Williams D.,Galway Technology Park
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2015
In many harsh environment or high current regions (e.g. West of Shetlands, East Africa and GoM) wellhead fatigue during drilling or workover activities can be a major concern. As a result extensive wellhead and conductor fatigue assessments are required in order to predict likely fatigue damage prior to landing the BOP on to the wellhead. These pre-drilling or predictive studies are based on a number of assumptions regarding actual environmental and soil conditions. In addition the uncertainty associated with the input data requires safety factors of 10 and 20 for wave and VIV effects respectively. As a result of these assumptions the predicted levels of fatigue damage to the wellhead may be highly conservative. In cases where wellhead and conductor fatigue life is a concern the operator may choose to deploy motion monitoring systems on the BOP stack so that actual fatigue loads recorded during drilling can be calculated. These systems can be configured to provide 'real-Time' updates on fatigue damage accumulation or can be used to record data for 'post- drilling' assessment. In each case the methodology applied to calculate stresses at fatigue hotspots is critical to the calculation of overall fatigue damage. The calculation of fatigue loads based on measured data is typically carried out by applying the measured BOP motions to a global finite element model of the drilling riser and wellhead system. However due to the large amounts of data involved this can be a very time consuming exercise and is not conducive to 'real-Time' presentation of results (e.g. for on-board systems). A proposed solution to this problem is to develop stress transfer functions (STFs) that relate BOP motion to stresses at critical fatigue hotspots. Thus 'real-Time' BOP motions and be instantly converted to 'real-Time' stresses. However, as is outlined in this paper, the frequency content of the system response can have a significant impact on the levels of stress calculated. If frequency dependent response is not accounted for a significant under-prediction in fatigue loads may occur. The objective of this paper is to outline a detailed methodology to derive STFs for critical fatigue hotspots in the wellhead and conductor. This methodology accounts for capturing the non-linear frequency dependence of the system and incorporating this into the STFs. In addition a methodology for rapidly calculating 'real-Time' fatigue damage accumulation in the wellhead and conductor system and presenting this data on-board is also outlined. © 2015 by ASME.
Kennedy M.,Sustainable Energy Authority of Ireland |
Dinh V.-N.,Galway Technology Park |
Dinh V.-N.,Trinity College Dublin |
Basu B.,Trinity College Dublin
Journal of Cleaner Production | Year: 2016
Through a modelling-based contribution, this paper critically reviews and explores the impact of low carbon heat policies to induce technological policy development. The paper interrogates an Irish government funded sustainable energy financed scheme (the 'Greener Homes Scheme'), launched in 2006 and aimed at the deployment of low carbon technology in the residential sector. This paper analyses 31,560 technology installations supported under this scheme and it utilises artificial neural network modelling as a method of better analysing and understanding the effects, relationships and dependencies that influence consumer decision making and responses to new technological policies. It is responding to a perceived limited understanding of the variables that influence a wider adoption of low carbon technologies and the opportunities and potential that could result in a wider appreciation of the broader impact of market barriers. It builds up on the artificial neural networks modelling work, explores its application in pattern recognition and interprets its influence in predicting customer behaviour. The paper provides an enhanced understanding of the various factors that influence consumer selection of one low carbon technology over another. Evaluation of the results revealed that the developed artificial neural network model (generic 7-6-4 neurons layered architecture) is the most appropriate tool and suitable network in predicting indices, based on certain social conditions, on the choice of certain low carbon technologies. © 2015 Elsevier Ltd. All rights reserved.
Holdt S.L.,Technical University of Denmark |
Kraan S.,Galway Technology Park
Journal of Applied Phycology | Year: 2011
Seaweed is more than the wrap that keeps rice together in sushi. Seaweed biomass is already used for a wide range of other products in food, including stabilising agents. Biorefineries with seaweed as feedstock are attracting worldwide interest and include low-volume, high value-added products and vice versa. Scientific research on bioactive compounds in seaweed usually takes place on just a few species and compounds. This paper reviews worldwide research on bioactive compounds, mainly of nine genera or species of seaweed, which are also available in European temperate Atlantic waters, i. e. Laminaria sp., Fucus sp., Ascophyllum nodosum, Chondrus crispus, Porphyra sp., Ulva sp., Sargassum sp., Gracilaria sp. and Palmaria palmata. In addition, Undaria pinnatifida is included in this review as this is globally one of the most commonly produced, investigated and available species. Fewer examples of other species abundant worldwide have also been included. This review will supply fundamental information for biorefineries in Atlantic Europe using seaweed as feedstock. Preliminary selection of one or several candidate seaweed species will be possible based on the summary tables and previous research described in this review. This applies either to the choice of high value-added bioactive products to be exploited in an available species or to the choice of seaweed species when a bioactive compound is desired. Data are presented in tables with species, effect and test organism (if present) with examples of uses to enhance comparisons. In addition, scientific experiments performed on seaweed used as animal feed are presented, and EU, US and Japanese legislation on functional foods is reviewed. © 2011 Springer Science+Business Media B.V.
Williams D.,Galway Technology Park |
Ashton P.,National University of Ireland
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE | Year: 2014
As has been noted in industry publications and conferences in the recent past the use of more modern deepwater capable 5th and 6th generation semisubmersible drilling rigs in relatively shallow water applications (when compared to design water depth) is likely to become more commonplace. Water depths of 500m or less will necessitate the use of mooring systems in order to maintain position close to the well centre whilst drilling. For fatigue assessments of moored MODUs, the current industry practice to estimate fatigue damage in the drilling riser and the wellhead, using global riser analysis techniques, is to consider both wave and VIV fatigue effects. Standard wave fatigue analysis considers two key response parameters, firstly the impact of the hydrodynamic loading on the riser joints due to drag forces, inertia and added mass effects, and secondly the effects of vessel motions on the riser system and wellhead loading. Standard practice for wave fatigue analysis is to consider only first order motion effects as described by the vessel RAO (response amplitude operator). However, for a moored MODU low frequency (100s-200s period) vessel response can have a significant impact on the overall vessel motions. The actual response and magnitude of MODU motion will be influenced by the size and displacement of the vessel in addition to the configuration of the mooring system. First order lateral motions for a semisubmersible tend to increase as wave period is increased and therefore at lower periods first order motions can be quite low. However, the opposite can be said of wave drift forces that contribute to second order response. Although the wave drift forces are largest for lower wave periods, these low period drift forces have a significant influence on the resulting long period second order response of a moored MODU. This has important implications for drilling riser and wellhead fatigue analysis as in many cases the critical seastates for fatigue damage are low period seastates with a large number of occurrences. Thus the current global analysis techniques for fatigue calculations may lead to an underestimation of fatigue damage contribution from low period seastates. The purpose of this paper is to present the key conclusions and findings of a study carried out in order to determine the effects of low frequency moored MODU motions on wellhead fatigue. These results are derived from a case study of a moored 6th generation semi-submersible drilling vessel in 500m water depth. Copyright © 2014 by ASME.
Calvey D.,Galway Technology Park |
Mee L.,National University of Ireland
Journal of Renal Care | Year: 2011
The phenomenon of experiencing life dependent on haemodialysis is infinitely multi-faceted. It effects all aspects of people's lives, and not only their lives, but those of the people around them. Busy dialysis units often do not have time to explore these effects on the lives of their patients outside the clinical setting. Aims: The aim of this qualitative study was to step into the lives of seven patients once they were outside the dialysis unit. Method: Seven chronic haemodialysis patients were selected and interviewed using an in-depth semi-structured approach, following the philosophy of Heidegger. Data was analysed using Colaizzi's seven-stage process. Results: The strongest common theme emerged through descriptions of the patient's 'Sense of Self', within which emerged sub-themes; The Future Self, The Living Self, The Mortal/Fragile Self and The Growing/Learning Self. These were further explored and related back to importance of awareness of such findings within the renal haemodialysis practice setting. © 2011 European Dialysis and Transplant Nurses Association/European Renal Care Association.