Discussion of Natalya N. Warner, Philippe E. Tissot, Storm flooding sensitivity to sea level rise for Galveston Bay, Texas, Ocean Engineering 44 (2012), 23-32
- Authors: Boretti, Alberto
- Date: 2012
- Type: Text , Journal article
- Relation: Ocean Engineering Vol. 55, no. (2012), p. 235-237
- Full Text: false
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- Description: Discussion of Natalya N. Warner, Philippe E. Tissot, Storm flooding sensitivity to sea level rise for Galveston Bay, Texas, Ocean Engineering 44 (2012), 23-32
Evaluation of slug flow-induced flexural loading in pipelines using a surrogate model
- Authors: Sultan, Ibrahim , Reda, Ahmed , Forbes, Gareth
- Date: 2013
- Type: Text , Journal article
- Relation: Journal of Offshore Mechanics and Arctic Engineering Vol. 135, no. 3 (2013), p. 8
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- Description: Slug flow induces vibration in pipelines, which may, in some cases, result in fatigue failure. This can result from dynamic stresses, induced by the deflection and bending moment in the pipe span, growing to levels above the endurance limits of the pipeline material. As such, it is of paramount importance to understand and quantify the size of the pipeline response to slug flow under given speed and damping conditions. This paper utilizes the results of an optimization procedure to devise a surrogate closed-form model, which can be employed to calculate the maximum values of the pipeline loadings at given values of speed and damping parameters. The surrogate model is intended to replace the computationally costly numerical procedure needed for the analysis. The maximum values of the lateral deflection and bending moment, along with their locations, have been calculated using the optimization method of stochastic perturbation and successive approximations ( SPSA). The accuracy of the proposed surrogate model will be validated numerically, and the model will be subsequently used in a numerical example to demonstrate its applicability in industrial situations. An accompanying spreadsheet with this worked example is also given.
- Description: C1
When is a subsea anchor required for a short pipeline/SCR system?
- Authors: Reda, Ahmed , McKee, Kristoffer , Howard, Ian , Sultan, Ibrahim
- Date: 2019
- Type: Text , Journal article
- Relation: International Journal of Pressure Vessels and Piping Vol. 171, no. (2019), p. 278-298
- Full Text: false
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- Description: Connection of floating production vessels to subsea pipelines requires careful consideration of the stresses placed on the steel catenary riser (SCR), subsea spool and pipeline end termination (PLET). Due to vessel motion, environmental conditions, flow conditions and pipeline temperature gradients during start-up/shut-down and operation, the forces on all sections of the subsea pipeline system may deviate from their static configurations. Pipeline risers, PLETs and spools have design limits that must not be exceeded in order to ensure the integrity of the pipeline/SCR system. The operational/dynamic loads on the pipeline/SCR system cause expansion and contraction of the pipeline at the riser and free end locations, and these also need to be kept within the pipeline system design limits. The most appropriate method to account for the pipeline system movement is to ensure the pipeline has sufficiently long run-out to accommodate the pipeline system loading or to provide anchoring locations for the pipeline section. This paper addresses, with examples and calculations, the criteria that must be considered during the design of the pipeline/SCR system to determine if hold-back anchors are needed and their optimum locations in the system. The criteria for the anchoring are valid for short pipelines with route bend and no lateral buckling.
Pipeline slug flow dynamic load characterization
- Authors: Reda, Ahmed , Forbes, Gareth , Sultan, Ibrahim , Howard, Ian
- Date: 2019
- Type: Text , Journal article
- Relation: Journal of Offshore Mechanics and Arctic Engineering Vol. 141, no. 1 (2019), p. 1-8
- Full Text: false
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- Description: Flow of gas in pipelines is subject to thermodynamic conditions which produces twophase bulks (i.e., slugs) within the axial pipeline flow. These moving slugs apply a moving load on the free spanning pipe sections, which consequently undergo variable bending stresses, and flexural deflections. Both the maximum pipeline stress and deflection due to the slug flow loads need to be understood in the design of pipeline spans. However, calculation of a moving mass on a free spanning pipeline is not trivial and the required mathematical model is burdensome for general pipeline design engineering. The work in this paper is intended to investigate the conditions under which simplified analysis would produce a safe pipeline design which can be used by practicing pipeline design engineers. The simulated finite element models presented here prove that replacing the moving mass of the slug by a moving force will produce adequately accurate results at low speeds where the mass of the slug is much smaller than the mass of the pipe section. This result is significant, as the assumption of point load simplifies the analysis to a considerable extent. Since most applications fall within the speed and mass ratio which justify employing this simplified analysis, the work presented here offers a powerful design tool to estimate fatigue stresses and lateral deflections without the need of expensive timeconsuming inputs from specialized practitioners.
3D Integrated numerical model for fluid-structures-seabed interaction (FSSI) : Elastic dense seabed foundation
- Authors: Jianhong, Ye , Jeng, Dong-Shen , Chan, Andrew , Wang, R. , Zhu, Q. C.
- Date: 2016
- Type: Text , Journal article
- Relation: Ocean Engineering Vol. 115, no. (2016), p. 107-122
- Full Text: false
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- Description: Economic losses and property damage due to the failure of offshore structures are huge each year in the world, under the attack of endless conventional wave, occasional tropical storms or typhoons, and possible tsunami. Wave-induced dynamics of offshore structures and their seabed foundation attract a great deal of attention from researchers and ocean engineers. Previous literature investigated the wave-structures-seabed interaction generally adopting 2D models and decoupled way. In this study, taking a caisson breakwater as the typical offshore structure, the simple linear interaction between ocean wave, a caisson breakwater and its poro-elastic seabed foundation is investigated by utilizing a three-dimensional integrated numerical model FSSI-CAS 3D. The numerical results indicate that FSSI-CAS 3D can effectively and sufficiently capture a variation of phenomena of wave-induced dynamics of offshore structures, and momentary liquefaction in its dense poro-elastic seabed foundation. This study demonstrates great promise of using the developed integrated numerical model in offshore industry to predict the dynamic response and stability of offshore structures by ocean engineers in design stage. © 2016 Elsevier Ltd. All rights reserved.
Pipeline walking and anchoring considerations in the presence of riser motion and inclined seabed
- Authors: Reda, Ahmed , Sultan, Ibrahim , Howard, Ian , Forbes, Gareth , McKee, Kristoffer
- Date: 2018
- Type: Text , Journal article
- Relation: International Journal of Pressure Vessels and Piping Vol. 162, no. (2018), p. 71-85
- Full Text: false
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- Description: Steel Catenary Risers (SCRs), are increasingly becoming an attractive option for many deepwater field developments. SCRs are typically used to transport fluids between floating production vessels and pipelines. Typical uses may also involve the transport of produced fluids from a subsea production system to a floating production vessel or the transport of gas or water for re-injection into the producing reservoirs. The floating production vessel on which the steel catenary riser is supported will be subject to motions caused by environmental loads, and influenced by the mooring system and other risers. Horizontal movement of the vessel causes changes in the riser catenary configuration in near, mean, and far positions. On the seabed, the riser is connected to a pipeline that extends for some distance from the riser touchdown point, to its tie-in point on a pipeline or other facility. Effective tension at the touchdown point is necessary to maintain the riser configuration which may cause the pipeline to walk in the axial direction. The development of axial walking is in part due to the pull experienced on the pipeline at the touchdown point from the SCR tension. In this paper, the results of the effective axial force and the pipeline end expansion using a finite element study are presented to highlight the effect that the changing SCR tension, combined with the thermal transients and a global seabed slope along the pipeline length, has on the pipeline walking. Additionally, the paper provides some guidance in regards to the selection of the optimum location for the hold-back anchors, to ensure that pipeline walking does not compromise the integrity of both the SCR and the pipeline system. In general, the results show that SCR bottom tension provides the dominant walking mechanism and can exceed the other walking mechanisms associated with thermal transients and seabed slope. For a straight short pipeline, in the range of 2–3 km, where there is no lateral buckling, it is recommended to install the anchor towards the PLET (Pipeline End Termination) and away from the SCR transition point.
Focusing on the patterns and characteristics of extraordinarily severe gas explosion accidents in Chinese coal mines
- Authors: Zhang, Jinjia , Cliff, David , Xu, Kaili , You, Greg
- Date: 2018
- Type: Text , Journal article
- Relation: Process Safety and Environmental Protection Vol. 117, no. (2018), p. 390-398
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- Description: Extraordinarily severe gas explosion accidents (ESGEAs) (thirty fatalities or more in one accident) have a high occurrence frequency in Chinese coal mines. There are 126 ESGEAs that occurred in China from 1950 to 2015, and they were investigated through statistical methods in this study to review the overall circumstances and to provide quantitative information on ESGEAs. Statistical characteristics about accident-related factors, such as gas accumulation, ignition sources, operating locations, accident time, coal mine regions and coal mine ownership, were assessed in this paper. The statistical analysis shows that disorganized ventilation fan management was the most frequent cause of gas accumulation in ESGEAs, while illegal blasting was the most prominent cause of the ignition source in ESGEAs. Furthermore, ESGEAs were found to occur frequently in certain provinces (e.g., Shanxi, Henan and Heilongjiang) and during November and December of the year. Moreover, most accidents and the largest death tolls generally occur in state-owned coal mines. Based on the results of statistical studies, some countermeasures were proposed in this study.
Statistical analysis the characteristics of extraordinarily severe coal mine accidents (ESCMAs) in China from 1950 to 2018
- Authors: Zhang, Jinjia , Xu, Kaili , Reniers, Genserik , You, Greg
- Date: 2020
- Type: Text , Journal article
- Relation: Process Safety and Environmental Protection Vol. 133, no. (2020), p. 332-340
- Full Text: false
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- Description: Extraordinarily severe coal mine accidents (ESCMAs) are characteristized by thirty fatalities or more in one accident. In this paper, such ESCMAs are analyzed using 188 cases which occurred in Chinese underground coal mines. The analysis shows that the number of ESCMAs and the death toll have decreased steadily over time. Gas explosions, mine water inrushes, and coal dust explosions are the three major types of ESCMAs. Among the causes of ESCMAs, inadequate implementation of safety measures, deliberate violations and electromechanical equipment faults are the three top causes of ESCMAs, accounting for 27.13 %, 21.81 %, and 15.96 % of incidences, respectively. Meanwhile, ESCMAs frequently occur in the heading face, especially gas explosions, mine water inrushes and coal and gas outbursts. Furthermore, ESCMAs reoccur often in certain provinces, such as Shanxi, Henan and Heilongjiang, and mostly during November and December in each year. The results of statistical studies have presented useful information for the prevention of ESCMAs in order to reduce the probability of such disastrous accidents. © 2019 Institution of Chemical Engineers
Design of subsea cables/umbilicals for in-service abrasion - part 1 : case studies
- Authors: Reda, Ahmed , Thiedeman, James , Elgazzar, Mohamed , Shahin, Mohamed , Sultan, Ibrahim , McKee, Kristoffer
- Date: 2021
- Type: Text , Journal article
- Relation: Ocean Engineering Vol. 234, no. (2021), p.
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- Description: Submarine cables play a vital role in a myriad of industries around the globe, including power transmission and communication. Failure of submarine cables can have significant economic and technical implications worldwide. Current design methods for submarine cables focus on the ultimate limit states that address the cables structural integrity and on-bottom stability. However, abrasion of the outer protective layers (i.e. yarn and extruded sheaths) can progressively lead to damage and failure of submarine cables when the integrity of the armour sheathing is compromised. This paper documents several case studies of severe abrasion of submarine cables/umbilicals and undertaken corrective measures. The paper also presents some guidelines to be considered in the design process of submarine cables concerning abrasion. The findings of this paper suggest that abrasion should be considered a limit state that must be addressed in the design process of submarine cables and umbilicals. A detailed analysis of the underlying abrasion failure mechanisms is presented and explained in a companion paper (i.e., Part II: Mechanisms). © 2021 Elsevier Ltd
Design of subsea cables/umbilicals for in-service abrasion - part 2 : mechanisms
- Authors: Reda, Ahmed , Elgazzar, Mohamed , Thiedeman, James , McKee, Kristoffer , Sultan, Ibrahim , Shahin, Mohamed
- Date: 2021
- Type: Text , Journal article
- Relation: Ocean Engineering Vol. 234, no. (2021), p.
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- Description: This paper is the second of two companion papers about the design of subsea cables/umbilicals for in-service abrasion. Several case studies of severe abrasion of submarine cables/umbilicals and corrective measures undertaken have been documented and presented in the first paper (Part I: Case Studies). The mechanisms of failure due to abrasion are explained in this paper. The effect of repeated lateral movement on LLDPE (linear low-density polyethylene) extruded outer sheaths of two cable samples was investigated. In the first test, a cable sample was displaced the equivalent of 12 km over a crushed mineral aggregate while in the second test, a cable was subjected to 3 km of displacement under conditions that replicated the touchdown point of a dynamic cable. The results of the first test indicated that the overall abrasion was low and acceptable. In the second test however, the outer sheath was completely worn through. The authors recommend the thickness of the outer sheath be increased for cables where uniform abrasion is expected, and high abrasion protection units be employed where localized abrasion is expected. Empirical data is provided to support these recommendations. © 2021 Elsevier Ltd