14.pipeline integrity management external

Asset Management Services

Pipeline Integrity Management Services

Germanischer Lloyd Service/Product Description

Contents

Service Description and Values Generated

Detailed Method Statement

External Corrosion Management

Fitness for Service Assessments

Geotechnics and Ground Movement

In-Line Inspection Services

Integrity Management System Audits

Investigation of Pipeline Incidents

TD/1 Surveys (Affirmation of MOP forOnshore Pipelines)

Pipeline Uprating

Welding Technology Services

Grouted Tee

Internal Corrosion Management

Case Studies and Examples

Investigation of AC Interference Problemon High Pressure Pipeline

Guidance on SCC Risks on a PipelineOperators Network

Coating and Backfill Interaction

CP Decision Support Tool

Dent Assessment on a 30 Oil Pipeline

Advances in Interaction Rules for CorrosionDefects in Pipeline Using FE Analysis andFull Scale Testing

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Pipeline Integrity ManagementServices

Service Title: Asset Management Services

Lead Practice: GL Asset Management (UK)

Germanischer Lloyd Service/Product Description

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Service Descriptionand Values Generated:

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SERVICE DESCRIPTION

Case Studies and Examples

Fracture Mechanics Assessment of a Defective PigTrap

Fatigue Assessment of Dented Pipeline

Metallic Gas and Water Mains Affected by GroundMovement

Pipeline Affected by Collapse of Quarry Face

Deep Basement Construction - Large DiameterCast Iron Gas Main Affected by Ground Movement

Effect of Slope Instability of High Pressure Pipeline

In-Line Inspection Vehicle Development

In-Line Inspection Data Analysis

In-Line Inspection Scheduling

Review of Operations and Maintenance Practice

China Joint Venture LNG Pipeline

Investigation of Pipeline Incidents

TD/1 Surveys

Pipeline Uprating

Design and Qualification of Repair Procedures forBellows Attachment Welding

Grouted TeeTM

Weldability Testing of 48 Diameter X80 EuropipeProduction

Corrosion Control of a Sour Gas Pipeline

Naphtha Pipeline Integrity Management Study

Sour Export Pipeline Study

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Germanischer Lloyd (GL) offers a complete pipelineintegrity service and many variations to the basic serviceare possible. Clients may wish a complete PIMS to beprovided for them, an audit/review of their existingsystem or anything in between these two.

GLs incident investigation service is just one part of acomplete integrity package that GL can supply to processplant operators and Gas and Oil producers. This is one ofGLs strengths and can generate a considerable amount ofrevenue.

This service is primarily aimed at clients whose pipelinesare designed and operated to IGE/TD/1. It can howeverbe promoted as a best practice offering for all onshoregas pipelines operating in populated areas. The actualdetailed implementation could be adapted to suit otherpipeline codes e.g. ASME 31.8.

National and international oil and gas (and water?)pipeline owners and operators.

Oil and gas majors with new assets or joint ventures.

Small scale operators with limited experience in pipelineintegrity management.

Oil, gas, and water pipeline owners and operators.

Pipeline contractors and consulting firms.

Major Gas/Oil operators in the Middle East and NorthAfrica.

Gas operators in the UK.

4DETAILED METHOD STATEMENT

a. External Corrosion Management

The coating choice and the method by which the pipeline coating isapplied will dictate the long term protection afforded to a pipeline.

As with the coating system, the design, operation and monitoring ofthe cathodic protection system will also have an impact on thein-service performance of the pipeline.

Control, mitigation and management of corrosion anomalies such asAC and DC corrosion, MIC and SCC will safeguard the integrity of apipeline and extend intervals between inspections and ultimately itsservice life.

Coating Selection

The generic choice of a pipeline coating system will significantlyinfluence the protection it affords during, handling, construction,commissioning and service. Small-scale laboratory evaluation isgenerally performed to rank and select materials prior to theirfull-scale application. This process evaluates the coatings physical,chemical and mechanical properties with reference to those propertiesthat are essential for successful in-service performance. The factorsduring application that influence the long term performance of acoating system e.g. surface preparation, application temperature andtime at temperature must be fully appreciated in order to optimiseperformance. GL has significant experience of coating selection andsmall and large scale evaluation programme generated over the last40 years.

Coating Application

A technical audit is often required at the coating application facility,prior to large scale production coating, to establish whether the plantis capable of controlling the parameters required to achieve theultimate properties of a pipeline coating, and that operatives aresuitably trained to operate this equipment. The technical audit shouldreview the following:

Facilities for storage of uncoated and coated pipes

Contamination assessment and cleaning prior to coating

Surface preparation

Chemical pretreatment

Coating application/curing

Testing and inspection

Coating protection for storage and transport

GL has been providing technical audits in coating application facilitiesfor a range of customers over many years.

Procedure Qualification Testing

In order to confirm that a coating applicator is competent to apply thespecified coating material, procedure qualification trials must beconducted. The purpose of the procedure qualification trial is toestablish that the coating applicator is capable of applying the coatingmaterial in accordance with the coating specification and produce acoating which is capable of passing the performance criteria requiredby the specification. In general, testing will evaluate the followingproperties of the coating.

Adhesion

Cure/Hardness

Impact resistance

Flexibility

Water soak resistance

Cathodic disbonding resistance

Strain polarisation resistance

Once procedure qualification testing has been successfully performedproduction coating can commence.

GL instigated the requirements for procedure qualification testingprior to production coatings, and have been active in performingqualification testing of a range of coating materials applied tolinepipe, fittings and field joints.

5DETAILED METHOD STATEMENT

Coating Condition Assessment

As part of the pipeline commissioning process, it is necessary toperform a coating condition assessment to minimise any coatingdamage which may have been sustained during the pipelineconstruction activities. Any coating damage found must be excavatedand repaired. Two techniques are employed to locate coating damageon buried pipelines viz. the Pearson technique and a techniquereferred to as Direct Current Voltage Gradient (DCVG) measurement.The purpose of these surveys is to locate coating damage that may beassociated with mechanical damage to the pipe. Location and repairof coating damage will minimise the current requirement from thecathodic protection system.

GL has developed detailed work procedures for the various surveytechniques and has been active in their application.

Management Procedures for Cathodic Protection of Pipelines

To ensure a high level of safety and reliability in operation, it isessential that buried steel pipework associated with transmission anddistribution systems is designed, installed and commissioned towithstand the potentially harmful effects of corrosion and thatcorrosion control systems employed are monitored to ensurecontinued effectiveness. The procedures used for the managementof cathodic protection systems should encompass the requirementsfor design, construction, installation, validation and monitoring.

Design

Before undertaking the design of a cathodic protection system,detailed information on the plant to be protected will be required.This will normally involve a site survey to determine the factors (e.g.soil type and resistivity) relating to the overall corrosion controlprogramme. The design will take account of the route plan, pipeparameters, coating types, the requirement for insulationjoints/flanges, proximity to power lines etc. An important choice interms of the design is whether a sacrificial or impressed system isrequired.

Protection Criteria

Any cathodic protection system must meet the protection criteriaspecified by the company or international standards being adopted.In general, the following criteria apply when measured against acopper/copper sulphate reference electrode:

A polarised pipe to soil potential more negative thanminus 850mV

A polarised pipe to soil potential more negative thanminus 950mV where sulphur reducing bacteria is knownto be present

An ON potential more negative than minus 1250mV

Following successful commissioning of the cathodic protection systemthe following checks will be required.

Electrical isolation of the carrier pipe and sleeves to beconfirmed

The operation of insulation joints and flanges to bechecked

That the CP criteria referred to above is being met

In order to establish that the cathodic protection system is operatingin compliance with company or international cathodic protectioncodes, validation of the system is required. This is achieved bymeasuring the output parameters (voltage and current) of the TRsalong the pipeline route, the On and instant off potentials at testposts, and by performing close interval potential surveys.

Routine Monitoring

Routine coating condition and CP monitoring is required to confirmthat the cathodic protection system is operating in compliance withthe codes. As well as monitoring pipe to soil potentials etc.,interaction testing to mitigate the effects on third party pipelines willbe required along with checks for interference from AC (overheadpower lines) and DC (traction systems) electrical sources.

GL has been involved in developing policy and procedures for CP de-sign, validation and monitoring.

Review, Mitigation and Management of Corrosion Anomalies

Stray DC Corrosion

Stray DC current can have a significant effect on pipelines in areas ofcoating damage. The main source of this interference is from DCelectric transit systems that run close-by the buried structure. In mostDC transit systems, the power (load current) to operate the 'train' is fedvia an overhead feeder connected to the positive pole of the DCsupply. This load current is returned to the negative pole of the DCsupply via the tracks. Unfortunately, as the tracks are laid at groundlevel, complete insulation from earth is unlikely and therefore some ofthe load current may take an earth path back to the DC supply.Pipelines close to a DC system constitute a good return path for aportion of this current. If a pipe offers a less resistant path, the currentwill travel along it, creating an anodic area where the currentdissipates. DC corrosion is usually characterised by localised deeppitting.

Most codes and recommended practices related to CP monitoringand control should require interaction testing to be performed in straycurrent areas and appropriate action to be taken to mitigate theproblem. On-line inspection or direct assessment in areas of coatingdamage will confirm the effectiveness of the action taken.

DC Influences

When a cathodic protection system is sited near other buriedneighbouring structures or services, corrosion may occur to one orother of these due to interference. DC current, applied to cathodicallyprotect a pipeline can be picked up by these buried structures. Wherethis current is dissipated at coating defects, the structure mayexperience corrosion. DC current interference may also occur as aconsequence of DC traction systems.

Most codes and recommended practices related to CP monitoringand control require interaction testing to be performed in straycurrent areas and appropriate action to be taken to mitigate theproblem. On-line inspection or direct assessment in areas of coatingdamage will confirm the effectiveness of this action.

CP Shielding

An electrically isolating object e.g. a rock or stone, in contact, or inclose proximity to a pipe can cause electrical shielding. This form ofshielding can prevent the CP current reaching open coating defects.Electrical shielding is also a concern under disbonded coatings.

On-line inspection will identify metal loss that may result as aconsequence of CP shielding.

AC Corrosion

AC currents, most commonly induced onto buried structures byoverhead power lines or traction systems, may result in AC corrosion.Although there appears to be no consensus concerning themechanism of AC corrosion, it is reasoned that it is caused by theirreversibility of the corrosion reaction. The corrosion features thatresult are generally localised, hemi-spherical and crater like and havea smooth surface. AC corrosion rates can be as high as 2 mm/year.

The requirement to routinely monitor AC voltage and current shouldbe incorporated into the various codes and recommended practices.If a problem is found to exist, various means of mitigating this can beinstigated. Metal loss due to AC corrosion will be detected throughOn-line inspection or direct assessment in areas of coating damage.

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DETAILED METHOD STATEMENT

Microbially Induced Corrosion (MIC)

Corrosion induced by the activity of bacteria, most generally inanaerobic environments, is characterised by large craters, striationsrunning parallel to the longitudinal pipe axis, the presence of sulphateand sulphide compounds and a smell of hydrogen sulphide.

MIC corrosion rates are reported to occur between 0.2 and 0.7mm/year, and to develop preferentially in anaerobic, wet and boggysoils. External MIC has been reported on bitumen/asphalt coatedpipelines and those coated with PE (tapes and HSSs) havingbituminous-based mastics.

Metal loss due to MIC will be detected through On-line inspection.Pipelines that are coated with asphalt/bitumen, and tapes or HSSsemploying bitumen-based adhesives will be at greatest risk.

Stress Corrosion Cracking (SCC)

Stress corrosion cracking is a form of "environmentally assistedcracking" where the surrounding environment, the pipe material andstress act together to reduce the strength or load carrying capacity ofa pipe. Two types of SCC are known and are referred to as high pHand near-neutral pH SCC.

High pH SCC occurs in a relatively narrow cathodic potential range(-600 to -830 mV ref. Cu/CuSO4), in the presence of a carbonate/bicarbonate environment and at a pH greater than 9. High pH SCC istypically experienced downstream of compressor stations (where thepipe temperature is elevated) and is associated with disbonded ordamaged coatings. In the cathodic potential range and environmentrequired for high pH SCC, a protective film forms on the metalsurface. If the pipe is subjected to plastic strain, this protective film willcrack and create the opportunity for SCC to occur. Stress corrosion

cracks will continue to grow only if the rate of plastic deformationoccurs more quickly than the rate at which the protective filmre-forms. High pH SCC occurs intergranularly.

Although the mechanism of near neutral SCC is not fully understood,it is thought to involve metal dissolution and the ingress of hydrogeninto the steel, the hydrogen facilitates crack growth by promotingreduced ductility in the steel. Cracks are probably initiated at corrosionpits on the steel surface containing a localised environment with apH low enough to produce atomic hydrogen. The low pH solution isproduced by dissolution of CO2 in the groundwater. Some of theatomic hydrogen enters the steel, degrading the mechanicalproperties locally so that cracks can initiate or grow. The plastic stresslevel necessary to produce cracking may not be related entirely tofracturing the embrittled steel. It may also contribute to rupturing theprotective film, allowing hydrogen to reach and penetrate the steel.Near neutral SCC occurs primarily transgranularly.

On-line inspection with tools employing ultrasonic or transversemagnetic flux leakage principles may be successful in detecting SCC.Lines should be targeted which have been protected with CTE, asphaltand tapes applied over mechanically cleaned surfaces.

GL has significant experience of all of the corrosion anomalies thatcan threaten the integrity of a pipeline system. GL has providedconsultancy to a range of customers who have wished to confirm thata particular corrosion mechanism is occurring on their pipeline andhow to mitigate/manage the problem.

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AC Corrosion

b. Fitness for Service Assessments

GL consultants have extensive experience and knowledge inconducting comprehensive fitness for service assessments of pipelinesusing stress analysis techniques, defect assessment and fracturemechanics assessment methods. This capability has been applied inassessing a wide variety of different types of defects and damagetypes (including: arc strike, general and pitting corrosion, cracks andspalling, smooth and kinked dents, gouges, smooth dents pluscracks/spalling/gouges, and stress corrosion cracking), and can betailored to provide damage assessment procedures in line withindividual company requirements.

We have excellent knowledge of the UK Pressure Systems SafetyRegulations, 2000 (PSSR) and relevant US Code of Federal Regulations(e.g. CFR 192 and 195). We also have a very good understanding ofthe capabilities of in-line inspection (ILI) tools, to interpret the resultsfrom inspections and to then undertake defect assessments.

GL routinely undertakes assessments of damaged transmissionpipelines for an international clientele of asset owners / operatorsworldwide. We have in-depth knowledge and experience in the useof industry recognised assessment methods such as:

ASME B31G

API 579

RSTRENG

DNV RPF101

BS7910

For any fitness for service assessment, information is required on theinput parameters. These include:

Original equipment design data

Operational and maintenance history

Expected future service

Information specific to the assessment such as defectsizes, stress state, location of flaws, and materialproperties such as tensile strength and fracturetoughness

Fitness for Service can then be demonstrated using methods such asstress analysis, defect assessment and fracture mechanics approaches.These are described as follows:

Stress Analysis

Fitness for Service can be demonstrated using higher level assessmentmethods such as FEA. GL can undertake work ranging from the stressanalysis of individual structural components such as branchconnections, hot tap tees, threaded well bore casing strings anddamaged (corroded or dented) pipelines. GL consultants have thecapabilities to undertake advanced non-linear, static/dynamic analysis,vibration, thermal and fatigue analyses. We use these capabilities toundertake fitness-for-service assessments of pressure systems and inconjunction with full scale testing facilities to develop defectassessment methods for pipelines. GL uses an extensive range of FEand associated software tools that are mounted on both SUN Unixnetwork and PC based Windows system. The software tools we useinclude:

ABAQUS (Standard and Explicit) FE analysis program

MSC/PATRAN and ABAQUS CAE FE pre-and post-processorprograms

PC based software such as MathCad and MATLAB

In addition to the above, our consultants can write customisedprograms, user subroutines, etc. in order to overcome the limitationsin proprietary software. Areas of expertise include:

Linear and non-linear analysis. Where necessary,non-linear effects can be included in the analysis; this canbe through the modelling of non-linear materialbehaviour, geometric non-linearity and contact

Buckling, postbuckling and collapse analysis of pipelines

Soil structure interaction

Steady state and transient heat transfer analysis

Fatigue and fracture mechanics; cracked body analysis

Design by analysis

Windows is a trademark of MicrosoftTM corporation

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Defect Assessment

Defect assessment is a deterministic approach used to assess theintegrity and fitness for service of defects found on pipelines. Defectsare features which affect the structural integrity and may be locatedon the surface of the pipe wall or actually inside the material of thepipe. There are numerous codes that can be used to assess defectsand are summarised in documents such as the Pipeline DefectAssessment Manual used for pipelines, which our consultants fullyunderstand the best methods to use. We have in-depth knowledgeand experience in the use of industry recognised assessment methodssuch as:

ASME B31G

API 579

RSTRENG

DNV RPF101

BS7910

Sources for defect data include pipeline intelligent inspection tools orother NDT methods. Using in-house expertise, appropriate assessmentmethods can then be chosen and applied to demonstratefitness-for-service in order to satisfy regulatory requirements andoperators integrity management strategy.

Damage assessment capabilities include the following types ofdefects:

i) Manufacturing Damage,

Manufacturing features are often a discontinuity in thegeometry of the pipe or shell such as a reduction in wallthickness or in the material itself.

ii) Construction Damage,

Construction defects may include girth weld defects orseam weld defects caused by lack of fill or misalignmentand in the most severe case cracking. Also, other forms ofdamage may occur such as indentation damage,corrosion at the girth weld, or even damage to theexternal coating.

iii)3rd Party Interference,

3rd party damage is often the most severe form ofdamage resulting in failure of the pipe or requiringimmediate repair. Often this involves mechanical damagesuch as a gouge resulting in metal loss of the pipe wall,or distortion of the pipe wall such as a dent.

iv)Operational Damage.

Defects arising from operational usage include externalcorrosion caused by damaged or disbonded coatingwhere the Cathodic Protection System is not effective.Also internal corrosion caused by water in the product,and even other forms of corrosion namely SweetCorrosion and Sour Corrosion may occur in pipelines.

GL has developed methods for the assessment ofcorrosion defects in pipelines through a combination offinite element analysis and full scale burst testing. Thesemethods have been included in guidance documentssuch as the British Standard BS7910. GL is continuing todevelop methods for assessing the integrity of corrodedpipelines for Pipeline Research Council International.

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Fracture Mechanics

BS7910 and similar codes such as the UK nuclear industry code R6and API 579, carry out fracture assessments using the FailureAssessment Diagram (FAD). This provides a graphical method forassessing the proximity of a loaded structure containing a defect tofailure by fracture and plastic collapse mechanisms. Proximity tofracture is characterised by the fracture ratio parameter Kr andproximity to plastic collapse is characterised by the parameter Lr. Aloaded structure can therefore be represented as an assessment pointon the FAD following calculation of Lr and Kr.

This approach is used in levels 1 to 3 of BS7910 to determine theacceptability of cracks by plotting a point on the diagram. Whendeciding which level to use, this depends on the input data availableand conservatism required. These levels can be summarised as:

Level 1 is a simplified assessment method when there islimited data on material properties,

Level 2 is the normal assessment route, and

Level 3 is based on a ductile tearing resistance analysis.

Using the fracture mechanics approach, our consultants candetermine whether a defect is SAFE or UNSAFE based on the FailureAssessment Diagram. Finally, using the fatigue assessment approachesdescribed in BS7910, we can then determine the remaining fatiguelife and future integrity of the structure if subjected to cyclic loading.

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c. Geotechnics and Ground Movement

The safe and adequate performance of pipelines and piping atinstallations under conditions of external loading is achieved by:

Quantification of pipeline loads and supports bycharacterising the inherent variability in the geologicalenvironment to specified confidence levels.

Ensuring compliance with relevant codes and standards.

Fitness-for-purpose assessments that recognise limitstates relevant to the applied loads with appropriate levelsof safety.

Estimates of probabilities of failure and system reliabilityfor uncontrolled geological hazards such as landslipevents.

Geotechnical Aspects

Pipelines sustain loads from a range of sources covering engineeringactivities such as earthworks and other surface construction,tunnelling, transient live loads on road and rail networks and alsoconstruction and mining plant, and subsidence events due to miningfor example. Natural hazards include landslides, earthquakes, naturalsubsidence, and erosion and exposure typically around water coursesleading to spanning and potentially hydraulic loading.

We have expertise to investigate and interpret all forms of groundloading and geological hazards, and quantify instability, movementand load transfer to pipeline structures.

Pipeline Integrity Aspects

The performance of a pipeline depends on the imposed loads, groundsupport and the pipeline structural response. We deal with this byidentifying and quantifying ground loading processes, soil/pipeinteractions and pipeline performance capabilities.

Pipeline integrity is assessed through well-established principlesincluding ground investigations, material testing, structuralcalculations using pipe stress analysis software and pipelinemonitoring.

The results of integrity assessments are evaluated based on relevantperformance limits. The findings may warrant monitoring, protection,or replacement works. We have experience in the specification,installation, data collection and interpretation for indirect and directmethods of monitoring. Satisfactory monitoring of pipelineperformance is typically achieved by a combination of themeasurement of existing stress levels, recording changes in pipelinestrains and geotechnical instrumentation or topographic surveying asappropriate.

d. In-Line Inspection Services

While there is rarely a standard method for work in this field, wewould naturally begin by working with the customer to understandprecisely what is required from a project. Then we would select theright specialists from our team of scientists and engineers, includingpeople who have extensive long-term experience in the area of ILI andhave worked on product development and exploitation for specialistILI vendors.

For any work that involves making use of ILI data that has alreadybeen collected we gather pipeline and inspection information. Whereuncertainties exist in the data - for example, with regard to actualmaterial properties (as distinct from material specifications) andinspection errors - these can be accounted for in a probabilistic limitstate assessment using the techniques of structural reliability analysis.If there are questions about interpretation of ILI results (see Case Study n)then we would resolve these by examining recorded data, asavailable, to form an independent opinion on the interpretation.

e. Integrity Management System Audits

In general an audit or review of a Pipeline Integrity ManagementSystem will begin with a Gap Analysis. This entails a thorough reviewof the Operators activities, including the following:

Compliance with national legislation and localrequirements

Integrity threats and mitigations in place

- Onshore mechanical damage, corrosion, groundmovement etc

- Offshore mechanical damage, stress/fatigue typematerial failures, internal and external corrosion etc

Quantitative risk assessments undertaken

Engineering documentation

Pipeline records and fault data

Quality, health, safety and environmental issues

Pipeline operations and maintenance

- Work scheduling- Record keeping- Routine and non routine activities- Pipeline cleaning

Internal pipeline inspection - ILI

External pipeline inspection

- Onshore - above groundsurveys etc- Offshore - ROV surveys etc

Modification and repair process

Emergency management

Defect assessment and repair methods

Training and competency of staff

Safe control of operations

Continuous improvement processes in place

The Pipeline Integrity Management System under review can then beassessed for compliance with prevailing regulations and compared tointernational best practice. Recommendations can be made to theOperator as to how they can improve their processes and systems.

Generally in such a project there will be a Phase 2 which comprisesgap closure actions. Depending on the results from the gap analysisthis might entail a complete overhaul of an Operators EngineeringDocumentation System or it may involve some rationalisation andrepackaging to ensure that the PIMS is clear and coherent.

Typical Onshore Pipeline Damage/Failure Data

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f. Investigation of Pipeline Incidents

The majority of incidents on pipelines usually involve some form ofmechanical damage being caused to the outside of the pipe surface.In some cases, corrosion may also be the cause of a pipeline failure.In both scenarios, if the damage or corrosion is extensive, this maycause the process fluid to escape.

Incidents involving surface damage to the pipeline where no processfluid has escaped are usually easier to investigate and assess. Typically,this type of assessment involves using a range of mechanicalmeasuring systems to map out the damaged area, non destructivetesting examinations such as ultrasonics, magnetic particle inspectionand/or dye penetrants to detect for defects and cracking in thedamaged area, a photographic survey and if required, cuttings of thepipe material are taken for analysis to confirm the grade of pipematerial. At the end of the onsite investigation, GL will produce atechnical report on the findings from the onsite inspections and willmake a number of recommendations to enable the pipeline to be putback into service.

If the damage or corrosion has caused a through wall hole andprocess fluid has escaped, then the operator will usually have toshutdown the pipeline and fit an emergency wraparound clamp tocontain the leak. GL have been involved in a number of these typesof incidents and provided support to the client that required a numberof GL consultant engineers covering a range of disciplines to producea solution. In the majority of cases, through wall leaks have beenrepaired using a specially fabricated wraparound fitting, called anepoxy repair sleeve. No welding is required with this type of fittingand can be fitted in approximately half the time and at a fraction ofthe cost when compared to a welded fitting.

g. TD/1 Surveys (Affirmation of MOP for Onshore Pipelines)

A full survey of the pipeline route must be carried out in order todetermine the extent of developments. This can be undertaken by aline walk or by means of aerial photography or video. Measurementof population density is based on this survey and the method ofcalculating this is described in IGE/TD/1.

Infringements from changes in proximities, population density ortraffic density identified from the survey should be evaluated as soonas possible by means of a quantitative risk assessment (QRA). Anymeasures identified by the QRA which are viewed as reasonablypracticable in reducing the risk should subsequently beimplemented.

In addition to the proximity review the following issues are alsosubject to review:

Materials & fittingsRoad crossingsValve maintenanceHydrostatic testingRail crossingsGround movementAnnual & 5 year MOP recordsWatercourse crossingsPipeline damage historyFatigue lifeExposed crossingsPipeline leakage historyWeld qualityOther crossingsActual pipe details

In addition to all of the above items, pipeline strip maps,photographs, pressure system drawings and other relevant data areused to produce a Fitness for Purpose Report of the pipeline underreview. This report will recommend a suitable Maximum OperatingPressure for the pipeline. The report will include areas of noncompliance where remedial work is required before the MOP can beapplied.

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Town gas service (manufactured & reformed)SleevesEnvironmental issuesDepth of coverImpact protectionRecordsBuilding proximity distancesCathodic protectionAbandoned sectionsPopulation density (typeR&S areas)Condition monitoringOfftakes & spurlinesLA planning proposals

h. Pipeline Uprating

The general approach is:

Collation of all relevant design, construction andoperation data for the pipeline

Assessment of the pipeline at the proposed up-ratedpressure in accordance with the up-ratingrecommendations contained in the pipeline operatingcode. Where major design non-compliance is identified,then a detailed fitness-for-purpose assessment is carriedout to determine whether it is acceptable or not

Where a pipeline infringes surrounding infrastructurethen established risk analysis techniques are used toassess both individual and societal risks. Where the risksare demonstrated to be clearly within the pipelineoperators acceptance criteria, then they are deemedacceptable

In all cases where the pipeline design factor at aninfringement exceed 0.72 then potential risk reductionmeasures are considered and the safety benefits areevaluated in accordance with the As Low As ReasonablyPractical (ALARP) principle

All required modifications are identified and then requireddetail designs are prepared and the modifications areimplemented

The pipeline is revalidated using in-line inspectiontechniques and all necessary repairs are then identifiedand implemented

Following satisfactory completion of modifications andrepairs, the pipeline pressure is raised to the up-ratedMaximum Allowable Operating Pressure (MAOP)

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i. Welding Technology Services

GL staff have been involved, in many cases, in the development andqualification testing of procedures and consumables for theconstruction of pipelines, process plant and ancillary high pressureequipment. GL carries out weldability studies on all candidate linepipeand components used in the UK National Grid Transmission system inaccordance with the requirements of National Grid specificationT/SP/MPQ/1. For line pipe this involves the production of a full scalegirth weld under simulated field conditions, to an approvedprocedure and including such factors as lifting and manipulation tosimulate movement of the line-up clamps following deposition of thehot pass.

Additionally repair special procedures are tested and qualified beforebeing putting into service.

Welding consultancy services are also required when new or difficultmaterials are involved, such as those employed for high temperatureor sour service environments and include materials such as Inconel,duplex stainless steels or linepipe clad with these materials. In thesecases very specific welding procedure specifications are drawn up andinitial production welding is carried out under the supervision ofGL expert staff.

GL also carries out welding prequalification of high pressurecomponents produced by new suppliers, and an investigation of thewelding procedures and consumables employed by candidatecompanies is an integral part of this. Site visits are carried out andsupervision of component production ensures that they meet therelevant requirements for specific companies and individual projectsand can be welded into the system without problems.

GL also supplies expert assistance in the selection and application ofmethods for weld repair of pipelines, process plant and high pressureequipment. This is supplemented by expertise in inspection whichensures that defective areas are professionally repaired and returnedto service in fully reliable condition.

j. Grouted Tee

The Grouted Tee involves placing two half shells around the pipe andbolting them together. The shells, with a specified wall thickness,have a similar material grade to the parent pipe. The shells are sizedto allow a generous gap between the bore of the shells and theoutside diameter of the parent pipe. This annular gap is filled withgrout, when cured this transfers additional structural loading in thepipe to the tee shell.

Pressure containment is achieved via the "saddle" seal, which ispositioned next to the opening of the main pipe. The sealingspecification is unusual and demanding. The primary functionaccommodates large variations in the annular gap between pipe andshell. It also has to cope with a grit blasted surface preparation,which is equivalent to SIS 05-59-00 Sa 2.5 finish. It also needs towithstand elevated temperatures during the drilling operation. Moreover, the saddle seal has been designed to be independent of thequality of the grout and on its own should maintain the integrity ofthe pressure containment.

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k. Internal Corrosion Management

GLs approach to corrosion management is to consider the fluids,materials and safety aspects as an integrated whole. In most respectsthe transported fluids dictate the materials and corrosion controlmethods used for pipelines while occasionally the materialstechnology available will shape the feasible transportation options.Ultimately the objective is to produce a pipeline with an acceptablerisk of failure. Thus, all these aspects have to be addressed whenconsidering internal corrosion management.

The production of a corrosion management system would generallyinvolve the following stages:

1. Gather process data e.g. temperatures, pressures andfluid compositions during both normal operation andupset conditions

2. Consider the pipeline safety risk assessment in order to:

Identify major hazards Identify HAZOP actions related to corrosion and

materials Determine acceptable level of risk

3. Conduct corrosion risk assessment including:

Calculation of internal corrosion rates Assessment of stress corrosion cracking threat Assessment of erosion threat

4. Produce corrosion management scheme

Select materials (corrosion resistant alloys or carbonsteel with corrosion allowance)

Select corrosion control methods (e.g. inhibition,coatings)

Select corrosion monitoring methods and locations Produce corrosion data management strategy and

select tools Devise suitable key performance indicators (KPI) for

corrosion management Document change procedure for revising scheme if

process parameters are altered (e.g. after uprating) Produce pipeline corrosion management

guide/manual

5. Feed back the corrosion management activities into thepipeline safety case and risk assessment as mitigatingfactors

Corrosion inhibitor selection is an important aspect of internalcorrosion management for pipelines. The figure below shows thework flow commonly used when GL undertakes inhibitor selection forpipelines:

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CASE STUDIES

a. Investigation of AC Interference Problem on High PressurePipeline

Date: 2003Customer: Shell UK LtdSavings: Prevention of pipeline rupture

Issue:

The client had experienced up to 40% loss in pipe wall thickness ona high pressure ethylene pipeline within 3 4 years of commissioning.It was initially thought that the metal loss was due to microbiallyinfluenced corrosion (MIC).

Methodology and Results:

The pipeline was coated with a fusion bonded epoxy mainlinecoating, which does not support the proliferation of bacteria requiredfor MIC to occur. The pipeline was observed to be running in parallelwith a high voltage power line for distances in excess of 1 km andhigh AC potentials and current densities were recorded on the line.Features specific to AC corrosion were noted during directexamination including:

Hardening of the soil adjacent to corrosion features

Smooth, hemispherical metal loss features

Significant build up of calcite salts within corrosionfeature

Confirmation of the corrosion mechanism, which was occurring at arate of 1.3mm/year allowed more regular ILI to be scheduled andmitigating action to be taken.

Savings:

Confirmation of the corrosion mechanism allowed a pipeline ruptureto be avoided along with the associated loss of gas and supply to thecustomer.

b. Guidance on SCC Risks on a Pipeline Operators Network

Date: 2006Customer: Major Pipeline Operating CompanySavings: Preventing pipeline rupture due to SCC

Issue:

The client requested GL to review the mechanisms by which nearneutral and high pH SCC occur on pipelines and to prepareprocedures for management of SCC risk.

Methodology & Results:

Stress corrosion cracking is a form of "environmentally assistedcracking" where the surrounding environment, the pipe material andstress act together to reduce the strength or load carrying capacity ofa pipe. Two types of SCC are known and are referred to as high pHand near-neutral pH SCC.

GL reviewed the mechanisms by which SCC occur on a pipeline andassessed the probability of near neutral and high pH SCC initiatingon the clients pipeline network. Where a risk was perceived to bepresent, guidance was produced on the actual risk SCC poses to apipelines integrity, the timeframe in which remedial action wouldneed be taken, the conditions under which pipelines could remain inservice, the methods of establishing the extent of SCC and how theSCC risk could be managed and controlled in the future.

Savings:

The work allowed the client to identify and target areas at highestrisk by better understanding the factors that contribute to SCC. Theprocedures developed by GL have allowed the client to modifyconditions thereby minimising risk and maximising the timeframe inwhich remedial action can be undertaken.

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CASE STUDIES

c. Coating and Backfill Interaction

Date: 2006Customer: BP Exploration and Operating Company LimitedSavings: Eliminating the requirement for selective padding

Issue:

The client was constructing a pipeline in a remote, environmentallysensitive region of the World, where the importation of selectivematerial for bedding and padding of the pipeline was not practicable.As a consequence, the only means of providing suitable bedding andpadding material was to process indigenous spoil, on site, by amethod of crushing and screening. The number of crushing andscreening units required to would have a major impact onconstruction costs. The aim of this project was to identify themaximum particle size of bedding and padding that could beaccommodated during backfilling, commissioning and service.


Pipeline construction often involves the importation of significantamounts of selective backfill to prevent mechanical damage of theexternal coating during construction and operation. Importation ofbackfill is extremely expensive, may be impractical in the more remoteregions of the world and may present problems in environmentallysensitive areas.

By understanding the links between geotechnical ground analysis,trench excavation equipment and performance and backfill materials,it was possible to identify appropriate external pipe coatings forparticular ground conditions. In addition, it was also possible toreduce the amount of imported backfill or the processingrequirements to match the mechanical resistance of the coating.

The data generated during this project enabled an algorithm/decisionmaking chart to be developed which allowed the operator to comparepipeline coating/backfill options based on technical and financialconsiderations.

Savings:

This work resulted in a significant reduction in construction costs byminimising the number of crushing and screening units required onsite. There was also a significant reduction in the environmentalimpact of having to import selective bedding and padding materialsonto site.

Backfilling

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CASE STUDIES

d. CP Decision Support Tool

Date: 2008Customer: Major Pipeline Operating CompanySavings: Compliance with the regulatory authority

Issue:

The client operated a number of pipelines that did not comply withthe minimum criteria for CP. The regulatory authority was aware of theproblem and placed a requirement on the client to demonstrate howthey were going to prioritise pipelines for remedial action.


GL developed a software programme to allow the prioritisation ofnon-compliant pipelines/pipeline sections, based on the integritythreat that being under protected posed.

The programme utilised information that was readily available fromthe original pipeline design data, from coating and CP surveys, fromin-line inspections and from adhoc exploratory excavations on thepipeline. The algorithms used within the programme considered thelikely failure mode (rupture or leak) that might result from beingunprotected, the timescale in which failure might occur (based on thedate when CP was first lost, the pipe wall thickness and the likelycorrosion rate) and safely and economic considerations.

The output of the programme was a priority ranking and a timescalefor remedial action.

Savings:

The CP decision support tool was accepted by the regulatory authorityas a transparent means of prioritising remedial action, therebypreventing improvement notices being issued to the operator.Development of the tool kick started the process of revalidatingnon-compliant pipelines.

e. Dent Assessment on a 30 Oil Pipeline

Date: 2007Customer: Middle East OperatorSavings: Savings were made due to potential loss of

containment and system shutdown

Issue:

A major Middle Eastern Operator had requested GL to undertake aninitial assessment of the integrity of a 30 diameter subsea main oilpipeline, which had sustained dent damage. The operator hadindicated that several in-line inspection tools had been damaged dueto the restriction in the pipe cross section. The dent was located onthe top of the pipe, and in close proximity to the seam weld. Theoperator therefore provided GL with a damage survey report whichincluded a map of the dent shape, identification of the peak dentdepth, and results of a visual inspection and magnetic particleinspection of the damage area on the outer pipe surface.


The purpose of the work was to provide the operator with an initialassessment of the severity of the dent damage in relation to theability of the pipeline to operate at its original design capacity andcontinue to be inspected using in-line inspection tools. Assessmentwas undertaken based on the guidance given in the Pipeline DefectAssessment Manual (PDAM) and background documentation toPDAM. Using information taken from full scale burst and fatigue testdata from vessels and ring specimens in PDAM, the data showed thatboth the static strength and fatigue performance of a pipe with adented weld could be significantly reduced. With the informationavailable and the uncertainty surrounding the quality of the material(pipe and weld) and the possibility of additional welding defects anddamage associated with the inspection tool, the recommendationwas that the damage should be repaired or replaced.

Savings:

Following recommendations for repair and the implications of anyfuture pressure increases, savings were made due to potential loss ofcontainment and system shutdown.

f. Advances in Interaction Rules for Corrosion Defects inPipelines Using FE Analysis and Full Scale Testing

Date: 2007Customer: PRCISavings: Considerably improving the accuracy of pipeline defect

assessment and thereby helping to reduce operatingcosts for pipeline operators by improving repair criteria.

Issue:

There still remain a number of limitations in the existing methods forassessing corrosion damage in pipelines (ASME B31.G, RSTRENG,API579, BS7910). GL has been undertaking a large programme ofwork on behalf of Pipeline Research Council International, Inc. (PRCI)to develop methods for:

Assessing interaction of corrosion defects

Assessing corrosion defects in pipelines of low toughness

Assessing pipelines subject to significant external loading

Assessing corroded pipelines subject to cyclic loading

Extending assessment methods for pipelines constructedfrom higher strength steels

Corrosion metal loss is one of the major damage mechanisms in oil andgas transmission pipelines. The pipeline industry widely uses the ASMEB31G and the RSTRENG methods for assessing the remaining strengthof corroded pipelines. These methods were developed using an earlyfracture mechanics relationship for the toughness- independent failureof pressurised pipes and were empirically calibrated against a databaseof around 80 full-scale burst tests for thin wall pipes, dominated bypipes of material grades B and X52.


GL recently undertook a comprehensive review on behalf of PipelineResearch Council International, Inc. (PRCI) of the existing andemerging methods for assessing corroded pipelines. This reviewidentified that the existing criteria used by the pipeline industry toassess interaction of metal loss defects is based on limitedexperimental data and has not been adequately validated. Existingpractice within the pipeline industry is to assume that defect clustersinteract when they are spaced six wall thicknesses (6t) from eachother. The development of new criteria for defect grouping andinteraction would considerably improve the accuracy of pipelinedefect assessment and thereby help to reduce operating costs forpipeline operators. GL undertook a comprehensive non-linear FEstudy and full scale burst testing program to develop new guidancefor interaction of metal loss defects in pipelines. It was concludedfrom this work that the 6t criterion used at present can be overconservative, particularly when assessing interaction of small pit likecorrosion defects. The output of this work will be included in a defectassessment guidance document for the pipeline industry.

Non-Linear Finite Element Models of Pipelines with Corrosion Damage

Savings:

Savings were made due to improvements in the accuracy of pipelinedefect assessment, which thereby helps to reduce operating costs forpipeline operators through significant improvements in repair criteria.

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CASE STUDIES

21

CASE STUDIES

g. Fracture Mechanics Assessment of a Defective Pig Trap

Date: 2007Customer: United UtilitiesSavings: Cost of temporary pig trap and system downtime

due to installation

Issue:

GL were required to conduct a detailed assessment of a reported crackindication found on the closure casting of a pig trap located at anAGI facility in the UK. Following defect measurement in February2007, this was recorded at approximately 3-4 mm. A number of pigruns were then subsequently conducted. The defect was thenre-measured and reported to have a maximum depth of 5.3 mm.Measurements suggested that the defect had therefore grown sincethe pigging runs were conducted in 2007. The operator of the sitefacility intended to conduct further pig runs in February 2008 andhence required an assessment to determine whether the defect wassafe for the intended pig runs.


The approach that GL used was based on a BS7910 level 2a fracturemechanics assessment. Using fracture mechanics calculations and useof the FAD (Failure Assessment Diagram), the aim was to determinewhether the current size of crack was safe under the current designconditions and safe for the intended pig runs. Finally using a BS7910fatigue assessment of the crack, fatigue calculations were thenconducted to determine the remaining fatigue life of the reporteddefect and whether further pressure cycles can be tolerated due tothe intended pig runs. The fatigue assessment results showed thatthe defective area was likely to endure a large number of cycles beforefailure. Consequently it was concluded that the defect would enduresufficient further pressure cycles to conduct the intended piggingruns.

Savings:

Ultimately the operator would have had to install a temporary pigtrap to conduct the required pigging runs. Following this, the temporary trap would have been removed and a new trap installed inits place resulting in costly delays and system downtime. Byconducting a fracture mechanics assessment, GL have saved the clientcosts associated with installing a temporary pig, inspection delays andsystem downtime.

h. Fatigue Assessment of Dented Pipeline

Date: 2006Customer: UK OperatorSavings: The fatigue assessment confirmed the remaining

fatigue life of the reported dents, pendingconfirmation that no further defects were present,was acceptable for the design life of the pipeline.

Issue:

The UK operator had requested GL to undertake a fatigue assessmentof two smooth dents found on one of their pipelines. The dents wereinspected during a calliper survey undertaken by T D Williamson, andwere reported as being no greater than 3% of the pipe diameter indepth. The dents were originally discovered in 1995 and the operatorsuspected they had been there since pipeline commissioning.


The assessment method used was developed by GL and isrecommended for Industry use by EPRG. The results from theassessment were also supported by a series of full-scale fatigue testson dented linepipe undertaken for National Grid. Fatigue life of thepipeline dents, initially assuming an unconstrained plain dent wasthen calculated using the method recommended for use by the EPRG.Results of the assessment showed that for smooth and defect freedents, the fatigue life was in excess of the design life of the pipeline.However, recommendations were made to confirm that no additionaldefects were present such as internal or external surface cracking.

Savings:

This fatigue assessment confirmed the remaining fatigue life of thereported dents, pending confirmation that no further defects werepresent, was acceptable for the design life of the pipeline. The resultwas that savings were made by the operator through unnecessaryrepairs.

22

CASE STUDIES

23

CASE STUDIES

i. Metallic Gas and Water Mains Affected by GroundMovement

Date: 2007Customer: UK Gas and Water Distribution CompanySavings: Specification of pipeline protection

Issue:

A new high speed rail link in the UK involved the construction ofapproximately 19km of twin bore tunnel below east London. The civilengineering work took place in the vicinity of a network of utilityservices. A total of 261 metallic gas and water distribution mainsrequire an integrity assessment due to the potential groundmovement from the tunnel construction. Of these mains units therewere approximately 73 that cross existing bridge structures locatedwithin the influence zone above the tunnel. If overstressing due tothe tunnelling occurred, diversion or protection of the mains wouldbe required.


The work has involved the selection of geometric and materialparameters for mains units, the selection of dimension and levelvalues for individual bridge structures and tunnelling geometries, thecalculation of ground and structure movements, the structuralanalysis of mains response to loading and restraints, and the checkingof calculated stress increments and joint disturbance levels againstacceptance limits.

Soil load transfer assumptions were considered over a range in orderto embrace the uncertainty over actual ground conditions around themains unit. This permits the sensitivity of piping response to bequantified and reduced uncertainty.

Benefits:

Many of the mains had demonstrated that overstressing due to thetunnelling is very unlikely to occur, therefore can be left in place andavoid expensive diversion or unnecessary protection.

Schematic showing pipeline level, bridgedimensions and tunnel details

PIPELINE model for a cast iron main crosses a bridge structureshowing applied ground movements due to twin tunnel

j. Pipeline Affected by Collapse of Quarry Face

Date: 2006Customer: UK Gas Transmission CompanySavings: Improved pipeline integrity

Issue:

An 18 steel pipeline located on the boundary of a sand and gravelpit became exposed by the collapse of a quarry face. The pipeline wasconstructed prior to the requirement for 100% inspection of girthwelds and therefore could be at risk of tensile fracture when subjectedto increased longitudinal tensile stresses. The operator required aninvestigation into the nature of the loading on the pipeline and theidentification of measures to maintain the pipeline integrity.


Immediate action was taken to stabilise the slope by designing andconstructing a buttress embankment against the quarry face.Excavations onto the pipeline indicated the presence of voids andlateral and vertical deflections consistent with failure of the quarryface. Pipeline profile measurements were carried out to establish thestress state and welds were inspected and repaired where necessary.The pipeline curvatures indicated yield magnitude stresses haddeveloped. A de-stressing operation was undertaken involvinguncovering and lifting the pipeline to reduce the pipeline stresses andrestore the as-laid profile. The stress relief was closely monitored byfitting strain gauges to the pipeline and these demonstrated that theground movement loads were successfully reduced. Detailedreinstatement guidance was specified in order to provide sufficientsupport to the pipeline in the new position.

Benefits:

Rapid reaction to a site incident averted the development of apotentially dangerous leak failure. A coordinated investigation andremediation exercise confirmed the condition of the pipeline andenabled appropriate remedial measures to be taken to ensure thepipeline operated within safe limits.

24

CASE STUDIES

A section of pipe being supported by airbags to relieve soil loadingA section of the exposed pipeline,showing the horizontal bending

25

CASE STUDIES

k. Deep Basement Construction Large Diameter Cast IronGas Main Affected by Ground Movement

Date: 2006Customer: UK Gas Distribution CompanySavings: Appropriate pipeline protection

Issue:

A hotel development in Central London involved the construction ofa 12-storey block with four basement levels. The basementconstruction involved excavation to a depth of 20m and theinstallation of a segmental diaphragm wall of 33 panels with totalwidth of 44m and up to 29m below ground level.

Two large diameter cast iron low pressure gas distribution mains arewithin the site boundary and the closest gas main is only 4m fromthe diaphragm wall.

Ground movement and surface loading associated with the hotelconstruction may cause some disturbance to the gas mains. This levelof disturbance need to be assessed in order to confirm that the gasmains would continue to operate within safe limits.


As part of the integrity evaluation, a condition assessment on the twomains was carried out. Two trial pits were excavated on site toestablish the exact location of the mains, to obtain samples of the pipebackfill materials for laboratory testing, and to carry out a conditionand support assessment on the mains. Although the mains were laidcirca 1880 and corroded externally, they were still in an acceptablecondition. Their remaining metal thickness was never less than 75%of the British Standard manufacturing minimum thickness value.

The structural analysis has been performed using GL in-house pipelinestress analysis programs PIPELINE and SURFLOAD. Both short termand long term ground movement from the basement excavation, together with construction traffic loading have been considered.

The integrity assessment shows that ground movements caused bythe basement construction raised the stress level in the mains andcaused the joints to articulate. Stress levels in the mains were alsoincreased due to the effects of construction traffic. However, theamounts were within acceptance limits.

Benefits:

The integrity assessment shows that, with appropriate temporaryprotection at the ground surface, the gas mains can be operatedsafely during and after the basement construction. This resulted insignificant cost saving in unnecessary protective measures andpossible diversion.

Surface corrosion of the 24 Gas Main

24 Gas Main 36 Gas Main

l. Effect of Slope Instability on High Pressure Pipeline

Date: 2006Customer: UK gas Transmission CompanySavings: Improved pipeline monitoring

Issue:

A 24 diameter pipeline is known to be routed through an area proneto natural slope instability in West Yorkshire. Two slope failures haveaffected the pipeline in recent years resulting in two phases of pipelineconstruction to avoid active areas of movement. The operatorrequired a fitness-for-purpose assessment of the current pipelineconfiguration to determine whether it has adequate performance forpotential future slope failures.

The pipe shown in this photograph sprang out of line when cut


The slope was examined to identify landslip dimensions andmovements that would represent design ground movement levels forthe fitness-for-purpose assessment. In addition to confirming the pipehad adequate strength and toughness, curved wide plate testing wascommissioned to determine the strain capacity of field girth welds.

Performance limits were selected based on tensile strain capacity, axialbuckling due to overload and lateral buckling due to the maximummovement capacity. The structural analysis considered the beam andring performance of the pipeline subject to a range of landslidegeometries and used thermal strain measurements to guide theselection of appropriate longitudinal fixity conditions.

The structural calculations of the pipeline behaviour from slopeinstability identified that the critical performance limit was bucklingfrom movement overload. The level of slope movement was identifiedto exceed 2m and the development is progressive allowing sufficienttime for intervention activities to take place.

Aerial photograph showing the pipeline route, the region of landslipand the surrounding area

Benefits:

The assessment identified that, with appropriate monitoring andsurveillance activities, the pipeline is fit-for-purpose. The outcome ofthe work avoided the need for costly upgrading or diversion work andthe need for widespread slope stabilisation measures.

26

CASE STUDIES

27

CASE STUDIES

m. In-Line Inspection Vehicle Development

Date: 2007Customer: China Pipeline OperatorSavings: Improved inspection

A team of consultants worked with the China Petroleum PipelineInspection Technologies company to design and build a newhigh-resolution magnetic flux leakage (MFL) ILI system. This projectstarted from a blank sheet of paper with the aim of delivering astate-of the-art inspection system having outstanding performancefor inspection range, maximum pipeline flow speed, detectionsensitivity and defect discrimination. Work covered all aspects ofhardware and software, including development and coding ofalgorithms for automated data analysis. Following an intensivetwo-year programme of work, which included substantial periodsspent in China with the customer and their local contractors, the newILI system was shown in trials in live gas transmission pipelines tomeet all of its specified requirements.

n. In-Line Inspection Data Analysis

Date: 2007Customer: China Pipeline OperatorSavings: Avoidance of excavations

An operator had conducted two ILI operations on the same pipelinesegment; one inspection used a calliper tool to identify denting whilethe other was conducted using high-resolution MFL for metal lossdetection. The calliper inspection reported a number of dents,including two of sufficient magnitude to require excavation and repairaccording to the operators standards. However, the locations of thesetwo dents were such that excavations would have been extremelydisruptive and expensive. GL were approached by the operator to givean opinion on whether the relevant calliper signals were, in fact, dueto dents.

GL specialists examined both the low-resolution (single channel)calliper record and flux signals from the MFL tool. Having performeda careful correlation of the two records it was possible to concludethat the two dent responses were actually caused by (a) a protrudingweldolet fitting and (b) bore reduction at an unusually heavy-walledforged bend. The operator was thus able to avoid digging at eitherdent location.

o. In-Line Inspection Scheduling

Date: 2007Customer: China Pipeline OperatorSavings: Optimised inspection schedule

A major operator of high pressure pipelines required a method forscheduling ILI that would maintain consistent reliability with respectto the corrosion threat.

GL applied their expertise in the field of structural reliability analysis totake information from the most recent in-line inspection and modelthe development of reported metal loss over time, allowing absolutefailure probabilities to be calculated for any time after the inspection.Our approach to this problem uses statistical and probabilistictechniques to represent uncertainties in pipe dimensions and materialproperties, defect dimensions and corrosion growth rates. GLproprietary software then applies these uncertainties with appropriatelimit state functions to quantify the time-dependent likelihood offailure for an ILI segment. Thus, the date of next inspection can bechosen so as to keep this failure probability below any requiredthreshold.

p. Review of Operations and Maintenance Practice

Date: 2006Customer: Middle East Pipeline OperatorSavings: Pipeline integrity management strategy

A gas transmission company were operating a small network in theUAE. As part of a major growth strategy they were constructing anew gas import pipeline and taking over responsibility for part of anexisting gas network.

The operator contracted GL to undertake a study of their currentOperations and Maintenance practices as well as those in use for thenetwork they were about to take over. GL undertook a gap analysisand compared the findings against best practice used by other worldclass operators. The next step was to consolidate practices, processesand documentation from the existing and new networks into acoherent Pipeline Integrity Management Strategy.

The gap closure actions entailed the production of a completeEngineering Documentation System to allow the successful adoptionand integration of the new network into the existing company assetbase. The PIMS was designed so that it can be readily adapted andupdated as required in the future.

28

CASE STUDIES

29

CASE STUDIES

q. China Joint Venture LNG Pipeline

Date: 2006Customer: International Pipeline OperatorSavings: Developed pipeline integrity strategy

A major oil and gas pipeline operator is working in partnership witha locally owned enterprise in China to export gas through atransmission pipeline from an LNG receiving terminal. GL wascontracted by the oil major to undertake a review of the PipelineIntegrity Management System in place to see that it was adequate.The review covered the following issues:

Management strategy

Pipelines operations and maintenance management

Emergency management

Data management

Engineering documentation

Following an in-country visit to gather information and interviewoperational staff, GL subsequently prepared a report and apresentation for the joint venture company management. Thisprovided a PIMS strategy and process diagrams to provide the clientwith a road map towards achieving best practice.

r. Investigation of Pipeline Incidents

Date: OngoingCustomer: UK Gas SupplierSavings: Incident report compliance

Over the past 12 years, GL have been contracted to a major UK gassupplier to provide an incident consultancy service for both their highpressure and low pressure gas distribution systems. Various incidentshave occurred over the intervening years and have involved bothpipeline corrosion and mechanical damage to the pipeline. Theincidents have ranged from minor to severe, but have all been dealtwith quickly and efficiently by GLs team of specialist incident consultants.

GL have also performed a number of investigations involving incidentson process plant. This area of work whilst smaller than pipelineincidents is growing in size. GL have investigated process plantincidents both the within UK and abroad for a number of majorenergy companies.

s. T/D1 Surveys

Date: 2007 - 2011Customer: National GridSavings: Re-affirms M.O.P

GL have recently commenced a contract to survey approx 50 pipelinesections per year over a 4 year period for the largest gas pipelineoperator in the UK (approx 12,000km in total). GL were well placedto win this work having extensive previous experience of deliveringthis service in various parts of the UK, including East Anglia, NorthLondon, Wales and West, South of England and Scotland. GL alsodeveloped the Maintenance Procedure (T/PM/MAINT/5) upon whichthe detailed aspects of the survey are based.

The TD/1 resurvey begins with the existing TD/1 Report (undertaken4 years previously). A data gathering phase reviewing all the itemslisted above then commences. A major aspect of this is pipeline faults,modifications and repairs experienced in the intervening period. Inparallel with this an infrastructure survey will commence using aerialphotographs. A close comparison is carried out between the newphotographs and those from the previous survey. From this, newdevelopments and potential encroachments are identified. These arelater confirmed via on site surveys. Any changes to area type (e.g. typeR area becoming type S) can then be assessed. If necessary pipelineQuantitative Risk Assessments can also be undertaken.

The final deliverable for the client is a TD/1 Report in line with IGE/TD/1and T/PM/MAINT/5. This report gives the client the information theyrequire to allow them to re-affirm the Maximum Operating Pressurefor the pipeline section in question for the next 4 years.

t. Pipeline Uprating

Date: 2004Customer: TranscoSavings: Avoids new construction

Transco successfully uprated >1000km of pipelineutilising systems and methods developed by GL

GL worked with Transco in developing the systems andmethods

GL has incorporated previous learning points within cur-rent methodology

GL, as principal contractor, has successfully uprated375km of pipeline for Transco when GL executed allworks from feasibility study, through assessment and siteremedials, to pressure-raise

GL has worked via other principle contractors to providecomplete uprate safety justifications for Transco

GL offer modular up-rating work packages that cover anentire project or any discreet part thereof

30

CASE STUDIES

31

CASE STUDIES

u. Design and Qualification of Repair Procedures for BellowsAttachment Welding

Date: 2008Customer: Pipeline OperatorSavings: Improved welding procedure

A GL report on the bellows connection concluded that the bellows onthe pipeline required a weld repair to be undertaken on the crackedfillet welds. The bellows configuration is shown in Figure A of thatreport, reproduced below:

Consequently, according to British Standard BS 6990, prior to weldingonto the live pipeline, it is necessary to qualify a procedure, simulatingthe cooling effect of the gas which complicates the qualification. Thequalification set-up should simulate actual flow conditions.

The weld procedure (below) has been developed to minimise the riskof lamellar tearing. For weld procedure qualification, plate materialrepresenting the nearest equivalent currently available material isused.

Proposed weld procedure for the repair. Qualification of thisprocedure is in progress.

Weld Repair instructions:

Weld repairs to cracked fillet welds in bellows unit to becarried out after qualification of the attached weld repairprocedure and following decommissioning and purgingof pipeline 2.

Ensure all necessary risk assessments and safety checkshave been undertaken and procedures are followed,including safe control of operations (non routineoperation) and entry into confined spaces.

Prior to repair, determine chemical analysis of carrier pipeand box material by on-site material sampling of thecarrier pipe and restraining box material in accordancewith T/PM/Q/10 (ref clause 12 and appendix B). Reportresults to GL for assessment.

Remove the two fillet weld cracks in bellows 2 by grindingin accordance with T/PM/P/11 appendix F.

Confirm defect removal by visual inspection and MPI.

Check carrier pipe for defects by UT & MPI belowintended area of weld repair prior to welding.

Perform weld repair in accordance with attachedprocedure: WPS/A/Tinsley/01FR (subject to qualification).

Completed repair welds to be subjected to visualinspection and MPI.

Cracking located in bellows attachment fillet welds.

v. Grouted Tee

Date: OngoingCustomer: VariousSavings: Avoids welding and pipeline decommissioning

National Grid Transmission Above 7 bar

National Grid Distribution below 7 bar

BP (Forties 36 pipeline) Approved for high spiked crudeoil application

Tullow Oil Class 600 56 bar

Ineos Chlor (Runcorn former ICI plant)

Laing Above 55 bar system

Murphy below 7 bar

BG International thin wall applications

Comgas (Sao Paulo, Brazil) CLASS 600 17 & 35 bar ringmains.

Phoenix Natural Gas (Belfast, N Ireland) (1 operation -One Grouted Tee installation)

Edison Welding Institute (Columbus, USA) StainlessSteel and Titanium flow lines

34

CASE STUDIES

36 x 36 - Feeder 7 - July 2003

35

CASE STUDIES

National Grid - Marsworth Pressure Reduction

Date of Installation: Pipeline Diameter: Pipeline Material: Pipeline Wall Thickness: Operating Pressure: Size of Tee installed:

BGI / ComGas - Sao Paulo, Brazil


Bishop Auckland Test Loop


National Grid - Feeder #7 Transmission pipeline


Tullow Oil - Bacton, United Kingdom

Date of Installation: Pipeline Diameter: Pipeline Material: Pipeline Wall Thickness: Operating Pressure: Size of Tee installed: Duration of Installation: Client name & contact No.

Installation of 4 high pressure double branch Grouted Tee fittingsfor flow isolation, stopple operation. o 4 bypass connections October 2004 12 Steel (API 5L Grade X42) 7.9 mm 34.5 bar 12 Equal Tee (Class 300) Double branch

Two Grouted Tees were installed, one either side of an existing block valve.The installations were used to create a full-bore bypass around the block valve. October 2003 20 Steel (API 5L Grade X65) 4.5 mm 31 bar 20 Equal Tee (Class 300)

Controlled pipeline loop at GLs test facility at Bishop Auckland

October 2000 24 Steel (API 5L Grade X52) 12.5 mm 58 bar 24 Equal Tee (Class 600)

One CLASS600 Grouted Tee was installed onto Transcos transmissionpipeline to allow for a new pipeline tie-in. June 2003 36 Steel (API 5L Grade X65) 15.9 mm 75 bar 36 Equal Tee (Class 600)

Two Grouted Tees were installed linking two incoming offshore pipelines. The Grouted Tee wasconsidered because of Tullow Oils polices of zero hot work, except during a plant shut down.August 2004 20 & 24 API 5L Grade X52 20mm & 24mm 56 ar 18 off 20 & 18 off 24 (Class 600) 15 hours per Grouted Tee plus Grout curing Michael Webster 01263 725084

w. Weldability Testing of 48 Diameter X80 Europipe Production

Date: 2007Customer: National Grid (Milford Haven extension)Savings: Approved procedures and manufacturing

Weldability testing entails the production of a full-scale girth weldbetween two 12m pipe joints under field conditions and includingthe manipulation of the partially-completed weld to simulate theremoval and movement of the line-up clamp. Following production ofthe complete girth weld, the joint is subjected to X-ray inspection andmust pass required codes (T/SP/P/2 or API 1104 requirements) and isthen subjected to a full suite of mechanical tests. Followingsatisfactory results from these investigations, the welding procedureand the linepipe manufacturing route are qualified for supply toNational Grid.

x. Corrosion Control of a Sour Gas Pipeline

Date: 2006Customer: North Africa Offshore OperatorSavings: Identified corrosion inhibitor

Description:

A major operator produced sour gas and condensate from a field locatedin the Mediterranean. The field infrastructure consists of a number ofplatforms to dehydrate the produced fluids, which are then transportedto the onshore gas processing plant via a multiphase pipeline.

Issues:

The processing plant on the platforms and the multiphase pipelinewere manufactured in carbon steel. Corrosion protection is requiredand this is provided by corrosion inhibitor injection. The inhibitor inuse was dosed at high rate to ensure sufficient protection resulting ina high cost of treatment.

Application:

GL carried out a chemicals selection programme with the aim ofidentifying a corrosion inhibitor treatment providing the optimumbalance between dose rate, cost and environmental impact. Theprogramme included a review of vendor-supplied data, corrosioninhibitor performance evaluation in laboratory autoclave tests, (underrepresentative conditions) and field trials.

Results:

A suitable inhibitor meeting the performance criteria was identified.Dosing was optimised and the following benefits were delivered:

50% reduction in the chemical unit price Improved corrosion inhibition performance 33% reduction in the chemical dose rate Lower environmental impact Increased plant integrity Increased corrosion awareness (improved corrosion

management strategy)

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CASE STUDIES

Girth welding of 48 X80 pipeduring weldability testing

Simulation lifting of 48 joint afterhot pass deposition.

Sample welding procedurequalification record from the48 X80 trials, showing jointdesign, consumables, pre-heatrequirements, pass sequenceand other details.

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CASE STUDIES

y. Naphtha Pipeline Integrity Management Study

Date: 2005Customer: Far East Offshore OperatorSavings: Corrosion management

Background:

GL was contacted by a gas company operating in the Far East to offerrecommendations for corrosion management of a naphtha subseapipeline. A recent in-line inspection revealed that the pipeline hadundergone internal corrosion (equating to 10-25% metal loss). As thepipeline was required to operate for a further 20 years, GL was askedto devise a cost-effective lifetime integrity management strategy.

Solution:

GL applied its broad knowledge and experience in failureinvestigation and pipeline corrosion management to determine thereason for internal corrosion and identify the most cost-effectiveintegrity management solution. GL applied risk basedlifecycle-costing methods to compare the viable reconditioningstrategies. We also delivered an implementation plan and corrosionmonitoring strategy to demonstrate long-term effectiveness.

Benefits:

GL demonstrated that both corrosion inhibition and in-situ coatingwould allow a 20-year life for the pipeline. However, based on uponNPV cost and ease of implementation, corrosion inhibition was thepreferred option. NPV for inhibition over 20 years was only one thirdof the coating NPV costs. GL also demonstrated that the in-situ coat-ing option would require complex project management in order to ac-complish the work between naphtha shipments.

z. Sour Export Pipeline Study

Date: 2006Customer: Major Oil Production CompanySavings: Materials and evaluation

Background:

A new ultra sour oil field was to be developed in the environmentallysensitive Caspian sea. It was thus vital that the oil export pipelines didnot suffer any leaks during operation to avoid pollution damage. Onemember of the joint venture suggested the use of corrosion resistantalloy pipelines to avoid any risk of leaks, however this would involvecosts of $2 billion just for the alloy so another solution was needed.The oil company asked GL to consider the materials andcorrosion control options for the pipeline.

Solution:

GL evaluated the corrosivity of the produced fluids byconsidering the acid gas composition, water content, pressures andtemperatures. These parameters were used for sour gas corrosionmodelling using both industry standard methods (e.g. DeWaard andMilliams) and software specifically developed by GL (PrCSM). Sourcracking mechanisms such as sulphide stress cracking andhydrogen induced cracking were also considered in the study. Theresults of the modelling and an economic study were used tocompare various materials options for the pipeline. The options were:

Sour resistant carbon steel with corrosion inhibition

Nickel alloy lined pipe

Nickel alloy clad pipe

Solid nickel alloy pipe

Results and Benefits:

The study showed that sour resistant carbon steel with corrosioninhibition could be used for the sour oil export lines with anacceptable risk of failure. The small quantities of water present withinthe pipelines allowed corrosion inhibition to reduce corrosion ratesand the cracking risk to a minimal value.

Germanischer Lloyd does not warrant or assume any kind of liability for theup-to-date nature, accuracy, completeness or quality of the information provided.Liability claims against Germanischer Lloyd arising out of or in connection withmaterial or non-material loss or damage caused by the use or non-use of informationprovided, including the use of incorrect or incomplete information, are excludedunless such loss or damage is caused by the proven wilful misconduct or grosslynegligent conduct of Germanischer Lloyd.All offers are subject to alteration and are non-binding. Germanischer Lloyd expresslyreserves the right without notice to change, supplement or delete parts of the pagesor the entire offer or to stop the publication temporarily or definitively.

Germanischer LloydIndustrial Services GmbH

Oil and Gas

Steinhft 9

20459 Hamburg, Germany

Phone +49 40 36149-7700

Fax +49 40 36149-1781

[email protected]

www.gl-group.com/glis

Issue no.001 15.05.2008

Asset Management Services

Plant Integrity Management Services

Pipeline Integrity Management Services

Production Optimisation (Includes RAMand Gas Processing)

Dynamic and Steady State Simulation

Rotating Equipment Performance &Condition Monitoring includingEmissions Reporting

Gas Quality and Interchangeability

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