Design and Construction Challenges of a Roped Insulated Pipeline

2020 ◽  
Author(s):  
Neetu Prasad ◽  
Graeme King ◽  
Arfeen Najeeb
Keyword(s):  
Ground Surface ◽  
Large Temperature ◽  
Worst Case ◽  
Oil Pipeline ◽  
Upheaval Buckling ◽  
Timely Completion ◽  
Construction Contractor ◽  
Cold Bends ◽  
And Control ◽  
Design And Construction

Abstract Thermally insulated hot buried pipelines pose a unique set of challenges. This paper discusses those challenges and how they were met during design and construction of the 150 km long Husky LLB Direct Pipeline, the longest thermally insulated oil pipeline in Canada. Thermal insulation materials are soft and can be easily damaged during construction and backfilling, and by large restraining forces at bends when the pipeline is operating at high temperatures. The large temperature difference between pipeline installation temperature and maximum operating temperature leads to large axial compressive forces that can cause movement at bends, crush insulation, increase temperatures at ground surface, cause loss of restraint, and in the worst case, lead to upheaval buckling and loss of containment. Special design and construction features to deal with these challenges, including insulation specifications, insulation of pipe bends, pipeline pre-straining, long radius bends, deeper burial, and pipeline roping, were therefore necessary. After pipe has been insulated with polyurethane foam it cannot be bent in standard field bending machines used for uninsulated pipes because the foam is too soft. The induction bends and cold bends that are shop insulated after bending are expensive. The Project minimized the number of these expensive insulated bends by using an engineered ditch bottom profile. This meant that shop bends were only needed to reduce excavation depth at sharp changes in ground surface elevation where the roped profile required excessive grading. Care was therefore necessary in the selection and development of specifications for the insulation system and shop fabricated bends, and to design and construct a ditch profile to minimize forces on the insulation and control upheaval buckling. Close co-ordination with vendors and the construction contractor was crucial for a successful and timely completion.

Meteorological Sub-Committee. Aeronautical Research Committee. The Formation of Ice on Aircraft.

1937 ◽  
Vol 41 (319) ◽  
pp. 595-608
Author(s):  
H. Noth ◽  
W. Polte
Keyword(s):  
Ground Surface ◽  
Ice Formation ◽  
Relative Speed ◽  
Research Committee ◽  
Worst Case ◽  
Danger Zone ◽  
Considerable Length

The main reasons why trouble due to ice formation on aircraft was not experienced so much in the earlier days of flying as now were two-fold, (a) The greatly restricted amount of flying done during the winter and (b) the absence of means whereby flight in cloud for any considerable length of time was possible.The degree to which ice forms, however, differs widely. Since much depends on the relative speed of the aircraft, free balloons are practically excluded. In the worst case ice cannot form on such aircraft to the extent to which heavy glazed frost is observed on the ground, unless the balloon pilot is a very bad navigator and remains in the danger zone longer than would be required for the ground surface to be coated with glazed frost.

Field Observations of Cyclical Pipe-Soil Interactions in Permafrost Terrain, KP 5, Norman Wells Pipeline, Canada

2000 ◽  
Author(s):  
Margo M. Burgess ◽  
Scott Wilkie ◽  
Rick Doblanko ◽  
Ibrahim Konuk
Keyword(s):  
Small Diameter ◽  
Ground Surface ◽  
Thermal Conditions ◽  
Field Work ◽  
Low Density ◽  
Freezing And Thawing ◽  
Near Surface ◽  
Oil Pipeline ◽  
Right Of Way ◽  
Discontinuous Permafrost

The Norman Wells pipeline is an 869 km long, small diameter, buried, ambient temperature, oil pipeline operated by Enbridge Pipeline (NW) Inc. in the discontinuous permafrost zone of northwestern Canada. Since operation began in 1985, average oil temperatures entering the line have been maintained slightly below 0°C, initially through constant chilling year round and since 1993 through a seasonal cycling of temperatures through a range from −4 to +9°C. At one location, 5 km from the inlet at Norman Wells, on level terrain in an area of widespread permafrost, uplift of a 20 m segment of line was observed in the early 1990s. The uplift gradually increased and by 1997 the pipe was exposed 0.5 m above the ground surface. Detailed studies at the site have included field investigations of terrain and thermal conditions, repeated pipe and ground surface elevation surveys, and annual Geopig surveys. The field work has revealed that the section of line was buried in low density soils, thawed to depths of 4 m on-right-of-way, and not subjected to complete refreezing in winter. The thaw depths are related to surface or near-surface flows from a nearby natural spring, as well as to the development of a thaw bulb around the pipe in the cleared right-of-way. Icings indicative of perennial water flow occur commonly at this location in the winter. The pipe experienced annual cycles of heave and settlement (on the order of 0.5 m) due to seasonal freezing and thawing within the surrounding low density soils. The pipe reached its highest elevation at the end of each winter freezing season, and its lowest elevation at the end of the summer thaw period. Superimposed on this heave/settlement cycle was an additional step-like cycle of increasing pipe strain related to thermal expansion and contraction of the pipe. A remedial program was initiated in the winter of 1997–98 in order to curtail the cumulative uplift of the pipe, reduce the increasing maximum annual pipe strain and ensure pipe safety. A 0.5 m cover of sandbags and coarse rock was placed over the exposed pipe segment. Continued pipe elevation monitoring and annual Geopig surveys have indicated that both seasonal heave/settlement and strains have been reduced subsequent to the remedial loading. Introduction of a gravel berm has also altered both the surrounding hydrologic and ground thermal regimes.

Integrated Optimization of Structure and Control in Ultra-Precision Motion Systems

2019 ◽  
Author(s):  
Jing Wang ◽  
Ming Zhang ◽  
Yu Zhu ◽  
Xin Li ◽  
Leijie Wang
Keyword(s):  
Complex Dynamics ◽  
System Level ◽  
Structural Topology ◽  
Worst Case ◽  
Integrated Optimization ◽  
Motion System ◽  
Material Interpolation ◽  
Ultra Precision ◽  
Precision Motion ◽  
And Control

Abstract Ever-increasing demands for precision and efficiency in ultra-precision motion systems will result in a lightweight and flexible motion system with complex dynamics. In this paper, a systematic approach is proposed where control gains, 3D structural topology and actuator configuration are integrated into optimization to derive a system-level optimal design which possesses a high vibration control performance, and still satisfies multiple design constraints. A material interpolation model with high accuracy is proposed for the integrated optimization, a simple integral equation utilizing R-functions and level-set functions is established to represent complex non-overlapping constraints of actuators. Over-actuation degrees are utilized to actively control the dominant flexible modes. Responses of residual flexible modes are restricted by increasing the coincidence of their nodal areas at actuators (sensors) locations. The objective function is the constructed worst-case vibration energy of the flexible modes. A dual-loop solving strategy combining the genetic algorithm and the modified optimal criteria method is adopted to solve the optimization problem. A fine stage in the wafer stage is designed to prove the effectiveness of the proposed method.

scholarly journals Assessment of Freeze–Thaw Hazards and Water Features along the China–Russia Crude Oil Pipeline in Permafrost Regions

2020 ◽  
Vol 12 (21) ◽  
pp. 3576
Author(s):  
Mingtang Chai ◽  
Guoyu Li ◽  
Wei Ma ◽  
Yapeng Cao ◽  
Gang Wu ◽  
...  
Keyword(s):  
Crude Oil ◽  
Dominant Role ◽  
Ground Surface ◽  
Influential Factors ◽  
Landsat 8 ◽  
Model Calculations ◽  
Surface Flows ◽  
Oil Pipeline ◽  
Freeze Thaw ◽  
Permafrost Regions

The China–Russia crude oil pipeline (CRCOP) traverses rivers, forests, and mountains over permafrost regions in northeastern China. Water accumulates beside the pipe embankment, which disturbs the hydrothermal balance of permafrost underlying the pipeline. Ground surface flows along the pipeline erode the pipe embankment, which threatens the CRCOP’s operational safety. Additionally, frost heave and thaw settlement can induce differential deformation of the pipes. Therefore, it is necessary to acquire the spatial distribution of water features along the CRCOP, and analyze the various hazard probabilities and their controlling factors. In this paper, information regarding the permafrost type, buried depth of the pipe, soil type, landforms, and vegetation were collected along the CRCOP every 2 km. Ponding and erosive damage caused by surface flows were measured via field investigations and remote sensing images. Two hundred and sixty-four pond sites were extracted from Landsat 8 images, in which the areas of 46.8% of the ponds were larger than 500 m2. Several influential factors related to freeze–thaw hazards and erosive damage were selected and put into a logistic regression model to determine their corresponding risk probabilities. The results reflected the distributions, and forecasted the occurrences, of freeze–thaw hazards and erosive damage. The sections of pipe with the highest risks of freeze–thaw and erosive damage accounted for 2.4% and 6.7%, respectively, of the pipeline. Permafrost type and the position where runoff encounters the pipeline were the dominant influences on the freeze–thaw hazards, while the runoff–pipe position, buried depth of the pipe, and landform types played a dominant role in erosive damage along the CRCOP. Combined with the geographic information system (GIS), field surveys, image interpretation and model calculations are effective methods for assessing the various hazards along the CRCOP in permafrost regions.

Pipeline Integrity Analyses for Construction in Mountainous Areas

2014 ◽  
Author(s):  
Fan Zhang ◽  
Ming Liu ◽  
Yong-Yi Wang ◽  
Ryan Surface ◽  
Adam Phillips
Keyword(s):  
Mountainous Terrain ◽  
Mountainous Areas ◽  
Mountain Areas ◽  
Element Analysis ◽  
Upheaval Buckling ◽  
Section Design ◽  
Cold Bends ◽  
Pipeline Design ◽  
Operating Cycles

The construction of a pipeline in mountainous terrain often exposes great challenges compared to that on flat land. To accommodate the terrain and resultantly complex route, the pipeline design must incorporate a large quantity of cold bends and elbow fittings. A recently constructed project provides a prime example of a pipeline crossing such terrain. The challenging construction conditions and the bends and elbows make the assessment of stress impacting long-term pipeline integrity critical, yet difficult. This paper focuses on three specific aspects of long-term integrity for construction in mountain areas using advanced finite element analysis (FEA). The first scenario is tie-in welding. Tie-in welding connects separate pipeline segments constructed independently. In general practice, considerable lengths of pipe are left unburied to reduce the potential resultant stress due to the misalignment between the pipes at the tie-in weld location. However, in mountainous terrain the length of unburied pipe may be constrained by field conditions of the tie-in location. The implications are amplified at a tie-in adjacent to bends or elbows. The second scenario is hydrostatic testing. The gravitational weight of water generates additional internal pressure in the pipeline segments at low elevations. In areas of significant elevation change, hydrostatic test section design defines the segments based on the maximum allowable hoop stress level calculated for straight pipe. However the bends and elbows often encounter increased combined stresses at such locations that may not be adequately considered. The last scenario is ratcheting. Exacerbated by complex routing and profile, pipelines constructed in mountainous areas are at risk to develop significant uplift in the soil at bend locations during hydrostatic testing and initial operating cycles. If such uplift displacement accumulates during subsequent operating cycles, a phenomenon known as ratcheting, the pipe may eventually fail by upheaval buckling. This paper evaluates the above scenarios of a NPS 30 section of pipeline consisting of several segments with wall thicknesses varying from 12.0 mm through 19.6 mm, and contains frequent bends and elbows. The pipeline route is mountainous with slopes exceeding 70 degrees, and includes a tunnel immediately adjacent to water crossings and steep slopes. Tie-in welds are made in tight confines at either end. Analysis based on this project profile provides detailed information and insight into the design and construction of pipelines in mountainous terrain.

scholarly journals Response, Remediation and Risk Management of a Crude Oil Pipeline Spill

1998 ◽  
Author(s):  
J. T. Doupe ◽  
W. R. Livingstone
Keyword(s):  
Crude Oil ◽  
Action Plan ◽  
Human Health Risk ◽  
Ground Surface ◽  
Flood Plain ◽  
Ecological Impacts ◽  
Monitoring Wells ◽  
Oil Pipeline ◽  
Subgrade Soils ◽  
Major River

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.

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