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nvironmental protection and thesafe operation of pipelines with-in it are two of the primary con-cerns facing the Oil and Gas

Industry today. In the United Statesalone, since 1989 there have been morethan 5,700 pipeline accidents, resultingin 1,500 injuries, 325 fatalities and $850million of environmental damage.Consequently, the effective detection of

leaks plays a significant part in helpingto control this problem and is a primeconsideration for pipeline operatingcompanies worldwide.

Drivers for the installation of a leakdetection system include: Statutory requirements Minimized environmental and finan-

cial impact of a leak Improved public image Minimized litigationThere are many buying criteria to

consider when selecting a leak detec-tion system, but the primary needs ofthe pipeline company can be summa-

rized as follows:A new system: Must be better in terms of perform-

ance than any existing system Must maximize use of existing instru-

ments to minimize cost Must be user-friendly Must minimize false alarms

Software-Based LeakDetection Systems

Software-based leak detection sys-tems for fluid pipelines have beenaround for some 30 years and are fre-quently a subject for debate. During thelast ten years, they have developed to

the point whereby the software and theemployed methodologies have becomeaccepted as a standard supply compo-nent in the safe and optimized operationof a pipeline. This includes mathemati-cal model-based approaches that weretraditionally regarded as being difficultto understand and expensive.

Rapid configuration tools, improvedimplementation strategies and enhancedsoftware robustness, mean a model-basedsolution is now frequently the most cost-effective solution.

ESI Approach

E

To Leak Detection

Energy Solutions International has 25years of experience in providing practicalsolutions to leak detection, with more than300 installations worldwide. This covers theliquids, natural gas and complete range ofchemical pipeline sectors and can protec-tion across all normal and abnormal operat-ing conditions whether applied on a singlepipeline or complex pipeline network.

Its tool box of software includes all ofthe leak detection techniques now avail-able to the market, namely: Volume/Mass balance without inven-

tory correction. Volume/Mass balance with inventory

correction based on simplistic calcu-lations and available instrumentation.

Volume/Mass balance with inventorycorrection based on a real-time model.

Unexpected flow and pressure devia-tions based on real-time models.

Analysis of flow and pressure pointvariations as a result of daily operationin comparison to the signature of a leak.

Solutions work with any combination ofinstrumentation that is available. The soft-

ware complies and performs to API stan-dards and forms the basis for authorityapproval/operating in many countries.

Selecting Appropriate

MethodologyA practical approach is available for

what appears to be a complicated issue.Based upon available instrument informa-tion, telemetry and pipeline operating con-ditions, product managers can provideguidelines for the system performance.

Selection of the appropriate methodolo-gy is a decision based upon an engineer-ing assessment, considering performancecriteria and cost.

Leak DetectionPerformance:

Its Impact On CostAlthough there is no industry standardapproach to installation of a leak detectionsystem, product managers recognize thatperformance of the system (as defined bythe sensitivity, reliability and robustness) isthe most important factor to considerbecause it impacts significantly uponimplementation and maintenance costs.

Careful consideration must be given tothe required telemetry and instrumentationthat is needed to support the chosenmethodology and its sensitivity needs asthis will fundamentally affect the cost ofthe overall installation.

As an example, what may appear to

be a trivial decision, when specifying a1% accurate leak detection systeminstead of, say 3%, may increase imple-mentation costs by 500%. Similarly, themaintenance costs are highly dependenton choice of performance.

All leak detection methodologies gen-erate a response following a leak (a devi-ation in either pressure or flow of arecordable magnitude) that can be sub-ject to analysis. The ability to employboth statistical analysis and filtering tech-niques with annunciation on detection ofa true leak is essential.

The methodologies fall broadly into two

categoriesthose that use a balance of

Mathematical-Based Approach

Selecting And Installing A Software-Based Leak Detection System

by Jonathan Theakston andGregers Larnaes

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volume or mass and those that monitor thesignature of a leak. Methods that utilizethe signature of a leak are required todetect the leak as it occurs, otherwise it

will be undetected indefinitely. Those thatuse a balance methodology can be contin-ually assessed, as the effect of the leak onthe response is persistent.

It is also important to promote flexibili-ty when it comes to installing leak detec-tion systems, depending on the needs ofthe end user. Managers can provide andinstall pre-configured systems or can sup-ply standard licensed-based products forconfiguration and installation by the enduser only. If needed, they support familiarsolution techniques for the same method-ology within the same product.

A PartnershipApproach To Installation

A partnership approach is developed,be it for a fast-track installation using rapidconfiguration tools and improved imple-mentation strategies or a more traditionalengineering study-based approach.

1. Fast Track InstallationThe leak detection software is installed

by the manufacturer and together with thepipeline operator is integrated with theSCADA system. For most pipelines, thisexercise takes several weeks before thereis evidence of leak detection in operationin real life. This approach has advantagesover the traditional, extensive engineeringdesk studiesin that it establishes: the actual performance of the existing

instrumentation and telemetry systems;

how changing between differentmodes of operation is being repre-sented by the instrumentation.

In practice, these parameters determinethe limitations of any leak detection sys-tem. Knowledge of the actual performanceinformation is therefore fundamental forthe strategy decided upon, based on real-

life performance. There is no other way toestablish an equivalent level of knowledgefor a decision.

With this information it is possible toassess: the ultimate leak detection perform-

ancetime to detect a leak of a givensize and the accuracy of leak location

that can be achieved under thevariety of actual operating scenarios;

the benefits of alternative leak detec-tion methods.

And perhaps most importantly, thepipeline company can decide the beststrategy of implementation that matchestheir specific needs. Even at this stage it is

worth emphasizing that targeting for theultimate performance will most likelynot offer the best balance between theefforts needed to maintain the system andthe benefit achieved.

The decision on performance deter-mines operating costs during the entire lifecycle of a project.

2. Engineering Study-Based ApproachPrior to selection of a leak detection sys-

tem, a comprehensive engineering study isundertaken. This study considers the trueperformance that can be achieved with theavailable instrumentation and identify the

improvements that can be made withupgraded or additional instrumentation.

A successful system requires continuedparticipation in and a recognized owner-ship of the installation by the end user.

With more complex systems, a phasedinstallation to allow the end user to grad-ually familiarize and gain confidence in

the system will be suggested.The operators contribution to ensure con-

tinued, robust and accurate performanceincludes the adherence to recommendedinstrumentation, telecommunication, com-puter infrastructure and configuration.

With these basic but highly importantfactors in place, the end user will be ableto take comfort in the fact that the instal-lation will provide the best possible per-formance for its defined objectives.

From Installation ToProduction & SystemOptimization:

When deciding on the operating param-eters of the leak detection software, pro-duction managers recommend a cautiousapproach with a focus on simplicity andensuring that the system does not generateany nuisance alarms. It is an important fea-ture of the software that it tunes itself tothe pipeline, and in so doing it can beobserved that the performance improves

with no external influence.The application will also support imple-

mentation plans where the pipeline com-pany can gradually improve the perform-ance of the system by manual adjustmentand/or upgrades of the instrumentationand telemetry. P&GJ