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Design and Construction: General

1998;():619-623. doi:10.1115/IPC1998-2071.
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Since the early 1970’s, the pipeline construction and operation industry has supported the development and implementation of various material standards and specifications. The emphases within the pipeline energy industry was to standardize manufacturing and performance testing processes in the provision of a product which would ensure public safety and reliability of service. The pipeline segment of the energy industry has succeeded in incorporating minimum quality levels by way of industry standards, codes, regulatory requirements and propriety company standards. In addition to these minimum product requirements quality assurance programs have been introduced to enhance the likelihood of conformance to the applicable requirements. In 1975, Canada became the first country to prepare and publish quality system standards for commercial use (Z299 standards). International quality system standards development proliferated in the following years, leading to the establishment of the ISO/TC 176 work team which subsequently led to the issue of the internationally accepted ISO 9000 series of standards.

This paper will review both the concept and stages of development of CSA pipe and coating standards. It will also analyze the impact that international standards for Quality Management Systems are having in establishing systematic approaches to assessing levels of quality during material manufacture. Finally, a vision of the possible road to the future will be drawn and the positive impacts for the pipeline industry will be projected from a full life cycle cost perspective.

Commentary by Dr. Valentin Fuster
1998;():625-630. doi:10.1115/IPC1998-2072.
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The Australian Standard AS 2885 - 1997 Pipelines Gas and Liquid Petroleum contains mandatory risk assessment procedures which are deeply integrated into route selection, design and operation and maintenance. The procedures require systematic identification and assessment of threats which are specific to the pipeline, the location, the threat itself and its effect on the pipeline. External interference protection design is one fundamental step in the risk assessment procedure which involves formal specification of physical measures for the prevention of damage and procedural measures for the prevention if incidents with the potential to cause external interference. A land classification system based on land use and design which separates the design factor for pressure containment from the requirements for other engineering parameters combine to ensure that economy, reliability and public safety are optimised together. A fracture control plan is required as part of the integrated design process and the plan requires formal and systematic treatment of fluid composition and type and fracture arrest length. The welding section of the standard differs significantly from API 1104 and includes fitness-for-purpose defect acceptance limits based on the EPRG guidelines.

Commentary by Dr. Valentin Fuster
1998;():631-635. doi:10.1115/IPC1998-2073.
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As an alternative to radiography, a field-proven mechanized ultrasonic inspection system is discussed. Called Rotoscan, this system has been developed for inspection of girth welds during construction of long-distance pipelines, both on- and offshore. It is characterized by high inspection speed and instant recording of results. Unlike prevailing radiography, it provides immediate feedback to the welders.

Recent technical improvements in flaw sizing and recording have allowed the application of rejection/acceptance criteria for weld defects based on fracture mechanics principles. The development and actual use of such modern acceptance criteria, particularly in Canada, supported the introduction of mechanised ultrasonic inspection. World wide applications proved that, contrary to expectations, ultrasonic inspection does not lead to higher weld repair rates than radiography does. Between early 1989 and now, over 5.000 km of pipeline (300.000 welds) were inspected with Rotoscan and its reliability proven.

The introduction of colour enhanced transit distance “C-scan mapping”, producing a coherent picture based on the signal’s transit distance, enabled the system to cope with most existing ultrasonic procedures and acceptance criteria, because of its capability to detect and quantify volumetric defects. Moreover, the integrated simultaneous Time Of Flight Diffraction (TOFD) function enables through-thickness sizing of defect. The present system is capable of achieving a high Probability Of Detection (POD) together with a low False Call Rate (FCR).

In the meantime, Rotoscan has been qualified in various countries, for different customers and for a variety of weld processes, pipe diameters and wall thicknesses. Because of its features, the now mature system has demonstrated its capabilities also for use on lay barges as an alternative to high-speed radiography.

Commentary by Dr. Valentin Fuster
1998;():637-643. doi:10.1115/IPC1998-2074.
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Gas pipeline ultrasonic inspection girth weld systems have been well established for typical Canadian conditions, primarily through the efforts of TCPL and NOVA. However, the specific weld profiles, wall thickness, environment and operating conditions found in Canada do not necessarily represent girth weld inspections elsewhere. This paper describes some different inspection conditions, and some of the possible solutions, which may or may not have been implemented to date. For example, the extreme Canadian weather may require heating transducer wedges, or using dummy wedges to measure temperature. Sandy or salty conditions may require different designs and materials. Different weld profiles will require different ultrasonic set-ups, as will different inspection specifications. For flexibility, it is possible to design expandable inspection heads with replaceable probe modules, and to include extra ultrasonic transducers for TOFD or additional scans. Tight time constraints can lead to quick-release levers for speedy head changes, as well as modular, replaceable components. Since the operator is critical in the inspection, a number of software additions can be added to speed inspection, interpretation and set-up. For example, defect locations can be automatically displayed on the weld profile to aid interpretation. A table of defects can be shown so the operator can click on a selected defect to automatically display the appropriate scan region. Defects can be analyzed automatically by length and amplitude to determine accept/reject. Calibration set-up for a particular transducer can be recalled simply by clicking on the appropriate zone in the weld display. Automated recording and acceptance of calibration scans can be performed.

Topics: Inspection , Pipelines
Commentary by Dr. Valentin Fuster
1998;():645-652. doi:10.1115/IPC1998-2075.
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The author will focus on the properties of three layer epoxy/ polyethylene coating for pipe, based on the experience developed in the lab, coating plant and in the field.

The demands of the respective Canadian and other international standards will be looked at with the purpose to evaluate respective merits of various specifications.

Special attention will be paid to the properties of the coating involving pipelines operating at elevated temperature, especially running through permanently wet areas, such as permafrost.

Lab results will be correlated with the real life experience.

Three layer Epoxy/ Polyethylene coatings will be compared to other commonly used coatings in the industry with the object to assess respective benefits and projected longevity versus cost.

Commentary by Dr. Valentin Fuster
1998;():653-657. doi:10.1115/IPC1998-2076.
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The effect of carbon black, ultraviolet (UV) stabilizer and color pigment on the mechanical property of polyethylene (PE) has been investigated. The transition of fracture mode from ductile to brittle upon UV exposure is identified through microscopic examination of fracture surface. This transition is responsible for the degradation of mechanical properties.

The carbon black doped PE shows excellent UV resistance regardless of the presence of UV stabilizer. The mechanical properties of the PE remained unchanged even after 50-days UV exposure. The ductile fracture mode is also maintained in this case. The addition of red color pigment exhibited a very poor UV resistance.

Commentary by Dr. Valentin Fuster

Design and Construction: Materials

1998;():659-664. doi:10.1115/IPC1998-2077.
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Grade 550 (X80) pipeline steels are now the basis of a standard platform for the design and construction of large-diameter pipeline projects at NOVA Gas Transmission (NGT). Their introduction in 1995 and further application in 1997 have provided material savings, provided greater gas flow capacity and fuel gas savings and, once again, shown NGT to be an industry leader in successfully developing and applying new technology in response to business needs. The paper will outline the development of a Canadian capability to supply these steels, discuss design aspects including fracture initiation and arrest and weld/pipe strength mismatch, the overall cost efficient approach to material and weld requirements, and pipeline construction using mechanized welding with mechanized ultrasonic inspection and alternative weld acceptance standards. Future directions at NGT with respect to higher strength steels will also be described.

Commentary by Dr. Valentin Fuster
1998;():665-672. doi:10.1115/IPC1998-2078.
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New large diameter pipeline projects for transmission of gas from western Canada propose the use of operating pressures as high as 12kPa (1740 psi). These operating pressures will require linepipe with increased wall thickness. As well, X80 grades are now an economic alternative to X70 for these major projects. X80 was first commercially produced in North America by IPSCO in 1994. However, to extend IPSCO’s capability to heavier gauges, a significant metallurgical development program was necessary. Particular attention has focussed on achieving more demanding impact toughness requirements. This program has resulted in the successful production of X80 linepipe in gauges as heavy as 15.3 mm. The paper will review the experimental development of heavy gauge linepipe.

Topics: Gages
Commentary by Dr. Valentin Fuster
1998;():673-687. doi:10.1115/IPC1998-2079.
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During the past 20 years the Australian Pipeline Industry has achieved significant economic improvements in the design and construction of natural gas transmission pipeline networks. This improvement is based on the use of thin walled high strength high pressure pipelines which serve relatively small markets separated by long distances from gas reserves.

The Industry in conjunction with the WTIA/APIA Research Panel 7 and the Cooperative Research Centre for Materials Welding & Joining, have developed a research program with a number of key deliverables which aim to improve the overall economics of pipeline design, construction, inspection and maintenance activities by providing the level of assurance necessary to confidently build reliable pipelines using high strength linepipe including X80 grade.

This paper details recent developments in the Australian Pipeline Industry and the coordinated research and development program to advance the economic use of high strength pipeline technology under Australian conditions.

Topics: Welding , Pipelines
Commentary by Dr. Valentin Fuster
1998;():689-698. doi:10.1115/IPC1998-2080.
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Hollow bead is an elongated linear pore aligned with the weld axis. The sporadic appearance of epidemics of hollow bead defects during the construction of pipelines has for years been responsible for increasing the cost and time required for completion of a number of projects in many parts of the world. The inability to identify the cause of this defect has been one of the major obstacles in attempting to reduce its occurrence. As a result of this situation, following an important pipeline construction project which was seriously disrupted by problems with hollow bead, a number of Australian companies contributed to a major three year programme of research undertaken by the Cooperative Research Centre for Materials Welding and Joining. A systematic study of the effects of a range of parameters including welding variables, parent metal composition, joint geometry, surface condition and welding consumables has been undertaken. The data obtained has been used to ascertain their influence on the occurrence of hollow bead pores, and to provide guidelines for field welding practice which provide a high level of confidence that hollow bead can be eliminated as a practical problem in pipeline construction.

Commentary by Dr. Valentin Fuster
1998;():699-704. doi:10.1115/IPC1998-2081.
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The applicability of Drop Weight Tear Test specimen to evaluate the ductile to brittle transition temperature of thick wall pipes (30 mm and 40 mm wall thickness) has been investigated by comparing West Jefferson tests at different temperatures and laboratory data.

The traditional API pressed notch specimen has been used with full and reduced thickness, together with chevron notch and weld notch starters. The different crack initiation methods have been examined with the goal of providing an easier test specimen, with reduced fracture energy.

The 85% shear area transition temperature indicated by the different test specimen show a reasonable similarity, but the higher costs of preparation of the alternative notch geometries limit their adequacy in substituting the traditional pressed notch specimen.

Good agreement has been found between standard DWTT specimen and full-scale test transition temperature. The results of this program together with literature data, confirm the validity of the DWTT specimen to measure the ductile to brittle transition temperature for thermomechanical rolled linepipe steels of thickness up to 40 mm.

The reduced thickness specimens conservatively predicted full scale behaviour.

Commentary by Dr. Valentin Fuster
1998;():705-710. doi:10.1115/IPC1998-2082.
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A practical technique is investigated for the determination of dynamic stresses in pipelines through the use of Finite Element Method (FEM) and field measurement vibrations at selected points. Numerical simulation of a harmonically loaded pipeline structure is used to establish the validity of the technique in the frequency domain. The analysis is carried out for a fixed-hinged pipe model. The results show that lack of coincidence between the vibration measurement points (VMPs) and the exciting force, or the use of only translational vibration measurements (TVMs) produce an approximate stress picture. The extent of the “error” in these cases is found to depend on the density of the VMPs and the proximity between these points and the exciting force location. A safety-related risk assessment is applied to find the minimum distance between measuring points that is needed to meet design codes reliability specifications.

Commentary by Dr. Valentin Fuster
1998;():711-721. doi:10.1115/IPC1998-2083.
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Eight pipes, manufactured between 1952 and 1981, have been collected from various Canadian pipeline companies and tested. They include six pipes from the field made in the 1950’s and 1960’s of X52 grade, one experimental pipe manufactured in the early 1970’s of X65 grade, and a modern clean steel of X70 grade manufactured in 1981. The steels have been characterized by chemical composition, grain size, yield and tensile strengths, notch toughness (Charpy V-notch absorbed energy), and fracture toughness (J-integral and crack-tip opening displacement). The modern steel has much lower carbon content and much smaller grain size compared to the pipes manufactured in the 1950’s and 1960’s. The former is a fully-killed controlled-rolled steel while the latter are semi-killed ferrite-pearlite steels.

All eight pipes have ferrite-pearlite microstructures, with the average grain size ranging from 4 to 14 μm. The transverse yield strength was found to be significantly higher (by about 20%) than the longitudinal yield strength. Notch toughness and fracture toughness were similar for pipes manufactured in the 1950’s and 1960’s. In comparison, the modern steel has much higher toughness and higher strength.

J-integral and CTOD δ were found to be related by J = m σyδ with m = 1.8 and σy the transverse yield strength. The J-integral at 0.2 mm crack growth was consistent with a linear correlation with the upper-shelf Charpy energy. All the steels in this study fractured by ductile tearing in slow loading in spite of the low toughness of the older steels. It is suggested that, in the absence of Charpy upper shelf data, a reasonable representative toughness for resistance to axial surface flaws propagating by ductile tearing is J = 120±15 kJ/m2.

Topics: Pipes
Commentary by Dr. Valentin Fuster
1998;():723-731. doi:10.1115/IPC1998-2084.
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The consequences of a dynamic fracture in a gas-transmission pipeline require that pipelines be designed to avoid such incidents at a high level of certainty. For this reason, the related phenomonology has been studied since the early 1970s when the possibility of a dynamic ductile fracture was recognized. Full-scale experiments were done to characterize the fracture and gas dynamics associated with this process and empirical models were developed as a means to represent these experiments in a design or analysis setting. Such experiments focused on pure methane gas, and in the early days used steels with toughnesses less than 100 J, consistent with the steel making capabilities of the 1970s. Subsequently, interest shifted to larger diameter, higher pressure, higher BTU “rich” gases requiring higher toughness steels. The full-scale tests conducted to validate the arrest toughness levels determined that these empirical models were non-conservative.

This paper presents a relationship between the dynamic crack propagation resistance and the apparent crack propagation resistance as measured by Charpy vee-notch (CVN) test specimens. This relationship is used in conjunction with the existing Battelle empirical criterion for dynamic-fracture arrest to determine the apparent toughness required to arrest a propagating ductile fracture in gas-transmission pipelines. The validity of this relationship is illustrated by successful predictions of arrest toughness in pipelines under a range of conditions including rich gases and high-toughness steels, including those showing a rising upper-shelf behavior.

Commentary by Dr. Valentin Fuster

Design and Construction: Geotechnical

1998;():733-740. doi:10.1115/IPC1998-2085.
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Ground liquefaction during earthquakes can produce a significant amount of lateral ground displacement. For buried gas pipelines, deformation and strain are likely to be concentrated on the pipe bends. Closing and opening in-plane bending experiments were conducted for various kinds of pipe bends until the measured strain exceeded 25% using pipe specimens of a diameter from 100 to 300 mm. The deformation behavior was different between the closing mode and the opening one. In the closing mode, an ovalization was observed in the central cross section of the bend, and internal pressure was maintained in all experiments. On the other hand, unique behavior was observed in the opening mode. When the pipe diameter was 300 mm (Do/t=43), local buckling was observed at the center of the bend. However, when Do/t was less than 32 (200 mm in diameter), the flexural rigidity of the bend became much higher than that of a straight pipe, and buckling and rupture were observed in the straight pipe. Finite element analyses were carried out using linear shell elements, and the validity of the numerical modeling technique over 25% of plastic strain was confirmed.

Commentary by Dr. Valentin Fuster
1998;():741-748. doi:10.1115/IPC1998-2086.
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The performance of pipeline systems under seismic loading is an important consideration in regions subject to earthquakes. This paper briefly describes a study to evaluate the vulnerability of a natural gas transmission system to seismic hazards, along with some of the remedial treatment options which are being considered. The study was carried out for BC Gas Utility Ltd. in the Greater Vancouver Region of British Columbia. The results of the study are being used by BC Gas in emergency response planning and remedial treatment activities to limit their risk exposure.

The paper describes the approach used to assess liquefaction and lateral spreading risks, and remedial treatment options which were considered. This involved generation of design seismic ground motions, seismic hazard mapping, geotechnical investigations to determine the subsurface conditions, and geotechnical and structural numerical modeling and analysis to assess pipeline performance and remedial treatment options.

Several different approaches to remediation are described; one involves ground treatment to reduce the risk of unacceptable ground deformations; another involves structural modifications to improve the resistance of the pipeline to seismic motions, while another makes use of directional drilling to re-align the pipe below infirm areas.

Commentary by Dr. Valentin Fuster
1998;():749-756. doi:10.1115/IPC1998-2087.
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This study was initiated to examine the stress and deformation characteristics of the pipelines which were subjected to various environmental conditions in order to confirm their integrity. As the part of them, this paper presents the analysis results for the effect of ground subsidence combined with main loads on buried natural gas pipelines. The ground subsidence which can occur for buried gas pipeline has been classified to the three cases.

Finite element method was used to analyze the effect of ground subsidence on pipeline of 26 inch (0.660 m) and 30 inch (0.762 m) diameter used as high pressure (70 Kgf/cm2(686.4 Pascal)) main pipelines.

This paper shows the result of stress analysis for the pipelines subjected to those three case ground subsidence. Comparing these results with safety criterion of KOGAS (0.9 σ y), maximum allowable settlement and loads have been calculated.

Commentary by Dr. Valentin Fuster
1998;():757-762. doi:10.1115/IPC1998-2088.
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Structural response analyses of pipelines using computer models, such as AutoPIPE, incorporate soil “springs” to model the restraint provided by pipeline bedding and padding. These “springs” are referred to as spring constants and are most frequently determined from a limited number of sources in the literature. In some cases representative soil properties are used with theoretical and empirical formulae such as those presented by Nyman (1984). This technique which is referred to herein as the ASCE technique has been used by Alyeska Pipeline Service Company (Alyeska) engineers in their calculations of structural response of the buried pipeline along the Trans Alaska Pipeline System (TAPS) (Hart et al, 1998).

This paper describes a field study at a pipeline inspection dig in which spring constants were determined directly from a series of field tests to develop a better understanding of the pipeline restraint the bedding and padding is providing for the pipe. Four other papers which cover other aspects of the work performed at this site are also a part of this conference (Hart et al, 1998, Norton et al, 1998, Stevick et al, 1998, Tonkins et al, 1998).

The field work included the drilling of multiple boreholes in which drive samples were taken at about 1 to 2 meter (3 to 5 foot) intervals. In each borehole, pressuremeter tests were also conducted at the same intervals as the drive samples. At two levels in the open pipe trench plate, load tests were conducted. Both nuclear and sand cone density tests were made at several levels in the pipe trench.

Results of these tests were correlated to each other. Stress strain relationships were developed from the pressuremeter test and plate load test data which were used independently to develop spring constants. Spring constants were found to vary with the strain level in the soils and were correlated to the drive sample blow count data. Recommended methods for estimating spring constants are presented.

Commentary by Dr. Valentin Fuster
1998;():763-770. doi:10.1115/IPC1998-2089.
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The new Canadian limit states pipeline design standard (CSA Z662-96, Appendix C - Limit States Design) incorporates deformation or strain-based design criteria to prevent pipe rupture and or buckling and limit ovality due to bending. These criteria are different and in some instances, much more conservative than those contained in the Canadian offshore pipeline design standard (chapter 11 of CSA Z662-96) and similar standards used in other countries. This study was completed to review the ovality, buckling (including wrinkling) and rupture criteria included in current Canadian pipeline design standards (CSA Z662-96) and define its basic differences with respect to other standards.

The deformation or strain based design criteria formulations in Z662 are compared with those contained in design standards, industry association recommendations and classification society rules from Norway, Britain, Germany, Australia and the USA to illustrate their differences and relative levels of conservatism. In addition, current and on-going research efforts were reviewed to identify the state-of-the-art in pipeline strain-based design, since this research could form the basis for future amendments to existing pipeline design standards.

Based on the findings of this review, recommended changes to the limit states pipeline design formulation are given to better reflect the strain-based (non-linear or post-yield) design and assessment approaches included in the Canadian offshore or foreign pipeline design approaches. In addition, an analytical basis for pipeline ovality and buckling design criteria are recommended.

Topics: Piping design
Commentary by Dr. Valentin Fuster
1998;():771-778. doi:10.1115/IPC1998-2090.
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Recent research on longitudinal pipe-soil interaction shows that traditional analysis models are inadequate and too conservative, especially when cohesive soils are involved. The practical implication for SNAM, whose network extends over the entire Italian territory where slow ground movements inducing longitudinal soil-pipe interaction are frequent, is that the management of the gas pipeline has to rely mainly on field measurements.

The correct assessment of the interaction forces was therefore included as an important part of a wider research program, whose aim is to perform pipe risk analysis by which the structural vulnerability for some SNAM typical scenarios can be quantified as a function of such parameters as the pipe section geometry, the type of soil, the burial depth, the length of pipeline section involved and the magnitude of the soil imposed displacements.

Experimental activities specifically regarding longitudinal, static, interaction problems were carried out; in particular pull-out tests were performed on two out of use pipelines, having two different diameters: 8” and 24”. For each site, four different test conditions were investigated where type and compaction state of the material surrounding the pipe varies. The behaviour of the pipe embedded in the original clayey backfill was compared to that observed after such fill was excavated and replaced around the pipe, to simulate conditions after standard stress relieving works. Different fills where then used, made of either granular soil or granulite; this latter was used in order to ascertain the possible benefits of using light artificial materials to mitigate soil-pipe interaction phenomena. Site testing was accompanied by a careful geotechnical investigation both in the field and in laboratory that included direct shear tests of interfaces using coated steel pipe specimens.

A comparison between the results obtained and the existing state of the art is presented. This comparison allowed to verify the effectiveness of some interpretative models, and in particular the convenience of adopting effective stress based models rather than pure cohesive ones (i.e. total stress), even in the case of clayey soils.

Topics: Pipelines , Soil
Commentary by Dr. Valentin Fuster
1998;():779-787. doi:10.1115/IPC1998-2091.
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The ability of oil and gas pipelines to respond safely to soil movements is an important consideration in pipeline design and route selection. There are a number of suggested methods of analysing pipeline/soil interaction in the literature most of which consider the pipeline to be connected to the soil via a series of discrete nonlinear springs. Many of these methods have generally been based on soil/structure interaction studies developed for other types of buried structures such as anchor plates and vertical piles. There are few pipeline-specific theoretical or experimental results available for comparison and validation of accepted design/analysis methods. To remediate this lack of large-scale pipeline-specific data, a full-scale pipeline/soil interaction test facility has been established in St. John’s Newfoundland. This paper presents a description of the test facility, details on experimental procedures, and comparative results from lateral and axial testing in sand and clay.

Topics: Pipelines , Soil
Commentary by Dr. Valentin Fuster
1998;():789-796. doi:10.1115/IPC1998-2092.
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This paper reports the results of experimental and numerical investigations into the behaviour of buried high-pressure piping supported by flat concrete footings known as ‘sleepers.’ In the study, a series of full-size line pipes are examined to determine their deformational behaviour when subjected to sleeper – pipe contact forces. Of particular concern are the distortion of the cross-section and the identification of potential buckling or wrinkling problems. Test results show that the pipes behave in a stable and ductile manner, but that the cross-sectional deformation can be considerable. A numerical model of sleeper-supported pipe, which includes non-linear material properties and accounts for large strains and deformations, is described. This model is found to represent sleeper – pipe interaction behaviour well. It is concluded that the analytical methods are sufficiently accurate to predict the behaviour of a pipe under the action of a known sleeper – pipe contact force. These analyses can be used to predict pipe behaviour directly and will be of assistance in the development of a simplified design technique.

Topics: Modeling , Pipes
Commentary by Dr. Valentin Fuster
1998;():797-806. doi:10.1115/IPC1998-2093.
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For the past four years, NOVA Gas Transmission Ltd. (NGTL) has included the backfill shear strength in buoyancy control design for natural gas pipelines built and operated in muskeg soil laden terrain. Incorporation of muskeg soil shear strength has resulted in major cost reductions. In typical muskeg soil laden terrain, the weighting requirement for NPS 4 and smaller pipelines has been eliminated, while the need for weighting of larger pipelines has been significantly reduced.

Traditionally, muskeg soil shear strength has not been considered due to an absence of adequate theoretical and performance data. NGTL has constructed a series of laboratory and field studies in an attempt to quantify the contribution of “muskeg soil shear strength.” The results of this research program, when combined with a rudimentary field investigation, are part of NGTL’s current buoyancy control design methodology for pipelines traversing muskeg soil laden terrain.

This paper presents a practical methodology used by NGTL for buoyancy control. Design examples are provided to calculate two design components; the maximum tolerable muskeg depth and optimum weight spacing. The paper concludes with a discussion of construction and operational considerations which influence buoyancy control design.

Commentary by Dr. Valentin Fuster

Design and Construction: Hydraulics

1998;():807-811. doi:10.1115/IPC1998-2094.
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In the development of new pipeline projects, all too often assumptions that are made in the initial stages of the business development opportunity are, for the most part, overly conservative. This inaccuracy is carried out through to the operation of the pipeline system and most assumptions do not change with subsequent expansions in the future until a conscious effort is made to determine and monitor those significant parameters that impact the pipeline’s overall performance.

In highly complex systems such as NOVA Gas Transmission Ltd.’s (NGTL’s) pipeline network, with over 21400 Km of pipe segments of different sizes and ages, for an accurate determination of pressure drop while 12 BCF of gas, on average, is flowing through our network, we need a technique to precisely assess the values of friction factor and heat transfer coefficient. These values have a profound impact on the accuracy of the hydraulic simulations.

The calculated values of pressure, flow rate, and temperature may be distorted by imprecise values of some parameters, such as friction factor or heat transfer coefficient. Thus, a proper estimation of these parameters is of great importance to the successful numerical flow simulation. Both friction factor and heat transfer coefficient are very difficult to measure; therefore, their values can only be assessed by solving an inverse problem (i.e. parameter identification process).

Since the parameter estimation procedure reported in this paper requires multiple solution of inviscid gasdynamics differential equations, describing the gas flow through the pipeline system, a multidomain solution method has been applied to effectively solve the parameter identification problem.

Commentary by Dr. Valentin Fuster
1998;():813-820. doi:10.1115/IPC1998-2095.
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The connection of a new pipeline lateral or loop to an existing high pressure pipeline system has always been fraught with high costs and the potential for major system impacts. Pipeline owners and operators have historically had to choose between a traditional cold connection with its high associated costs and a less expensive but more mysterious hot tap.

Although the cost savings of a hot tap have always been considerable, they were not always sufficient to justify the risk of complications during the branch weld or hot tap or during the subsequent operation of the system. Despite their extraordinary costs and throughput impacts, the perceived certainties of cold connections were often sufficient to justify their regular use.

The recent Kyoto Protocol on Climate Change has resulted in new commitments by the world’s governments to reduce greenhouse gas emissions. For the North American gas industry, these initiatives could result in voluntary compliance objectives, incentive based programs or legislated reforms — any of which will have significant impacts on current practices.

TransCanada PipeLines Limited (TransCanada) has successfully managed the risk/reward conundrum and completed more than 700 large diameter (NPS 12 to NPS 30) horizontal high pressure hot taps without incident since 1960. TCPL’s research and development work has enabled it to refine its procedures to the point where it can now complete branch welding and hot tapping work with minimal effects on throughput, negligible emissions and no system integrity impacts. For TransCanada, the direct advantages of a hot tap over a cold connection have resulted in the avoidance of gross revenue losses of $1 million or more per hot tap, no environmental emissions, seamless service and no impacts whatsoever to shippers. TransCanada PipeLines Services Ltd. (TPSL) has further streamlined the supporting field procedures and now provides a complete turn key service to industry.

Commentary by Dr. Valentin Fuster

Pipeline Automation and Measurement: Pipeline Simulation and Diagnosis

1998;():821-833. doi:10.1115/IPC1998-2096.
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During the summer of 1996, the TransAlaska Pipeline System (TAPS) experienced a vibration problem near Thompson Pass which is 25 miles north of Valdez and is part of the Chugach Mountain Range, the most southerly of the three mountain ranges which the pipeline crosses on its route from Prudhoe Bay to the Port of Valdez. The vibrations could, on occasion, be detected by residents living near the pipeline at the bottom of the pass. Close to the source of the phenomena, small bushes could be seen moving in response to the seismic shocks and a noise similar to “mortars firing in the distance” could be heard.

Alyeska Pipeline Service Company initiated an extensive investigation and quickly determined that the seismic shocks were a result of pressure pulses originating near the slackline-packline interface. This only occurred when the slackline-packline interface was positioned near a terraced portion of the pipeline topography on the downstream side of the pass. This knowledge allowed Alyeska Pipeline to control the pulsations by backpressuring the pipeline and moving the slackline-packline interface well above the terrace location.

Commentary by Dr. Valentin Fuster
1998;():835-841. doi:10.1115/IPC1998-2097.
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In order to decrease the false alarm rate and improve the sensitivity of pipeline fault diagnosis system, three artificial intelligence based methods are first proposed. Neural networks with the input matrix composed by stress wave characteristics in time domain or frequency domain is proposed to classify various situations of the pipeline, in order to detect the leakage from pipeline online running data. Context-free grammar of symbolic representation of the negative wave form is used and a negative wave form parsing system with application to syntactic pattern recognition based on the representation is described. New complex thermal and hydraulic models, in which the flow regime, viscosity-temperature characteristics, density-temperature characteristics and specific heat-temperature characteristics, etc., of the running fluid in the pipelines are set up for non-isothermal pipeline carrying higher temperature fluid or in ambient environment.

Commentary by Dr. Valentin Fuster
1998;():843-850. doi:10.1115/IPC1998-2098.
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In an attempt simulate the hydraulic conditions actually exhibited in a pipeline, several simplifications have traditionally been made to reduce the computational requirements and complexity of the simulation models.

Recent advances in computer technology and solution techniques have allowed many of these simplifications to be removed. This paper discusses the benefit of the proper simulation of several of these areas. Transient vs. Steady state simulation, Two-phase vs. Single-phase simulation, Newtonian vs. Non-Newtonian fluid flow, Multi-component boiling and condensation in wet gas.

The effects of these features on leak detection, line pack, pressure loss, and inventory analysis are discussed, as well as the effects on pipeline design, operator training, and real time decision support.

Commentary by Dr. Valentin Fuster

Pipeline Automation and Measurement: Leak Detection and Advanced Applications

1998;():851-857. doi:10.1115/IPC1998-2099.
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There are many causes for a pipeline to leak. Third party punctures usually result in sizable leaks. The onset of such leaks generates a sudden change in the pipeline pressure and flow. Methods exist that rely upon these sudden changes for leak detection. Leaks previously undetected are not detectable by such methods. These pre-existing leaks are usually small in size but can exist for long time. The cumulation of leaked products may pose a greater hazard then the larger and sudden leaks. The operational experience of major pipeline company in the United States has demonstrated that all leak detection methods have their limitations, and that complementary leak detection methods should be used simultaneously (Mears 1993). Hence, we propose a leak detection system that uses, simultaneously, two independent but complementary methodologies: mass balance and transient flow simulations.

Commentary by Dr. Valentin Fuster
1998;():859-867. doi:10.1115/IPC1998-2100.
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Leak detection systems for liquid pipelines are installed to minimize spillage in case of a leak. Therefore reliability, sensitivity and detection time under practical operating conditions are the most important parameters of a leak detection system. Noise factors to be considered among others are unknown fluid property data, friction factor, instrument errors, transient flow, slack-line operation and SCADA update time. The opening characteristics and the size of leaks differ considerably from case to case.

Each software-based leak detection method available today has its particular strength. As long as just one or two of these methods are applied to a pipeline a compromise has to be found for the key parameters of the leak detection system.

The paper proposed illustrates how a combination of several different software-based leak detection methods together with observer-type system identification and a knowledge-based evaluation can improve leak detection. Special focus is given to leak detection and automated leak locating under transient flow conditions. Practical results are shown for a crude oil pipeline and a product pipeline.

Topics: Leakage
Commentary by Dr. Valentin Fuster
1998;():869-878. doi:10.1115/IPC1998-2101.
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III-V semiconductor diode lasers can be used to make accurate measurements of the concentrations of gases. In this paper the field of trace gas detection using III-V semiconductor diode lasers will be reviewed with an emphasis on suitable applications of this technology in pipeline monitoring.

III-V semiconductor diode lasers emit light in the near infrared (NIR) with wavelengths ranging from 1 to 2 μm. Many molecules have absorption lines in this spectral range which makes them contenders for detection with diode laser technology. Molecules relevant to the pipeline industry that can be detected using diode laser systems include H2S, C2H4, C2H2, HF, CO2, CO, O2, NH3, HC1, NO, NO2, HCN, H2O and CH4.

Diode laser detection systems may be well suited for many pipeline related applications. Portable field-screening detection systems may be possible, such as hand-held systems which can be used to pinpoint leaks for compressor station inspection. Airborne (∼200 km/h) and mobile (∼40 km/h) systems which can be used for pipeline and urban area inspection may also be feasible. Stationary systems can be integrated into pipeline systems to provide real-time remote gas monitoring for Supervisory Control and Data Acquisition (SCADA) systems. Detection sensitivities of parts per million (ppm) or better are achievable for many gases. A single diode laser detector can be designed to detect more than one gas leading to versatile multipurpose systems. As III-V diode laser based gas detection systems exploit the same technologies as the highly successful telecommunications industry they have the potential to be low in cost, reliable, and easy to operate and maintain.

We will present an overview of state-of-the-art III-V diode laser detection systems. System performance will be evaluated and the usefulness of these types of detection systems will be demonstrated.

Commentary by Dr. Valentin Fuster
1998;():879-886. doi:10.1115/IPC1998-2102.
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In 1994, Teikoku Oil Co., Ltd. (TOC) and NKK Corp. established a joint pilot project to provide pipeline application and evaluation of NKK’s gas hydraulic simulation engine (GASTRAN), and to co-develop a Demand Forecasting Model (DFC). When the pilot project finished in March 1997, a commercial system, Support Operation and Monitoring Application of Pipeline Simulator (SMAPS), was installed in TOC’s operation center.

SMAPS programs include a real time simulator, an off-line planning simulator, demand and supply database, SCADA interface program, and the DFC. The real-time simulator provides actual initial conditions to the off-line simulator. In addition, the demand and supply database facilitates inputting the data for each sales point and applying real time demand forecasts from DFC.

SMAPS has been mainly used to evaluate pipeline operation and monitor pipeline situations. Future plans include expanding usage for pipeline construction and maintenance and improving employee training.

Topics: Pipelines
Commentary by Dr. Valentin Fuster
1998;():887-893. doi:10.1115/IPC1998-2103.
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Teikoku Oil Co. Ltd. (TOC) and NKK Corp. established a joint pilot project in 1994 in order to provide pipeline application and evaluation of NKK’s gas hydraulic simulation engine (GASTRAN) and to co-develop a Demand Forecasting Model (DFC). When the pilot project finished in March 1997, a commercial system, called Support Operation and Monitoring Application of Pipeline Simulator (SMAPS), was installed in TOC’s operation center.

The DFC, which is based on an artificial neural network architecture, has several advantages for sales forecasting especially as several dozen delivery points that have different sales patterns are connected to the pipeline network. The results from DFC can be easily used for scenarios in off-line simulation to predict future pipeline situations when it is attached to the SMAPS system. It automatically assists the pipeline operator by reducing his workload and evaluating operation plans.

Commentary by Dr. Valentin Fuster

Pipeline Automation and Measurement: SCADA Systems

1998;():895-902. doi:10.1115/IPC1998-2104.
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Understanding Business Process needs is critical to successful implementation of new Information Technology. Understanding Information Technology capabilities is critical to successful evolution of Business Processes.

Supervisory Control and Data Acquisition (SCADA) systems have been in the gas industry since the 1960’s. Earlier systems provided some data or information from the remotely controlled locations and a few key inter-connections. Now, sophisticated networked systems which contain layers of information detail from field devices and other computerized processes, feed simulators designed to study the process, use expert systems to advise on capability, and provide excellent data and information retention and retrieval tools.

The potential to automate business processes is more complete than ever before. Computers can now help to manage integrated business processes where important data and information is moved regularly from one business process to another under the watchful eye of validation steps, at specified frequencies, with all the necessary reporting to process workers about the health, and performance, of the business process, process links, and the computer system.

The business must understand the benefits and constraints which technology offers to a business process, and find ways to evolve the process with the new technology in hand. The IT manager must understand the business process needs in order to provide the appropriate technology to enable the business process with quick-change capability when change is indicated.

This paper explores some of the relationships between the business process, and the technology impacting the process, on the way to producing a flexible, enduring, and friendly SCADA network, ready to interact with other SCADA systems, other internal processes, and the external world.

Commentary by Dr. Valentin Fuster
1998;():903-909. doi:10.1115/IPC1998-2105.
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This paper describes implementation of a SCADA system on the new Express pipeline (1300 km, 24 inch, crude oil pipeline). The project was executed in a 12 month period — approximately half the time of a typical pipeline SCADA project of this magnitude. The project was completed on schedule (June, 1997) and under budget.

Topics: Pipelines
Commentary by Dr. Valentin Fuster
1998;():911-918. doi:10.1115/IPC1998-2106.
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This paper discusses the merits of merging SCADA1 and gas measurement from a technical and economical perspective. Because traditional SCADA is largely limited to control room data used only for day to day operational purposes, the real-time metering data is not often utilized in the external revenue-generation business systems of the organization. In many cases, entirely separate measurement systems are utilized in isolation which often have few, if any, ties to the SCADA system which is capable of collecting pertinent measurement information.

Measurement data validation provides automatic data validation of flow measurement data upon retrieval from telemetered or non-telemetered data sources. Row measurement data can be supplied from field devices such as electronic flow computers or from other sources of flow measurement data such as manual operator entry, third party collection systems, chart integration sources, etc.

Flow measurement data undergoes a series of automated validation tests including single-run limit checking, meter run comparisons (at a given metering station) and historical validation tests (such as searching for frozen values). The outcome of these tests determines the data quality code assigned to each flow measurement reading (indicating the results of validation tests).

When combined with a real-time processing and data acquisition engine in a SCADA system that is capable of communicating with field devices via leased lines, VSAT, radio, dial-up, etc., many benefits can be realized.

Commentary by Dr. Valentin Fuster
1998;():919-926. doi:10.1115/IPC1998-2107.
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This paper will discuss some of the key features that have been implemented in the user interface component of IPL Energy’s Pipeline Control System (PCS).

IPL Energy operates the world’s largest crude oil and liquid pipeline system. In 1968, IPL Energy became one of the first pipeline companies in the world to implement computer based control of its pipeline systems, commonly referred to as SCADA (Supervisory Control And Data Acquisition). Since then, the SCADA system has been continually modified and improved in order to achieve high standards of reliability, safety, and operator functionality.

Unlike other SCADA systems, PCS has been developed from the ground up drawing from a wide range of experience and expertise in pipeline design, control, and operation. A brief overview of the past generations of SCADA systems will show how the user interface has evolved into the present system. The focus of the discussion will be on the Line Display, a single screen that can be used to operate a particular pipeline. The Line Display is the main operating screen used to control the pipeline and provides the operator with the current operating conditions, including operating pressures, pump statuses, and important alarms.

Commentary by Dr. Valentin Fuster

Pipeline Automation and Measurement: Metering and Measurement Systems

1998;():927-934. doi:10.1115/IPC1998-2108.
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The performance of two 8inch multi-path ultrasonic meters provided by Instromet and Daniel Industries is evaluated in the presence of a 19 tube bundle and the CPACL’ flow conditioner. These flow conditioners are placed downstream of a single elbow and two elbows out of plane. The ultrasonic meters are tested at several locations downstream of the flow conditioners. NOVA’s gravimetric meter prover is used to evaluate the performance of the meters. The present measurements indicate that the use of CPACL flow conditioner results in a near baseline performance of ultrasonic meters.

The two meters were also tested for pulsation effects using some of the solutions suggested by the manufacturers. Present tests indicate that the solutions were not effective enough and the meters are subject to errors when exposed to a pulsating flow.

Topics: Flow (Dynamics)
Commentary by Dr. Valentin Fuster
1998;():935-941. doi:10.1115/IPC1998-2109.
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Designers of ultrasonic meter stations with headers do not have any experimental data which can help to determine proper location of the multipath ultrasonic meter within the meter run. The results of meter tests are limited to such configurations as a single 90° elbows and two elbows out of plane. Because of the variety of header layouts used in practice any experimental information related to this piping configuration will be of limited use in the design process.

The proposed approach is based on the application of Computational Fluid Dynamics (CFD) methods to the evaluation of header effects on ultrasonic flow meter using a commercial CFD code combined with a numerical model of the ultrasonic meter.

The numerical simulation of the flow field in the header and meter runs and subsequent integration of the obtained velocity field in a numerical model of multipath ultrasonic meter were used to determine the optimal meter position. This approach was validated against available experimental data on the ultrasonic meter performance downstream of single and double elbow. The comparison of simulations and test data has shown very good agreement of trends exhibited by the meter. The trends were replicated by the simulator within approximately 1% for X/D ≥5 and within 0.5% for X/D ≥9.

Commentary by Dr. Valentin Fuster
1998;():943-946. doi:10.1115/IPC1998-2110.
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The increasing size and complexity of natural gas transmission and distribution systems in North America are leading to higher dependence on automated, remote communication and monitoring of meter station, compression, and pipeline facilities. Along with implementing new technology comes the need to maximise operating cost efficiencies while continuing to deliver reliable transportation service. Managing alarm conditions at over 1100 receipt and delivery meter stations in an efficient and effective manner has become increasingly important for NOVA Gas Transmission Ltd. (NGTL) to satisfy customer requirements for finalising individual gas accounts on a daily basis. As a result, NGTL has developed a “Meter Station Alarm Management Plan”. This paper describes the process developed and implemented by NGTL in categorising and prioritising measurement alarms and providing the right response, along with the benefits to be achieved.

Topics: Pipelines
Commentary by Dr. Valentin Fuster

Pipeline Automation and Measurement: Pipeline Training

1998;():947-952. doi:10.1115/IPC1998-2111.
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This paper details the authors’ experiences in using a pipeline simulator in pipeline operations training programs.

Pipeline simulators allow trainees to practice basic and advanced operating techniques in a “safe” environment. In the early stages of applied operator training, the simulator usually represents a fairly simple, generic pipeline. This allows clear illustration of operational concepts with a focus on specific tasks. In more advanced stages of an operator’s training cycle, the simulator can provide an exact simulation of the pipeline that the trainee will have to control in the future. Realistic scenarios can be presented and operator trainees are able to exercise almost all tasks and deal with any possible incident that may occur during the operation of a pipeline. Accurate records detailing trainees’ operational decisions during a simulator exercise are maintained and help in determining the skill level of different trainees. This information allows pinpointing of specific areas where more training may be needed.

At the same time, pipeline operations training which uses a simulator can address certification requirements. A simulator allows a company to set standards, and then to test operational skills and knowledge against those standards in a quantifiable and controllable manner. Since the performance of a trainee during a simulator training session is fully recorded, companies can use this record as a measure when qualifying operators.

Topics: Pipelines
Commentary by Dr. Valentin Fuster
1998;():953-961. doi:10.1115/IPC1998-2112.
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SCADA software training is undergoing a remodeling of technical training courseware to incorporate new cognitive learning approaches. In order to better facilitate the learning requirements of our customers’ knowledge domains, Valmet technical trainers are looking at ways to infuse concepts from cognitive science, constructivism and the models of andragogy into their training materials. This paper synthesizes the research undertaken by Valmet trainers towards building a training model for the delivery of future courseware. A pilot Train the Trainer course, aimed at helping intermediate to advanced learners acquire knowledge and hone problem-solving skills, has been created as a result of our research.

Commentary by Dr. Valentin Fuster

Environmental Issues: Planning

1998;():963-969. doi:10.1115/IPC1998-2113.
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In response to public pressure and in a desire to ensure that the public was adequately informed about potential projects, the National Energy Board (NEB) produced a Memorandum of Guidance with respect to its expectations regarding its Early Public Notification (EPN) program in 1990.

Over time, issues such as Stress Corrosion Cracking, Risk Assessment, Pipeline Integrity and Landowner Compensation have all significantly impacted the way companies have adjusted their approaches to the delivery of EPN programs.

In the future, the pipeline industry can expect that public consultation programs will increasingly become an essential component on both project specific and long range strategic communications planning. The purpose of this paper is to review the development and implementation of the EPN process and to propose future issues which may impact the planning and execution of consultation programs. The focus of this paper will be to:

A. Profile the evolution and delivery of EPN programs and review the communications tools typically used with EPN programs;

B. Examine the recent emergence of regional landowner interest groups and to review their effect on the regulatory process and issues such as pipeline integrity, pipeline safety and environmental stewardship;

C. Review how the pipeline industry has responded to public, Board and government initiatives regarding intervenor funding, and;

D. Provide insight into future EPN delivery systems as well as emerging trends with respect to public participation in the pipeline and resource sector.

Commentary by Dr. Valentin Fuster
1998;():971-976. doi:10.1115/IPC1998-2114.
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Currently, under Alberta’s Environmental Protection and Enhancement Act and regulations, all pipelines transporting natural gas with an index of 2690 or greater require an approval (Conservation and Reclamation Approval) for the conservation and reclamation activities associated with construction and reclamation of a pipeline. Administratively, Alberta Environmental Protection considers a pipeline requiring an Environmental Protection and Enhancement Act approval as a “Class 1” pipeline. The index is a calculation of length of pipe (in kilometers) multiplied by the outside pipe diameter (in millimeters).

NOVA Gas Transmission Ltd. (NGTL) has developed and implemented a Conservation & Reclamation (C&R) Standard to streamline the provincial C&R Application process. By re-formatting the currently accepted C&R Application into a Standard document, textual information submitted for an individual project has been reduced, without affecting the quality of environmental planning.

The Standard document compiles NGTL’s environmental standard practices and mitigative measures undertaken for all pipelines. It also explains NGTL’s decision-making processes during the design phase of a project.

The project-specific document presents issue focused site-specific environmental details in a simplified format The C&R Standard in combination with the project-specific submission form the NGTL C&R Application.

NGTL’s C&R Standard was developed within a concept which uses key building blocks to achieve industry accountability. This concept requires an organization to have performance measurement tools in place, and to demonstrate commitment to that performance in order to earn public confidence. Once this confidence is established and maintained, an organization can realize industry accountability. Considering this concept, NGTL leveraged past performance and experience by documenting our consistent approach to pipeline design, and our performance measurement criteria into the C&R Standard.

Fundamental to the development of the Standard was NGTL’s Platform Design Concept. Initially this design concept was adopted as an integral component of NGTL’s business need to reduce and streamline internal processes. This concept was then applied to external processes in an effort to meet business needs.

The Standard includes two primary components, Guiding Principles and Platforms. By combining NGTL Guiding Principles (‘What’ and ‘Why’) and NGTL Platforms (‘How’), the Concept provides a systematic design guide for all projects that allows NGTL to make the right decisions based on the right design criteria.

NGTL submitted the C&R Standard document to Alberta Environmental Protection for review in July 1997 and is currently implementing the Standard for all C&R Applications. This paper describes the development of the document as well as the implementation process and experience of the Standard.

Commentary by Dr. Valentin Fuster
1998;():977-982. doi:10.1115/IPC1998-2115.
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Protection of the environment has been and will continue to be a major issue facing the pipeline business around the world. Many of the decisions companies make relating to future investments and ongoing operations have environmental implications. These decisions can have significant cost implications that impact the bottom line of oil and gas transportation companies. Most companies do not track their environmental costs rigorously and thus, do not have a good understanding of the magnitude of these costs.

Recently, we have undertaken studies to define and identify the major environmental cost drivers in the industry. As part of these studies, we identified some potential measures of environmental performance and actually measured certain aspects of environmental performance in pipeline companies.

This paper will provide insights into the major environmental cost drivers in the industry and will define these cost drivers. It will provide some ideas on “what to measure” relating to environmental costs.

Implementing an environmental cost management system is not a trivial task. It is difficult to assess how much of the cost associated with a certain investment is related to the environment. This can only be determined on a project by project basis and will also be unique from company to company. Although there is no “cookbook” approach to implementing this system, this paper will provide some guidance for implementing such a system.

Commentary by Dr. Valentin Fuster
1998;():983-987. doi:10.1115/IPC1998-2116.
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This paper is to keep you informed of certain recent developments in the Alberta Energy and Utilities Board (AEUB) that is of particular interest to pipleline companies. Since these changes were first initiated, the Board has undertaken a significant transformation of the management of regulated wastes from the petroleum industry.

The passing of the G-58 guidelines will have far reaching effects on the business environment of the petroleum industry.

We have analyzed some of the more important aspects of this reform.

We continue to closely monitor changes from our western Canadian operations, particularly the impact of those changes on those generating regulated wastes in Alberta.

Commentary by Dr. Valentin Fuster

Environmental Issues: Operations

1998;():989-996. doi:10.1115/IPC1998-2117.
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In December 1995, an oil spill was discovered along a section of pipeline located near the bank of a major river, less than 1 km upstream of the water supply intake of a southern Alberta community. The spill, which involved light crude oil, was observed at ground surface over an area of approximately 3 000 m2 at the top of the river slope and had also migrated downslope through the subgrade soils and along the groundwater table toward the river.

The initial emergency response activities consisted of removing and disposing of oil-stained vegetation and snow, and the containment and recovery of free oil pooled on ground surface. Subsequent subsurface assessments involved the drilling of test holes and boreholes, and installation of groundwater monitoring/recovery wells. Based on the results of these assessments, a remedial action plan was developed. As part of this plan, some of the impacted soils were excavated and placed in lined treatment cells for bioremediation. The limits of the excavation were based on field screening measurements and on soil clean-up criteria developed through an assessment of the human health risk and ecological impacts.

Investigations conducted at the site also indicated that phase-separated crude oil had migrated further downslope and had accumulated at the water table within the flood plain sediments adjacent to the river. Therefore, remediation systems were installed to recover the oil, recover and treat the impacted groundwater, and prevent further migration of the impacted groundwater and oil toward the river. Impacted groundwater recovered from the flood plain deposits was treated onsite and was then injected back into the flood plain deposits via an infiltration gallery. The performance of the pumping and remediation systems was monitored regularly and water samples were recovered from the treatment system, selected monitoring wells and the river. Based on the results of these analyses, the quality of local groundwater steadily improved and the zone of impacted water was effectively contained.

Commentary by Dr. Valentin Fuster
1998;():997-1004. doi:10.1115/IPC1998-2118.
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As part of its Integrity Management Program, Trans Mountain Pipe Line hydrostatically tests sections of its pipeline system with water transported to test sites through the pipeline. After completion of the testing, the water continues through the pipeline to a water treatment facility where it is treated and discharged to the municipal sewer system.

Hydrostatic testing of an operating pipeline, although simple in concept, is a major undertaking. This paper will outline the technical aspects of Trans Mountain’s hydrostatic testing program including: test water transportation, environmental constraints, coordination of test activities and water treatment.

Commentary by Dr. Valentin Fuster
1998;():1005-1011. doi:10.1115/IPC1998-2119.
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Major leakages occurred during the last years demonstrate the risk involved with older pipeline systems in Eastern Europe and the FSU, which for the most part are not operated and maintained in accordance with nowadays safety standards.

The typical project approach to standardize the individual subsystem rather than engineering a customized approach, and unclear operating procedures are main causes for this situation.

Having little or no detailed information on condition of the individual systems makes it difficult to evaluate the risks involved. However, certain measures contribute to make a reasonable statement on the reliability of the system, to reduce the risk of environmental pollution significantly and to bring long term economic sustainability.

Using the experience gained through actual projects and with an individually well considered approach, a rehabilitation project in the FSU can be adequately assessed and carried out to ensure optimum deferred expenditure while meeting all relevant environmental and safety requirements.

Commentary by Dr. Valentin Fuster
1998;():1013-1022. doi:10.1115/IPC1998-2120.
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Findlay Creek is a small, coldwater stream which was crossed by a natural gas pipeline using conventional open-cut techniques in late August 1992. Pipeline crossing activities included the removal of a beaver dam which was located along the proposed alignment, the installation of a temporary road crossing, and the actual pipeline installation. A monitoring study was initiated to examine the impacts of pipeline construction on this stream including changes in the physical and biological regimes of the aquatic ecosystem. Results of this study indicate that the dramatic sediment loads (suspended sediment levels of up to 3000 mg/L) caused by pipeline construction were sufficient to cause changes to the channel morphology as well as the fish and invertebrate communities. By twelve weeks post-construction, partial recovery of habitats and aquatic communities was apparent. Changes to the physical channel parameters and the stream population structure documented in this study suggest that impacts to Findlay Creek were localized, and full recovery was documented in affected areas by the one year post construction sampling period. This study concurs with other research investigating the impacts of pipeline construction, in that impacts on the aquatic fauna appear to be localized in extent and short term in duration.

Commentary by Dr. Valentin Fuster

Environmental Issues: Construction

1998;():1023-1030. doi:10.1115/IPC1998-2121.
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Pipeline river crossings pose a significant challenge for pipeline owners and environmental regulators to balance the associated costs and risks, particularly where environmental impacts may occur. For years, NOVA Gas Transmission Ltd. (NGTL) has managed the regulatory approval process using a well-established process. However, regulatory expectations are increasingly neutral to the cost of crossing installations and are demanding a more thorough assessment of a wider variety of river crossing options, particularly trenchless technologies. As a result, NGTL has recently enhanced the internal process by incorporating a structured decision tool. This tool is able to quantitatively assess technical risks as well as ‘soft’ influences such as “Regulatory Relationship” and “Delay in Approval”. The result is a clear decision with the necessary buy-in, where all risks were identified quantitatively and well understood by decision makers.

Commentary by Dr. Valentin Fuster
1998;():1031-1034. doi:10.1115/IPC1998-2122.
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This paper describes how the use of an environmental management plan can effectively anticipate problems that may occur during pipeline construction and make dealing with them easier. Examples from a recently completed natural gas pipeline project in eastern Ontario and our experience with environmental inspection of other pipelines in various jurisdictions are used to do this. The focus of the paper will be on environmental issues associated with smaller diameter, extra high pressure distribution pipelines, which have a distinctly different set of environmental considerations than do transmission pipelines.

Topics: Inspection
Commentary by Dr. Valentin Fuster
1998;():1035-1040. doi:10.1115/IPC1998-2123.
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Sediment released during pipeline water crossings has the potential to negatively affect downstream aquatic resources. Regulation of pipeline water crossings has been directed through the application of allowable construction methods, timing constraints and numerical turbidity restrictions on construction permits. Past applications of turbidity restrictions are criticized for the following reasons: duration of exposure or sediment deposition effects are not considered; some applied restrictions are for the protection of primary productivity in lakes; and, defined mixing zones do not appear to incorporate expected levels of sediment generation, or sediment transport principles. Alternate approaches to defining permit restriction are proposed.

Commentary by Dr. Valentin Fuster
1998;():1041-1044. doi:10.1115/IPC1998-2124.
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Native prairie is recognized in Alberta for its significant ecological, cultural and economic value. Much of the remaining prairie in Alberta is under public ownership and is managed for multiple uses and values. This paper illustrates how public land managers and industry cooperate to minimize disturbance to this valuable resource. The emphasis at the planning stage is proper inventory and identification of sensitive landscape, plant and animal features on proposed alignments, followed by appropriate realignment or mitigative action. At the pre-construction phase, environmental training of staff has raised awareness about the value of the prairie resource. During construction, the implementation of traffic control plans, shut down criteria and innovative soil handling techniques have reduced the overall impact of activities. Use of special equipment, erosion control techniques and revegetation strategies during reclamation can enhance the recovery of prairie disturbances. Proper monitoring is an important component of successful reclamation, and can lead to modifications of methods and equipment that give better future protection to this valuable landscape.

Commentary by Dr. Valentin Fuster
1998;():1045-1050. doi:10.1115/IPC1998-2125.
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Sediment entrainment in rivers caused by pipeline watercourse crossing construction may represent a constraint on pipeline route selection and construction methods as designers attempt to develop a sediment and erosion control plan which meets regulatory approval without risk of costly delays. To avoid the risk of significant sediment entrainment, conventional open-cut crossing techniques may be replaced by more costly directional drilling methods. However, the concern over suspended sediment is greatest in high velocity rivers where the bed material includes a large fraction of fine sand, and in rivers with a large fraction of fine grained bed material which becomes suspended upon disturbance by construction activities. According to the current understanding of aquatic impacts due to elevated suspended sediment levels, the occurrence of suspended sediment may not be excessive at open-cut excavation in certain types of streams depending on the material consistency, fine sand content and river flow velocity (Anderson et al, 1996). Control of sand entrainment can normally be achieved by low cost sediment control systems during construction. Methods of prediction, impact assessment, and control of sediment entrainment have been developed so that high risk crossings can be identified and impacts minimized. The application of the study findings and best management practices (BMPs) for sediment control will allow developers to choose the most appropriate crossing method while avoiding potentially adverse impacts, based on a sound understanding of river sediment transport, bed material conditions and downstream aquatic resources.

Commentary by Dr. Valentin Fuster

Rotating Equipment Technology: Compressor Technology

1998;():1051-1056. doi:10.1115/IPC1998-2126.
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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.

Topics: Compressors , Testing , Surges
Commentary by Dr. Valentin Fuster
1998;():1057-1064. doi:10.1115/IPC1998-2127.
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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.

Commentary by Dr. Valentin Fuster

Rotating Equipment Technology: Pump Technology

1998;():1065-1072. doi:10.1115/IPC1998-2128.
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This paper reviews Trans Mountain’s recent experience with the installation of main line pumping units ranging in size from 670 to 1900 kw (500 to 2500 Hp). This includes a review of vibration problems encountered due to a structural resonance, how this problem was resolved and its impact on subsequent baseplate designs and their associated installation techniques.

Commentary by Dr. Valentin Fuster
1998;():1073-1078. doi:10.1115/IPC1998-2129.
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In this paper, a heat conduction equation and a dynamic thermoelastic equation are briefly deduced and established based on Continuum Mechanics.

First, an qualitative discussion is emphatically centered around the couple term and the dynamic term of the equation by means of the dimensional analysis and by considering the combination of the characteristics of the materials and of the thermal load effected on the nuclear power station pump under study.

Second, formulations of the FEM for non-coupled heated equations and quasi-static thermoelastic equations are derived in this paper.

Third, a half space thermal shock problem is used as a computational example in the highlighted research on the varying behavior of the dynamic thermal stress on the temperature slope. The conclusion of the paper provides reliable justification for applying the numerical method.

Finally, the distribution and variety of the temperature field, the thermal stress field and the thermal deformation field at various transient moments on the pump are given.

Commentary by Dr. Valentin Fuster
1998;():1079-1090. doi:10.1115/IPC1998-2130.
FREE TO VIEW

Key variables in the design of pipeline systems are pump efficiency, equipment reliability, and throughput flexibility since they significantly influence the pipeline operating costs.

Pumps commonly used in pipelines operate at high efficiency only at the Best Efficiency Point (BEP) capacity. Outside this capacity, efficiency decreases and the wasted energy is converted into harmful vibrations, noise and heat, contributing to premature pump failures. Conventional pumps do not provide capacity flexibility to a pipeline.

A horizontal split case pump with replaceable diffusers and capable of accommodating a series of impellers has been developed. An impeller/diffuser combination with a BEP capacity matching the pumping capacity is selected to maximise efficiency. Since it operates close to BEP capacity, minimal pump vibrations and noise improve pump reliability.

Hydraulic and mechanical design features of the pump, some concepts for the future and a discussion of the potential cost savings when used in pipeline systems are presented.

Commentary by Dr. Valentin Fuster

Rotating Equipment Technology: Driver Technology

1998;():1091-1094. doi:10.1115/IPC1998-2131.
FREE TO VIEW

This paper provides field data and installation history from one 5000 hp and four 4250 hp multi-level pulse width modulated (PWM ) medium voltage adjustable frequency drive systems which are used to control the speed of centrifugal pumps. The multi-level PWM drive has a number of advantages over alternative adjustable drive technologies for the pipeline industry. This is the first use of this multi-level PWM drive for pipeline operation and the first installation of this multi-level PWM drive with closed synchronous transfer. This paper briefly outlines the advantages of the AFD for the pipeline industry and the basic application concerns, which must be dealt with when they are used. The paper then describes the theory of operation of the multi-level PWM drive and the theoretical advantages of this drive technology. The last section of the paper is a summary and evaluation of field data.

Topics: Pipelines
Commentary by Dr. Valentin Fuster
1998;():1095-1106. doi:10.1115/IPC1998-2132.
FREE TO VIEW

Selecting, buying and installing an electric variable speed drive system (EVSDS) for a high power drive application is an activity with project character. It is not a product business.

In order to bring the audience to the same level of understanding, there is a chapter with an overview of different VSDS technologies. This overview also gives our opinion of what a large AC drive should be capable of. In the main part of the paper we will review the project handling process. The stages of this process cover project planning, all phases of the drive order, operation, maintenance, servicing and upgrading if needed, up to dismantlement. Focus is set on those issues that have the greatest impact on the reliability of the drive. Besides state-of-the-art technology, two important preconditions are required for a successful application of variable speed drive systems. These are proper drive integration into the drive environment and standardization based on modular structures.

By means of a case history we will report on a large AC drive project and the experience gained in this context.

This paper is in particular addressed to application engineers and persons who are involved in selection and operation of large VSDSs (from a few megawatt to hundreds of megawatt).

Topics: Reliability
Commentary by Dr. Valentin Fuster
1998;():1107-1110. doi:10.1115/IPC1998-2133.
FREE TO VIEW

Natural gas transmission systems have many sources of fugitive methane emissions that have been difficult to eliminate. This paper discusses an option for dealing with one such source for operations using turbo-compressor units fitted with dry gas seals. Dry seal leakage ultimately results in waste gas that is emitted to the atmosphere through the primary vent. A simple, cost effective, emission disposal mechanism for this application is to vent the seal leakage in to the gas turbine’s air intake. Explosion hazards are not created by the resultant ultra-lean fuel/air mixture, and once this mixture reaches the combustion chamber, where sufficient fuel is added to create a flammable mixture, significant oxidation of the seal vent gas is realized. In principle, this system is easily implemented with simple modifications to the existing vent piping. However, the inherent safety of ultra-lean fuel/air mixture applies only when the gas turbine is operating with gas turbine airflow overwhelming the seal leakage flow. A potential design solution for managing this emission avoidance mechanism including safe operation during gas turbine shutdown periods is detailed.

Commentary by Dr. Valentin Fuster
1998;():1111-1117. doi:10.1115/IPC1998-2134.
FREE TO VIEW

On March 17, 1997 Robicon Corporation was requested, by a large Alberta based oil company, to provide a proposal to manage a turn-key, crude oil, pump station project. The oil company had identified an immediate need to expand their North Eastern Alberta Pipe Line system to allow a higher thru-put into the Hardisty, Alberta area:

• the pipe line was capacity restricted and customer demand indicated an immediate requirement to increase pipe line thru-put by 70%;

• the capacity increase was required by June 30th or earlier.

Topics: Pumps
Commentary by Dr. Valentin Fuster

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