Computational Pipeline Monitoring for Liquid Pipelines
|Publication Date:||1 November 2002|
This publication focuses on the design, implementation, testing and operation of CPM systems that use an algorithmic approach to detect hydraulic anomalies in pipeline operating parameters. The primary purpose of these systems is to provide tools that assist pipeline controllers in detecting commodity releases that are within the sensitivity of the algorithm. It is intended that the CPM system would provide an alarm and display other related data to the pipeline controllers to aid in decision-making. The pipeline controllers would undertake an immediate investigation, confirm the reason for the alarm and initiate an operational response to the hydraulic anomaly when it represents an operational upset or commodity release
The purpose of this publication is to assist the pipeline operator in identifying issues relevant to the selection, implementation, testing, and operation of a CPM system. This document be used in conjunction with other API publications and applicable regulations.
This publication includes definitions, source and reference documents, concepts of data acquisition, discussion of design and operation of a pipeline as related to CPM, field instrumentation for CPM purposes, alarm credibility, pipeline controller response, incident analysis, record retention, maintenance, system testing, training, considerations for setting alarm limits, trending and recommendations for data presentation. The relationship between the pipeline controller and the CPM system is also discussed.
This publication is limited in scope to single-phase, liquid pipelines. It is recognized that no one particular methodology or technology may be applicable to all pipelines because each pipeline system is unique in design and operation. In addition, detectable limits are difficult to quantify because of the unique characteristics presented by each pipeline. Limits must be determined and validated on a system-by-system and perhaps a segment-by-segment basis. Figure B-1 (along with the discussion in Appendix B) provides a starting point for understanding where the practical detection limit of commodity releases starts. This publication is not all inclusive. The reader must have an intimate knowledge of the pipeline and may have to refer to other publications for background or additional information.
CPM is intended usually as a tool to be used by the pipeline controller in the safe operation of the pipeline. Effective operation of a pipeline requires that the pipeline controller be familiar with the pipeline and the tools at their disposal. CPM is not currently intended to replace human judgement and intervention in the shutdown of the affected pipeline segment(s) and the closure of remote control valves or directing field staff to close hand operated valves on the pipeline.
This publication complements but does not replace other procedures for monitoring the integrity of the line. CPM systems, as well as other commodity release detection techniques, have a detection threshold below which commodity release detection cannot be expected. Application of the information in this publication will not reduce the threshold at which a commodity release can be detected. For example, trained pipeline controllers analyzing SCADA-presented operating data can be effective at detecting certain sizes (i.e., larger) commodity releases. Third-party reports, pipeline patrols, and employee on-site examinations can also be effective procedures when used to verify the integrity of the pipeline within their applicability range.
Note: This publication is in keeping with standard industry practice and commonly used technology; however, it is not intended to exclude other effective commodity release detection methods.
This publication is written for liquid onshore or offshore trunkline systems but much of this content may be applicable to other piping systems such as selected gathering systems, production flow lines, marine vessel loading/unloading, and tank terminaling operations. CPM has typically been applied to steel pipeline systems but may be applied to pipelines constructed of other materials such as PVC, polyethylene, fiberglass, and concrete. The successful application of CPM may be limited by the characteristics of these other materials.
Pipeline systems vary widely in their physical characteristics including: diameter, length, pipe wall thickness, internal roughness coefficient, pipe composition, complexity of pipe networking, pipeline topology, pump station configuration, and instrumentation (quality, accuracy, placement). These same pipeline systems can also be categorized by operational factors such as: flow rate, magnitude and frequency of rate/pressure fluctuations, blending, batching, batch stripping schemes, product type, viscosity, density, sonic velocity, bulk modulus, vapor pressure, pressure, temperature, and heat transfer. The CPM methodology selected must be evaluated against what characteristics of the pipeline are known and what is required by the methodology to provide acceptable results. Most CPM technologies have not thus far proven themselves capable of providing satisfactory CPM operation during periodic or permanent slack line conditions. If this condition exists in a particular pipeline, then the CPM selection criteria for that pipeline will need to consider that operating condition.