As the primary means of refined products transportation, multi-product pipeline plays a vital role in connecting refineries to local markets. Once disruptions occur, it will cause security issue on oil supply to downstream markets, even on the economy and stability of society. Based on the conventional reliability theory and detailed scheduling method of multi-product pipeline considering hydraulic constraints, this paper firstly proposes a multi-module systemic approach for the supply reliability analysis of multi-product pipeline under pump units failure conditions. Pump units are important corollary equipment in multi-product pipeline and their failure would affect the pipeline normal operation and downstream oil supply greatly. The approach includes three modules, namely, pump units analysis module, pipeline system analysis module and reliability evaluation module. In the pump units analysis module, Failure Mode and Effects Analysis (FMEA) method is adopted to analyse the correlations between pump units failure modes and causes. The Monte Carlo simulation method is employed to generate different failure scenarios based on the estimated failure rate of pump units. In the pipeline system analysis module, the detailed scheduling method of multi-product pipeline is adopted to calculate the maximum supply capacity for all delivery stations under a specific scenario. Due to the difficulty in solving detailed scheduling problem considering hydraulic constraints directly, two mixed integer linear programming (MILP) models are established. In the reliability evaluation module, the indexes of shortage, probability and adequacy are calculated to analyse the supply reliability quantitatively from global perspective and individual perspective. Finally, the proposed approach is applied to a real-world multi-product pipeline in Zhejiang, China. It is proved that this approach could provide significant guidelines for the supply reliability analysis of multi-product pipeline.

Existing industry standards have established the compressive strain capacity of pipelines within an empirical basis. The compressive strain capacity is generally associated with the peak moment. This approach has evolved from elastic stability concepts used in structural engineering for unrestrained pipe segments subject to primary loading (i.e. force or load control) conditions. This limiting condition does not take advantage of the observed performance for buried pipelines, when subjected to displacement control events such as differential ground movement, where the pipe curvature can exceed the peak moment response without loss of pressure containment integrity. This inherent conservatism may have a negative impact on project economics or sanction where the compressive strain capacity, rather than tensile rupture limits, governs the strain based design methodology. For these conditions, alternative performance limits defining the pipe compressive strain capacity are required. A numerical study was conducted, using finite element methods, to examine possible alternative compressive strain criteria for use in strain-based design applications. The results from this study and the requirements to bring these concepts forward through integration with industry recommended practice are presented.

According to the 2015 AER database there are approximately 473,000 km of high pressure pipelines in Alberta alone, ∼93,000 km of which have been discontinued. Of these 93,000 km of discontinued lines approximately half have been abandoned. When a pipeline is abandoned it is typically flushed out, marked and has all corrosion protection and monitoring systems removed. In the absence of corrosion protection all pipelines will inevitably corrode. This can create long term issues for abandoned pipelines. Two of the critical issues are potential ground subsidence and the creation of unintended water conduits. Ground subsidence is caused when an abandoned pipeline corrodes to the point of allowing the surrounding soil to fall into the empty pipe. Ground stability issues can result depending on the size and depth of the pipeline. Stability issues can appear suddenly in the form of sinkholes, slow slumping troughs or cracks in the earth and anything in between. Regarding unintended water conduits the main concern centres on a pipeline under or near water crossings or in areas of saturated soil. The pipeline corrosion can eventually provide a mechanism for water (or other constituents) to enter and migrate through the empty pipe and then be discharged further down the line. This uncontrolled migration can potentially have environmental impacts depending on what gets transported and where it ends up being discharged. One common industry method to protect abandoned lines from the issues described above is to backfill them with foam or grout. Backfilling areas of abandoned lines can help protect against ground instability and subsidence as the line corrodes away. Creating plugs or cutting/capping abandoned pipelines can protect against the possibility of water conduits. The use of paste technology is not common to the industry in this regard however it can provide many benefits over current foams and grouts. This paper will discuss paste technology and it use as a backfill option for pipeline abandonment.

The challenges associated with the welding of high-strength pipeline steels, such as X-80 and X100, are well established. While there are many filler metals that provide either adequate strength or good impact toughness, it is difficult to find products that provide both. Add to that the need for all-position welding and high deposition rates, and the options become almost non-existent. Several years ago, Hobart ® Filler Metals began working on a line of flux-cored arc welding (FCAW) consumables that are unique in the welding industry. The products have a basic slag system, but do not operate like traditional EXXXT-5 electrodes. Traditional T-5 electrodes have a low-melting, fluid slag, which makes welding out-of-position especially difficult. They also have a high level of calcium fluoride, which affects the stability of the arc and causes weld spatter. While the weld metal mechanical properties and crack-resistance are excellent, the welder appeal and ease-of-use tend to be sorely lacking in most EXXXT-5 electrodes. The new approach utilizes aluminum for deoxidation, which has the added benefit of very clean weld deposits. The composition has been carefully optimized with appropriate levels of carbon, silicon, nickel and manganese. Alternative fluorine sources are used in place of calcium fluoride, which results in very good welder appeal and all-positional capabilities, including vertical down. The novel use of aluminum in a gas shielded process results in very low oxygen, nitrogen and sulfur content, providing exceptionally clean, tough weld deposits. Although the new products have been produced over a range of strength levels, the primary emphasis of this paper is on E691T5-GC (E101T5-GC) and E831T5-GC (E121T5-GC) electrodes. Testing shows that tensile strength levels ranging from 700–880 MPa (100–128 ksi) can be achieved, with toughness levels of 120 J at −60°C (90 ft-lbs at −76°F) or better. The highly basic slag, combined with low weld metal hydrogen (less than 4 ml/100 gm), provides excellent resistance to cracking. The product can be used in all positions, including vertically down, making it an especially appealing choice for welding high-strength pipe.

This paper introduces basic research conducted to develop a numerical analysis technique for water hammer analysis. The CIP (Cubic Interpolated Profile) scheme was applied to obtain more accurate results without greatly causing a spatial interpolation error depending on the Courant number in the method of characteristics. Regarding this technique, the authors derived a well-formed error formula by applying a linear stability analysis. Characteristics of the interpolation error were clarified by comparing existing interpolation schemes with the method of characteristics. The interpolation error of CIP scheme was superior to the Spatial Linear Interpolation Scheme, was approximately equal to the Time Linear Interpolation Scheme and the cubic spline interpolation scheme with sufficient number of computational grids. The calculation efficiency of the CIP scheme was superior to the other schemes excepting the Spatial Linear Interpolation Scheme.

In 1997 Alberta Natural Gas Co. Ltd (ANG) completed a field testing program of its centrifugal compressor fleet. Field performance and surge testing of centrifugal compressors in pipeline service was done for efficiency evaluation and to re-establish surge line control. By confirming the actual location of the surge line, surge controllers are adjusted to allow a more efficient and greater operating range resulting in fuel savings and operating flexibility. The results of this testing provides an accurate operating window for the compression equipment which is then transferred to a hydraulic analysis computer model used to provide accurate capacity estimates in support of additional gas transmission contractible volumes. As part of the surge testing, suction to impeller eye differential pressure readings (used for surge control) were evaluated to determine strength, stability and repeatability. Finally, baseline data was established to determine current compressor operating efficiencies and will be used to determine future efficiency degradation. ANG is a wholly owned subsidiary of TransCanada PipeLines, one of North America’s leading transporters of natural gas through its energy transmission businesses. ANG owns and operates the British Columbia segment of the Alberta-California pipeline system (ref Figure 1). Compression is provided at three compressor stations with eleven compressors totalling 187,000 installed ISO HP.

A surge control system for a natural gas centrifugal compressor station has been modified in order to reduce shutdowns caused by high discharge temperature and provide a more robust and stable operation. The process consists of a compressor driven by a 14 MW gas turbine and recycle piping, a 16” recycle valve, a PLC based surge control algorithm, a flow measurement element, and a compressor differential pressure transmitter. The control objective is to manipulate the recycle valve to maintain flow through the compressor to a setpoint determined from the differential pressure across the compressor. Field tests were conducted to measure the open loop process dynamics of the valve, piping, compressor and transmitters. From the test data, the relevant process dynamics were determined enabling the development of a first order plus dead time model of the system. The process dynamics are complex due to the gas dynamic effects of the station piping and tend to exhibit inverse and time delayed behavior. Large variations in process gain also create problems with obtaining a consistent flow response under different operating conditions. A stability analysis was completed and the control system was redesigned with several enhancements including derivative control, flow signal filtering, process linearization, and improved controller programming techniques. The results of the modifications are the compressor does not shut down when subjected to transients from other units, the compressor can be started against high head conditions, and the closed loop response time is ten times faster than the previous system. The new system has been in operation since May 1997.

Skid mounted surface pipelines have been used to cross four major creek valleys on the Westcoast Energy 762 mm Fort Nelson mainline where very large deep-seated slides are progressively failing. The surface pipeline segments range up to 2.2 km long and were used to cross very large slides on the creek approach slopes, or in one case, down valley sliding of the valley floor, which had resulted in major operational problems for the originally buried pipelines. The surface pipeline segments were used for slides where there were no other options for a conventional buried pipeline. During the studies to support the design of the surface pipelines, comprehensive geotechnical investigations included drilling, installation of slope indicators, and electric piezocone penetrometer testing to monitor subsurface pore water pressures and to detect deep seated slide surfaces. Typical peak movement rates of the slides varied to a maximum of several meters per year. The unstable soils were predominantly medium to high plastic silty clay tills and high plastic glaciolacustrine clays with residual internal angles of friction of 7.5 to 8.5°. The pipelines were placed on pressure treated timber skids on graded rights-of-ways (RoW) with comprehensive surface and subsurface water control. Aerial clear span crossings were used across the watercourses with geogrid reinforced abutments on the unstable soil. Geogrids were also used to add stability to structural fills and to reinforce an area of the RoW subject to encroachment from a rapidly moving earth flow up to 6 m deep. The general maintenance and operational guidelines are also discussed. Provincial and Federal regulatory concerns and their abatement are presented and discussed. Over the past five years of operation of the pipelines, one of the slopes moved 1.5 m in a twenty-four hour period and related total movements left a 5 m high head scarp on the RoW. Displacement of soil and areas of thrusting resulted in unsupported pipe spans of 35 m with negligible deleterious impact on the pipeline. This magnitude of movement would have almost certainly caused a failure of the original buried line. All of slopes have continued to move and would have caused a varying magnitude of operational problems had the pipelines still been buried.

The susceptibility of oil and gas pipelines to seismic damage has been demonstrated in earthquakes everywhere around the world. The latest examples of the dangerous failures are the ruptures of gas pipelines caused by Los-Angeles earthquake 1994 and oil pipelines caused by Sakhalin earthquake 1995. A significant part of oil and gas pipelines were designed some decades ago. Earthquake design specifications acting today are more restrictive than before. That is why pipelines built more than ten years ago are of major concern to managers and engineers. Basic approaches to the aseismic design of new pipelines and retrofitting of buried pipes and above-ground transmission pipelines and piping systems located in high risk seismic regions represent the main topic of the paper. A realistic assessment of earthquake damage potentials is needed to develop construction and retrofitting procedures. Supporting this type of constructing and rehabilitation activity for pipelines requires a better definition of key input parameters like area seismicity, the identification and characterization of ground moving hazards. The nonlinear approach for predicting spatial bending, torsion, and upheaval buckling of curved pipeline is applied for stress and stability analysis of buried pipelines under operational and seismic loading. The example of calculations useful for retrofit design of pipelines is given. An experience of damping devices application to mitigate seismic movement of above-ground pipelines has demonstrated an excellent ability to prevent damages during earthquake and operational dynamic loading. These devices are useful for above-ground pipeline retrofitting. To reduce uncertainty regarding the ability of a pipe to continue to hold pressure after seismic damages and retrofitting measures, it is important to develop the test programs, which should include investigations of buried and above-ground pipeline samples.

State of stress and deformation of buried oil-gas pipelines under, operation must meet appointed requirements on strength, deformability, general stability, etc. Fulfilment of those requirements while designing main and field pipelines in conditions of marshes and marshy soils is very problematical. The cause lies both in weak knowledge of peat reaction to longitidual and lateral displacements of the pipe and in impossibility on account of that to analize the pipe state of stress and deformation taking into consideration the joint pipe-soil deformation. Wide research into pipe-peat interaction has been carried out at the Institute of Construction (Republic of Komi, Russia). In the paper there are enumerated main principles on design, analysis and engineering of buried ballasted pipelines on marshes, which have been worked at the Institute. The practical value of the work results for improvement of pipelines reliability under operation is emphasized in the paper, too.

As the pipeline system of TransCanada Pipelines Ltd. (TransCanada) ages, cover at water crossings is continuously being adjusted to dynamic changes in weather patterns and local water crossing hydraulic characteristics. In an increased asset base of over 37 000 km of pipeline, this creates challenges to find and remediate crossings with high risks while maintaining the integrity of the whole system. A methodology has been developed to address the increasing demands of fiscal responsibility and pipeline integrity. The Scour Hazard Database Model (SHDM) provides the necessary tool to provide solutions to both of these challenges. The SHDM provides a stand alone prioritisation tool that is updateable and transparent. It can alert TransCanada to both immediate and potential pipeline exposures, in order that reactive and proactive solutions can be initiated. The SHDM contains descriptive pipeline information, local hydrologic data, channel hydraulic information, and scour hazard logic for over 2350 river and creek crossings throughout Canada. This information is used to produce a final rating value for comparing the potential for vertical and lateral pipeline exposures at each crossing. The vertical scour logic considers age of the crossing, modelled scour, natural degradation and any remedial work to determine the rating value. The lateral erosion logic uses channel form, location, lateral cover distances between the thalweg and pipeline, stream power, age of the crossing, and any remedial work to develop the lateral scour rating value. Furthermore, the exposed pipes are evaluated based on the potential failure mechanisms to determine failure probability. Included in the failure analysis are lateral stability, impact of debris, and fatigue. The failure probability and the consequence of the failure are used to rank the crossings and identify the requirement for maintenance activities.

There are strict regulatory requirements for pipeline construction at river and stream crossings. The requirements for monitoring, surveillance and maintenance of existing crossings on the other hand are limited to a few lines in Section 10 of CSA Z662-99. Systematic procedures for assessing stream channel stability are not readily available to the operators of pipelines. As a consequence, many monitoring and inspection programs focus more on detecting exposures than on preventing them. In this paper, the AEC Pipelines Ltd. approach to monitoring river and stream crossings is reviewed and discussed. The program involves application of basic geomorphic concepts and use of aerial photographs to define channel characteristics at crossing sites and to determine which crossings may be subject to future channel instability or erosion problems. From these in-house evaluations, decisions are made to either proceed with more in-depth assessments by river engineering specialists or continue with routine aerial and ground surveillance. As part of the overall program, procedures for completing routine channel surveys and a checklist of data to be gathered during regular reconnaissance trips have been developed.

Much research has been performed over the past twenty-five years to refine our basic understanding of tubular stability, which includes bifurcation, imperfect systems, factors influencing tubular stability and post-buckling behaviour. Tubular instability resulting from load combinations is not a trivial topic, particularly when inelastic material behaviour occurs. Many influencing factors must be considered when attempting to understand (and predict) the onset of instability. Many existing collapse predictive methods are either simplistic or involve advanced plasticity or finite element methods. Simplistic methods are typically semi-empirical, and contain a degree of uncertainty resulting in conservative collapse predictions. Nonetheless, they are generally considered satisfactory for design purposes. Advanced methods normally involve high-end calculations using specialized software programs that might not be available for general use. Therefore, a relatively easy-to-use method that accurately predicts the actual collapse resistance is, in many cases, the most desirable option. This paper presents a collapse predictive methodology, developed from a variety of research projects performed over the last fifteen years. The prediction method, which can easily be entered into a spreadsheet program, is applicable to most forms of tubular members, including pipelines. Applicable load combinations include external pressure, axial tension and bending. An overview of the parameters influencing collapse resistance is also provided, including manufacturing history, material modelling, and tubular geometry and imperfections. Also presented is a summary of accuracy of the method to predict some test results. The test database largely contains results of collapse tests on tubular members subject to only external pressure, and axial tension with external pressure. The adaptation of the method to include external pressure with bending is summarized, and the accuracy of the prediction method is demonstrated by predicting the results of the Oman-India and Blue Stream pipeline collapse test programs, and comparing these predictions with those of other well known methodologies.

OAO “GAZPROM” in collaboration with SNAM and Saipem have developed the first stage of the “Blue Stream” Project, which when completed will be unique for the world gas industry in terms of its parameters and route conditions. During this feasibility stage of the project the following new Research and development tasks were addressed: - deep water collapse problems (the depths reach 2150 m), including buckle propagation; - the problem of pipeline protection against an H 2 S environment (in the near bottom zone H 2 S concentration reaches more than 14 mg/1); - the problem of installing a reliable pipeline having a diameter of 610×31.8 mm at gas pressures of 25 Mpa while taking into account the subsea currents; - construction problems associated with the specified parameters. Solving such problems required an elaborate and complex set of design tasks and experiments with materials and construction conditions. Special requirements were developed for the pipes and fittings, external anti-corrosion coatings, and the cathodic protection of the pipeline. New procedural documents were developed for deep water pipelining that included: the calculation for determining the strength and stability of the offshore pipelines; an instruction manual for the onshore section of the pipeline designed to carry a gas pressure of 25 Mpa; the necessary software for thermal and hydraulic calculations for the gas pipeline under extremely high pressures.

A differential-algebraic system is presented to model unstable two-phase flows in pipe-riser systems. Equations derive from the space integration of an isothermal drift-flux model assuming quasi-equilibrium momentum balance. A linear analysis of this system gives a new stability criterion for gas-liquid flows in pipe-riser systems. This criterion is validated by laboratory experiments. Then, a nonlinear analysis shows that the severe slugging phenomenon is a hydrodynamic instability coming from a supercritical Hopf bifurcation.

When using nitrogen loaded surge relief valves it is believed that the relief valve is in control of the upper pressure limit of the pipeline. In reality, it is the nitrogen system together with the valve in a master and slave relationship that sets the upper threshold. The negative effects of changing temperature on the stability of a nitrogen loaded relief valve’s set point is well known but poorly understood. There have been many attempts to minimize this effect. Burying the plenum and using the soil as an insulator has proven to be ineffective. Manual adjustments are not cost effective. Regulators offer inconsistent performance and are often misapplied. Evolving technology now allows for this process to be automated. Set points can be held with remarkable accuracy and plenums no longer need to be buried.

Pembina Pipeline Corporation (Pembina) owns and operates close to 10,000 km of crude, natural gas liquids (NGL), and natural gas pipelines across North America, with the majority of assets in western Alberta and eastern British Columbia. The Pembina pipeline network includes over 1,600 river and stream crossings, most of which are subject to varying degrees of vertical and/or lateral erosion. 1,260 crossings were in Alberta at the onset of the study. Identifying potential lateral erosion hazards is a critical component of geohazard management program for pipeline integrity. In 2012, Pembina initiated a three-phase program to proactively address lateral-stability issues at river and stream crossings in Alberta: phase one identified and short-listed crossings that have potential lateral channel-shifting problems; phase two assessed which short-listed crossings have insufficient cover depth to accommodate the potential channel-shifting activities and ranked these crossings as high risk of exposure; and phase three will develop plans for repair and/or replacement of the high-risk crossings. Through this program, Pembina explores the significance of lateral erosion and encroachment at pipeline water crossings of various vintages, with regards to pipeline integrity. This paper provides discussion as to how crossing geohazard risks are identified, with particular emphasis on stream bank erosion, and how this fits into Pembina’s overall risk management program. As well, selected case studies are provided.

A major slope in southern Manitoba has been experiencing deep seated movements of approximately 60mm per year. This 24m high × 85m long slope contains a pipeline right of way with five large diameter crude oil lines that were constructed from 1950–1998. It is estimated that the slope has moved up to 3 meters since the pipeline installations. Management of the effects of this slope movement on the pipelines has involved cross-functional strategies that include geotechnical, integrity, and stress evaluations. A finite element analysis (FEA), which considers the interaction between the soil movement and pipeline, was generated to evaluate the pipeline stresses caused by the slope movements to date. The results indicated that the strain capacity on one of the pipelines may be near its limit. Correspondingly and in order to be conservative, a stress relief was conducted on three of the pipelines within the right-of-way. This mitigation involved excavating the pipelines 360 degrees which allowed for their decoupling from the surrounding soil, and the associated pipeline spring back was surveyed. Prior to backfilling, a low friction geotextile was installed around the excavated pipelines to help mitigate future movements. Drainage improvements and a toe berm were also installed to improve the slope stability. Several strain measurement technologies that have been the subject of previous Pipeline Research Council projects were also installed at the site. Stress probe measurements were taken before and after the stress relief; a fiber optic cable was installed; inline inspection bending strain measurements were analyzed; and the FEA analysis was used to model the strains before and after the stress relief. All of these technologies are compared to the measurements from strain gauges that were read both before and after the stress reliefs were conducted.

Based on two-fluid approach, a numerical model coupled with phase behavior model and hydro-thermodynamic model, is presented for simulating steady-state two phase flow in gas-condensate pipeline. In this model, two-fluid model is adopted for hydraulic computation and a simplified mixture energy equation is developed to couple hydraulic and thermodynamic calculation. SIMPLE algorithm is improved for application in one-dimensional steady-state simulation of two phase flow. Hydraulic and thermal is coupled as one-way coupling. The model was validated through comparison to field data from five operational gas-condensate pipelines. It turns out that the numerical simulation in this paper has good stability and convergence and is capable of simulating the steady-state flow in gas-condensate pipelines.

Landslides are one of the main threats in maintaining pipeline integrity and depend directly on natural geological and geotechnical conditions. External factors such as weather, rainfall, and others, can trigger land movements and displace the pipeline. The Ecuadorian OCP (Heavy Crude Oil Pipeline) is a buried pipeline going in an East to West direction, crossing 485 kilometers of the Ecuadorian territory. It starts in the Amazon Region (approximately 300 meters above sea level), and then climbs the Andes Mountains (4060 meters above sea level in its tallest portion), to then descend to the shores of the Pacific Ocean. The OCP pipeline crosses many regions with varying climates, varying rainfall patterns, variable morphologies, diversity of soils, and areas affected by tectonic faults, among others. In order to prevent pipeline failures, OCP Ecuador has instituted programs to perform preventive and corrective actions in order to handle the following geological concerns: • Intervention of a specialized geotechnical team to identify and monitor critical points along the pipeline route. This team identifies unstable sites based on the observations of cracks, land movements, or other visual deformations of the pipeline route and its surroundings. • Upkeep of the preventive program. • Execution of third-level studies required to understand specific unstable zones in detail: nature of the subsoil, underground water level, geo-mechanic characteristics, stability factor, and stabilization works. • Geotechnical instrumentation used: inclinometers to search the spread of movement, shifting direction, speed, (landslide location); strain gauges for preventive control of pipeline strain, alert levels, efficiency of stabilization works; and topographic surveys to monitor superficial movements. • Data processing and mapping on GIS Software. • Annual over-flights to detect massive landslides. • Internal inspectors (online-ILI) providing a wide range of information: geometry measurements, curvature monitoring, pipeline displacement, etc. In addition, it allows detection of probable zones depicting soil movement. The purpose of this technical paper is to present the methodology applied by OCP Ecuador to prevent failure of the pipeline along its route.