Assessment of Loading on the Carcass and Pressure Armour due to Environment Swelling of Polymer

2013 ◽  
Author(s):  
Upul S. Fernando ◽  
Michelle Davidson ◽  
Iwan Harries ◽  
Andrew Thompson ◽  
Terry Sheldrake
Keyword(s):  
Supercritical Co2 ◽  
Hoop Stress ◽  
Polymer Structure ◽  
Simple Analytical Model ◽  
Test Program ◽  
Empirical Procedure ◽  
Steel Wires ◽  
Flexible Pipes ◽  
Layer Structures ◽  
Service Conditions

Flexible pipes consist of multi-layer structures comprising polymer extrusions, tapes and insulation that are trapped between layers of helically-wrapped steel wires. Under certain pressure and temperature service conditions, and when the polymers are in contact with certain chemicals (such as supercritical CO2), these polymer layers may experience significant volumetric changes caused by permeation, solubility and absorption of chemicals into the polymer structure. The swelling of the polymer barrier can result in a significant increase in load on the carcass and pressure armour that may compromise the integrity of the pipe. This paper investigates the effect of the volumetric changes in the barrier and how that can influence the extra loading exerted on carcass and pressure armour under service conditions. A simple analytical model has been proposed to predict the extra loading acting on the carcass and the pressure armour. The proposed procedure has been validated using FE results. Experiments have been performed using a three-layer simulated setup and full-scale pipe to investigate the load acting on the carcass and pressure armour. A brief description of the test program and the results are presented. Tests clearly show that there is only a limited increase in hoop stress in the carcass or the pressure armour in pipes immersed in acetone, although the barrier swelled considerably under unconstrained conditions. An empirical procedure has been proposed to account for this swelling retardation behavior. The effect of the PVDF barrier swelling in pressurized supercritical CO2 environments is discussed.

Outer Cover Damages on Flexible Pipes: Corrosion and Integrity Challenges

2014 ◽  
Author(s):  
Morten Eriksen ◽  
Knut Inge Engelbreth
Keyword(s):  
Early Detection ◽  
Pipe Wall ◽  
Confined Water ◽  
Integrity Assessment ◽  
Corrosion Rates ◽  
Flexible Pipes ◽  
Hole Configuration ◽  
Outer Cover ◽  
Service Conditions ◽  
Reliable Methods

According to published statistics for flexible pipes, penetrating holes in outside covers of flexible pipes is one of the most frequent damage mechanisms. The corrosion and fatigue performances of tensile and pressure armour wires are directly influenced by the fluids in the pipe wall annulus. There are several incidents where cover damages have led to serious pipe failures. In this perspective the best strategy is to avoid cover damage, but for those cases where damage occurs it is essential to have systems in place for early detection, as well as capabilities for repair. Holes in the outside cover can create a range of different conditions in an annulus depending on location of the hole, configuration of the pipe and service conditions. CO2 driven corrosion in a confined water filled annulus has been investigated extensively and reported by several authors to give very low corrosion rates. However, the environments that armour wires are exposed to in certain parts of an annulus may differ significantly from confined water with CO2. One obvious example is the region around a penetrating hole in the outer cover where there may be repeated ingress of oxygenated seawater or air that mix with CO2 in the annulus. Such environments could cause high corrosion rates that may explain some observed failures. In many cases it is difficult to quantify the annulus environments precisely and suitable corrosion models have not been established. The consequences are large uncertainties in the prediction of corrosion type and rate, giving challenges for integrity assessment. This paper will identify and discuss unresolved corrosion issues related to outer cover damage linking it to field experience. Needs for developing further knowledge and models will be addressed. Efficient and reliable methods for repair of outer cover damage that can be mobilized soon are essential for restoring the integrity of pipes with damages to outer covers.

Challenges With Measuring Supercritical CO2 Compressor Performance When Approaching the Liquid-Vapor Dome

2021 ◽  
Author(s):  
Jason Mortzheim ◽  
Doug Hofer ◽  
Stephan Priebe ◽  
Aaron McClung ◽  
J. Jeffery Moore ◽  
...  
Keyword(s):  
Supercritical Fluid ◽  
Supercritical Co2 ◽  
Waste Heat ◽  
Density Measurement ◽  
Department Of Energy ◽  
Test Program ◽  
Property Variation ◽  
Southwest Research Institute ◽  
Compressor Performance ◽  
Liquid Vapor

Abstract A team led by General Electric Research (GER) and Southwest Research Institute (SwRI) was tasked to design, build and test an advanced 4MW CO2 compressor that would operate near the liquid-vapor dome for Carbon Dioxide (CO2). The US Department of Energy (DoE) Solar Technologies Office (SETO) funded program was targeted towards a Concentrated Solar Power (CSP) plant where optimum power cycle efficiency can be obtained when operated close to the liquid-vapor dome where CO2 is a supercritical fluid (sCO2) as compression power is reduced in the main compressor. However, the CSP cycle and other related supercritical CO2 cycles (fossil, nuclear, waste heat recovery) have considerable compression challenges both mechanically and aerodynamically when operating with a high density fluid that exceeds 70% the density of water. The subject of this paper is highlighting the challenge in determining compressor performance using industry standard measurements. This application is the highest density industrial-scale centrifugal compressor in the world at 720 kg/m3. This paper will investigate the uncertainty when measuring compressor efficiency using ASME PTC-10 instrumentation and the effect of the strong CO2 property variation when operating as a supercritical fluid, near the fluid-vapor dome. Prior work in this area by Wahl will be summarized and compared with the current compressor test program uncertainty. It will be shown that Wahl predicted high uncertainty as well although, the current testing program is even closer to the liquid-vapor dome than the test program under Wahl. The uncertainty analysis has shown that traditional PTC-10 temperature measurements lead to high levels of uncertainty for sCO2 compression near the liquid-vapor dome. The uncertainty is driven by the large changes in thermodynamic properties of sCO2. These property changes are affected by the measured pressure and temperature; however, temperature measurement error is the primary contributor to uncertainty. Because of this, looking at alternate sCO2 property measurements was investigated. Higher quality localized pressure calibration, improving flow measurement accuracy, and measuring density in addition to temperature all significantly improved efficiency uncertainty. The authors confirmed the most significant measurement change is to measure pressure and density through either a densitometer or a Coriolis flow meter which provides a density measurement in conjunction with flow rate accuracy.

Gas and Water Permeation in Flexible Pipes

2002 ◽  
Author(s):  
Tore Roberg Andersen ◽  
Jan Ivar Skar
Keyword(s):  
Large Scale ◽  
Cold Water ◽  
Small Scale ◽  
Test Results ◽  
Test Program ◽  
Flexible Pipe ◽  
Water Permeation ◽  
Flexible Pipes ◽  
Scale Test ◽  
Temperature And Pressure

A test program has been performed to obtain the permeation coefficients for methane, carbon dioxide and water in PVDF. Small-scale tests showed that water is transported through the PVDF inner sheath of the flexible pipes, and into the annulus. A large-scale test was carried out to verify the small-scale test results. It was performed in a 2″ flexible pipe with length 3 m. The bore temperature and pressure were 100°C and 50 bar, respectively. The pipe was submerged in cold water in order to get a correct temperature gradient in the pipe. The test showed that the annulus of flexible pipe with PVDF inner sheath would become water wet due to permeation, depending upon the bore and annulus conditions.

Midscale Qualification Testing of End Fittings for High Temperature Flexible Pipes

2013 ◽  
Author(s):  
Bjørn Melve ◽  
Einar Øren
Keyword(s):  
High Temperature ◽  
Critical Element ◽  
Test Program ◽  
Field Development ◽  
Flexible Pipes ◽  
Extensive Test ◽  
Qualification Testing ◽  
Flexible Risers ◽  
Sheath Material ◽  
Selection Of

The qualification of high temperature flexible risers was a critical element in the field development of the Norne and Åsgard fields. At a later stage this also included the Kristin field. The high temperature leads to the selection of PVDF as the liner (pressure sheath) material. Due to numerous leaks from pressure sheath sliding in the end fittings of risers with three layer PVDF liners in the middle of 90’s, it was necessary to requalify the end fitting design. An extensive test 10 year program was initiated where mid-scale riser samples were cycled between the minimum and maximum operating temperatures. In the 10 year long test program were some test pipes were subjected to more than 1000 cycles without pressure sheath sliding or a failure. The modified end fittings were qualified for service.

scholarly journals Polymer-inorganic composites based on Celgard matrices obtained using solutions of (aminopropyl)triethoxysilane in supercritical carbon dioxide

2019 ◽  
Vol 485 (4) ◽  
pp. 451-456
Author(s):  
I. V. Elmanovich ◽  
V. V. Zefirov ◽  
V. E. Sizov ◽  
M. S. Kondratenko ◽  
M. O. Gallyamov
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Co2 ◽  
Particle Distribution ◽  
Polymer Structure ◽  
Inorganic Nanoparticles ◽  
Amino Groups ◽  
Wetting Ability ◽  
Membrane Pores ◽  
Inorganic Composites ◽  
Inorganic Composite

A method has been developed for the fabrication of a polymer-inorganic composite material based on the Celgard polymer matrix by means of the introduction of silica nanoparticles with amino groups into the polymer structure through impregnation of porous structure with solutions of the aminosilane precursor in supercritical СO2. The presence of inorganic nanoparticles made it possible to noticeably enhance the hydrophilicity of the material, and the absolute wetting ability of supercritical CO2 was favorable for uniform particle distribution in membrane pores. The particles growing in membrane pores allowed one to reduce the pore size, which opens ways to control ion-transport selectivity.

MOLDI™: A Fluid Permeation Model to Calculate the Annulus Composition in Flexible Pipes — Validation With Medium Scale Tests, Full Scale Tests and Field Cases

2003 ◽  
Author(s):  
Carol Taravel-Condat ◽  
Marc Guichard ◽  
Joseph Martin
Keyword(s):  
Temperature Gradient ◽  
Element Model ◽  
Steel Part ◽  
Full Scale ◽  
Shielding Effect ◽  
Flexible Pipe ◽  
Fluid Mixture ◽  
Medium Scale ◽  
Steel Wires ◽  
Flexible Pipes

In flexible pipes, the steel wires in the annular space can sometimes be in contact with a corrosive environment containing condensed water or seawater and acid gases (CO2 and H2S), coming from the bore by permeation through internal polymer sheaths. In order to choose the most suitable steel wires to avoid hydrogen embrittlement and to evaluate their resistance to corrosion and corrosion fatigue, it is necessary to know the annulus composition. A finite element model named MOLDI™ has been developed in order to precisely calculate this environment. This model is composed of two major modules: The first one describes the time dependent permeation of fluids through the pipe layers. Concentration and pressure versus time are calculated assuming Fick and Henry’s laws. The shielding effect of steel wires on the plastic sheaths and the temperature gradient through the structure are taken into account. The second module uses a thermodynamic flash algorithm to calculate the phase equilibrium in the annulus, including water condensation. In order to validate this model, a permeation testing program has been initiated in 1997. It is based on medium and full scale permeation tests and field cases. For each test, the pressure build-up and the composition inside the annulus are measured and compared with the ones calculated with MOLDI™. Medium scale prototypes consist in a polymer tube surrounded by a steel part simulating the annulus geometry of a flexible pipe (shielding, free volume). One of the prototypes has been specially designed in order to be able to maintain a chosen temperature gradient between the bore and the external side. The full scale permeation tests are conducted on a piece of manufactured flexible pipe. At the beginning of the test, the bore is filled up with a pure gas or with a fluid mixture (gas–water–crude oil) under pressure and temperature. The permeation rate from the bore to the annulus is determined by recording the pressure build-up in the annulus versus time. The gas composition in the annulus is measured using a Gaseous Chromatography device. Field cases have also been used to validate MOLDI™. To do that, the annulus of flexible risers has been monitored on site and the measurements compared with MOLDI™ simulations. The validations conducted at the time being, using different polymer sheath materials and fluid mixtures, have shown that our permeation model predictions are in good agreement with experimental results. Consequently, MOLDI™ is considered as validated and is now used to calculate the annulus composition from the field conditions.

Qualification of High Strength Carbon Steel Wires for Use in Specific Annulus Environment of Flexible Pipes Containing CO2 and H2S

2006 ◽  
Author(s):  
Carol Taravel-Condat ◽  
Nicolas Desamais
Keyword(s):  
Carbon Steel ◽  
Corrosion Fatigue ◽  
High Strength ◽  
Full Scale ◽  
Small Scale ◽  
Annular Space ◽  
Flexible Pipe ◽  
Corrosion Rates ◽  
Steel Wires ◽  
Flexible Pipes

Flexible pipes have been used for many years in offshore applications for the transportation of crude oil, gas and water. Such structures are subjected to mechanical loads due to tension, high internal pressure and dynamic motions which are sustained by the use of high strength carbon steel wires. The steel wires are located in the annular space that may contain water and acid gas (CO2, H2S) which can be detrimental for steels. For that reason, risks of Sulfide Stress Corrosion Cracking (SSCC) and Hydrogen Induced Cracking (HIC) shall be considered. Moreover, for dynamic conditions, presence of corrosive environment in the annulus could significantly reduce the fatigue performance of flexible pipe compared to air environment. The annulus composition is calculated using a permeability model that has been validated with medium scale tests, full scale tests and field cases [1]. In parallel, corrosion and corrosion fatigue studies have shown that the annulus of a flexible pipe is a very confined space with over-saturation in iron and no renewal of oxygen. This results in a higher pH, much lower corrosion rates and less HIC and SSCC than one would expect based on normal environments. This paper presents, in a first part, the different results obtained during small scale corrosion and corrosion fatigue tests demonstrating the beneficial specificity of the annular space. In a second part, the paper presents the results of pH measurements and corrosion rates obtained during a full scale dynamic corrosion fatigue test in CO2/H2S environment validating the previous results. This test was conducted on a 6” pipe between 1999 and 2003. In a third part, the paper describes how the annulus specificities should be used today to determine the suitability of carbon steel wires for use in flexible flowlines and risers considering SSCC, HIC, corrosion and corrosion fatigue.

Electron Energy Analysis of Germanium and Silica Layers on Silicon Substrates

1975 ◽  
Vol 33 ◽  
pp. 96-97
Author(s):  
R. W. Ditchfield ◽  
A. G. Cullis
Keyword(s):  
Epitaxial Growth ◽  
Electron Energy ◽  
Silicon Substrates ◽  
Secondary Phases ◽  
Si Substrates ◽  
Transmission Electron ◽  
Layer Structures ◽  
Si Films ◽  
Electron Energy Loss ◽  
Growth Centres

An energy analyzing transmission electron microscope of the Möllenstedt type was used to measure the electron energy loss spectra given by various layer structures to a spatial resolution of 100Å. The technique is an important, method of microanalysis and has been used to identify secondary phases in alloys and impurity particles incorporated into epitaxial Si films.Layers Formed by the Epitaxial Growth of Ge on Si Substrates Following studies of the epitaxial growth of Ge on (111) Si substrates by vacuum evaporation, it was important to investigate the possible mixing of these two elements in the grown layers. These layers consisted of separate growth centres which were often triangular and oriented in the same sense, as shown in Fig. 1.

Computer programs for the calculation of x-ray intensities emitted by elements in multi-layer structures

1990 ◽  
Vol 48 (2) ◽  
pp. 216-217
Author(s):  
G.F. Bastin ◽  
H.J.M. Heijligers ◽  
J.M. Dijkstra
Keyword(s):  
Software Package ◽  
Light Element ◽  
Matrix Correction ◽  
Excellent Performance ◽  
Element Analysis ◽  
X Ray ◽  
Know How ◽  
Accurate Knowledge ◽  
Layer Structures ◽  
Bulk Matrix

For the calculation of X-ray intensities emitted by elements present in multi-layer systems it is vital to have an accurate knowledge of the x-ray ionization vs. mass-depth (ϕ(ρz)) curves as a function of accelerating voltage and atomic number of films and substrate. Once this knowledge is available the way is open to the analysis of thin films in which both the thicknesses as well as the compositions can usually be determined simultaneously.Our bulk matrix correction “PROZA” with its proven excellent performance for a wide variety of applications (e.g., ultra-light element analysis, extremes in accelerating voltage) has been used as the basis for the development of the software package discussed here. The PROZA program is based on our own modifications of the surface-centred Gaussian ϕ(ρz) model, originally introduced by Packwood and Brown. For its extension towards thin film applications it is required to know how the 4 Gaussian parameters α, β, γ and ϕ(o) for each element in each of the films are affected by the film thickness and the presence of other layers and the substrate.

Precision and bias in quantitative EDS: ASTM results

1992 ◽  
Vol 50 (2) ◽  
pp. 1654-1655
Author(s):  
John J. Friel
Keyword(s):  
Stainless Steel ◽  
Quantitative Analysis ◽  
Mechanical Alloy ◽  
Dead Time ◽  
Test Program ◽  
Round Robin Test ◽  
Wide Range ◽  
American Society ◽  
Takeoff Angle ◽  
Standardless Analysis

Committee E-04 on Metallography of the American Society for Testing and Materials (ASTM) conducted an interlaboratory round robin test program on quantitative energy dispersive spectroscopy (EDS). The test program was designed to produce data on which to base a precision and bias statement for quantitative analysis by EDS. Nine laboratories were sent specimens of two well characterized materials, a type 308 stainless steel, and a complex mechanical alloy from Inco Alloys International, Inconel® MA 6000. The stainless steel was chosen as an example of a straightforward analysis with no special problems. The mechanical alloy was selected because elements were present in a wide range of concentrations; K, L, and M lines were involved; and Ta was severely overlapped with W. The test aimed to establish limits of precision that could be routinely achieved by capable laboratories operating under real world conditions. The participants were first allowed to use their own best procedures, but later were instructed to repeat the analysis using specified conditions: 20 kV accelerating voltage, 200s live time, ∼25% dead time and ∼40° takeoff angle. They were also asked to run a standardless analysis.

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