API RP 1130 pdf download Computational Pipeline Monitoring for Liquids
The following categorizes and describes performance metrics for selection consideration. During the selection, theoperator may place more weight or importance on one metric or another. Asystem should achieve a satisfactorybalance between all four of these performance metrics. For a more complete description of these metrics pleaserefer to Annex c.
Reliability—The measure of the CPM’s ability to render accurate decisions about the possible existenceof a leak on the pipeline while operating within an envelope established by the CPM design. A system isconsidered more reliable if it consistently detects actual leaks without generating false alarms as defined bythe operator’s alarm management plan/program.
– Sensitivity—The composite measure of the size of a leak that a system can detect, and the time required forthe system to issue an alarm if a leak of that size should occur.
Accuracy—The validity of leak parameter estimates such as leak flow rate, total volume lost, type of fluid lost,and leak location are indications of CPM accuracy.
— Robustness—The measure of the CPM’s ability to continue to function and provide useful information even
under changing conditions of the pipeline (i.e. transients) or in conditions where data are lost or suspect.Asystem is considered robust if it continues to function under less than ideal conditions.
5 lnfrastructure Supports for CPM
A CPM is not a stand-alone system. It depends upon field instrumentation,communications, and may bedependent on Supervisory Control and Data Acquisition (SCADA) infrastructure as a data source(s) and avehicle to convey information to the controller (e.g. CPM data presentation and passing of CPM alarms).CPMsystems use rea-time data and may have other dependency interactions if the CPM is linked to a data historian.
5.1 Field lnstrumentation and Measurement
This portion of the recommended practice discusses the selection , installation, calibration and maintenance ofthe field instrumentation and the measurement that is necessary to adequately support a CPM system.
Different CPM applications may require specific types of instrumentation or levels of performance.Somemethodologies may need specialized instrumentation that is only used by the CPM.An operator may want toconsider the best practices for equipment and instrument installation as they relate to CPM. Instrumentationrequirements for a speciic CPM application should be integrated into the CPM installation and maintenanceprograms.
5.1.1 Selection of lnstrumentation and Measurement
Different CPM applications require specific types of instrumentation and measurement for levels of performance.Some methodologies may need specialized instrumentation and measurement that is only used by the CPM.
APIl Technical Report 1149, Pipeline Variable Uncertainties and Their Effects on Leak Detectability, outines theimportance of instrumentation and measurement to CPM performance. The calculations of API TR 1149 candemonstrate that additional and more accurate instrumentation and measurement increase CPM effectivenessand the calculations can be used to determine where the most cost-effective improvements can be made.Such analysis may be used repeatedly over the life of the pipeline system to achieve incremental performanceimprovement. The software developers or CPM providers may also be able to advise an operator on whichinstruments and measurements drive the CPM or influence the capabilities of the CPM applications as wellas advise on what effects additional or upgraded instrumentation and measurement may have upon the CPMsystem.
The quality of instrument data can afect the CPM system. Instruments should be selected considering the required measurement accuracy. Ranges and specifcations should be carefully matched to pipeline operating design, pressure, fow, temperature, density, viscosity, etc., to make best use of the instrumentation. Since instrumentation accuracy is generally stated in terms of percent of full range, the smallest available range greater than the desired range is preferable. There is no value in over specifcation of instrumentation and measurement accuracy if CPM performance is limited by the instrumentation or measurement loop accuracy, or repeatability and resolution of the SCADA system.