HPHT Subsea Connector Verification and Validation Using an API 17TR8 Methodology

2021 ◽  
Author(s):  
Barry Stewart ◽  
Sam Kwok Lun Lee
Keyword(s):  
Failure Modes ◽  
Production Systems ◽  
Three Dimensional ◽  
Full Scale ◽  
Verification And Validation ◽  
Combined Loading ◽  
Load Path ◽  
Capacity Curves ◽  
Industry Standards ◽  
Full Scale Tests

Abstract Wellhead connectors form a critical part of subsea tree production systems. Their location in the riser load path means that they are subjected to high levels of bending and tension loading in addition to internal pressure and cyclic loading. As more fields continue to be discovered and developed that are defined as High Pressure and/or High Temperature (HPHT) these loading conditions become even more arduous. In order to ensure the integrity of HPHT components, industry requirements for components are setout in API 17TR8. This technical report provides a design verification methodology for HPHT products and some requirements for validation testing. The methodology provides detail on the assessment of static structural and cyclic capacities but less detail on how to assess the functional and serviceability criteria for wellhead connectors. Similarly, API 17TR8 does not include prescriptive validation requirements for wellhead connectors and refers back to historical methods. This paper describes a practical application of the API 17TR8 methodology to the development of a 20k HPHT connector and how it was implemented to verify and validate the connector design through full scale tests to failure. A methodology was developed to meet the requirements of the relevant industry standards and applied to the connector to develop capacity charts for static combined loading. Verification was carried out on three dimensional 180° FEA models to ensure all non axi-symmetric loading is accurately captured. Connector capacities are defined based on API 17TR8 criteria with elastic plastic analysis (i.e. collapse load, local failure and ratcheting), functionality/serviceability criteria defined through a FMECA review and also including API STD 17G criteria including failure modes such as lock/unlock functionality, fracture based failure, mechanical disengagement, leakage and preload exceedance. These capacities are validated through full scale testing based on the requirements of API 17TR7 and API STD 17G with combined loading applied to the Normal, Extreme and Survival capacity curves (as defined by "as-built" FEA using actual material properties). Various test parameters such as strain gauge data, hub separation data, displacements, etc. were recorded and correlated to FEA prediction to prove the validity of the methodology. Further validation was carried out by applying a combined load up to the FEA predicted failure to confirm the design margins of the connector. Post-test review was carried out to review the suitability of the requirements set out in API 17TR8 and API STD 17G for the verification and validation of subsea connectors. The results build on previous test results to validate the effectiveness of the API 17TR8 code for verification and validation of connectors. The results show that real margins between failure of the connector and rated loads are higher than those defined in API 17TR8 and show that the methodology can be conservative.

A Validated Methodology to Establish Structural Capacities for Subsea Connector Families

2021 ◽  
Author(s):  
Michael John Stephens ◽  
Simon John Roberts ◽  
Derek James Bennet
Keyword(s):  
Failure Modes ◽  
Bending Moment ◽  
Full Scale ◽  
Structural Testing ◽  
Combined Loading ◽  
Test Sequence ◽  
Fea Model ◽  
Analysis Methodology ◽  
Industry Standards ◽  
Physical Testing

Abstract Understanding the structural limits of subsea connectors used in offshore environments is critical to ensure safe operations. The latest industry standards establish the requirement for physical testing to validate analysis methodologies for connector designs. In this paper, an analysis methodology, compliant with the latest API 17G standard, is presented for calculating structural capacities of non-preloaded connectors. The methodology has been developed for complex combined loading scenarios and validated using full-scale physical testing for different connector families. Detailed 3-D, non-linear, finite element models were developed for three different non-preloaded connections, which consisted of threaded and load shoulder connectors. A comprehensive set of combined tension and bending moment structural capacities at normal, extreme and survival conditions were calculated for each connection. The calculated capacities were validated for each connection by performing a test sequence using full-scale structural testing. A final tension or bending to failure test was also completed for each test connection to validate the physical failure mode, exceeding the latest API 17G requirements. For all connections tested, capacities calculated using the methodology were validated from the successful completion of the test sequences. The physical failure modes of the test connections also matched the predicted failure modes from the FEA, and the tensile or bending moment loading at physical collapse exceeded that predicted by the global collapse of the FEA model. Using the validated approach described in this paper significantly reduces the requirement of physical testing for connector families, establishing confidence in the structural limits that are critical for safe operations.

ASME Sec VIII Div. 3 and API TR 17TR8 Verification and Validation Methodology for Subsea Connectors

2020 ◽  
Author(s):  
Barry Stewart ◽  
Alejandro Andueza
Keyword(s):  
Production Systems ◽  
Scale Validation ◽  
Verification And Validation ◽  
Load Path ◽  
Industry Standards ◽  
High Pressure High Temperature ◽  
Challenging Environment ◽  
Actual Design ◽  
Validation Tests ◽  
Verification Techniques

Abstract Wellhead connectors form a critical part of subsea tree production systems. Their location in the riser load path means that they are subjected to high levels of bending and tension loading in addition to the internal pressure and cyclic loading. As such, they are essential equipment and various industry standards influence their design and qualification requirements. This is particularly true of High Pressure High Temperature (HPHT) equipment where heavier blowout preventers and larger rigs are required to deal with this challenging environment. Industry standards that cover wellhead connectors include a range of verification techniques based on different base analysis codes each of which uses different factors to determine a design margin. Some of the different methods may therefore lead to different actual design margins on the connector from failure to a safe working load. In order to meet the requirements of the industry and to ensure product integrity a HPHT verification and validation methodology based on API 17TR8 [1] and ASME VIII Div. 3 [2] is presented here for subsea wellhead connector designs. The results from a series of verification and full scale validation tests for a subsea wellhead connector family are presented and discussed. The results prove the design margins of the connectors using this methodology and allow for a full understanding of the limits and true performance of the design.

scholarly journals Mechanical Properties of Concrete Pipes with Pre-Existing Cracks

2020 ◽  
Vol 10 (4) ◽  
pp. 1545
Author(s):  
Zongyuan Zhang ◽  
Hongyuan Fang ◽  
Bin Li ◽  
Fuming Wang
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Bearing Capacity ◽  
Three Dimensional ◽  
Compressive Load ◽  
Full Scale ◽  
Element Analysis ◽  
Concrete Pipes ◽  
Concrete Pipe ◽  
Full Scale Tests

Concrete pipes are the most widely used municipal drainage pipes in China. When concrete pipes fall into years of disrepair, numerous problems appear. As one of the most common problems of concrete pipes, cracks impact on the deterioration of mechanical properties of pipes, which cannot be ignored. In the current work, normal concrete pipes and those with pre-existing cracks are tested on a full scale under an external compressive load. The effects of the length, depth, and location of cracks on the bearing capacity and mechanical properties of the concrete pipes are quantitatively analyzed. Based on the full-scale tests, three-dimensional finite element models of normal and cracked concrete pipes are developed, and the measured results are compared with the data of the finite element analysis. It is clear that the test measurements are in good agreement with the simulation results; the bearing capacity of a concrete pipe is inversely proportional to the length and depth of the crack, and the maximum circumferential strain of the pipe occurs at the location of the crack. The strain of the concrete pipe also reveals three stages of elasticity, plasticity, and failure as the external load rises. Finally, when the load series reaches the limit of the failure load of the concrete pipe with pre-existing cracks, the pipe breaks along the crack position.

Full-Scale Wrinkling Tests and Analyses of Large Diameter Corroded Pipes

1998 ◽  
Author(s):  
Marina Q. Smith ◽  
Daniel P. Nicolella ◽  
Christopher J. Waldhart
Keyword(s):  
Finite Element ◽  
Internal Pressure ◽  
Axial Compression ◽  
Wall Thickness ◽  
Full Scale ◽  
Operating Conditions ◽  
Material Behavior ◽  
Combined Loading ◽  
Longitudinal Bending ◽  
Full Scale Tests

The aging of pipeline infrastructures has increased concern for the integrity of pipelines exhibiting non-perforating wall loss and settlement induced bending. While pressure based guidelines exist which allow pipeline operators to define operational margins of safety against rupture (e.g.; ANSI/ASME B31-G and RSTRENG (Battelle, 1989)), reliable procedures for the prediction of wrinkling in degraded pipes subjected to combined loading are virtually non-existent. This paper describes full-scale testing and finite element investigations performed in support of the development of accurate wrinkling prediction procedures for the Alyeska Pipeline Service Company. The procedures are applicable to corroded pipes subjected to combined loading such as longitudinal bending, internal pressure, and axial compression. During the test program, full-scale 48-inch diameter sections of the trans-Alaska pipeline were subjected to internal pressure and loads designed to simulate longitudinal bending from settlement, axial compression from the transport of hot oil, and the axial restraint present in buried pipe. Load magnitudes were designed based on normal and maximum operating conditions. Corrosion in the pipe section is simulated by mechanically reducing the wall thickness of the pipe. The size and depth of the thinned region is defined prior to each test, and attempts to bound the dimensions of depth, axial length, and hoop length for the general corrosion observed in-service. The analytical program utilizes finite element analyses that include the nonlinear anisotropic material behavior of the pipe steel through use of a multilinear kinematic hardening plasticity model. As in the tests, corrosion is simulated in the analyses by a section of reduced wall thickness, and loads and boundary constraints applied to the numerical model exactly emulate those applied in the full-scale tests. Verification of the model accuracy is established through a critical comparison of the simulated pipe structural behavior and the full-scale tests. Results of the comparisons show good correlation with measurements of the pipe curvature, deflections, and moment capacity at wrinkling. The validated analysis procedure is subsequently used to conduct parameter studies, the results of which complete a database of wrinkling conditions for a variety of corrosion sizes and loading conditions.

Combined Loading Tests of Large Diameter Corroded Pipelines

2000 ◽  
Author(s):  
Marina Q. Smith ◽  
Christopher J. Waldhart
Keyword(s):  
Internal Pressure ◽  
Thermal Stresses ◽  
Failure Modes ◽  
Prediction Models ◽  
Large Diameter ◽  
Bending Moment ◽  
Combined Loading ◽  
Analytical Models ◽  
Bending Load ◽  
Full Scale Tests

Current methods for estimating the remaining strength of aging, corroded pipelines have been restricted to the capabilities of pressure based engineering models that rely on the definition of hoop stress in the pipe wall. Because in practice, pipelines are subjected to a variety of loading conditions (e.g.; axial bending from settlement and thermal stresses) that act in concert with those derived by internal pressure, a multi-year combined testing and analysis program was initiated by the Alyeska Pipeline Service Company aimed at developing computer tools for the prediction of rupture and wrinkling in corroded pipes. During the program, seventeen full-scale tests of mechanically corroded 48-inch diameter (1219-mm), X65 pipes subjected to internal pressure, axial bending, and axial compression were performed to provide data necessary for the verification of analytical models and failure prediction models. While all of the tests were designed to produce rupture, wrinkling, as defined by the occurrence of a limit moment during the application of bending loads, was produced in eleven of the tests either prior to or instead of rupture. Loading of the pipe was intended to simulate that which would be observed by a pipe in-service and included both load control and displacement control of the applied bending load, and in some tests, intended to define the amount of additional pressure required to cause burst after wrinkling was produced. Results of the tests showed that two different failure modes are produced depending on whether the bending moment is transmitted to the pipe as a fixed load or a fixed displacement, and consequently, the burst capacity of the corroded pipe may not be compromised by the presence of axial loads. This paper discusses the tests performed, including a description of the load schedule and corrosion geometries, and key results of the tests that were used in the development of a new strain-based burst prediction procedure for corroded pipes subjected to combined loads.

scholarly journals FE Models of GFRP and CFRP Strengthening of Reinforced Concrete Beams

2009 ◽  
Vol 2009 ◽  
pp. 1-13 ◽  
Author(s):  
Kasidit Chansawat ◽  
Tanarat Potisuk ◽  
Thomas H. Miller ◽  
Solomon C. Yim ◽  
Damian I. Kachlakev
Keyword(s):  
Reinforced Concrete ◽  
Failure Modes ◽  
Concrete Beams ◽  
Three Dimensional ◽  
Full Scale ◽  
Reinforced Concrete Beams ◽  
Flexural Strengthening ◽  
Frp Composites ◽  
Strengthened Beam ◽  
Three Dimensional Finite Element

Three-dimensional finite element (FE) models are developed to simulate the behavior of full-scale reinforced concrete beams strengthened with glass and carbon fiber-reinforced polymer sheets (an unstrengthened control beam, a flexural-strengthened beam, a shear-strengthened beam, and a beam with both shear and flexural strengthening). FE models use eight-node isoparametric elements with a smeared cracking approach for the concrete and three-dimensional layered elements to model the FRP composites. Analysis results are compared with data obtained from full-scale beam tests through the linear and nonlinear ranges up to failure. It was found that the FE models could identify qualitatively trends observed in the structural behavior of the full-scale beams. Predicted crack initiation patterns resemble the failure modes observed for the full-scale beam tests.

Numerical Simulations of Full-Scale Corroded Pipe Tests With Combined Loading

1997 ◽  
Vol 119 (4) ◽  
pp. 457-466 ◽  
Author(s):  
S. Roy ◽  
S. Grigory ◽  
M. Smith ◽  
M. F. Kanninen ◽  
M. Anderson
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Full Scale ◽  
Combined Loading ◽  
Pipe Failure ◽  
Element Analysis ◽  
Line Pipe ◽  
Safety Margins ◽  
Failure Predictions ◽  
Three Dimensional Finite Element

The ANSI/ASME B31G guideline has been useful to pipeline operators in assessing the integrity of corroded line pipe. Because large safety margins have had to be incorporated, the guidelines can be excessively conservative, which in turn can force costly repairs and replacements that may not actually be necessary. On the other hand, because the current guidelines consider only pressure loading and neglect bending and axial compression, they could give nonconservative failure predictions when combined loading exists. Therefore, a study was initiated to develop a theoretically sound methodology for assessing the integrity of corroded line pipe subjected to combined loading. A key step in the successful application of this methodology is the development of a sophisticated three-dimensional finite element procedure that can accurately simulate full-scale pipe tests under conditions of combined loading. This paper describes thirteen full-scale failure tests on artificially corroded pipes subjected to simultaneous internal pressure, bending, and longitudinal compression and presents a detailed account of the finite element analysis procedure that was developed to simulate these tests numerically. Additional finite element analyses that were conducted to investigate the effect of key parameters on failure, and to expand the corroded pipe failure database, are also discussed.

Adhesive Bond Stresses and Strains at Discontinuities and Cracks in Bonded Structures

1978 ◽  
Vol 100 (1) ◽  
pp. 16-24 ◽  
Author(s):  
L. J. Hart-Smith
Keyword(s):  
Failure Modes ◽  
Three Dimensional ◽  
Adhesive Bond ◽  
Structural Elements ◽  
Load Path ◽  
Stiffened Structures ◽  
Crack Tips ◽  
Complete Failure ◽  
Universal Applicability ◽  
Fast Fracture

This paper presents analysis procedures to be used for analyzing adhesively bonded structures containing cracks or discontinuities in the metal elements. The analyses are performed for a range of disbonds in each of four basic problems for stiffened structures: (1) stiffener broken at one station or with a finite length removed, sheet intact, (2) stiffener intact, sheet completely broken, (3) one-bay sheet crack, stiffeners intact, and (4) two-bay sheet crack, stiffener intact. Separate failure modes of disbond under shear loads, stiffener yield, and sheet fast fracture are investigated. The solutions are essentially planar (two-dimensional) and such three-dimensional effects as stiffener or sheet bending and peel stresses in the adhesives are not accounted for. The paper contains parametric studies for the governing variables and excellent agreement with test is demonstrated for the available test data (one-bay sheet crack). The analyses are approximate and not of universal applicability, but are simple to use with either pocket electronic calculators or digital computers. Known limitations of the theory are confined to situations in which the adhesive stresses are small and widespread rather than high and concentrated in a small identifiable zone adjacent to the discontinuity. The conconclusion drawn from the examples investigated is that disbonds can be initiated relatively easily at discontinuities in the metal structural elements, because the bond is very stiff, and that care is needed in proportioning the structural elements to control this potential problem. The analyses indicate also that the initial disbond is usually self-arresting and is not catastrophic. Higher loads are usually needed to propagate the disbond and, eventually, induce complete failure which is triggered by stiffener yield or fast fracture of the sheet at the crack tips. The sample cases point to the need to account for adhesive plasticity, stiffener yielding, and changes in load path as disbonds propagate.

A geosynthetic reinforcement solution to prevent the formation of localized sinkholes

2000 ◽  
Vol 37 (5) ◽  
pp. 987-999 ◽  
Author(s):  
P Villard ◽  
J P Gourc ◽  
H Giraud
Keyword(s):  
Surface Deformation ◽  
Numerical Study ◽  
Three Dimensional ◽  
Full Scale ◽  
Geosynthetic Reinforcement ◽  
The Road ◽  
Railway Line ◽  
Collapse Mechanisms ◽  
Full Scale Tests ◽  
Three Dimensional Finite Element

To prevent the appearance of localized sinkholes under roads and railway lines in areas at risk, a research program testing a geosynthetic reinforcement solution was carried out by a group of laboratories. The aim of the reinforcement is to limit surface deformation after the appearance of a sinkhole by making the surface settlement as compatible as possible with the geometrical safety criteria of the road or railway line until earth filling and repair works can be scheduled. Full-scale tests were carried out on reinforced, instrumented road and railway structures subjected to localized collapse. At the same time, a numerical study was carried out to gain a better understanding of the mechanisms involved (arch effect, membrane effect, and collapse mechanisms). The experimental results of the full-scale tests were analyzed and compared with the results of three-dimensional finite element modeling.Key words: localized sinkhole, karstic cavity, reinforcement, geosynthetic.

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