Liquid pipelines are integrated transportation networks providing multiple services for many shippers and customers.These systems may connect to multiple origins and destinations,and carry various products across long distances with changing elevation profiles,pipe dimensions and directions.Expectations are that the volumes received in the system are equivalent to the volumes delivered,with the exception of inventory changes.But in reality,every pipeline system will experience a loss or gain over time.Monitoring pipeline losses and gains employs tools and analysis methods developed specifically to troubleshoot pipeline variances.Evaluation of pipeline losses and gains uses basic statistical tools as well as intuitive and creative insight into what controls losses and gains.The basic tool for evaluating system performance is"Loss/Gain“,a measure of how well receipts,deliveries and inventory match up over a period of time.The concept is similar to that used for leak detection,but usually covers a longer time period.Loss/gain is a measure of the quality of the overall measurements in a system,and excessive loss/gain can signal the need for an investigation to identify causes and develop corrective actions.Good measurement can be enhanced by continuously monitoring the system,equipment and procedures to insure they are operating within acceptable limits.This monitoring may be accomplished by the use of Control Charts.This paper will review control charts and processes which may be used to monitor systems and offers troubleshooting guidelines to use when a pipeline system's loss/gain is out of tolerance.
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