Risk-Based Inspection Planning for Mooring Chain

2004 ◽  
Vol 126 (3) ◽  
pp. 250-257 ◽  
Author(s):  
Jan Mathisen ◽  
Kjell Larsen
Keyword(s):  
Probabilistic Modelling ◽  
Structural Components ◽  
Inspection Planning ◽  
Single Chain ◽  
Chain Link ◽  
Northern North Sea ◽  
A Chain ◽  
Series Systems ◽  
Chain Links ◽  
Mooring Chain

The use of risk-based inspection planning for offshore structural components is becoming quite familiar. This paper describes an application of this technique to mooring chain. In many cases, the technique is based on probabilistic modelling of fatigue crack growth in the structural components, and updating of the failure probability on the basis of inspections. The extension of this basis from a single component to very many components is necessary to tackle series systems, such as mooring chain, where a fatigue fracture can arise in any chain link. The theoretical basis for the analysis is described, including details of the model for stochastic dependency between the chain links. Results are shown that compare failure probabilities for a single chain link and a chain segment. The effects of various levels of inspection coverage are illustrated. An example of a cost optimal inspection plan is developed for mooring chain on an FPSO in the northern North Sea.

Risk-Based Inspection Planning for Mooring Chain

2002 ◽  
Author(s):  
Jan Mathisen ◽  
Kjell Larsen
Keyword(s):  
Probabilistic Modelling ◽  
Structural Components ◽  
Inspection Planning ◽  
Single Chain ◽  
Chain Link ◽  
Northern North Sea ◽  
A Chain ◽  
Series Systems ◽  
Chain Links ◽  
Mooring Chain

The use of risk-based inspection planning for offshore structural components is becoming quite familiar. This paper describes an application of this technique to mooring chain. In many cases, the technique is based on probabilistic modelling of fatigue crack growth in the structural components, and updating of the failure probability on the basis of inspections. The extension of this basis from a single component to very many components is necessary to tackle series systems, such as mooring chain, where a fatigue fracture can arise in any chain link. The theoretical basis for the analysis is described, including details of the model for stochastic dependency between the chain links. Results are shown that compare failure probabilities for a single chain link and a chain segment. The effects of various levels of inspection coverage are illustrated. An example of a cost optimal inspection plan is developed for mooring chain on an FPSO in the northern North Sea.

Out-of-Plane Bending Testing of Chain Links

2005 ◽  
Author(s):  
Cecil Melis ◽  
Phillipe Jean ◽  
Pedro Vargas
Keyword(s):  
Empirical Relationship ◽  
Chain Link ◽  
Out Of Plane ◽  
Bending Stresses ◽  
Test Frame ◽  
Scale Test ◽  
Plane Bending ◽  
A Chain ◽  
Chain Links ◽  
Mooring Chain

Several mooring chains of an off-loading buoy failed after only 8 months of service. These chains were designed according to conventional fatigue assessment using API RP 2SK T-N curves to a fatigue life or 20 years with a factor of safety equal to 3 on life. Of particular interest is that the mooring chain failure underwent significant mooring chain motions that caused interlink rotations. Although traditionally neglected, these interlink rotations, when combined with significant chain tensions can cause bending stresses in the chain links. In this paper we identify a mechanism, here identified as Out-of-Plane Bending (OPB) that explains the extensive fatigue damage causing the mooring chains of the off-loading buoy to fail. A full scale test frame was constructed that has the capacity of applying inter-link rotation to a pre-tensioned chain. Although the test frame limits the number of links that can be tested together as a chain, a significant amount of testing was performed for the following chain sizes: 1. 81 mm Studded Grade R3S. 2. 107 mm Studdless Grade RQ3. 3. 124 mm Studless Grade R4. 4. 146 mm Studless Grade RQ4. Various pretension levels were used, with instrumentation to extract link angles and chain link stresses. In this paper the OPB mechanism is explained, and the test frame and results are presented. An empirical relationship is found to predict the OPB stresses in the chain links as a function of pretension and inter-link rotation. The OPB stress relationship obtained was applied to the failed mooring chain of the off-loading buoy with reasonable agreement. To comply with Single Buoy Moorings (SBM) requirements addressing publication of internal research, many of the graphs included in this paper have had the stress values removed from the y-axis. However, with SBM’s management approval, some numerical references to stress amplitudes remain in the text. Overall, this limitation does not detract from the study, trends are evident and relevant comparisons can be made.

Influence of Clearance on the Dynamics of Chain CVT Drives

2006 ◽  
Author(s):  
Nilabh Srivastava ◽  
Yi Miao ◽  
Imtiaz U. Haque
Keyword(s):  
Dynamic Performance ◽  
Suitable Model ◽  
Multibody Model ◽  
System A ◽  
Automotive Transmission ◽  
Chain Link ◽  
Variable Transmission ◽  
Coulomb Approximation ◽  
A Chain ◽  
Chain Links

A continuously variable transmission (CVT) is an emerging automotive transmission technology that offers a continuum of gear ratios between desired limits. The present research focuses on developing models to understand the influence of clearance on the dynamic performance of a chain CVT drive. Clearances may arise in such a CVT during the assembly process or during extensive continual operation of the system, which further leads to wear and failure of the system. A detailed planar multibody model of a chain CVT is developed in order to accurately capture the dynamics characterized by the discrete structure of the chain, which causes polygonal excitations in the system. A suitable model for clearance between the chain links is embedded into this multibody model of the chain CVT. Friction between the chain link and the pulley sheaves is modeled using continuous Coulomb approximation theory. The mathematical models, the computational scheme, and the results corresponding to different loading scenarios are discussed. The results discuss the influence of clearance parameters on the dynamic performance, the axial force requirements, and the torque transmitting capacity of a chain CVT drive.

scholarly journals STRESS ANALYSIS AND TOPOLOGY OPTIMIZATION OF A CHAIN BUCKET ELEVATOR USING ANSYS

2021 ◽  
Vol 61 (1) ◽  
pp. 292-306
Author(s):  
Edward Yin ◽  
Emmanuel M. Seckley ◽  
Evans Kesse Asiedu ◽  
Stephen Cobbinah
Keyword(s):  
Topology Optimization ◽  
Maximum Load ◽  
Maintenance And Repair ◽  
Ratchet Mechanism ◽  
Repair Costs ◽  
Chain Link ◽  
Bucket Elevator ◽  
A Chain ◽  
Time Required ◽  
Chain Links

A failure of conveyor chain links in a production process can cause unscheduled shutdowns, which increase the throughput time coupled with damaged buckets and chain links, which increase maintenance and repair costs. Since failures of conveyor chains are inevitable, this research aims to modify the design of the chain bucket elevator by incorporating a ratchet mechanism, which will prevent the chain bucket assembly from dropping to the bottom of the chain bucket elevator whenever there is a chain-link failure and also avoid the jamming of the bucket chain assembly against one another when dropping to the bottom of the elevator during failure. The number of damaged buckets and chains will be minimal, thereby reducing the maintenance and repair costs. Also, the time required for replacing the failed chain link will be reduced, which in turn, will reduce the down-time, thereby increasing the production rate. The ratchet mechanism, which can withstand a maximum load of 38.10 kN, comprises a toothed wheel, a pawl, and a spring. An analytical method was employed for the initial analysis and the results were verified using the FEM. Topology Optimization was carried out on the beam and lever with results showing a 20% and 26% weight reduction from the original, respectively. The stresses induced in the beam and lever increased significantly by 36% and 47 %, respectively, because of the optimization, however, they remained within the acceptable limits.

Dynamics of CVT Chain Drives: Mechanichal Model and Verification

1997 ◽  
Author(s):  
Jürgen Srnik ◽  
Friedrich Pfeiffer
Keyword(s):  
Power Transmission ◽  
Contact Forces ◽  
Coulomb’S Friction ◽  
Joint Forces ◽  
Chain Link ◽  
Frictional Forces ◽  
Contact Situation ◽  
A Chain ◽  
Chain Drives ◽  
Chain Links

Abstract This paper deals with the dynamics of continuously variable (CVT) chain drives. According to the discrete structure of the chain, which causes the polygonal actions, the mechanical model contains each chain link and pulley as a separate body. While a chain link is part of a strand, only joint forces including friction act on the chain links, whereas in the contact situation additional impulsive and frictional forces in the contact zones between the chain link’s rocker pins and the tapered surfaces of the cone pulleys have to be taken into account. For the calculation of the contact forces Coulomb’s friction law as well as a time sparing continuous approximation are applied. Simulation results show the influence of the cone pulley’s deformation on the power transmission. They also show the repercussion of the polygonal action. Furthermore the chain’s pitch influence on the vibrational behavior of the transmission is discussed. A comparison of calculated and measured tensional forces verifies the model presented.

FEA of Out-of-Plane Fatigue Mechanism of Chain Links

2005 ◽  
Author(s):  
Pedro Vargas ◽  
Philippe Jean
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Factor Of Safety ◽  
Finite Element Models ◽  
Chain Link ◽  
Out Of Plane ◽  
Bending Stresses ◽  
Chain Links ◽  
Mooring Chain ◽  
Loading Procedure

Several mooring chains of an off-loading buoy failed after only 8 months of service. These chains were designed according to conventional fatigue assessment using API RP 2SK T-N curves to a fatigue life of 20 years with a factor of safety equal to 3 on life. Of particular interest is that the mooring chain failure underwent significant mooring chain motions that caused interlink rotations. Although traditionally neglected, these interlink rotations, when combined with significant chain tensions can cause bending stresses in the chain links. In this paper we identify a mechanism, here identified as Out-of-Plane Bending (OPB) that explains the extensive fatigue damage causing the mooring chains of the off-loading buoy to fail. A previous paper [4] presented experimental results of applying inter-link rotation to a pre-tensioned chain. Various pretension levels were used, with instrumentation to extract link angles and chain link stresses. In this paper, the physics of the OPB mechanism is examined through finite element models of the 124mm chain link tests. The various modes of interlink rotation are examined. The proof loading procedure that the chain undergoes at manufacture is identified as a likely cause for creating a tightly mated surface that is conducive to activating the OPB mechanism. To comply with Single Buoy Moorings (SBM) requirements addressing publication of internal research, many of the graphs included in this paper have had the stress values removed from the y-axis. However, with SBM’s management approval, some numerical references to stress amplitudes remain in the text. Overall, this limitation does not detract from the study, trends are evident and relevant comparisons can be made.

LIPOPOLYSACCHARIDE-SENSITIVE SERINE-PROTEASE ZYMOGEN (FACTOR C) OF LIMULUS HEMOCYTES: IDENTIFICATION AND ALIGNMENT OF PROTEOLYTIC FRAGMENTS PRODUCED DURING THE ACTIVATION SHOW THAT IT IS A NOVEL TYPE OF SERINE-PROTEASE

1987 ◽  
Author(s):  
F Tokunaga ◽  
T Miyata ◽  
T Nakamura ◽  
T Morita ◽  
S Iwanaga
Keyword(s):  
Serine Protease ◽  
Heavy Chain ◽  
Light Chain ◽  
Interleukin 2 ◽  
Coagulation Factor ◽  
Clotting Factor ◽  
Single Chain ◽  
Terminal Sequence ◽  
A Chain ◽  
Factor C

Limulus clotting factor, factor C, is a lipopolysaccharide (LPS)-sensitive serine-protease zymogen present in the hemocytes. It is a two-chain glycoprotein (M.W. = 123,000) composed of a heavy chain (M.W. = 80,000) and a light chain (M.W. = 43,000) T. Nakamura et al. (1986) Eur. J. Biochem. 154, 511-521 .On further studies of this zymogen, a single-chain factor C (M.W. = 123,000) was identified by Western blotting technique. The heavy chain had an NH2-terminal sequence of Ser-Gly-Val-Asp-, which was consistent with the NH2-terminal sequence of the single-chain factor C, indicating that the heavy chain is located in the NH2-terminal part of the zymogen. The light chain had an NH22-terminal sequence of Ser-Ser-Gln-Pro-. Incubation of the two-chain zymogen with LPS resulted in the cleavage of a Phe-Ile bond between residues 72 and 73 of the light chain. Concomitant with this cleavage, the A (72.amino acids) and B chains derived from the light chain was formed. The complete amino acid sequence of the A chain was determined by automated Edman degradation. The A chain contained a typical segment which is similar structuraly to those a family of repeats in human β2 -glycoprotein I, complement factors B, Clr, Cls, H, C4b-binding protein, 02, coagulation factor XIII b subunit, haptoglobin a chain, and interleukin 2 receptor. The NH2-terminal sequence of the B chain was Ile-Trp-Asn-Gly-. This chain contained the serine-active site sequence of -ASP-Ala-Cys-Ser-Gly-Asp-SER-Gly-Gly-Pro-.These results indicate that limulus factor C exists in the hemocytes in a single-chain zymogen form and is converted to an active serine-protease by hydrolysis of a specific Phe-Ile peptide bond. The correlation of limulus factor C and mammalian complement proteins was also suggested.

scholarly journals Oceanithermus desulfurans sp. nov., a novel thermophilic, sulfur-reducing bacterium isolated from a sulfide chimney in Suiyo Seamount

2004 ◽  
Vol 54 (5) ◽  
pp. 1561-1566 ◽  
Author(s):  
Koji Mori ◽  
Takeshi Kakegawa ◽  
Yowsuke Higashi ◽  
Ko-ichi Nakamura ◽  
Akihiko Maruyama ◽  
...  
Keyword(s):  
Sequence Similarity ◽  
Growth Conditions ◽  
Cellular Fatty Acid ◽  
Rrna Gene ◽  
Good Growth ◽  
Chain Link ◽  
Circular Structure ◽  
Hybridization Test ◽  
A Chain ◽  
Cellular Fatty Acid Profile

A novel thermophilic, microaerophilic, sulfur-reducing bacterium designated strain St55BT was isolated from a sulfide chimney in the hydrothermal field of Suiyo Seamount (Izu-Bonin Arc, Western Pacific). Cells of the isolate were rod-shaped and tended to form a chain-link circular structure (a rotund body) at exponential phase under good growth conditions. The isolate was a chemoheterotroph requiring yeast extract for growth. Although strain St55BT used oxygen as an electron acceptor, it could not form colonies in an oxygen concentration of more than 5 % (v/v). The isolate also used nitrate, nitrite or elemental sulfur in the absence of oxygen. A phylogenetic analysis based on the 16S rRNA gene sequence revealed that the isolate was closely related to Oceanithermus profundus, belonging to the phylum ‘Deinococcus–Thermus’ (sequence similarity 99·5 %). However, strain St55BT differed from O. profundus in terms of usage of electron donors, cellular fatty acid profile and DNA G+C content. In addition, a DNA–DNA hybridization test indicated low relatedness between the isolate and O. profundus. For the reasons given above, the name Oceanithermus desulfurans sp. nov. is proposed for strain St55BT (=NBRC 100063T=DSM 15757T).

scholarly journals Adaptable legged-magnetic adhesion tracked wheel robotic platform for misaligned mooring chain climbing and inspection

2018 ◽  
Vol 45 (5) ◽  
pp. 634-646 ◽  
Author(s):  
Mahesh Dissanayake ◽  
Tariq Pervez Sattar ◽  
Shehan Lowe ◽  
Ivan Pinson ◽  
Tat-hean Gan
Keyword(s):  
Offshore Structures ◽  
Daily Basis ◽  
Robotic Platform ◽  
Destructive Testing ◽  
Content Type ◽  
Integrity Assessment ◽  
Human Operators ◽  
Chain Links ◽  
Mooring Chain ◽  
Magnetic Adhesion

Purpose Mooring chains used to stabilise offshore floating platforms are often subjected to harsh environmental conditions on a daily basis, i.e. high tidal waves, storms, etc. Therefore, the integrity assessment of chain links is vital, and regular inspection is mandatory for offshore structures. The development of chain climbing robots is still in its infancy due to the complicated climbing structure presented by mooring chains. The purpose of this paper is to establish an automated climbing technique for mooring chain inspection. Design/methodology/approach This paper presents a Cartesian legged tracked-wheel crawler robot developed for mooring chain inspection. The proposed robot addresses the misalignment condition of the mooring chains which is commonly evident in in situ conditions. Findings The mooring chain link misalignment is investigated mathematically and used as a design parameter for the proposed robot. The robot is validated with laboratory-based climbing experiments. Practical implications Chain breaking can lead to vessel drift and serious damage such as riser rupture, production shutdown and hydrocarbon release. Currently, structural health monitoring of chain links is conducted using either remotely operated vehicles which come at a high cost or by manual means which increase the danger to human operators. The robot can be used as a platform to convey equipment, i.e. tools for non-destructive testing/evaluation applications. Originality/value This study has upgraded a previously designed magnetic adhesion tracked-wheel mooring chain climbing robot to address the misalignment issues of operational mooring chains. As a result of this study, the idea of an orthogonally placed Cartesian legged-magnetic adhesion tracked wheel robotic platform which can eliminate concerns related to the misaligned mooring chain climbing has been established.

scholarly journals The Structure of Amyloid Versus the Structure of Globular Proteins

2020 ◽  
Vol 21 (13) ◽  
pp. 4683 ◽  
Author(s):  
Piotr Fabian ◽  
Mateusz Banach ◽  
Katarzyna Stapor ◽  
Leszek Konieczny ◽  
Magdalena Ptak-Kaczor ◽  
...  
Keyword(s):  
Gaussian Distribution ◽  
Experimental Studies ◽  
Data Bank ◽  
Globular Proteins ◽  
Hydrophobic Core ◽  
Single Chain ◽  
Spherical Micelle ◽  
Globular Structure ◽  
A Chain ◽  
High Level

The issue of changing the structure of globular proteins into an amyloid form is in the focus of researchers' attention. Numerous experimental studies are carried out, and mathematical models to define the essence of amyloid transformation are sought. The present work focuses on the issue of the hydrophobic core structure in amyloids. The form of ordering the hydrophobic core in globular proteins is described by a 3D Gaussian distribution analog to the distribution of hydrophobicity in a spherical micelle. Amyloid fibril is a ribbon-like micelle made up of numerous individual chains, each representing a flat structure. The distribution of hydrophobicity within a single chain included in the fibril describes the 2D Gaussian distribution. Such a description expresses the location of polar residues on a circle with a center with a high level of hydrophobicity. The presence of this type of order in the amyloid forms available in Preotin Data Bank (PDB) (both in proto- and superfibrils) is demonstrated in the present work. In this system, it can be assumed that the amyloid transformation is a chain transition from 3D Gauss ordering to 2D Gauss ordering. This means changing the globular structure to a ribbon-like structure. This observation can provide a simple mathematical model for simulating the amyloid transformation of proteins.

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