ABSTRACT

The authors present a non-commercial overview of the various computer based methods for performing leak detection on pipelines in real-time. The paper includes descriptions of over/short analysis, single point pressure analysis, deviations analysis, and model compensated volume balance techniques. strengths and weaknesses of each of the methods is discussed along with the instrumentation and installation requirements necessary for successful implementation. The effectiveness of the metho& as a function of pipeline operating conditions or philosophies is also explored.

1 INTRODUCTION

Detection of leaks on pipelines using computer based methods is a subject not without controversy over the past twenty years. Several techniques have been implemented on many different pipelines with various levels of success. The success, or lack of it, on any given pipeline is a complicated function of many variables ranging from the expectations of the pipeline company and the commitment of the vendor to quality to the technical solution employed. The techniques employed to detect leaks using software solutions are also quite varied. Often, it is difficult for a pipeline company to discern what is the best solution for their particular pipeline and philosophy of operation. This paper will attempt an explanation of the most popular software solutions used to detect pipeline leaks. Instrumentation requirements will be described. It will also include a discussion of the strengths and weaknesses of each method and the types of pipelines on which each performs the best. Some discussion of the cost of installation of each method is also presented.

2 VOLUME BALANCE

One of the earliest computer methods developed to detect the presence of a leak on a pipeline was the Volume Balance Method. The method as it is used today is an extension of the old Over / Short analysis and is based on the principle of conservation of mass. The Volume Balance method is a non-model based leak detection solution.

2.1 Theory of Operation

The principle behind the volume balance approach is the conservation of mass. That is, that the amount of fluid that goes into the pipe over any time interval minus the amount that goes

2.3 Compensating for Line Pack Changes

Often the method called Volume Balance refers to one in which only the flows into and out of the pipeline are considered. This would be mathematically represented by only the first two terms in Equation (1). Volume Balance without any correction for changing line pack is most often done on crude oil pipelines or other liquid pipelines that are not batched. The volume balance approach contains the implicit assumption of steady state. That is, that whatever mass is injected into the pipeline over a given time interval is equal to the mass that is delivered. Since the time interval is arbitrary, the pipeline must be assumed to be in steady state all of the time. The smallest leak size which can be detected over any time interval

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