Wear of Outer Sheath Materials in Flexible Pipes: Testing Methodology

2017 ◽  
Author(s):  
Einar Øren ◽  
Marit Larsen ◽  
Frode Andres Kvilhaug ◽  
Bjørn Melve
Keyword(s):  
Measurement Method ◽  
Wear Test ◽  
Test Apparatus ◽  
Comparative Tests ◽  
Test Methodology ◽  
Outer Sheath ◽  
Flexible Pipes ◽  
Pin On Disc ◽  
Flexible Risers ◽  
Arch Support

Outer sheath wear of polymers in flexible risers has been experienced with risers anchored with guide tubes and bellmouths. In addition, wear damages have been observed at touch down points and on subsea arch support structures. A wear test methodology was developed with the purpose to mimic the observations from pipes in operation. The test apparatus used was similar to a pin-on-disc measurement method, but with emphasis on reproducing the exact environment and temperature. Comparative tests have been done between different materials, and for some conditions the differences are significant.

Qualified Assessment for Lifetime Extension of Flexible Risers

2015 ◽  
Author(s):  
Bernt J. Leira ◽  
Svein Are Løtveit ◽  
Stig Berge ◽  
Dag Fergestad ◽  
Nina Langhelle
Keyword(s):  
Flexible Riser ◽  
Term Operation ◽  
Integrity Assessment ◽  
Design Life ◽  
Outer Sheath ◽  
Flexible Pipes ◽  
Flexible Risers ◽  
Lifetime Extension

There have been many challenges with respect to long term operation of flexible pipes, in many cases with the need to replace or repair them before the end of the initial design life. The number of identified failure mechanisms and observed failure events is also increasing. In the present paper, some typical issues that arise during the process of integrity assessment and qualification for lifetime extension are outlined. More detailed considerations are illustrated in relation to a particular case study. This involves elaboration of the different steps which are required in order to be able to extend the lifetime of a flexible riser for the case of corrosive annulus environments. The particular case of an outer sheath damage is applied for the purpose of illustration.

New Advances in Flexible Riser Monitoring Techniques Using Optical Fiber Sensors

2012 ◽  
Author(s):  
Sérgio R. K. Morikawa ◽  
Arthur M. B. Braga ◽  
Claudio S. Camerini ◽  
Carla C. Kato ◽  
Roberth A. Llerena ◽  
...  
Keyword(s):  
Structural Damage ◽  
Laboratory Tests ◽  
Failure Modes ◽  
Fiber Optic ◽  
Gas Production ◽  
Strain Sensors ◽  
Brazilian Coast ◽  
Outer Sheath ◽  
Flexible Pipes ◽  
Flexible Risers

Petrobras oil and gas production in the deep and ultra deepwater fields in Campos Basin and other provinces off the Brazilian coast heavily relies on flexible pipes. Maximizing the availability and reliability of an extensive offshore pipeline network poses innumerous challenges to the Company, which is steadily moving towards a condition based approach to maintenance of their flexible risers. In this context, Petrobras, in cooperation with its academic partners, has launched a comprehensive R&D program named MONFLEX, focusing on novel techniques for structural monitoring of flexible risers. Years of field experience have demonstrated that one of the most frequent failure modes of flexible pipes is the sequential rupture of wires in their tensile armor layers [1]. The MONFLEX Program has explored a range of different technologies in order to timely detect and monitor the growth of this class of progressive structural damage. Some of the proposed approaches have relied on video cameras pointed towards fixedly mounted targets on the riser outer sheath, vibration and acoustic methods, these in a wide frequency range, and techniques based on fiber optic strain sensors. All three have been experimentally deployed in the field and are currently being evaluated. Among those, fiber optic monitoring is the one that has shown the better promise of becoming the chosen method for detecting wire ruptures in the riser’s armor layers. The fiber optic based monitoring system developed in the MONFLEX R&D Program has been named MODA, which, in Portuguese, stands for Direct Wire Optical Monitoring. The MODA system consists in instrumenting all the wires of the riser’s external tensile armor layer with fiber Bragg grating strain sensors. In flexible risers already in operation, a window in the polymeric outer sheath of the pipe is temporarily opened in order to allow the sensors installation, and then repaired with a protective, anticorrosive layer. Even though in MODA the strain sensors are installed in the external armor layer, full scale laboratory tests have demonstrated that the algorithm employed to treat and analyze the real time data provided by the system is capable of instantaneously detecting ruptures of wires either in the external or internal layers of the tensile armor. The proposed contribution will report the later results of extensive laboratory tests and field trials performed with the MODA system.

Determination of Steady-State Adhesive Wear Rate

2005 ◽  
Author(s):  
L. J. Yang
Keyword(s):  
Steady State ◽  
Wear Rate ◽  
Wear Test ◽  
Standard Test ◽  
Test Method ◽  
Testing Time ◽  
Wear Coefficient ◽  
Wear Rates ◽  
Test Methodology

Wear rates obtained from different investigators could vary significantly due to lack of a standard test method. A test methodology is therefore proposed in this paper to enable the steady-state wear rate to be determined more accurately, consistently, and efficiently. The wear test will be divided into four stages: (i) to conduct the transient wear test; (ii) to predict the steady-state wear coefficient with the required sliding distance based on the transient wear data by using Yang’s second wear coefficient equation; (iii) to conduct confirmation runs to obtain the measured steady-state wear coefficient value; and (iv) to convert the steady-state wear coefficient value into a steady-state wear rate. The proposed methodology is supported by wear data obtained previously on aluminium based matrix composite materials. It is capable of giving more accurate steady-state wear coefficient and wear rate values, as well as saving a lot of testing time and labour, by reducing the number of trial runs required to achieve the steady-state wear condition.

Cathodic Protection Design Consideration for an Offshore Flexible Riser Connected to an Impressed Current System

2021 ◽  
Author(s):  
Thierry Dequin ◽  
Clark Weldon ◽  
Matthew Hense
Keyword(s):  
Cathodic Protection ◽  
Sacrificial Anode ◽  
Flexible Riser ◽  
Flexible Pipe ◽  
Linear Resistance ◽  
Flexible Pipes ◽  
Flexible Risers ◽  
Impressed Current ◽  
Host Structure ◽  
Impressed Current Cathodic Protection

Abstract Flexible risers are regularly used to produce oil and gas in subsea production systems and by nature interconnect the subsea production system to the floating or fixed host facilities. Unbonded flexible pipes are made of a combination of metallic and non-metallic layers, each layer being individually terminated at each extremity by complex end fittings. Mostly submerged in seawater, the metallic parts require careful material selection and cathodic protection (CP) to survive the expected service life. Design engineers must determine whether the flexible pipe risers should be electrically connected to the host in order to receive cathodic protection current or be electrically isolated. If the host structure is equipped with a sacrificial anode system, then electrical continuity between the riser and the host structure is generally preferred. The exception is often when the riser and host structure are operated by separate organizations, in which case electrical isolation may be preferred simply to provide delineation of ownership between the two CP systems. The paper discusses these interface issues between hull and subsea where the hull is equipped with an impressed current cathodic protection (ICCP) system, and provides guidance for addressing them during flexible pipe CP design, operation, and monitoring. Specifically, CP design philosophies for flexible risers will be addressed with respect to manufacturing, installation and interface with the host structure’s Impressed Current Cathodic Protection (ICCP) system. The discussion will emphasize the importance of early coordination between the host structure ICCP system designers and the subsea SACP system designers, and will include recommendations for CP system computer modeling, CP system design operation and CP system monitoring. One of the challenges is to understand what to consider for the exposed surfaces in the flexible pipes and its multiple layers, and also the evaluation of the linear resistance of each riser segment. The linear resistance of the riser is a major determinant with respect to potential attenuation, which in turn largely determines the extent of current drain between the subsea sacrificial anode system and the hull ICCP system. To model the flexible riser CP system behavior for self-protection, linear resistance may be maximized, however the use of a realistic linear resistance is recommended for evaluation of the interaction between the host structure and subsea system. Realistic flexible linear resistance would also reduce conservatism in the CP design, potentially save time during the offshore campaign by reducing anode quantities, and also providing correct evaluation of drain current and stray currents.

Tribological Properties of Superhard PVD Coatings

1991 ◽  
Vol 239 ◽  
Author(s):  
O. Knotek ◽  
F. Löffler
Keyword(s):  
Tribological Properties ◽  
Hexagonal Lattice ◽  
Wear Test ◽  
Amorphous Structure ◽  
Hard Coatings ◽  
X Ray Diffraction ◽  
Ion Plating ◽  
Cathode Substrate ◽  
Pin On Disc ◽  
Reactive Gases

AbstractIn order to advance the development of extremely hard coatings, new homogeneous and metastable films were prepared by magnetron sputter ion plating (MSIP) and arc ion plating (AIP) in the DC. or RF. mode.In the present study coatings in the systems Ti-B-C-N, Si-C-N and amorphous carbon coatings (ADLC) were investigated and compared with other hard coatings. Multicomponent layers of different compositions and structures were deposited by varying the reactive gases methane (CH4) and nitrogen (N2) and the dominant process parameters (e. g. C/V-characteristic of the cathode, substrate bias).X-ray diffraction studies of the Ti-B-C-N coatings revealed either an amorphous structure or crystallization in a hexagonal lattice. The ADLC and Si-C-N coatings were always amorphous. Electron microprobe analysis and auger electron spectroscopy were used to determine the coating compositions.The tribological properties were determined by a ball on disc tribometer (e.g. friction coefficent), a pin on disc tribometer and a special abrasive wear test.

Characterizing the Wave Environment in the Fatigue Analysis of Flexible Risers

2005 ◽  
Vol 128 (2) ◽  
pp. 108-118 ◽  
Author(s):  
John M. Sheehan ◽  
Frank W. Grealish ◽  
Annette M. Harte ◽  
Russell J. Smith
Keyword(s):  
Cost Effective ◽  
Critical Issue ◽  
Fatigue Analysis ◽  
Flexible Pipes ◽  
Water Developments ◽  
Key Issues ◽  
Flexible Risers ◽  
Offshore Industry ◽  
Unbonded Flexible Pipes

As the offshore industry moves towards deeper water developments and continues to embrace harsh environments, unbonded flexible pipes are increasingly being utilized as a cost effective riser solution. Furthermore, with the advent of issues such as nonpristine annuli environments, the fatigue performance of these flexible risers is becoming a critical issue. This paper presents an overview of the comparisons between deterministic and stochastic global fatigue analysis techniques. Methods used to perform both deterministic and stochastic analyses are outlined, from performing the global analyses to using local models to generate armor wire stresses and subsequent fatigue damage. The paper identifies the key issues in the analysis performed and presents key results and conclusions with regard to the characterization of the wave environment in the global fatigue analysis of flexible risers.

Whistling of Pipes With Narrow Corrugations: Scale Model Tests and Consequences for Carcass Design

2013 ◽  
Author(s):  
Joachim Golliard ◽  
Stefan Belfroid ◽  
Erik Bendiksen ◽  
Casper Frimodt
Keyword(s):  
Prediction Model ◽  
Gas Production ◽  
Scale Model ◽  
Small Scale ◽  
Operational Conditions ◽  
Flexible Pipes ◽  
Cavity Opening ◽  
Flexible Risers ◽  
Onset Velocity ◽  
Operational Envelope

Pipes for gas production and transport with a corrugated inner surface, as used in flexible pipes, can be subject to Flow-Induced Pulsations when the flow velocity is larger than a certain velocity. This onset velocity is dependent on the geometry of the corrugations, the operational conditions and the geometry of the topside and subsea piping. In this paper, small-scale tests performed on corrugated tubes are reported. The tested geometries include both “classical” profiles, similar to the inner profile of agraff flexible risers, and profiles with less typical variations, such as narrower and/or deeper cavities, or irregular pitch. These tests were performed in order to evaluate the validity of a prediction model developed earlier for the onset of pulsations, for corrugated pipes with these kinds of atypical variations, which are found on a new type of carcass designs. The mechanism of Flow-Induced Pulsations in corrugated pipes is discussed, as well as the principle of the prediction model. The experimental results show that the validity of the model remains reasonable in most cases, except when the cavities are very narrow. In this case, the model becomes overly conservative. This limitation can be attributed to the fact that, for very narrow cavities, the cavity opening becomes too small compared to the boundary-layer momentum thickness, effectively destroying any instability of the shear layer. Furthermore, the shift towards higher frequencies of the acoustic source term due to narrower cavities, and the possible coupling with higher acoustic modes, is considered. The results of the analysis are used to evaluate the onset velocity and whistling behavior of a newly developed carcass design of flexible risers. A previous analysis has indicated that the particular geometry profile of the new design improves the whistling behavior by pushing the onset velocity outside the typical operational envelope of flexible risers. The analysis confirms that the new design will be less prone to whistling than flexible risers with classical agraff carcasses.

Analytical Methodology to Evaluate Flexible Risers Fatigue Lives at the Top Region

2019 ◽  
Author(s):  
Fernando Jorge Mendes de Sousa ◽  
Marcos Queija de Siqueira ◽  
José Renato Mendes de Sousa ◽  
George Carneiro Campello
Keyword(s):  
Fatigue Life ◽  
Structural Complexity ◽  
Analytical Methodology ◽  
Life Estimation ◽  
Flexible Pipes ◽  
Fatigue Life Estimation ◽  
Riser Design ◽  
Flexible Risers ◽  
Critical Regions ◽  
Computer Resources

Abstract Traditionally, fatigue life calculations are very expensive in terms of time and computer resources. They are usually performed during riser design phases, when several lines with similar characteristics need to be analyzed. While operating, when problems are detected, fatigue analyses are also necessary to help to decide if any action is needed. In both situations, end fittings and bendstiffeners are usually the critical regions. Considering the high number of flexible risers installed in Brazil and the structural complexity of this kind of structure, a robust and fast methodology to evaluate the fatigue life of flexible risers becomes attractive. In this way, this paper proposes a analytical/numerical methodology to evaluate the fatigue life at the top region of flexible pipes. Using the top imposed motions and taking into account the properties of all structures in the riser, it is possible to evaluate tension analytically. Combining tension and the rotations imposed at the top of the riser, curvatures are determined, and stresses can be calculated. Finally, SN curves and the Miner’s rule for damage accumulation allow the estimation of fatigue life. The obtained results indicate that the proposed methodology is conservative when compared to traditional ones. Also, it is very fast, allowing the fatigue life estimation in minutes.

Influence of Porosity and Alloy addition on the Wear behaviour of a Sinter-Forged C45 Steel using Taguchi Method

2020 ◽  
Author(s):  
NAVEEN EASWARAN ◽  
Shanmugam Ramasamy ◽  
Roshan Nagarajan ◽  
Ramanan Nandagopal ◽  
Sripada Ragavendra Keshava Narasimha
Keyword(s):  
Wear Resistance ◽  
Mass Loss ◽  
Wear Test ◽  
Theoretical Density ◽  
Wear Behaviour ◽  
Dry Sliding Wear ◽  
Input Parameters ◽  
Alloy Addition ◽  
Pin On Disc ◽  
Alloy Steels

Elemental powders of Atomized Iron (Fe), Carbon (C) and Molybdenum (Mo) were weighed and mixed in a pot mill to yield the composition of C45, C45-1%Mo and C45-2%Mo Steels, then compacted and sintered. The Sintered preforms had a density- 75% of the Theoretical Density. Then the Sintered preforms were subjected to densification to get two densities- 80% and 85% of the theoretical density through Forging. The sintered and densified preforms of alloy steels were subsequently machined to get the required wear test specimens.The experiments were conducted on a Pin-on-disc Tribometer, conforming to ASTM G99 standards, on a rotating EN32 disc. Using Minitab 16 software, the Dry Sliding wear experiments were planned using L27 Orthogonal Array.The % Theoretical Density of the Specimens (1-%Porosity), % Mo Addition, Load and Sliding Velocity were taken as input parameters, mass loss was the output parameter. It was observed that the increasing density of alloy steels adversely affects the wear resistance of the alloy steels and mass loss is increased. It was found that the addition of Mo significantly improves the wear resistance of the alloy steels irrespective of the densities .Empirical correlations for mass loss with respect to input parameters had been developed.

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