Assessment of Recent Experimental Data on Collapse Capacity of UOE Pipeline

2012 ◽  
Author(s):  
Erica Marley ◽  
Olav Aamlid ◽  
Leif Collberg
Keyword(s):  
Deep Water ◽  
External Pressure ◽  
Recent Experimental Data ◽  
Safety Factors ◽  
Governing Parameter ◽  
Collapse Pressure ◽  
Capacity Model ◽  
Water Pipelines ◽  
Offshore Industry ◽  
Water Depths

Recent developments in the offshore industry are resulting in an increasing demand for deep water pipelines. At greater water depths, the external pressure will be the governing parameter for wall thickness design, and the failure mode is collapse. DNV’s reliability based standard, DNV-OS-F101, uses the collapse capacity model and corresponding safety factors calibrated in the SUPERB Joint Industry Project, finalized in the mid 1990’s. Since then, a vast amount of research on collapse capacity of deep water pipelines is performed, indicating that it is time to re-visit the design equation and safety factors currently in use. This paper firstly summarizes the relevant collapse pressure equations for pipeline design. Secondly, the major points related to collapse capacity in SUPERB and DNV-OS-F101 are presented. Furthermore, results from an assessment of newer collapse tests of pipelines are described. Focus is on larger (UOE) pipes with D/t ratios less than 25, corresponding to water depths beyond 1000 m. The test results are compared to the outcome of earlier experimental projects. A difference between older and more recent tests is observed, with the newer having a considerably higher collapse capacity. Finally, a calibration of safety factors is performed, compared to existing factors and discussed.

Developments in Testing and Manufacture of Thick-Walled Pipe

2017 ◽  
Author(s):  
Alastair Walker ◽  
Jayden Chee ◽  
Peter Roberts
Keyword(s):  
Safety Factor ◽  
Deep Water ◽  
Maximum Level ◽  
External Pressure ◽  
Full Scale ◽  
Test Facility ◽  
Collapse Pressure ◽  
Pipe Joints ◽  
Collapse Failure ◽  
Pipe Joint

Over the past 20 years there has been a considerable development of the capability to design and manufacture thick walled pipe to manufacture pipelines to operate in ultra-deep water. Design guidance is available in DNV OS F101 [1] in which the safety from pressure collapse failure during pipeline installation is determined by the use of a safety factor. The safety factor has been calibrated using the Load and Resistance Factor Design (LRFD) method in comparison with collapse pressure test results available at the time of preparation of DNV guidance. Because of the huge financial implications of loss of a very long pipeline during installation in ultra-deep water it has been the practice further to base the design of such a pipeline on specific pipe joint collapse tests in conjunction with the DNV information. Pressure testing full-scale pipe joints is an expensive undertaking that requires a suitable pressure chamber. Only a few chambers capable of applying pressures corresponding to very deep water are available in the world and transport of the pipes from the pipe mill to a suitable test facility may be very inconvenient and certainly expensive. This paper describes an alternative approach which could provide data that would enable the preparation of a safe approach specific to the pipeline diameter and design water depth. The approach could enable optimisation of the pipe design, particularly the pipe wall thickness. The proposed method is based on replacing costly full scale pipe tests by corresponding tests on ring specimens cut and machined from manufactured pipe joints. The proposal to use ring testing as the basis for design has been included successfully in the design of pipe for a recent ultra-deep water project [2]. The paper describes equipment used to subject the rings to external pressure and reports on tests carried out to validate the correspondence between the ring collapse pressure and that for the pipe joint from which the ring was obtained. Based on results from such tests it is concluded in this paper that ring pressure collapse testing is indeed a valid method to use as the basis for the design pipes in the next stage of ultra-deep water, i.e. increasing the capability to install pipeline in water depths down to 3500m from the current maximum level of 2500m.

Lateral Buckling of Armor Wires in Flexible Pipes: Reaching 3000m Water Depth

2011 ◽  
Author(s):  
Philippe Secher ◽  
Fabrice Bectarte ◽  
Antoine Felix-Henry
Keyword(s):  
Deep Water ◽  
Failure Modes ◽  
External Pressure ◽  
Internal Diameter ◽  
Flexible Pipe ◽  
Lateral Buckling ◽  
Flexible Pipes ◽  
Valid Solution ◽  
Sour Service ◽  
Water Depths

This paper presents the latest progress on the armor wires lateral buckling phenomena with the qualification of flexible pipes for water depths up to 3,000m. The design challenges specific to ultra deep water are governed by the effect of the external pressure: Armor wires lateral buckling is one of the failure modes that needs to be addressed when the flexible pipe is empty and subject to dynamic curvature cycling. As a first step, the lateral buckling mechanism is described and driving parameters are discussed. Then, the program objective is presented together with flexible pipe designs: - Subsea dynamic Jumpers applications; - Sweet and Sour Service; - Internal diameters up to 11″. Dedicated flexible pipe components were selected to address the severe loading conditions encountered in water depths up to 3,000m. Hydrostatic collapse resistance was addressed by a thick inner carcass layer and a PSI pressure vault. Armor wires lateral buckling was addressed by the design and industrialization of new tensile armor wires. The pipe samples were manufactured using industrial production process in the factories in France and Brazil. The available testing protocols are then presented discussing their advantages and drawbacks. For this campaign, a combination of Deep Immersion Performances (DIP) tests and tests in hyperbaric chambers was selected. The DIP test campaign was performed End 2009 beginning 2010 in the Gulf of Mexico using one of Technip Installation Vessel. These tests replicated the actual design conditions to which a flexible pipe would be subjected during installation and operation. The results clearly demonstrated the suitability of flexible pipes as a valid solution for ultra deep water applications. In addition, the DIP tests results were compared to the tests in hyperbaric chambers giving consistent results. This campaign provided design limitations of the new designs for both 9″ and 11″ internal diameter flexible pipes, in sweet and sour service in water depths up to 3,000m.

Deep Water Current Observations in Lankahuasa Area in the Mexican Gulf of Mexico

2006 ◽  
Author(s):  
C. Garcia Govea ◽  
Juan Jose´ Corte´s Romero ◽  
O. Valle Molina
Keyword(s):  
Water Column ◽  
Deep Water ◽  
Oil Industry ◽  
Water Current ◽  
Current Profile ◽  
The North ◽  
Deep Waters ◽  
Offshore Industry ◽  
Near Future ◽  
Water Depths

In preparation for the near future deep-water exploitation in the Mexican oil industry, the Mexican Petroleum Institute and Pemex carried out the first oceanographic sub-surface mooring installation in deep waters, in Lankahuasa area in 1500 m water depth. The aim of this project is to supply the necessary water column information for planning, installation, development and production activities for the Mexican offshore industry. Parameters measured include, current velocities, current direction, internal waves as well as traditional water quality measurements. Profiles of conductivity, temperature and Depth (CTD) from 100 m up to 2,500 m water depths were obtained from cruises where samples were taken over a wide area during January and February 2005. Salinity and density are calculated from CTD data. Oceanographical parameters were measured by 3 ADCP (Acoustic Doppler Current Profile) and by 2 current meters in the entire water column. The oceanographic situation during the deployment was characterized by the presence of an anticyclonic (clockwise rotating) eddy and a cyclonic one in the area, located to the north of 21° N. Both eddies were slowly propagating in a general southward direction.

Comparative Structural Analyses Between Sandwich and Steel Pipelines for Ultra-Deep Water

2002 ◽  
Author(s):  
I. P. Pasqualino ◽  
B. C. Pinheiro ◽  
S. F. Estefen
Keyword(s):  
Thermal Insulation ◽  
Deep Water ◽  
External Pressure ◽  
Core Material ◽  
Mechanical Resistance ◽  
Insulation Material ◽  
Ongoing Research ◽  
Structural Resistance ◽  
Water Pipelines ◽  
Pipe Systems

Pipe-in-pipe systems are usually composed of two concentric metal pipes with or without an insulation material in the annulus region. Design requirements for ultra-deep water pipelines motivated the development of a new pipe-in-pipe conception in which the annulus is filled with materials that combine low cost, adequate thermal insulation properties and good mechanical resistance. The aim of this ongoing research project is to evaluate the structural performance of sandwich pipes with two different options of core material. Because of their wide availability and relatively low costs, the materials considered in this study were cement and polypropylene for the annulus, with pipes made of API X-60 grade steel. In this paper, a three-dimensional finite element model considering material and geometric nonlinear behavior was developed. This numerical model was used to perform a parametric study to determine the collapse envelopes of different pipe-in-pipe configurations under combined bending and external pressure. The collapse envelopes were compared with others obtained for steel pipelines of equivalent collapse pressure. The study showed that the pipe-in-pipe systems with either cement or polypropylene cores are feasible options to ultra-deep water pipelines fulfilling concomitantly both the requirements of structural resistance and thermal insulation.

Elastoplastic Collapse of Tubes Under External Pressure

1970 ◽  
Vol 92 (4) ◽  
pp. 735-742 ◽  
Author(s):  
O. Heise ◽  
E. P. Esztergar
Keyword(s):  
Safety Factor ◽  
External Pressure ◽  
Code Design ◽  
Test Results ◽  
Plastic Range ◽  
Safety Factors ◽  
Characteristic Ratio ◽  
Collapse Pressure ◽  
Asme Code ◽  
Current Design

The specific objective of this paper is to develop external pressure design safety factors that are consistent with theory, test results, and service experience for application in pressure vessel codes. The standard methods of collapse pressure predictions for the buckling of tubes in the elastic and the plastic ranges are briefly reviewed. Test results on tubes made of various materials were collected from the literature and are compared with the corresponding predictions. For thin tubes which buckle in the elastic range, the correlation between the theory and experimentally measured collapse pressure is shown to be poor, justifying the large safety factors used in current design practice. For intermediate and thick tubes which buckle in the plastic range, it is demonstrated that the correlation of test results and theory improves significantly with decreasing radius-to-thickness ratio of the tubes. The range of improved correlation is identified by a material dependent “characteristic ratio” of tube radius and wall thickness. Based on the experimental evidence, a variable safety factor is proposed for inclusion in the ASME Code design charts. A simple formula for the conversion of the present plastic range allowable pressure into the new increased allowable pressure is presented. The consequences of the variable safety factor are discussed with respect to the resulting actual margin of safety, the economic advantages, and the requirements for the development of design rules for the creep range.

Flexible Riser Resistance Against Combined Axial Compression, Bending, and Torsion in Ultra-Deep Water Depths

2005 ◽  
Author(s):  
Marcelo Brack ◽  
Le´a M. B. Troina ◽  
Jose´ Renato M. de Sousa
Keyword(s):  
Axial Compression ◽  
Deep Water ◽  
Failure Modes ◽  
External Pressure ◽  
Combined Loading ◽  
Test Procedures ◽  
Pipe Length ◽  
Potential Failure ◽  
Technical Specifications ◽  
Water Depths

The experience in the Brazilian offshore production systems is to adopt the traditional riser solution composed of unbonded flexible pipes at a free-hanging catenary configuration. In deep waters, the tendency has been to use different pipe length sections (normally two), each of them designed to resist typical loadings. At the bottom, pipe structure is dimensioned against external pressure, axial compression, bending and torsion, for example. The theoretical prediction of riser responses under the crescent combined loading conditions is a key issue at the TDP region. The potential failure modes are buckling of the armour tendons and also rupture of the high resistance tapes. Much effort has been done in order to have available, from the market, larger envelopes of certified methodologies and qualified products, applicable to the Brazilian ultra-deep scenarios. Since 2002, an extensive R&D Program has been conducted (i) to improve current design evaluation tools & criteria and (ii) to establish representative test procedures and scope, for prototype qualification against the potential failure modes associated with combined axial compression, bending and torsion, at the TDP regions of bottom riser sections in ultra-deep water depths. This paper describes the main steps of the R&D Program, as below: I. Improvement of computational tools to better represent the behavior of the tendons, II. Consolidation of a new strategy for structural analysis, under more realistic conditions, III. Issue of a more adequate set of pipe technical specifications, and IV. Review of both theoretical and experimental results obtained from Feasibility Technical Studies and offshore field tests, respectively. Some examples and results are showed to illustrate, step by step, the whole process covered by the cited Program. Finally, the authors document their main conclusions for further discussion.

Numerical study on the lateral breakout behaviour of deep-water pipelines in clays with surficial crust

2020 ◽  
Vol 218 ◽  
pp. 108239
Author(s):  
Abhishek Ghosh Dastider ◽  
Neelanjan Sarkar ◽  
Santiram Chatterjee
Keyword(s):  
Deep Water ◽  
Numerical Study ◽  
Water Pipelines

Mechanical Qualification of Dynamic Deep Water Power Cable

2011 ◽  
Author(s):  
Roger Slora ◽  
Stian Karlsen ◽  
Per Arne Osborg
Keyword(s):  
Water Depth ◽  
Deep Water ◽  
Failure Modes ◽  
Electrical Power ◽  
Oil And Gas Industry ◽  
Electrical Heating ◽  
Power Cable ◽  
Water Power ◽  
System Integrity ◽  
Water Depths

There is an increasing demand for subsea electrical power transmission in the oil- and gas industry. Electrical power is mainly required for subsea pumps, compressors and for direct electrical heating of pipelines. The majority of subsea processing equipment is installed at water depths less than 1000 meters. However, projects located offshore Africa, Brazil and in the Gulf of Mexico are reported to be in water depths down to 3000 meters. Hence, Nexans initiated a development programme to qualify a dynamic deep water power cable. The qualification programme was based on DNV-RP-A203. An overall project plan, consisting of feasibility study, concept selection and pre-engineering was outlined as defined in DNV-OSS-401. An armoured three-phase power cable concept assumed suspended from a semi-submersible vessel at 3000 m water depth was selected as qualification basis. As proven cable technology was selected, the overall qualification scope is classified as class 2 according to DNV-RP-A203. Presumed high conductor stress at 3000 m water depth made basis for the identified failure modes. An optimised prototype cable, with the aim of reducing the failure mode risks, was designed based on extensive testing and analyses of various test cables. Analyses confirmed that the prototype cable will withstand the extreme loads and fatigue damage during a service life of 30 years with good margins. The system integrity, consisting of prototype cable and end terminations, was verified by means of tension tests. The electrical integrity was intact after tensioning to 2040 kN, which corresponds to 13 000 m static water depth. A full scale flex test of the prototype cable verified the extreme and fatigue analyses. Hence, the prototype cable is qualified for 3000 m water depth.

scholarly journals Rational Modeling of Ultimate Pipe Strength Under Bending and External Pressure

2000 ◽  
Author(s):  
André C. Nogueira ◽  
Glenn A. Lanan
Keyword(s):  
Deep Water ◽  
Limit State ◽  
Local Buckling ◽  
External Pressure ◽  
Pressure Effects ◽  
Combined Loading ◽  
Empirical Prediction ◽  
Limit State Design ◽  
Controlled Conditions ◽  
Offshore Pipeline

The capacity of pipelines to resist collapse or local buckling under a combination of external pressure and bending moment is a major aspect of offshore pipeline design. The importance of this loading combination increases as oil and gas projects in ultra deep-water, beyond 2,000-m water depths, are becoming reality. The industry is now accepting, and codes are explicitly incorporating, limit state design concepts such as the distinction between load controlled and displacement controlled conditions. Thus, deep-water pipeline installation and limit state design procedures are increasing the need to understand fundamental principles of offshore pipeline performance. Design codes, such as API 1111 (1999) or DNV (1996, 2000), present equations that quantify pipeline capacities under combined loading in offshore pipelines. However, these equations are based on empirical data fitting, with or without reliability considerations. Palmer (1994) pointed out that “it is surprising to discover that theoretical prediction [of tubular members under combined loading] has lagged behind empirical prediction, and that many of the formula have no real theoretical backup beyond dimensional analysis.” This paper addresses the ultimate strength of pipelines under combined bending and external pressure, especially for diameter-to-thickness ratios, D/t, less than 40, which are typically used for deep water applications. The model is original and has a rational basis. It includes considerations of ovalization, anisotropy (such as those caused by the UOE pipe fabrication process), load controlled, and displaced controlled conditions. First, plastic analysis is reviewed, then pipe local buckling under pure bending is analyzed and used to develop the strength model. Load controlled and displacement controlled conditions are a natural consequence of the formulation, as well as cross section ovalization. Secondly, external pressure effects are addressed. Model predictions compare very favorably to experimental collapse test results.

Clamped torispherical shells under external pressure — some new results

1988 ◽  
Vol 23 (1) ◽  
pp. 9-24 ◽  
Author(s):  
J Blachut ◽  
G D Galletly
Keyword(s):  
Failure Mode ◽  
External Pressure ◽  
Spherical Cap ◽  
Geometric Imperfections ◽  
Collapse Pressure ◽  
Modes Of Failure ◽  
Shell Buckling ◽  
Bifurcation Buckling ◽  
Initial Geometric Imperfections ◽  
The One

Perfect clamped torispherical shells subjected to external pressure are analysed in the paper using the BOSOR 5 shell buckling program. Various values of the knuckle radius-to-diameter ratio ( r/D) and the spherical cap radius-to-thickness ratio ( Rs/ t) were studied, as well as four values of σyp, the yield point of the material. Buckling/collapse pressures, modes of failure and the development of plastic zones in the shell wall were determined. A simple diagram is presented which enables the failure mode in these shells to be predicted. The collapse pressures, pc, were also plotted against the parameter Λs (√( pyp/ pcr)). When the controlling failure mode was axisymmetric yielding in the knuckle, the collapse pressure curves depended on the value of σyp, which is unusual. However, when the controlling failure mode was bifurcation buckling (at the crown/knuckle junction), the collapse pressure curves for the various values of σyp all merged, i.e., they were independent of σyp. This latter situation is the one which normally occurs with the buckling of cylindrical and hemispherical shells. A limited investigation was also made into the effects of axisymmetric initial geometric imperfections on the strength of externally-pressurised torispherical shells. When the failure mode was axisymmetric yielding in the knuckle, initial imperfections of moderate size did not affect the collapse pressures. In the cases where bifurcation buckling at the crown/knuckle junction occurred, small initial geometric imperfections at the apex did not affect the buckling pressure, but axisymmetric imperfections at the buckle location did influence it. With the other failure mode (i.e., axisymmetric yielding collapse at the crown of the shell), initial geometric imperfections caused a reduction in the torisphere's strength.

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