Triggers for the Transient State of a Pipeline in Material Balance Systems Used in Real-Time Transient Hydraulic Modeling

2014 ◽  
Author(s):  
Noorallah Rostamy ◽  
Norense Okungbowa ◽  
John D. Yurchevich
Keyword(s):  
Steady State ◽  
Material Balance ◽  
Transient State ◽  
Leak Detection ◽  
Hydraulic Modeling ◽  
False Alarms ◽  
Threshold Method ◽  
Flow Meter ◽  
Transient Event ◽  
Number Of False Alarms

Computational Pipeline Monitoring (CPM) leak detection in liquid pipelines can be unreliable or have a high number of false alarms during transient hydraulic events. This paper presents techniques for avoiding these false alarms and for improving leak detectability during steady state operations. Application of this approach has improved both the sensitivity and reliability of CPM-based leak detection systems. When a pipeline is in steady-state operation, the leak detection thresholds can be reduced. When a transient is detected, the thresholds are increased to a higher value. Because of known errors in data measurement and the time at which the measurement was made, large uncertainties in the line-pack prediction can exist during these transient events. In this paper, CPM reliability is improved using dual thresholds; tight threshold for near steady state and relaxed threshold for transient operation. In the presented study, different transient triggers in a pipeline have been implemented to the dual threshold method in order to show the effect of transient thresholds on the reliability of the CPM models or the reduction in the number of false alarms. When the CPM model determines that a transient event is occurring, the imbalance threshold is increased to a pre-set higher value. The transient threshold will remain high until the transient event diminishes, then the thresholds will return to their original steady-state value after a pre-set wait period. This applies to each leak detection window and to each flow meter-to-flow meter section in the CPM model. Detailed information about the dual thresholds approach and the transient triggers is provided in the full paper. Results from the implementation of this method and the quantitative improvement of the CPM reliability and sensitivity will also be presented.

Field Test of a Leak Detection System: Planning, Execution and Results

2010 ◽  
Author(s):  
Daniel Sampaio da Silva ◽  
Si´lvio A. Melo Filho ◽  
Mauro Niehues de Farias ◽  
Anderson Pacheco
Keyword(s):  
Steady State ◽  
Field Test ◽  
Communication Systems ◽  
Detection System ◽  
Transient State ◽  
Leak Detection ◽  
Point Of View ◽  
Measuring System ◽  
Operational Parameters ◽  
Pump Station

The OLAPA pipeline (Oleoduto Arauca´ria–Paranagua´) is a 12in diameter pipeline and, with its 97,6 km in length, crosses a mountain region called “Serra do Mar” attaining elevations of about 900m in a dense forest region. Besides that, this pipeline crosses cities, farms, rivers, including a short submerse stretch in the Paranagua´’s bay. An incident in this pipeline could result in severe consequences, especially under the environmental point of view. Therefore, this pipeline was chosen to test the performance of a new leak detector system in Transpetro. The test consists in comparing the theoretical results with practical values of alarm times obtained from a controlled removal of product in an adequate point, in the middle of the pipeline, simulating a real leak. The system chosen to be tested was the LeakWarn system, which is a computational system that uses the mass balance principle with line pack change to analyze the pipeline operational parameters in order to alert when there is a risk of product leak. This test had the objective to evaluate the LDS and help Transpetro’s management team to analyze and decide whether or not to replace its current leak management system, since this new one showed the expected results and was compatible with the excellence level already achieved in the company. The field test was performed in July 7th 2009, through a vent valve far from the ends of the pipeline and it was made in three different conditions: 1) A big leak in the steady state of operation; 2) A small leak also in the steady state of operation; and 3) A big leak in the transient state of operation (immediately after the pump station start up). In order to proceed this test, a multidisciplinary team was assigned and several resources were used such as: Two tank trucks, a specially designed leakage line with control valves, measuring system, flexible hoses, communication systems and emergency equipments. The complete operation was monitored from the Control Center in Transpetro’s Headquarter, Rio de Janeiro. This paper describes the way the tests were performed and presents the results in order to contribute with useful information to be used in any field test for any other leak detection system. It shows how planning were done in order to insure that all operations would be performed according to strict procedures and in a safe way. It also describes the milestones and the work of each team involved in the activity, as well as their constraints and difficulties that had to be overcome during the planning and execution phases, that lasted approximately one year.

A Pipeline LDS Trial: Comparing Compensated Volume Balance Against SPRT Statistical Based LDS in a Brazilian Pipeline

2004 ◽  
Author(s):  
Renan Martins Baptista ◽  
Andre´ Luiz Guedes Maricato ◽  
Paulo Anchieta Masiero ◽  
Jose´ Lima da Silva
Keyword(s):  
Steady State ◽  
Statistical Analysis ◽  
Field Trials ◽  
False Alarms ◽  
Sensitivity Curve ◽  
Operational Conditions ◽  
Testing Period ◽  
Number Of False Alarms ◽  
Volume Balance ◽  
Leak Location

This paper describes field trials for two different technologies (built in two commercial products) for leak detection, location and quantification systems (LDS). Modified Compensated Volumetric Balance was tested against SPRT Statistical Analysis, and the obtained results were analyzed/commented. The tests were carried out in a 43 km long 20 in. pipeline (PREPSP), carrying different batches of crude oils, located in the state of Bahia, Brazil. Actual leaks under shut in, steady state, pump transient startup and shutdown operational conditions were introduced, and the performance of both technologies analysed. For each of those conditions and technologies, a sensitivity curve was plotted, leak location and its quantification was tabled, compared and commented. Finally, reliability data for both technologies (essentially, number of false alarms and non-expected misbehavior) were gathered for a two weeks testing period.

scholarly journals Adaptive Early Warning Method Based on Similar Proportion and Probability Model

2020 ◽  
Vol 10 (12) ◽  
pp. 4278
Author(s):  
Yazhou Li ◽  
Wei Dai ◽  
Tingting Huang ◽  
Meihua Shi ◽  
Weifang Zhang
Keyword(s):  
Early Warning ◽  
Probability Model ◽  
Similar Proportion ◽  
False Alarms ◽  
Mechanical Equipment ◽  
Threshold Method ◽  
Health States ◽  
Number Of False Alarms ◽  
Fixed Threshold ◽  
Equipment State

This paper presents a multi-state adaptive early warning method for mechanical equipment and proposes an adaptive dynamic update model of the equipment alarm threshold based on a similar proportion and state probability model. Based on the similarity of historical equipment, the initial thresholds of different health states of equipment can be determined. The equipment status is divided into four categories and analyzed, which can better represent its status and provide more detailed and reasonable guidance. The obtained dynamic alarm lines at all levels can regulate the operation range of equipment in the different health states. Compared to the traditional method of a fixed threshold, this method can effectively reduce the number of false alarms and attains a higher prediction accuracy, which demonstrates its effectiveness and superiority. Finally, the method was verified by means of lifetime data of a rolling bearings. The results show that the model improves the timely detection of the abnormal state of the equipment, greatly reduces the false alarm rate, and even overcomes the limitation of independence between the fixed threshold method and equipment state. Moreover, multi-state division can accurately diagnose the current equipment state, which should be considered in maintenance decision-making.

Evaluating the Reliability and Sensitivity of a Leak Detection System on a Liquid Pipeline

2006 ◽  
Author(s):  
Michael Twomey
Keyword(s):  
Detection System ◽  
Evaluation Process ◽  
Leak Detection ◽  
False Alarms ◽  
Detection Systems ◽  
Number Of False Alarms ◽  
Main Challenge ◽  
Bid Evaluation ◽  
Performance Limitations

Detecting leaks in a liquid pipeline is not the most difficult task for a leak detection system (LDS); detecting leaks without giving false leak alarms is the main challenge. An operator will have trouble identifying a real leak if he has to sift through many false alarms. Therefore pipeline leak trials should test the reliability (number of false alarms) of a leak detection system as well as its ability to detect real leaks. This paper reviews how a number of pipeline operators tested their leak detection systems with simulated leaks, verifying the reliability as well as the sensitivity of their new leak detection systems. These simulated leaks were introduced by removing product from the pipeline by bleeding. The paper also outlines a simple table based on the API 1155 guidelines to evaluate software based leak detection systems that can be used as part of the bid evaluation process to hold the leak detection vendor accountable to deliver the performance promised in his bid proposal. This paper high-lights some of the performance limitations to watch for when selecting and testing an LDS, For example; will a pipeline leak detection system detect the quoted minimum leak if the normal operations include transients? Does the system block leak alarms to reduce frequent false alarms? Are the leak detection times based on the time it takes to declare a “Leak Warning” or on the time it takes to declare a “Leak Alarm”? Finally, the paper discusses how to perform more realistic leak tests.

scholarly journals Multi-Machine Repairable System with One Unreliable Server and Variable Repair Rate

Mathematics ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1299
Author(s):  
Shengli Lv
Keyword(s):  
Steady State ◽  
Transient State ◽  
Repairable System ◽  
Repair Rate ◽  
Numerical Illustration ◽  
Transform Method ◽  
Unreliable Server ◽  
Busy Time ◽  
The Mean ◽  
Mean Time

This paper analyzed the multi-machine repairable system with one unreliable server and one repairman. The machines may break at any time. One server oversees servicing the machine breakdown. The server may fail at any time with different failure rates in idle time and busy time. One repairman is responsible for repairing the server failure; the repair rate is variable to adapt to whether the machines are all functioning normally or not. All the time distributions are exponential. Using the quasi-birth-death(QBD) process theory, the steady-state availability of the machines, the steady-state availability of the server, and other steady-state indices of the system are given. The transient-state indices of the system, including the reliability of the machines and the reliability of the server, are obtained by solving the transient-state probabilistic differential equations. The Laplace–Stieltjes transform method is used to ascertain the mean time to the first breakdown of the system and the mean time to the first failure of the server. The case analysis and numerical illustration are presented to visualize the effects of the system parameters on various performance indices.

A New Approach to Pipeline Leak Detection Using Electromagnetic Sensing

2016 ◽  
Author(s):  
Chris Dawson ◽  
Stuart Inkpen ◽  
Chris Nolan ◽  
David Bonnell
Keyword(s):  
Leak Detection ◽  
False Alarms ◽  
Detection Accuracy ◽  
Minimal Risk ◽  
Detection Systems ◽  
Acoustic Signatures ◽  
Cost System ◽  
Trade Offs ◽  
In Situ Sensors ◽  
Operational Range

Many different approaches have been adopted for identifying leaks in pipelines. Leak detection systems, however, generally suffer from a number of difficulties and limitations. For existing and new pipelines, these inevitably force significant trade-offs to be made between detection accuracy, operational range, responsiveness, deployment cost, system reliability, and overall effectiveness. Existing leak detection systems frequently rely on the measurement of secondary effects such as temperature changes, acoustic signatures or flow differences to infer the existence of a leak. This paper presents an alternative approach to leak detection employing electromagnetic measurements of the material in the vicinity of the pipeline that can potentially overcome some of the difficulties encountered with existing approaches. This sensing technique makes direct measurements of the material near the pipeline resulting in reliable detection and minimal risk of false alarms. The technology has been used successfully in other industries to make critical measurements of materials under challenging circumstances. A number of prototype sensors were constructed using this technology and they were tested by an independent research laboratory. The test results show that sensors based on this technique exhibit a strong capability to detect oil, and to distinguish oil from water (a key challenge with in-situ sensors).

Thermo-structural analysis of a honeycomb-type volumetric absorber for concentrated solar power applications

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Masoud Behzad ◽  
Benjamin Herrmann ◽  
Williams R. Calderón-Muñoz ◽  
José M. Cardemil ◽  
Rodrigo Barraza
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
Steady State ◽  
Discrete Model ◽  
Continuum Model ◽  
Transient State ◽  
Operating Conditions ◽  
Steady State Condition ◽  
Content Type ◽  
The Continuum

Purpose Volumetric air receivers experience high thermal stress as a consequence of the intense radiation flux they are exposed to when used for heat and/or power generation. This study aims to propose a proper design that is required for the absorber and its holder to ensure efficient heat transfer between the fluid and solid phases and to avoid system failure due to thermal stress. Design/methodology/approach The design and modeling processes are applied to both the absorber and its holder. A multi-channel explicit geometry design and a discrete model is applied to the absorber to investigate the conjugate heat transfer and thermo-mechanical stress levels present in the steady-state condition. The discrete model is used to calibrate the initial state of the continuum model that is then used to investigate the transient operating states representing cloud-passing events. Findings The steady-state results constitute promising findings for operating the system at the desired airflow temperature of 700°C. In addition, we identified regions with high temperatures and high-stress values. Furthermore, the transient state model is capable of capturing the heat transfer and fluid dynamics phenomena, allowing the boundaries to be checked under normal operating conditions. Originality/value Thermal stress analysis of the absorber and the steady/transient-state thermal analysis of the absorber/holder were conducted. Steady-state heat transfer in the explicit model was used to calibrate the initial steady-state of the continuum model.

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