Buckling and Unstable Collapse of Seamless Pipes and Tubes

2010 ◽  
Author(s):  
F. Van den Abeele ◽  
J. Bar ◽  
S. Jakani
Keyword(s):  
Yield Stress ◽  
Wall Thickness ◽  
Compressive Loading ◽  
External Pressure ◽  
Pipe Production ◽  
Transition Range ◽  
Collapse Pressure ◽  
Initial Imperfections ◽  
Collapse Resistance ◽  
Wide Range

Deepwater pipelines and high pressure casing and tubing are prone to buckling and unstable collapse under compressive loading and external pressure. The most important parameters governing the unstable collapse behaviour of perfectly round pipes and tubes are the circumferential yield stress of the material, the Young’s modulus and the ratio of diameter over thickness (D/t). Initial imperfections in the geometric shape of the pipe, like wall thickness variations or ovality, can have a pronounced influence on the collapse resistance of a pipe. Local dents can reduce the collapse pressure significantly, and trigger propagating buckles along the line. In this paper, buckling and unstable collapse of seamless pipes and tubes are studied. First, collapse pressure experiments for High Collapse Casing grades L80HC and P110HC are presented, showing that the seamless pipe production at ArcelorMittal Tubular Products in Ostrava (Czech Republic) is under tight quality control and complies with the API standards. Then, the critical collapse pressure is calculated for different scenarios. Depending on the ratio of diameter to wall thickness, four regimes are identified: yielding collapse, followed by plastic collapse, a transition range, and finally elastic collapse. For each condition, closed form expressions are derived for the critical collapse pressures. In addition, simplified design equations are reviewed to quickly estimate the collapse pressure. Then, the influence of initial imperfections on the collapse resistance is studied. Both the effects of geometric imperfections (ovality and wall thickness eccentricity) and material properties (especially yield stress and residual stresses) are addressed. In the end, an enhanced design equation is proposed to predict the critical collapse pressure of dented seamless pipes. This equation is validated by collapse experiments, can account for different initial imperfections, and is valid for a wide range of D/t ratios.

Improved Prediction of External Pressure Collapse of Seamless Pipe

2009 ◽  
Author(s):  
Josef Navarro ◽  
Philip Cooper
Keyword(s):  
Cross Section ◽  
Wall Thickness ◽  
Design Method ◽  
External Pressure ◽  
Thickness Variation ◽  
Seamless Pipe ◽  
Line Pipe ◽  
Collapse Pressure ◽  
Average Wall Thickness ◽  
Improved Design

Seamless pipe typically features well controlled average wall thickness around its cross-section, but is prone to significant local thickness variation arising from the manufacturing process. Pipeline design codes, such as DNV OS-F101, provide little guidance on how to treat thickness variation whilst designing for collapse resistance. Standard practice is to consider minimum wall thickness across the whole cross-section, an assumption that two dimensional finite element simulations have proven conservative. This justifies the need for an improved design method. A program of simulations has been carried out to investigate the effect of wall thickness variation on collapse pressure. A modification to the DNV OS-F101 collapse design equation using average wall thickness over the whole crossection together with a fabrication factor is presented based on the results of this study. The fabrication factor de-rates the collapse pressure according to the amount of thickness variation present. The correction has been calibrated for thickness variations up to the maximum permitted by typical line pipe specifications. A number of FE trials demonstrate that the proposed formula predicts simulated collapse pressures with 98% accuracy. Adopting this method could provide significant wall thickness savings for deep water flowlines which in turn could lead to a reduction in steel costs and transportation and lay vessel requirements.

Collapse of Worn Casing

1977 ◽  
Vol 99 (1) ◽  
pp. 208-214 ◽  
Author(s):  
C. E. Murphey
Keyword(s):  
Yield Strength ◽  
Lower Bounds ◽  
Wall Thickness ◽  
Axial Load ◽  
External Pressure ◽  
Upper And Lower Bounds ◽  
Percentage Reduction ◽  
Steel Tubes ◽  
Collapse Pressure ◽  
Severe Wear

Collapse tests were performed on one-in. dia steel tubes with flats milled on the exterior to simulate worn casing. External pressure and axial load were applied to the tubs having a range of wall thickness, yield strength, and degree of wear. Empirical correlation of the data and comparison with elastic collapse calculations indicate the percentage reduction in collapse pressure due to wear. This reduction is predictable within upper and lower bounds. While the milled external flat may not accurately simulate severe internal wear, the correlation is adequate for less than severe wear to give an indication of remaining strength.

Effect of Human Factor on OCTG Collapse Testing

2018 ◽  
Author(s):  
Mihail Minescu ◽  
Catalin Teodoriu ◽  
Mihaela Caltaru ◽  
Marius Badicioiu
Keyword(s):  
Manufacturing Process ◽  
Human Error ◽  
Human Factor ◽  
Testing Procedure ◽  
External Pressure ◽  
High Quality ◽  
Collapse Pressure ◽  
The Past ◽  
Collapse Resistance ◽  
Metal Pipes

Well construction relies on metal pipes called casing to maintain its integrity during the life of the well. From surface to the target depths the inserted casings are used to prevent well collapse, hence being exposed to external pressure loads. Also the casing in place must hold the internal pressure during well operations, which is called burst resistance. During the past decades the manufacturing process of casing and tubing has been dramatically improved, but their testing has suffer very little changes. It is known to date that API calculation of collapse resistance is very conservative, most of the modern pipe mills being able to deliver pipes with higher collapse pressure than API calculated values. The paper will describe the actual testing procedure of collapse testing of pipes and critically discuss about the human error that is introduced during these measurements. The results shows that only through high quality laboratory standards, such errors can be mitigated, while automation must be carefully considered.

Modeling of the Collapse and Propagation Behavior of UOE SAW Pipes Under External Pressure: Influence of Thermal Treatments for Typical Coating Applications

2012 ◽  
Author(s):  
Luciano O. Mantovano ◽  
Santiago Serebrinsky ◽  
Hugo A. Ernst ◽  
Teresa Perez ◽  
Martin Valdez ◽  
...  
Keyword(s):  
Finite Element ◽  
Experimental Testing ◽  
Large Diameter ◽  
Model Development ◽  
External Pressure ◽  
Sensitivity Analyses ◽  
Thermal Treatments ◽  
Collapse Pressure ◽  
Collapse Resistance ◽  
Comparison Of The Results

Large diameter UOE pipes are being increasingly used for the construction of offshore pipelines. Since oil discoveries are moving towards ultra deep water areas, collapse resistance is a key factor in the design of the pipelines. It has been demonstrated in previous works that the application of typical coating thermal treatments increases the collapse resistance of the pipes recovering the original strength of the plate. To improve the understanding of these effects, the Tenaris has embarked on a program of both, experimental testing and finite element modeling. Previous phases of this work formulated the basis for model development and described the 2D approach taken to model the various stages of manufacture, from the plate to the final pipe and the collapse test. More recent developments included some modeling enhancements, sensitivity analyses, and comparison of predictions to the results of full scale collapse testing. In the present work, 3D finite element analyses of collapse were performed and compared with the latest collapse and propagation tests performed by Tenaris, where the effect of typical coating thermal treatments was studied and significant increments in the collapse pressure of pipes were obtained. The numerical results show a good agreement with the experimental ones and could predict the increment produced in the collapse pressure by the effect of the thermal treatments. Comparison of the results with the predictions from API RP 1111 and DNV OS-F101 equations was also performed. The outcomes of this study will be employed to further optimize the collapse resistance of subsea linepipe in order to reduce material and offshore installation costs through the increment of the fabrication factor as stated in the DNV OSF101 standard.

Mechanical Test on Pipe Collapse under External Pressure

2011 ◽  
Vol 291-294 ◽  
pp. 1255-1258
Author(s):  
Kang Yong
Keyword(s):  
Theoretical Analysis ◽  
Mechanical Test ◽  
External Pressure ◽  
Test Methods ◽  
Steel Pipe ◽  
Collapse Pressure ◽  
Collapse Resistance ◽  
Pressure Test

Many factors result in pipe collapses under certain external pressure. The relations among them have been studied by the pipe collapse tests. This pepper focused on the test analyses of steel pipe collapse resistance. Those include a pipe collapse pressure test under external pressure and illustrate both test and preparing theoretical analysis, and results of the collapse pressure with the effects on the tendency of ovality. In addition to various pipe collapse data and mechanical test methods, this study will offer a summary of the findings for the further intention of theories researches.

Predicting Hydrostatic Collapse of Pipes Using Finite Element Analysis

2014 ◽  
Author(s):  
Ajit Bastola ◽  
Junkan Wang ◽  
Ali Mirzaee-Sisan ◽  
James Njuguna
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Residual Stresses ◽  
Wall Thickness ◽  
Limit State ◽  
Close Correlation ◽  
Element Analysis ◽  
Collapse Pressure ◽  
Strain Behavior ◽  
Wide Range

A pipeline’s resistance to collapse is governed by geometric imperfections, material properties and residual stresses. The offshore pipeline design code DNV-OS-F101 provides a method for predicting collapse of pipelines with diameter to wall thickness (D/t) ratios between 15 and 45. This paper examined the various factors that could influence the collapse resistance of several pipe geometries, such as ovality, eccentricity, material stress-strain behavior and residual stresses in the hoop and longitudinal directions. A total of 132 cases were carried out, using 2D and 3D Nonlinear Finite Element Analysis, to predict the collapse pressure of several realistic pipe geometries. Results of this study suggest that the DNV-OS-F101 predictions are conservative and applicable for a wide range of D/t ratios. While there is close correlation between Finite Element prediction and DNV-OS-F101 prediction, there is a degree of conservatism at low D/t ratios using DNV-OS-F101 equations. Hence there would be scope for further optimization of pipe wall thickness design against the collapse limit state at low D/t ratios.

Effect of Consolidation and Sintering Parameters on the Mechanical Responses of Nanocrystalline Al-Fe Alloy Processed by Mechanical Alloying

2015 ◽  
Vol 719-720 ◽  
pp. 87-90
Author(s):  
Muneer Baig ◽  
Hany Rizk Ammar ◽  
Asiful Hossain Seikh ◽  
Mohammad Asif Alam ◽  
Jabair Ali Mohammed
Keyword(s):  
Mechanical Alloying ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Compressive Loading ◽  
Rate Sensitivity ◽  
Testing Temperature ◽  
Fine Grained ◽  
Mechanical Responses ◽  
Wide Range ◽  
High Frequency Induction

In this investigation, bulk ultra-fine grained and nanocrystalline Al-2 wt.% Fe alloy was produced by mechanical alloying (MA). The powder was mechanically milled in an attritor for 3 hours and yielded an average crystal size of ~63 nm. The consolidation and sintering was performed using a high frequency induction sintering (HFIS) machine at a constant pressure of 50 MPa. The prepared bulk samples were subjected to uniaxial compressive loading over wide range of strain rates for large deformation. To evaluate the effect of sintering conditions and testing temperature on the strain rate sensitivity, strain rate jump experiments were performed at high temperature. The strain rate sensitivity of the processed alloy increased with an increase in temperature. The density of the bulk samples were found to be between 95 to 97%. The average Vickers micro hardness was found to be 132 Hv0.1.

INVESTIGATING THE INFLUENCE OF ENVIRONMENTAL CONDITIONING ON EPOXY RESINS AT QUASISTATIC AND HIGH STRAIN RATES FOR MATERIAL OPERATING LIMIT

2021 ◽  
Author(s):  
SAGAR M. DOSHI, SAGAR M. DOSHI, ◽  
NITHINKUMAR MANOHARAN ◽  
BAZLE Z. (GAMA) HAQUE, ◽  
JOSEPH DEITZEL ◽  
JOHN W. GILLESPIE, JR.
Keyword(s):  
Mechanical Properties ◽  
Epoxy Resin ◽  
Yield Stress ◽  
High Strain ◽  
Operating Conditions ◽  
Strain Rates ◽  
High Strain Rates ◽  
Stress Strain ◽  
Wide Range ◽  
Environmental Aging

Epoxy resin-based composite panels used for armors may be subjected to a wide range of operating temperatures (-55°C to 76°C) and high strain rates on the order of 103-104 s-1. Over the life cycle, various environmental factors also affect the resin properties and hence influence the performance of the composites. Therefore, it is critical to determine the stress-strain behavior of the epoxy resin over a wide range of strain rates and temperatures for accurate multi-scale modeling of composites and to investigate the influence of environmental aging on the resin properties. Additionally, the characterization of key mechanical properties such as yield stress, modulus, and energy absorption (i.e. area under the stress-strain curve) at varying temperatures and moisture can provide critical data to calculate the material operating limits. In this study, we characterize mechanical properties of neat epoxy resin, SC-15 (currently used in structural armor) and RDL-RDC using uniaxial compression testing. RDL-RDC, developed by Huntsman Corporation, has a glass transition temperature of ~ 120°C, compared to ~ 85°C of SC-15. A split Hopkinson pressure bar is used for high strain rate testing. Quasistatic testing is conducted using a screw-driven testing machine (Instron 4484) at 10-3 s-1 and 10-1 s-1 strain rates and varying temperatures. The yield stress is fit to a modified Eyring model over the varying strain rates at room temperature. For rapid investigation of resistance to environmental aging, accelerated aging tests are conducted by immersing the specimens in 100°C water for 48 hours. Specimens are conditioned in an environmental chamber at 76 °C and 88% RH until they reach equilibrium. Tests are then conducted at five different temperatures from 0°C to 95°C, and key mechanical properties are then plotted vs. temperature. The results presented are an important step towards developing a methodology to identify environmental operating conditions for composite ground vehicle applications.

Uncertainty in Collapse Strength Prediction of Sandwich Pipelines

2021 ◽  
Author(s):  
U. Bhardwaj ◽  
A. P. Teixeira ◽  
C. Guedes Soares
Keyword(s):  
Probabilistic Models ◽  
Uncertainty Propagation ◽  
Simulation Method ◽  
External Pressure ◽  
Design Parameters ◽  
Collapse Strength ◽  
Parameters Uncertainty ◽  
Wide Range ◽  
Model Predictions ◽  
Strength Models

Abstract This paper assesses the uncertainty in the collapse strength of sandwich pipelines under external pressure predicted by various strength models in three categories based on interlayer adhesion conditions. First, the validity of the strength models is verified by comparing their predictions with sandwich pipeline collapse test data and the corresponding model uncertainty factors are derived. Then, a parametric analysis of deterministic collapse strength predictions by models is conducted, illustrating insights of models’ behaviour for a wide range of design configurations. Furthermore, the uncertainty among different model predictions is perceived at different configurations of outer and inner pipes and core thicknesses. A case study of a realistic sandwich pipeline is developed, and probabilistic models are defined to basic design parameters. Uncertainty propagation of models’ predictions is assessed by the Monte Carlo simulation method. Finally, the strength model predictions of sandwich pipelines are compared to that of an equivalent single walled pipe.

On Some Factors Affecting Casing Collapse Resistance under External Pressure

2020 ◽  
Author(s):  
Bisen Lin ◽  
David Coe ◽  
Richard Harris ◽  
Timothy Thomas
Keyword(s):  
External Pressure ◽  
Factors Affecting ◽  
Collapse Resistance ◽  
Casing Collapse
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