Pressure Reductions and Pipeline Excavation

2004 ◽  
Author(s):  
Robert I. Coote ◽  
J. Kyle Keith
Keyword(s):  
Pressure Level ◽  
Literature Survey ◽  
Operating Pressure ◽  
Design Codes ◽  
Pressure Reduction ◽  
Interview Process ◽  
Maintenance Activities ◽  
Pipeline Design

Pipeline companies often reduce the pressure while performing maintenance activities and integrity excavations on in-service pipelines. Despite this practice, pipeline design codes, regulations and industry publications offer little guidance on what factors should be considered to determine how much, if any, the pressure should be reduced from operating levels during excavation activities. Also, it is not commonly understood what level of safety is introduced with these reductions and what historical operating pressure level should be used as the basis for the reductions. A literature survey and an interview process with CEPA member companies summarized common industry practices and determined factors to be considered when assessing if and how much of a pressure reduction is appropriate while excavating an operating energy pipeline.

Assessment of the Reliability Level Embedded in Pipeline Design Codes

2014 ◽  
Author(s):  
Sviatoslav Timashev ◽  
Anna Bushinskaya
Keyword(s):  
Limit State ◽  
Random Variables ◽  
State Function ◽  
Operating Pressure ◽  
Pipe Material ◽  
Design Codes ◽  
Statistical Parameters ◽  
Reliability Level ◽  
Long Time ◽  
Pipeline Design

Recently a long time discussion among specialists about the meaning of the probabilities of failure (POF) produced by different reliability analysis methods surfaced in pipeline journals. This paper, which was a long time in the making, is a follow-up on the discussion and analyses the actual reliability level which was empirically embedded in codes for pipeline design [B31G, B31Gmod, Shell92 and Battelle (PCORRC)] and Building Standard (BR) Main Pipelines #2.05.06-85, using a real pipeline as an example. Assessment of the actual reliability level empirically embedded in BR is based on assessing the order of the quintiles of strength parameters (design values of tensile strength and yield strength of the pipe material) and load (internal pressure) on the pipeline. This approach allows direct connection of the deterministic safety coefficients used in the BR with the level of reliability of the pipelines associated with these coefficients. The actual reliability level, empirically embedded in international codes, is calculated as the probability that the limit state function (LSF) of ideal pipeline (without defects) is positive. LSF = Pf − Pop, where Pf is the failure pressure of an ideal pipe, which is estimated by any design code; Pop is the operating pressure. The failure and operating pressure are considered as random variables. The expression for this probability was obtained analytically and in closed form. Recommendations are also presented for choosing probability distributions and statistical parameters for random variables RVs. Extensive calculations permitted revealing the reliability levels which are actually present in the analyzed international pipeline design codes. In a nutshell, the paper proves that the international codes under consideration are very reliable, as they produce very safe designs of pipelines with very low POF, and, hence, provide large safety coefficients, and that the algorithm developed in the paper permits connecting the current level of pipeline degradation (in terms of POF), with its current safety coefficient, which, in this case, is a function of time. All calculating in the paper where performed using MathCAD. Illustrations of these calculations are also presented in the paper.

In-Field Application of Steel Strip Reinforcement for Pipeline External Rehabilitation

2010 ◽  
Author(s):  
Nicholas J. Venero ◽  
Tim J. M. Bond ◽  
Raymond N. Burke ◽  
David J. Miles
Keyword(s):  
Steel Strip ◽  
New Technology ◽  
High Strength ◽  
Field Application ◽  
Operating Conditions ◽  
Operating Pressure ◽  
Precise Control ◽  
Ultra High Strength Steel ◽  
Structural Adhesive ◽  
Pipeline Design

A new technology for external rehabilitation of pipelines, known as XHab™, has been developed. This method involves wrapping multiple layers of ultra-high strength steel (UHSS) strip in a helical form continuously over an extended length of pipeline using a dedicated forming and wrapping machine. The reinforcement afforded by the strip can be used to bring a defective section of pipe (e.g. externally corroded or dented) back to its original allowable operating conditions, or even to increase the allowable operating pressure if the desired operating conditions exceed the original pipeline design limits. This paper describes the design, manufacture and testing process for a self-propelled wrapping machine for in-field rehabilitation. The wrapping apparatus consists of several major components including an opening sufficiently wide to receive the pipe, a movement assembly, a winding head, a preforming device, an accumulator and an oscillating adhesive applicator. The wrapping apparatus uses the winding head to wrap the reinforcing steel strip around the pipe. The movement assembly uses a pair of tracks in contact with the pipe to drive the wrapping apparatus along which enables helical wrapping of the reinforcing strip material. The oscillating adhesive assembly applies structural adhesive to the pipe immediately before the strip is wound. The winding head, motive assembly and adhesive applicator are electronically synchronized to one another to enable precise control of pitch and adhesive volume. The paper also describes the field application of XHab including mobilization/demobilization of equipment and interaction with other rehabilitation equipment, as well as specific aspects such as initiation and termination of wrapping, protection of rehabilitated area and implementation of cathodic protection.

scholarly journals Simultaneous Sensor Placement and Pressure Reducing Valve Localization for Pressure Control of Water Distribution Systems

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1352 ◽  
Author(s):  
Cao ◽  
Hopfgarten ◽  
Ostfeld ◽  
Salomons ◽  
Li
Keyword(s):  
Control System ◽  
Distribution Systems ◽  
Water Distribution ◽  
Water Distribution Systems ◽  
Pressure Control ◽  
Operating Pressure ◽  
Pressure Reduction ◽  
Suggested Approach ◽  
Operation Conditions ◽  
Pressure Reducing Valve

Many studies on pressure sensor (PS) placement and pressure reducing valve (PRV) localization in water distribution systems (WDSs) have been made with the objective of improving water leakage detection and pressure reduction, respectively. However, due to varying operation conditions, it is expected to realize pressure control using a number of PSs and PRVs to keep minimum operating pressure in real-time. This study aims to investigate the PS placement and PRV localization for the purpose of pressure control system design for WDSs. For such a control system, a PS should be positioned to represent the pressure patterns of a region of the WDS. Correspondingly, a PRV should be located to achieve a maximum pressure reduction between two neighboring regions. According to these considerations, an approach based on the k-means++ method for simultaneously determining the numbers and positions of both PSs and PRVs is proposed. Results from three case studies are presented to demonstrate the effectiveness of the suggested approach. It is shown that the sensors positioned have a high accuracy of pressure representation and the valves localized lead to a significant pressure reduction.

Exergy Control for a Flat-Plate Collector/Rankine Cycle Solar Power System

1991 ◽  
Vol 113 (2) ◽  
pp. 89-93 ◽  
Author(s):  
Giampaolo Manfrida ◽  
Shukuru J. M. Kawambwa
Keyword(s):  
Heat Transfer ◽  
Ambient Temperature ◽  
Thermal Performance ◽  
Saturated Vapor ◽  
Rankine Cycle ◽  
Pressure Level ◽  
Heat Transfer Fluid ◽  
Second Law ◽  
Operating Pressure ◽  
Performance Study

A performance study is presented of a Rankine organic cycle powered by a low temperature solar collector. In this work a two-phase collector is considered where the heat transfer fluid is vaporized and its saturated vapor expands in a turbine according to a Rankine cycle. The collector system is divided into a boiling and a nonboiling (subcooled) part: The limit between the two depends upon the value of flow rate and radiation. A modified form of the Bliss equation is used to model the thermal performance of the collector in terms of thermal efficiency versus DTI [DTI= (Absorber average temperature-Ambient temperature)/ Solar Radiation]. The system is analyzed by second-law analysis, and it includes several exergy losses of different types (heat transfer, heat loss, etc.) which determine the overall exergy balance. Different working fluids are considered, and optimization to a certain extent is demonstrated from this point of view. In order to minimize irreversibilities and guarantee the most efficient conversion processes, the most important point is the right selection of the collector operating pressure level, which depends on the instantaneous value of radiation and ambient temperature (as well as on the collector thermal performance). The choice of the optimal pressure level is done by means of second-law arguments; the flow rates across the collector, the turbine, and the condenser are consequently determined. A simulation over a typical sunny day in Florence, Italy allows the calculation of the expected daily performance.

Testing and Analysis of Steel Strip Reinforcement for Pipeline External Rehabilitation

2010 ◽  
Author(s):  
David J. Miles ◽  
Tim J. M. Bond ◽  
Raymond N. Burke ◽  
Ruben van Schalkwijk
Keyword(s):  
Steel Strip ◽  
New Technology ◽  
High Strength ◽  
Full Scale ◽  
Operating Conditions ◽  
Operating Pressure ◽  
Batch Tests ◽  
Girth Welds ◽  
The Individual ◽  
Pipeline Design

A new technology for external rehabilitation of pipelines, known as XHab™, has been developed. This method involves wrapping multiple layers of ultra-high strength steel strip (UHSS) in a helical form continuously over an extended length of pipeline using a dedicated forming and wrapping machine. The reinforcement afforded by the strip can be used to bring a defective section of pipe (e.g. externally corroded or dented) back to its original allowable operating conditions, or even to increase the allowable operating pressure if the desired operating conditions exceed the original pipeline design limits. This paper describes the full scale burst testing and analysis of defective pipes which have been repaired using the XHab process. The full scale test sections are 30″ × 0.5″ API 5L X52 DSAW pipe and include the following specimens: • Bare pipe with no defects; • Bare pipe with single machined defect; • Wrapped pipe with single machined defect and designed reinforcement; • Wrapped pipe with single machined defect and insufficient reinforcement; • Wrapped pipe with interacting defect array and designed reinforcement. The above full scale burst tests are supplemented by FEA models using ABAQUS. The material models for the steel pipe, UHSS strip, defect patch material and strip adhesive are based on measured data from the batch tests and tuned against the control burst test results. The structural behavior in the individual metallic and non-metallic elements can therefore be examined more closely, particularly in the region of the defect and where the wrapped strip crosses seam and girth welds.

Assessment of the Complexity of Stress/Strain Conditions of X100 Steel Pipeline and the Effect on the Steel Corrosion and Failure Pressure Prediction

2012 ◽  
Author(s):  
Luyao Xu ◽  
Frank Y. Cheng
Keyword(s):  
Steel Corrosion ◽  
Local Stress ◽  
High Strength ◽  
Complex Stress ◽  
Fe Model ◽  
Operating Pressure ◽  
Stress Strain ◽  
Failure Pressure ◽  
Corrosion Defects ◽  
Pipeline Design

In this work, a finite element (FE) model was developed to simulate the complex stress/strain conditions potentially exerted on the northern pipelines due to the synergism of internal pressure, soil strain and local stress/strain concentration at corrosion defects. The effects of pre-strain on corrosion of the steel and the pipeline failure pressure were investigated. Results demonstrated that a high intensity stress/strain field generates preferentially at the bottom of corrosion defect. The increase of operating pressure would increase the stress concentration at defect and the plastically deformed area. Both tensile and compressive soil strains increase the stress intensity and plastic deformation. Thus, a pipe containing corrosion defects or mechanical dents is susceptible to hoop cracking or local bulking under the tensile and compressive soil strains, respectively. Moreover, while an elastic strain enhances slightly the steel corrosion, the effect of plastic strain is much remarkable. In optimal pipeline design, the reliable risk assessment of high-strength steel pipelines should consider the corrosion enhancement and defect propagation under the complex stress/strain conditions.

Recent Concepts for the Welding of High Strain Pipelines

2009 ◽  
Author(s):  
Brian D. Newbury ◽  
Martin W. Hukle ◽  
Mark D. Crawford ◽  
Joshua Sleigh ◽  
Steven A. Altstadt ◽  
...  
Keyword(s):  
Large Scale ◽  
High Strain ◽  
Soil Liquefaction ◽  
Operating Pressure ◽  
Line Pipe ◽  
Strain Capacity ◽  
Soil Movement ◽  
Specific Material ◽  
Pipeline Design ◽  
Design And Testing

Standard allowable stress-based pipeline designs (strain demand ≤ 0.5%) are now giving way to more complex strain-based designs (strain demand higher than 0.5%) as the locations of future pipelines move into regions of increased strain demand. The increase in required levels of strain demand are attributed to seismic activity, soil movement, soil liquefaction, frost heave, thaw settlement, ice scour or a combination thereof. Pipelines in high strain demand regions are typically limited by the strain capacity of the girth weld. As strain-based pipeline design has matured, it has become evident that specific material properties (both weld metal and line pipe), defect size, defect location, misalignment, and operating pressure each affect the strain capacity of the pipeline. This paper reviews proposed design and testing methodologies for the qualification of strain-based design welding procedures. These methods have been applied in the development and qualification of welding procedures for the construction of pipelines subject to longitudinal tensile strains in excess of 2%. Strain-based design requires considerably more effort than traditional design in terms of girth weld qualification and testing. To ensure adequate girth weld strain capacity for strain-based design the testing includes large scale and full-scale pressurized testing for design validation.

A Synthesized Approach to Pressure Reduction for Investigating Mechanical Damage

2010 ◽  
Author(s):  
M. J. Rosenfeld
Keyword(s):  
Mechanical Damage ◽  
Operating Pressure ◽  
Pressure Reduction ◽  
Qualitative Information ◽  
Level 1 ◽  
Level 2

It is often recommended that the operating pressure of a pipeline be reduced prior to investigating suspected mechanical damage in the field, due to the unknown severity of the damage. The primary question is: knowing only what can be inferred from in-line inspection and the characteristics of the pipeline, what is the appropriate amount of pressure reduction? Secondarily, operators also question whether the same pressure reduction is necessary for all pipelines, e.g. different Location Classes, and all modes of damage, e.g. rock-induced damage as opposed to encroachment damage. Two levels of assessment are provided: a conservative “Level 1” assessment relying on mainly qualitative information and requiring no calculation, and a “Level 2” assessment that is considerably more involved but which could justify a smaller pressure reduction in response to the damage. The choice of assessment level will depend on the information available to the operator, as well as on the degree of conservatism the operator desires to invoke.

scholarly journals EXPERIMENTAL EVALUATION OF PERFORMANCE AND MECHANICAL RELIABILITY FOR HIGH PRESSURE CO2 INTEGRALLY GEARED COMPRESSOR

2020 ◽  
Vol 4 ◽  
pp. 128-144
Author(s):  
Toshiaki Baba ◽  
Koumei Fujioka ◽  
Hirotoshi Arihara ◽  
Yoshitaka Baba ◽  
Takuya Iwata
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
Fluid Dynamic ◽  
Pressure Level ◽  
Operating Conditions ◽  
Operating Pressure ◽  
Mechanical Reliability ◽  
Blade Vibration ◽  
Co2 Gas ◽  
Excitation Method

Energy saving has become a trend as well as a countermeasure for global environmental issues. It can be one of the efficient solutions for reducing energy consumptions by adopting integrally geared compressors instead of inline compressors for industrial plants. The development of key technologies for the design centrifugal compressor such as CFD, FEM, Rotor dynamic Analysis has enabled integrally geared centrifugal compressors for higher pressure applications than ever. A commercial size, 5 stages integrally geared CO2 centrifugal compressor of 20MPaG discharge pressure level was designed, manufactured and evaluated the fluid dynamic performances and rotor stability. It was installed in OEM’s factory and the full load and full pressure test was carried out using real CO2 gas. The actual compressor fluid dynamic performance has shown superior results even at high pressure supercritical gas conditions at the high pressure stages of the compressor. The mechanical performances such as rotor vibration and bearing temperature were also measured and observed that the vibration was substantially low and within safe limits even at high pressure operating conditions above 20MPaG. Also the authors established a novel on Direct Rotor Excitation Method to experimentally investigate the rotor stability even at a high operating pressure level of 20MPaG. With this technique the measurements of the actual rotor natural frequencies and the damping ratios (log decrement) during high pressure operating conditions provided more precise results rather than conventional casing excitation method. The open impeller blade vibration was measured during running condition by using a non-contact blade vibration measurement technique. This measurement results revealed that impeller blades stress against the centrifugal force and the external excitation force was very low compared to the allowable stress value of the impeller material. The fluid dynamic characteristics and mechanical reliability are assessed as acceptable including super critical gas condition of CO2 gas.

Effect of Internal Pressure on Free Spanning Pipelines

2010 ◽  
Author(s):  
Olav Fyrileiv
Keyword(s):  
Internal Pressure ◽  
Natural Frequency ◽  
Structural Integrity ◽  
State Of The Art ◽  
Structural Response ◽  
Design Codes ◽  
Submarine Pipeline ◽  
Water Flow Velocity ◽  
Intervention Costs ◽  
Pipeline Design

Free span assessment has more and more become an important part of modern pipeline design. The reason for this is partly that the remaining hydrocarbon reservoirs are located in more challenging places, e.g. with very uneven seabed. Another explanation is that the pipeline design codes a few decades ago did not allow for vibrating free spans, while the modern, state-of-the-art pipeline codes, such as DNV-OS-F101 “Submarine Pipeline Systems” (2007) [1] and its Recommended Practices, opens for long spans that are allowed to vibrate as long as the structural integrity is ensured. By opening for longer free spans significant seabed intervention costs associated with trenching, rock dumping and supporting spans by other means are saved. One of the governing parameters to ensure the structural integrity of free spans is the natural frequency of the span. This is a parameter that the designer can to some degree control by means of moderate seabed intervention, e.g. span support. Since the natural frequency of the span together with the water flow velocity normal to the span determine the vibrations and the cyclic loading it is of vital importance to be able to estimate a realistic value of this frequency. The natural frequency is influenced by several effects. One of them is the effect of the internal pressure. This may represent a challenge since the effect of the pressure is the opposite of what one instantaneously thinks is correct. Quite recently some discussion about the effect of internal pressure on free spans were raised and some experimental data presented that claimed to prove that the way the internal pressure was handled in the DNV-RP-F105 “Free Spanning Pipelines” (2006) [2] is wrong. The intention of this paper is to show how the internal pressure influences on the structural response of free spans, and that the DNV codes and standard non-linear FE software, e.g. Abaqus, handle this effect in an adequate manner.

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