP) and integrity management processes.
Material Verification is an integral part of MAOP reconfirmation within §192.624 and is, in particular, an essential pre-requisite for the Engineering Critical Assessment (ECA) method.
Material properties and attributes must be verified when used in remaining strength or predicted failure pressure calculations for metal loss and cracks, respectively, per §192.712.
Threat Identification and Data Integration
Material properties and attributes are required as part of Prescriptive Integrity Management Programs as part of ASME B31.8S (incorporated by reference with 49 CFR 192).
HOW TO MANAGE
An Efficient Strategy for Material Verification
The most efficient strategy to complete the Material Verification process is to make use of all available data to build the most complete picture possible of the pipeline material properties and attributes, and minimize knowledge gaps. An assessment can then be made to identify which gaps in the data must be addressed in order to support the strategic aims, whether that is regulatory compliance or to address a specific integrity risk.
For piggable pipelines, use of ILI data can dramatically reduce the number of excavations required to close out any gaps in data. Instead of sampling a small percentage of the pipes within the segment, ILI gathers data on every pipe so excavations are only required to validate ILI data when required for regulatory compliance or to verify accuracy. This also enhances the ability to improve excavation plans and resource management.
ROSEN’s Material Verification Framework illustrates how multiple data sources can be brought together and evaluated to progress through the Material Verification task in an effective and efficient process. Understanding that every pipeline is different, each element of the framework is applied as needed to achieve the operator’s individual aims: a customizable solution that can take any pipeline from its current state of knowledge to achieving full compliance or beyond.
After defining the strategic aims, the following key steps are particularly important to implement a Material Verification Program:
- Gather all available data from multiple sources:
- Identify and review existing pipeline records
- Conduct in-line inspection (ILI) to provide material property and attribute data on every pipe
- Conduct non-destructive (in-situ) testing to supplement and validate the ILI data
- Perform destructive (laboratory) testing where required, e.g. for toughness data
- Align and integrate the collected data to define traceable, verifiable and complete data for the pipe populations, material properties and attributes.
- Implement the findings into the System of Record and Integrity Management Program.
Strategy– US Gas Transmission Pipelines
ROSEN has a comprehensive understanding of the new PHMSA regulations for US gas transmission pipelines and the solutions that can be implemented to address them. The strategy that ROSEN creates, defines answers to the following key questions:
- Which areas of regulations must be addressed and where?
- What outcomes do I want to achieve?
- What data do I need to collect, and how do I collect it?
- When do I need to complete the process?
- How can the process be optimized and aligned with my current Integrity Management Program?
In addition, subject matter experts (SME) with expertise in integrity management, materials science and metallurgy, NDT and testing, can provide consultancy to support operators as they progress through the Material Verification process.
Once the strategy and project aims have been achieved, the current status of compliance and pipeline knowledge must be defined. This involves gathering, aligning, evaluating and integrating data to create the most complete knowledge possible from multiple sources:
Review and alignment of existing pipeline information
A comprehensive review and alignment of pipeline records (e.g. as-built drawings, pipe books, mill certificates, hydro test pressure records, etc.) provides an initial indication of the current status of compliance. Where required for regulatory compliance, the data must be categorized with respect to its TVC status.
The data from records can be used on its own to define populations and thereby progress to the next stages of the process. However, if the pipeline is piggable then data from previous inspections or planned inspections is invaluable in assessing the status of existing data, and supporting an accurate population assessment.
Accurate Inspection Data Collection
ROSEN offers a range of innovative non-destructive testing (NDT) through in-line inspection services to support data gathering and initial analysis for the Pipeline Material Verification process with a combined diagnostics approach, encompassing:
Pre-ILI Cleaning for increased first run success
At any stage of a pipeline system, debris can deposit and collect within the line. Especially in times when production decreases, resulting in reduced flow rates and increased accumulation of debris in the pipelines, cleaning prior to in-line inspections (ILI) is essential. The sensor technologies used in pipeline inspections require cleanliness to achieve reliable and accurate ILI results, resulting in high data quality and enabling accurate integrity assessments. This not only increases first run success, but also reduces operational risks and potential costs.
Pipe Grade Sensors (PGS) for strength and pipe grade determination, and population assessment
ROSEN’s pipe grade sensors provide yield strength (YS) and ultimate tensile strength (UTS) for every pipe spool, which can be supported and validated by non-destructive in-field testing. This data can be used to verify existing records and expectations, or to provide data for areas with unknown grade. By collecting data on every pipe, outliers and rogue pipes can be detected down to the individual component level.
Equally as valuable is the population assessment provided. By evaluating the strength data in combination with other datasets reported by ILI, every pipe in the inspected section is grouped into a population of pipes with equivalent material properties and attributes. This comprehensive view of the different populations permits an optimized strategy to be implemented to close out the Material Verification Program.
MFL-A (axial magnetic flux leakage) for pipe type differentiation (seamless vs. welded)
The Magnetic Flux Leakage (MFL) technology is the right choice to reliably and effectively detect and characterize internal and external metal loss features. In addition, MFL-A can detect the presence of a seam weld or identify pipes as seamless. By combining this data with the population assessment, the confidence is increased further by considering groups of equivalent pipes in combination.
Mechanical Dipper and Eddy Current (XT) for diameter determination
The XT technology, as a combination of mechanical caliper measurements with eddy current proximity sensors, provides unrivalled industry-renowned data sets of the highest quality for both liquid and gas pipelines. The dual-sensor technology applied enables precise mapping and sizing of ID anomalies by providing full circumferential and axial coverage. For visualization and modeling, detailed and accurate 3D representations of any geometric anomaly can be generated. Additional information includes the identification and characterization of bends and small changes in internal diameter, as well as the distinction to debris, scale or wax deposits. Combined with MFL technology, WT schedules can be accurately determined.
In-Field Validation Services
Verifying the in-line inspection (ILI) performance and the analysis process in the field using non-destructive, in-situ techniques, is an essential part of pipeline integrity management. Once collected, the results are reviewed and evaluated by subject matter experts with experience in material properties and testing to provide total confidence in material property and attribute verification.
Where material is already available, or it is feasible to remove samples from service, destructive laboratory testing provides the most accurate solution to determine material properties. For measurement of fracture toughness or Charpy testing, destructive testing is the only solution currently available. ROSEN’s test facility is able to conduct material characterization including tensile testing, chemical composition, metallography, and weld characterization.
These technology solutions provide the means to gather all data necessary to close out the Material Verification Program and re-establish a comprehensive knowledge of the pipeline material properties. Each technology has its unique benefits and challenges and it is important to select the most appropriate combination of solutions to most efficiently progress through the process.
A significant amount of data may be generated that requires combined evaluation and interpretation. The different data sets must be considered in the context of their accuracy and limitations, and brought together to form a final assignment of material properties and attributes to fulfil regulatory requirements or to assimilate into the operator’s system of record for the pipeline.
Once the final assignment of material properties and attributes is completed, the results can be implemented within integrity assessments with full confidence in the accuracy and completeness of the data.
Understanding the risks that a pipeline system is facing is crucial to investigate inspection and maintenance strategies and to implement a cost-effective maintenance and remediation program. It is important to have a robust knowledge of the different pipe materials present within a pipeline, and to support each population with accurate and representative material property data.
Pipeline risks are often a function of the different pipe populations present. Different populations may contain different resident integrity threats since these can be a function of the manufacturer, manufacturing process, and manufacturing date. Different pipe populations, crucially, also have different material properties and attributes, and will therefore have a different tolerance to flaws.
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The US regulation change for gas transmission pipelines includes prescriptive for reconfirmation of MAOP when TVC pressure test records are not available. Operators are able to select from six methods to reconfirm MAOP. Two of these methods require TVC material property and attributes to be documented. When the records are not available operators are obliged to collect the data per §192.607, as a regulatory requirement.
The conversion of existing pipelines to hydrogen or blended hydrogen service requires operators to identify and understand the different materials present in the pipeline. The presence of hydrogen can reduce ductility and fracture toughness and increase fatigue crack growth rates. Different pipe materials may experience these effects to different extents, and higher strength steels may in fact be more susceptible to such effects. It is important to quantify the actual performance of these materials under hydrogen service and take account of this within engineering assessments and integrity management programs to ensure safe operation.
ROSEN’s structured approach to Pipeline Material Verification ensures that all different pipe materials are identified and categorized through the population approach, and strength values are reported for every pipe. This ensures that higher pipe grades are identified and that outliers are identified down to the individual component level.
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The data from the material property verification can be used as input to the feature assessments. This ensures that the anomalies detected by ILI are assessed using accurate and representative material property and attribute data and the appropriate response decisions are made. Using accurate data means that unsafe situations are avoided and, conversely, that valuable resource is not wasted by using overly conservative inputs. This is particularly important for US gas transmission applications, where regulatory change has introduced a requirement for traceable, verifiable, and complete (TVC) records for material properties and attributes when performing calculations as part of an Engineering Critical Assessment, §192.624, and §192.712.
After analyzing and assessing the in-line inspection data, operators are able to make short-term decisions to ensure the performance, life and safety of their asset. However, ROSEN's Material Verification Framework takes a more proactive, forward-looking approach by incorporating the management "step".
A customized management plan pulls together all relevant pieces and delivers the optimum combination of activities including ILI, integrity assessments, and verification findings to ensure safety. In addition, a plan like this allows operators to take the right maintenance steps at the right time.
As outlined above, more regulations now require that all pipeline records be traceable, verifiable and complete. With the amount of data steadily growing, the establishment of a system of record where all available data is readily accessible is becoming an increasingly critical issue for pipeline operators.
Our asset integrity management solution NIMA delivers the data you need, in the way that you need it, to make better integrity management decisions.
Find out more about NIMA
Standards and regulations explicitly require all personnel to be competent and qualified in their respective areas of responsibility. Learning, knowledge sharing, regular dialogue and continuous collaboration among stakeholders in the pipeline industry is therefore indispensable in order to increase and maintain individual and organizational competence at a high level.
ROSEN is committed to supporting the sharing of knowledge in the industry and has developed training courses, education programs and qualifications specific to addressing threats. These also include courses on material properties, various regulations and integrity management of pipelines.
Find out more about Competence Training