Heavy Gauge UOE Pipe With Improved Compressive Strength for Offshore Pipeline

2012 ◽  
Author(s):  
Nobuyuki Ishikawa ◽  
Hitoshi Sueyoshi ◽  
Kimihiro Nishimura ◽  
Osamu Yamamoto ◽  
Akihiko Tanizawa ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Bauschinger Effect ◽  
External Pressure ◽  
Accelerated Cooling ◽  
Second Phase ◽  
Fundamental Study ◽  
Soft Phase ◽  
Collapse Pressure ◽  
Bainitic Microstructure ◽  
Line Process

Offshore gas pipeline development has been expanding toward deeper water region that requires pipes to have strong resistance against collapse by external pressure. Collapse pressure is mainly dominated by pipe roundness and compressive strength. In order to improve compressive strength, it is quite important to understand the Bauschinger effect caused by cyclic deformation during pipe forming. Compressive strength is reduced by the Bauschinger effect since compression in the circumferential direction is applied after the pipe expansion. Therefore, prevention of Bauschinger effect is an important issue for improving compressive strength of pipes. In this paper, the effect of microstructure on the Bauschinger effect was investigated. It was proved that microstructure that consists of a hard second phase shows a large strength reduction in reverse loading, since a mixed microstructure with soft phase and hard phase enhances the Bauschinger effect. In order to obtain homogeneous bainitic microstructure, advanced plate production technology, where heat treatment on-line process (HOP) is applied after accelerated cooling, was developed. The steel produced by HOP process exhibits a fine bainitic microstructure with very low amount of hard second phase such as MA constituent. It was demonstrated that the trial produced pipe with HOP process has a higher compressive strength than conventional pipes. In addition to the fundamental study on compressive strength, further investigations were conducted to optimize other material properties for offshore linepipe, such as DWTT property, resistance to hydrogen induced cracking and HAZ toughness to comply with DNV requirements. Production tests of Grade X65 linepipe with the 38mm WT and 876mm OD was carried out. Material and mechanical properties of these heavy gauge linepipes were introduced.

Externally Pressurized Hemispherical Fibre-Reinforced Plastic Shells

1992 ◽  
Vol 206 (3) ◽  
pp. 179-191 ◽  
Author(s):  
J Blachut ◽  
G D Galletly
Keyword(s):  
Compressive Strength ◽  
Carbon Fibre ◽  
External Pressure ◽  
Experimental Result ◽  
Spherical Cap ◽  
Collapse Pressure ◽  
Reinforced Plastic ◽  
Cfrp Composite ◽  
Carbon Fibre Reinforced Plastic ◽  
Clamped Edge

The results of external pressure tests on ten 0.8 m diameter torispherical shells made from FRP (fibre-reinforced plastic) were discussed in a recent paper by the authors. In the present paper, the results of similar tests on six hemispherical FRP shells are given. Four of the hemispheres were made from single sheets of woven pre-preg (three of carbon-fibre-reinforced plastic and one of glass-fibre-reinforced plastic): two of those made from carbon-fibre-reinforced plastic (CFRP) were petalled, that is they were made by butt-jointing together pieces of composite cloth. The diameter-average thickness (D/tav) ratios of the hemispherical domes varied from 66 to 108. The BOSOR 4 program was used to predict the stresses in the composite shells and their buckling pressures; the Tsai-Wu equation (in stress space) was utilized for the material failure criterion. For all the shells in this investigation, the controlling failure mode appeared to be first-ply failure (FPF). The latter is, of course, influenced by the compressive strength of the composite. Assuming a reasonable value for this (for example 570 N/mm2 for CFRP) gave ratios of Pexpt/PFPF which were in the range 1.05–1.19. In all cases, the experimental result was higher than the theoretical prediction, that is it was on the safe side. The authors measured the compressive strength of the CFRP composite experimentally. They obtained values in the range 510 ± 100 N/mm2. These were less than values obtained at Imperial College (664 ± 44 N/mm2). At the moment, it is not known why this wide variation in compressive strength was obtained. More work needs to be done on this aspect of the problem. Each of the butt-jointed CFRP hemispherical domes was weaker than its unjointed counterpart. In part, this is due to the increase in thickness of the unjointed hemispheres near the clamped edge, where the failures originated. With the CFRP torispherical domes, the failure location was at the spherical cap/knuckle junction (that is away from the clamped edge) and the butt-jointed torispherical dome turned out to be stronger than its unjointed counterpart. The 30-ply CFRP hemisphere (D/tav = 66) was 1.4 times as strong as the 36-ply GFRP hemisphere (D/tav = 73). In addition, the 30-ply CFRP hemisphere had the same collapse pressure as a geometrically similar welded steel hemisphere which had D/t ≈ 113 and a = σYP = 645 N/mm2. The CFRP dome would be much ligher than the steel one, in the ratio 1:2.8.

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.

Macroscopic and Microscopic Properties of High Performance Concrete with Partial Replacement of Cement by Fly Ash

2019 ◽  
Vol 292 ◽  
pp. 108-113 ◽  
Author(s):  
Josef Fládr ◽  
Petr Bílý ◽  
Roman Chylík ◽  
Zdeněk Prošek
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Fly Ash ◽  
High Performance ◽  
High Performance Concrete ◽  
Partial Replacement ◽  
Experimental Program ◽  
Second Phase ◽  
Depth Of Penetration ◽  
Cement Replacement

The paper describes an experimental program focused on the research of high performance concrete with partial replacement of cement by fly ash. Four mixtures were investigated: reference mixture and mixtures with 10 %, 20 % and 30 % cement weight replaced by fly ash. In the first stage, the effect of cement replacement was observed. The second phase aimed at the influence of homogenization process for the selected 30% replacement on concrete properties. The analysis of macroscopic properties followed compressive strength, elastic modulus and depth of penetration of water under pressure. Microscopic analysis concentrated on the study of elastic modulus, porosity and mineralogical composition of cement matrix using scanning electron microscopy, spectral analysis and nanoindentation. The macroscopic results showed that the replacement of cement by fly ash notably improved compressive strength of concrete and significantly decreased the depth of penetration of water under pressure, while the improvement rate increased with increasing cement replacement (strength improved by 18 %, depth of penetration by 95 % at 30% replacement). Static elastic modulus was practically unaffected. Microscopic investigation showed impact of fly ash on both structure and phase mechanical performance of the material.

scholarly journals Lime Treatment of Coal Bottom Ash for Use in Road Pavements: Application to El Jadida Zone in Morocco

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2674 ◽  
Author(s):  
Souad El Moudni El Alami ◽  
Raja Moussaoui ◽  
Mohamed Monkade ◽  
Khaled Lahlou ◽  
Navid Hasheminejad ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Low Cost ◽  
Thermal Power ◽  
Experimental Studies ◽  
Bottom Ash ◽  
Coal Ash ◽  
Road Construction ◽  
Dry Density ◽  
Second Phase ◽  
Lime Treatment

Industrial waste causes environmental, economic, and social problems. In Morocco, the Jorf Lasfar Thermal Power Station produces two types of coal ash with enormous quantities: fly ash (FA) and Bottom ash (BA). FA is recovered in cement while BA is stored in landfills. To reduce the effects of BA disposal in landfills, several experimental studies have tested the possibility of their recovery in the road construction, especially as a subbase. In the first phase of this study, the BA underwent a physicochemical and geotechnical characterization. The results obtained show that the BA should be treated to improve its mechanical properties. The most commonly used materials are lime and cement. In the selected low-cost treatment, which is the subject of the second phase of the study, lime is used to improve the low pozzolanicity of BA while calcarenite sand is used to increase the compactness. Several mixtures containing BA, lime, and calcarenite sand were prepared. Each of these mixtures was compacted in modified Proctor molds and then subjected to a series of tests to study the following characteristics: compressive strength, dry and wet California Bearing Ratio (CBR), dry density and swelling. The composition of each mixture was based on an experimental design approach. The results show that the values of the compressive strength, the dry density, and the CBR index have increased after treatment, potentially leading to a valorization of the treated BA for use in a subbase.

A Simple Procedure for the Prediction of the Collapse Pressure of Pipelines With Narrow and Long Corrosion Defects: Uncertainty and Sensibility Analysis

2018 ◽  
Author(s):  
Nara Oliveira ◽  
Theodoro Netto
Keyword(s):  
Simple Procedure ◽  
Experimental Tests ◽  
External Pressure ◽  
Experimental Program ◽  
Small Scale ◽  
Test Results ◽  
Collapse Pressure ◽  
Operational Conditions ◽  
Sensibility Analysis ◽  
Corrosion Defects

The collapse pressure of pipelines containing corrosion defects is usually predicted by deterministic methods, either numerically or through empirical formulations. The severity of each individual corrosion defect can be determined by comparing the differential pressure during operation with the estimated collapse pressure. A simple deterministic procedure for estimating the collapse pressure of pipes with narrow and long defects has been recently proposed by Netto (2010). This formulation was based on a combined small-scale experimental program and nonlinear numerical analyses accounting for different materials and defect geometries. However, loads and resistance parameters have uncertainties which define the basic reliability problem. These uncertainties are mailyrelated to the geometric and material parameters of the pipe and the operational conditions. This paper presents additional experimental tests on corroded pipes under external pressure. The collapse pressure calculated using the equation proposed by Netto (2010) is compared with this new set of experiments and also with test results available in open literature. These results are used to estimate the equation uncertainty. Finally, a sensitivity analysis is performed to identify how geometric parameters of the defects influence the reduction of collapse pressure.

Buckling Design of Imperfect Welded Hemispherical Shells Subjected to External Pressure

1991 ◽  
Vol 205 (3) ◽  
pp. 175-188 ◽  
Author(s):  
G D Galletly ◽  
J Blachut
Keyword(s):  
Experimental Information ◽  
External Pressure ◽  
Design Stage ◽  
Arc Length ◽  
Spherical Shells ◽  
Geometric Imperfections ◽  
Collapse Pressure ◽  
Buckling Resistance ◽  
Initial Geometric Imperfections ◽  
Hemispherical Shells

Welded hemispherical or spherical shells in practice have initial geometric imperfections in them that are random in nature. These imperfections determine the buckling resistance of a shell to external pressure but their magnitudes will not be known until after the shell has been built. If suitable simplified, but realistic, imperfection shapes can be found, then a reasonably accurate theoretical prediction of a spherical shell's buckling/collapse pressure should be possible at the design stage. The main aim of the present paper is to show that the test results obtained at the David Taylor Model Basin (DTMB) on 28 welded hemispherical shells (having diameters of 0.75 and 1.68 m) can be predicted quite well using such simplified shape imperfections. This was done in two ways. In the first, equations for determining the theoretical collapse pressures of externally pressurized imperfect spherical shells were utilized. The only imperfection parameter used in these equations is δ0, the amplitude of the inward radial deviation of the pole of the shell. Two values for δ0 were studied but the best overall agreement between test and theory was found using δ0 = 0.05 ✓ (Rt). This produced ratios of experimental to numerical collapse pressures in the range 0.98–1.30 (in most cases the test result was the higher). The second approach also used simplified imperfection shapes, but in conjunction with the shell buckling program BOSOR 5. The arc length of the imperfection was taken as simp = k ✓ (Rt) (with k = 3.0 or 3.5) and its amplitude as δ0 = 0.05√(Rt). Using this procedure on the 28 DTMB shells gave satisfactory agreement between the experimental and the computer predictions (in the range 0.92–1.20). These results are very encouraging. The foregoing method is, however, only a first step in the computerized buckling design of welded spherical shells and it needs to be checked against spherical shells having other values of R/t. In addition, more experimental information on the initial geometric imperfections in welded spherical shells (and how they vary with R/t) is desirable. A comparison is also given in the paper of the collapse pressures of spherical shells, as obtained from codes, with those predicted by computer analyses when the maximum shape deviations allowed by the codes are employed in the computer programs. The computed collapse pressures are frequently higher than the values given by the buckling strength curves in the codes. On the other hand, some amplitudes of imperfections studied in the paper give acceptable results. It would be helpful to designers if agreement could be reached on an imperfection shape (amplitude and arc length) that was generally acceptable. Residual stresses are not considered in this paper. They might be expected to decrease a spherical shell's buckling resistance to external pressure. However, experimentally, this does not always happen.

Effect of Steel Properties on Buckling Pressure of Corroded Pipelines

2017 ◽  
Vol 898 ◽  
pp. 741-748 ◽  
Author(s):  
Meng Li ◽  
Hong Zhang ◽  
Meng Ying Xia ◽  
Kai Wu ◽  
Jing Tian Wu ◽  
...  
Keyword(s):  
Finite Element ◽  
Yield Strength ◽  
Strain Hardening ◽  
Corrosion Damage ◽  
Element Model ◽  
External Pressure ◽  
Strain Hardening Exponent ◽  
The Finite Element Method ◽  
Collapse Pressure ◽  
Steel Properties

Due to the harsh environment for submarine pipelines, corrosion damage of the pipeline steels is inevitable. After the corrosion damage, pipelines are prone to failure and may cause serious consequences. The analysis of the effects of different steel properties on the collapse pressure of pipelines with corrosion defects is of importance for the option of appropriate pipeline and avoiding accidents. Based on the finite element method, the finite element model of the pipeline with defects under external pressure was built. Firstly, the accuracy of the numerical model was validated by comparing with previous experimental results. The effects of yield strength and strain hardening exponent on collapse pressure of pipelines with different sizes of defect were discussed in detail. Results showed that the yield strength and strain hardening exponent have different influences on collapse pressure: the collapse pressure increases with the increasing yield strength, and the collapse pressure decreases with the increasing strain hardening exponent.

Assembly of Compound Tubes Under Hydraulic Pressure

2006 ◽  
Vol 128 (2) ◽  
pp. 208-211 ◽  
Author(s):  
Tony D. Andrews
Keyword(s):  
Wear Resistance ◽  
Compressive Strength ◽  
Plastic Strain ◽  
Compressive Stress ◽  
Bauschinger Effect ◽  
No Reduction ◽  
Hydraulic Pressure ◽  
Maximum Compressive Stress ◽  
Compressive Stresses ◽  
Shrink Fit

This paper describes a method for inserting a tapered liner into a sleeve while the latter is expanded by hydraulic pressure. The technique avoids many of the limitations associated with traditional shrink fit techniques and autofrettage. The sleeve and liner are manufactured with internal and external tapers, respectively, to give the appropriate interference for the finished compound tube. The liner is mounted on a rod and positioned loosely inside the sleeve. The ends of the sleeve are sealed with plugs, which allow the rod to protrude through each end and which also have hydraulic oil inlets. Once the assembly has been pressurized, the rod is pushed into the vessel to move the liner further into the sleeve generating an interference once the pressure in the sleeve is removed. Insertion of a relatively thin liner can generate high residual compressive stresses at the bore, similar to autofrettage but with a shallower gradient away from the bore. Because the liner is not subjected to plastic strain during manufacture, there is no reduction in compressive strength due to the Bauschinger effect and the maximum compressive stress obtainable is greater than that from traditional autofrettage routes. Such high stresses lead to excess tension in the sleeve, which must be reduced by autofrettaging the sleeve prior to assembly of the compound tube. Such a configuration is suitable for inserting a part-length liner at the chamber for strength and/or wear resistance and tensile stresses can be eliminated to prevent failure of brittle materials, such as ceramics.

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