National Institute of Ocean Technology

Pallikaranai, India

National Institute of Ocean Technology

Pallikaranai, India
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Vedachalam N.,National Institute of Ocean Technology | Ramadass G.A.,National Institute of Ocean Technology
Applied Ocean Research | Year: 2017

A reliable Dynamic Positioning (DP) system is the key requirement for critical offshore activities. This paper presents the quantitative reliability assessment for offshore multi-megawatt capacity electric DP systems based on the present technological maturity and the offshore industry-reported component failure rates. It is identified that the International Maritime Organization defined DP1, DP2 DP3 architectures with fully redundant power generators and electric variable speed thrusters could have mean time to fail periods of 0.3, 2.1 and 2.5 years respectively. In the analyzed DP2 architecture, the power generation cum management system, the computer control cum sensors system and the thruster systems contribute to 17%, 42%, and 41% of the total DP system failures. The results presented could be used for reliability-centered design and maintenance planning of multi megawatt capacity DP systems. © 2017 Elsevier Ltd

Mohammed Fayaz A.,University of Madras | Girilal M.,University of Madras | Venkatesan R.,National Institute of Ocean Technology | Kalaichelvan P.T.,University of Madras
Colloids and Surfaces B: Biointerfaces | Year: 2011

Metal nanoparticles, in general, and gold nanoparticles, in particular, are very attractive because of their size- and shape-dependent properties. Biosynthesis of anisotropic gold nanoparticles using aqueous extract of Madhuca longifolia and their potential as IR blockers has been demonstrated. The tyrosine residue was identified as the active functional group for gold ion reduction. These gold nanoparticles were characterized by of UV-Vis spectrophotometer, FTIR, TEM and HrTEM. The presence of proteins was identified by FTIR, SDS-PAGE, UV-Vis and fluorescence spectroscopy. The micrograph revealed the formation of anisotropic gold nanoaprticles. The biologically synthesized gold nanotriangles can be easily coated in the glass windows which are highly efficient in absorbing IR radiations. © 2011 Elsevier B.V.

Inbakandan D.,Sathyabama University | Inbakandan D.,Annamalai University | Venkatesan R.,National Institute of Ocean Technology | Ajmal Khan S.,Annamalai University
Colloids and Surfaces B: Biointerfaces | Year: 2010

The growing trend of exploring bacteria, fungi, actinomycetes and plant materials for the biosynthesis of nanoparticles is considered as eco friendly and a green technological approach. In this backdrop the present study reports the synthesis of gold (Au) nanoparticles from gold precursor using the extract derived from the marine sponge, Acanthella elongata (Dendy, 1905) belonging to the primitive phylum Porifera. Water-soluble organics present in the marine sponge extract were mainly responsible for the reduction of gold ions to nano-sized Au particles. The sponge extract added to 10-3M HAuCl4 aqueous solution at 45°C changed to pinkish ruby red color solution and confirm the bioreduction within 4h with continuous stirring. UV-visible spectrum of the aqueous medium containing gold nanoparticles showed a peak around 526nm. High-resolution transmission electron micrographs (HR-TEM) confirmed the monodispersed and spherical shaped with the size ranges from 7 to 20nm, however a maximum number of particles were in 15nm diameter. Through Fourier transform infrared spectroscopy (FT-IR) analysis, the reducing agent in the marine sponge extract was identified which is attributed for the biosynthesis of gold colloids. The XRD analysis respects the Bragg's law and confirmed the crystalline nature of the gold nanoparticles. © 2010 Elsevier B.V.

Jain P.,Indian Institute of Technology Bombay | Deo M.C.,Indian Institute of Technology Bombay | Latha G.,National Institute of Ocean Technology | Rajendran V.,National Institute of Ocean Technology
Ocean Modelling | Year: 2011

Operational activities in the ocean like planning for structural repairs or fishing expeditions require real time prediction of waves over typical time duration of say a few hours. Such predictions can be made by using a numerical model or a time series model employing continuously recorded waves. This paper presents another option to do so and it is based on a different time series approach in which the input is in the form of preceding wind speed and wind direction observations. This would be useful for those stations where the costly wave buoys are not deployed and instead only meteorological buoys measuring wind are moored. The technique employs alternative artificial intelligence approaches of an artificial neural network (ANN), genetic programming (GP) and model tree (MT) to carry out the time series modeling of wind to obtain waves. Wind observations at four offshore sites along the east coast of India were used. For calibration purpose the wave data was generated using a numerical model. The predicted waves obtained using the proposed time series models when compared with the numerically generated waves showed good resemblance in terms of the selected error criteria. Large differences across the chosen techniques of ANN, GP, MT were not noticed. Wave hindcasting at the same time step and the predictions over shorter lead times were better than the predictions over longer lead times. The proposed method is a cost effective and convenient option when a site-specific information is desired. © 2010.

Low temperature thermal desalination (LTTD) process involves flash evaporation of a seawater at 28–29°C in a single-stage evaporator maintained at a vacuum of around 25–27 m bar (abs). The seawater was splashed inside an evaporator through a 0.1 m diameter upward facing nozzles of around 24 nos arranged evenly throughout the evaporator and generated vapour was condensed in the shell and tube condenser using cooling water available at 12–13°C sucked from the deep sea through a long HDPE pipe. The main objective of this study was to find out the effect of geometry of the upward facing nozzles on the flash evaporation rate as well as on the non-equilibrium temperature difference (NETD) of the flashing process. Two different spout nozzle geometries with 0.37–0.87 m height were used in the experiment. The study indicated that the flashing rate increased by 0.9% (average) and and the NETD (Two – Tsat) decreased by 0.7°C (average), respectively, when nozzle height was increased by 0.87 m. Mechanism that controlled these two factors were identified and discussed in this paper. Drawbacks of 0.37 m nozzle geometry was also discussed. It was reported in literature that 4% yield ratio was obtained for a nozzle injection pressure of 1 bar for a similar desalination process. But in the present study, a maximum of 1.12% yield ratio was obtained with a nozzle injection pressure of around 0.17 bar. In this work,the effect of the process parameters on the liquid flashing in a LTTD desalination process was investigated and discussed. In order to fine tune the evaporator design for the future LTTD plants, the experimental results of flash evaporation were compared with two mathematical models obtained from the literature. While comparing the results, it was observed that the model which used actual heat (Twi – Two) made a good agreement with the experimental data compared to the other model that used superheat (Twi – Tsat). From the experimental study, it was observed that the NETD (i.e. thermal loss) measured was found to be higher than the predicted value. The reason that caused the difference in the NETD value was investigated and discussed. Suitable suggestions to reduce these NETD in the flashing process were also presented. © 2016 Balaban Desalination Publications. All rights reserved.

Vedachalam N.,National Institute of Ocean Technology | Ramadass G.A.,National Institute of Ocean Technology | Atmanand M.A.,National Institute of Ocean Technology
Applied Ocean Research | Year: 2014

Human Occupied Vehicle operations are required for deep water activities such as high resolution bathymetry, biological and geological surveys, search activities, salvage operations and engineering support for underwater operations. As this involves direct human presence, the system has to be extremely reliable. Based on applicable standards, reliability analysis is done on 5 key representative functions with the assumption that the submersible is utilized for ten deep water missions per year. Analysis is done on the results obtained to find the influence of the subsystems on the reliability of the overall submersible. Analysis include, influence of battery technologies and reliability centered battery and hydraulic system configurations. Dependence of seal sizes and seal seat surface finish on the leak tight integrity of the personnel sphere is also discussed. It is found that for submersible housing 75. kWh energy storage batteries, the probability of failure of the hard tank buoyancy ascent function with lead acid batteries configured for 300. V terminal voltages and non-redundant hydraulic configuration is 37.74%. The probability of failure can be reduced to 5.24% with lead acid batteries with terminal voltage configured to 120. V and with redundant hydraulic configuration. The results presented shall serve as a model for designers to arrive at the required trade-off between the capital expenditure and the required reliability. © 2014 Elsevier Ltd.

Subramoniam T.,National Institute of Ocean Technology
Fisheries Science | Year: 2011

Crustaceans produce complex yolk proteins to meet the substrate and energy requirements of embryonic development. Early electron microscopic investigations point to a biphasic yolk synthesis, first within the ovary, followed by heterosynthesis at extra-ovarian sites. Recent advances in molecular techniques have enhanced our understanding of the genetic control of yolk synthesis in crustaceans. Amino acid sequencing of crustacean vitellogenin (Vg) has enabled the elucidation of the cDNA sequence associated with it, the identification of genes, and the examination of their expression patterns in different tissues. Yolk processing in crustaeans involves cleavage of the pro-Vg at consensus sites by subtilisin-like endoproteases within the hepatopancreas, hemolymph and oocytes. The structural elucidation of crustacean yolk proteins, as well as the comparison of amino acid sequences of vitellogenins from various crustacean species, has revealed molecular phylogenetic relationships not only among them but also with other large lipid transfer lipoproteins of disparate function. The combinatorial effects of eyestalk neuropeptides and a variety of trophic hormones achieve the hormonal coordination of molting and reproduction. Biogenic amines secreted by the central nervous system may also play an integrative role by stimulating neuropeptide secretion. © 2010 The Japanese Society of Fisheries Science.

Ashokan M.,National Institute of Ocean Technology | Latha G.,National Institute of Ocean Technology | Ramesh R.,Anna University
Applied Acoustics | Year: 2015

Ocean ambient noise time series data were measured in shallow waters off the East coast of India from 09/12/2011 to 20/01/2012 and off the West coast of India from 16/05/2012 to 03/07/2012 at around 30 m ocean depth using hydrophones placed at 15 m depth in the mid water column. The measurements of wind and rain were recorded by an anemometer and precipitation type rain gauge mounted on a buoy. The objective of this work is to analyse the ambient noise caused by rain and determining the rain parameters such as rain drop size, rain fall rate, terminal velocity, impact angle, etc. This is the first time such open sea measurements of noise have been made in Indian seas along with environmental parameters and influence of rain on ambient noise field is studied. © 2014 Elsevier Ltd. All rights reserved.

Narayanaswamy V.,National Institute of Ocean Technology
Underwater Technology | Year: 2014

Reliable power supply is required for operating subsea installations, such as enhanced oil recovery systems, tidal power generator systems and benthic environment monitoring stations. Electrical and electronic systems need to be operated inside pressure-rated or pressure-compensated enclosures so as to protect them from external seawater and hydrostatic pressure. Such enclosures are nitrogen filled, partially oil filled, fully oil filled or pressure compensated. System breakdowns lead to huge production losses and loss of critical environmental data. Reliability and, hence, the useful life of the internal systems depend mainly on the internal ambient temperature and relative humidity levels. The present paper discusses the need for efficient thermal and humidity management, methods currently adopted in the industry and their limitations in long-term operation. Solutions to carry out effective thermal and humidity management in future subsea electric systems, with the objective of reduced maintenance over the design lifetime of the system, are discussed. The proposed thermal management techniques include use of static fans, thermoelectric coolers, acoustic-based heat transfer and bio-fouling control methods. Proposed humidity management techniques include thermo-siphon-based water removal, and in situ subseabased molecular sieve oil filtration. Further, the advantages of pressure compensation in overcoming the thermal and enclosure structural challenges are explained. The ongoing global efforts in the development of pressure-tolerant systems, significant findings on the component behaviour to pressure and the need for accelerating pressure-tolerant electronic developments are discussed.

Narayanaswamy V.,National Institute Of Ocean Technology
Applied Ocean Research | Year: 2013

This paper reviews the major challenges involved in reliable electric power delivery to remote deep water enhanced oil recovery (EOR) systems. As the oil well matures, top side based booster systems are not economical, and hence, subsea based booster systems are required. Such EOR processes require subsea systems to be operated at varying power and voltage levels, and this requires establishing subsea power stations with long tiebacks from the shore. Subsea stations carry out safe voltage step-down, distribution and conversion of electrical power in the order of mega watts. Breakdowns in subsea based EOR systems lead to huge production losses, and system retrieval for repair and maintenance is very costly and time consuming, and therefore systems need to be highly reliable. This paper describes the technical challenges involved in subsea variable speed motor drives, long step out power transmission, subsea energy storage requirements for safe start up and emergency shutdown, thermal and humidity management inside pressure rated enclosures, fault localization, pressure tolerant electronics and bio-fouling. Emerging advancements in electrical, power electronic, power transmission, energy storage and packaging technologies are reviewed, giving the confidence that the present technical maturity would be able to drive the development of reliable subsea based EOR systems. © 2013 Elsevier Ltd.

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