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Copyright © 2001 Scientific Surveys Ltd. All rights reserved. 1

An intelligent pigging project: start to finishby William R Gwartney, Jr, and Ed Schaefer

TDW Pipeline Surveys, USA

Contents of this Paper:

• Introduction

• The operator's decision

• Considerations

• Why do I want to inspect my pipeline?

• What are my objectives?

• What unique features do I have in my pipeline?

• What historical data do I have on my pipeline?

• What is the best inspection tool for my pipeline?

• What are the contracting and establishing requirements?

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Pipeline Pigging and Integrity Monitoring Conference: Houston, 1992

2 Copyright© 2001 Scientific Surveys Ltd. All rights reserved.

Introduction

Pipeline operators today face the dilemma of increasing costs, aging pipelines, high demand for products, andstringent safety regulations. The pressures from all of these factors seem to demand decisions which are polarized:each solution seems to be in direct opposition to the other.

The pressures of return-on-investment demand that pipeline operators get full value for their investment of company resources. Every expenditure must be made only after assessing the cost as compared to the need.Management can no longer afford to "send an elephant to crush an ant". The solution to problems must meetspecifications which have been developed by people who are fully aware of all aspects of the problem to besolved, and of the impact the solution will have on the company.

The demand for products to be transported to remote markets by pipeline has increased significantly in the past 20years as the population of the world has virtually exploded. This population growth has changed the boundaries of the cities to the extent that areas which were once farm land are now the center of dense housing developments.This growth in population and expansion has created two basic problems for pipeline companies:

1. Increased demand for products has caused a demand for higher throughput which, in turn, demandshigher operating pressures.

2. Higher housing density demands that the pipeline operator prove that his pipeline meets the coderequirements for the changing environment.

In each case, the demand for more precise non-destructive testing methods becomes evident.

The operator's decision

When operating pipeline, companies decide to inspect their pipeline, they have several decisions to make and withthese decisions they lay the foundation for the outcome of the final results of the inspection survey. The followingis an outline of the considerations and suggestions of how the decision can make the job better for both the

pipeline operator and the supplier of the inspection service.

Considerations

1. Why do I want to inspect my pipeline?

2. What are my objectives?

3. What unique features do I have in my pipeline?

4. What historical data do I have on my pipeline?

5. What is the best inspection tool for my pipeline?

6. What are the contracting and establishing requirements?

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An intelligent pigging project: start to finish


Why do I want to inspect my pipeline?

The number-one reason for deciding to inspect the pipeline is safety, as well as to protect its largest investment,the pipeline. In addition to protecting their pipeline, most operating companies are trying to obtain as muchbaseline information as possible to support risk-management studies and to support suspected governmentregulations and possible legislation. A partial listing of the reasons for the pipeline inspection are:

To extend the pipeline life

The pipeline infrastructure around the world has reached a level of maturity approaching the design life of thesystem. Even though maintenance levels increase with the age of the pipeline, most lines can be operated safelyfor many years into the future. One requirement for this safe operation is the ability to inspect the pipe andmonitor certain critical operations on-stream without interrupting the flow of the pipeline.

To locate known or suspected pipe-wall defects in the pipeline

Typical defects found in transmission pipelines are:

• metal loss

corrosion

gouging

• spalling

• laminations

• mill defects

• product deposits

• chemical build-up or encrusted deposits

• stress corrosion cracking (SCC)

• hydrogen stress cracking (HSC)

• fatigue cracking

• geometry defects

ovality

wrinkles

buckles

dents

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To locate known or suspected leaks in the pipeline

Leak detection is an important need in the transmission pipeline industry. Many leaks come from isolated pittedareas in the pipeline. When pits are truly isolated, they are very difficult to find, since the difference in spurioussignals received by an instrumented inspection tool and an isolated pit are nearly the same.

Some work has been done in the past to develop a sonic tool which will locate leaks by the sound made by

different shapes of holes in the pipeline. However, this method is still not totally perfected.

Government requirements

The pressures of government regulation on the pipeline industry have increased around the world. Allgovernments, to varying degrees, are requiring that pipeline operators prove that their pipelines are in safeoperating condition and are free from defects, which effectively lower their operating specifications.

For example, there is pending legislation today in the USA to require pipeline operators to inspect their entiresystem every five years. This would require a program of inspection at the rate of 20% of the system every year.

The problem is not just the inspection tools and their cost, but it is also the ability to access the pipeline. Many

lines are not designed for pigging; they may have reduced-diameter valves or dual line sizes in the same run of pipeline. They also may not have launchers and receivers to insert the tools on-stream. Obviously, modification of lines to allow in-line inspection tools to be used can be an extremely expensive operation.

What are my objectives?

The following points need to be considered in establishing a set of standards to qualify the inspection tool andmethod of inspection with the least amount of interruption to normal operating procedures:

• detect, quantify, and accurately locate pipe defects

• provide a high level of discrimination between spurious and true defects

• make repair and replacement decisions from the data furnished by the pipeline inspection service

• re-certify the pipeline to its original design specifications

• complete all work with minimum interference to pipeline service and at the least possible total

• cost to operator

These are just a few points that need to be reviewed and considered during the discussion process, and need to bealtered to meet unique conditions for your particular pipeline.

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What unique features do I have in my pipeline?

Knowing all the features of most pipelines is almost an impossible task because of field repairs, changes inpipeline direction, lost records, etc.

In order to avoid major field problems, the operating company should be aware of possible problems that maydelay the inspection process.

Any of the following items may present problems for various inspection tools in certain diameter ranges, andshould be included with the bid document.

• back-to-back bends or in-line tees

• dual-diameter pipeline

• size and radius of bends

• sections of heavy-wall pipe

• seamless or ERW pipe

• type of construction

• internal coatings and type, and thickness

• flow rate

• is the pipeline designed for pigging?

• possible dents or third-party damage

• special or miter bends

• operating pressures and product temperature

• check valves

(Note: Bend radius of most elbows or tube turns can be the single most common cause for problems withinspection tools...3R or 3D? Interpretation of this term can be 18in or 36in radius in a 12-in diameter pipeline,depending on an individual's age or background. In order to avoid this problem, list radius in inches or millimetersto avoid any misunderstanding.)

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What historical data do I have on my pipeline?

Providing historical data to internal inspection companies will add to the quality of the information provided inthe final report. This valuable information will benefit both parties in locating problem areas, and speed-up thereporting process.

Historical data can include any of the following items or things you feel will benefit the quality of the informationsupplied by the inspection company. It should include a completed questionnaire with the following information:

• pipeline size, length, wall thickness, etc.

• location

• maps

• special needs or expectations

• required timing of the survey

• inspection specifications

• geometry survey reports (if available)

• as-built drawings (if available)

• operating pressure and product

• is a pigging program in place?

• who will be responsible for pipeline cleaning or preparation?

• special safety training or equipment required for the project

• product samples if ultrasonic inspection is being considered

What is the best inspection tool for my pipeline?

During the selection process, several factors need to be considered and evaluated:

• ease of understanding inspection results

• what additional information is available from the inspection survey

• benefits of one tools' technology versus another

• cost of the inspection survey in comparison to the information obtained

• is the running of a dummy tool provided with the survey

• additional operating costs not covered in the inspection contract

• is analysis software available

• a good understanding of the technology being selected

All these items need to be factored into the selection of the best tool for a given pipeline. In some cases, thelowest cost per mile (kilometer) is not the best selection or in the best interest of the company making theselection.

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What are the contracting and establishing requirements?

Determining or selecting the best technology for a given project or pipeline is a key element, but one should alsoconsider the impact of the actual job and the events that precede the inspection survey. Often, small points of issue regarding pipeline design, pipeline cleaning, mis-communication between companies...all can cause majordelays in the inspection process.

On awarding a contract, the following key points need to be reviewed and discussed:

• request a pre-job meeting

• establish or review cleaning program prior to the pipeline inspection

• review tool preparation and testing procedures

• what does the typical final report contain

Pipeline cleaning

Pipeline preparation and cleaning is a critical element in any inspection program, be it flux-leakage or ultrasonic,increasing the potential for better inspection results. Overlooking or de-emphasizing the cleaning process can, andin most cases will, result in extra inspection charges and possible standing-rate charges.

Many inspection companies can provide cleaning services that can compliment the corrosion survey, orrecommend several independent contractors that would be able to assist in the cleaning process.

Benchmarker placement

Depending on the inspection service selected for a corrosion survey, this will dictate the method of benchmarkingthe pipeline. For increasing the accuracy of locating possible problem areas, several types are being used:

• above-ground receivers

• magnets placed on the pipeline

• above-ground transmitting coils

Regardless of the type of marking system is being used, be sure that all locations are accessible and accuratelylocated in advance of the actual survey.

Final report

Final reports provide specialized information in various forms, and should contain some of the items present in

the sample report provided in Addendum 2. Familiarity with the information and data provided by any inspectioncompany will normally ease many concerns or problems in interpretation of these results. Several inspectionservices are offering additional software support to compliment the data provided in these reports, and should beconsidered for additional information not being provided in most reports. Keep in mind that most of thesesoftware programs are meant to compliment final reports rather than act as a replacement for wall-loss analysisbeing provided by the inspection company.

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