Improved Structural Integrity for Arctic Designs by Ignition Isolation Control

2011 ◽  
Author(s):  
Joar Dalheim ◽  
Sverre Nodland ◽  
Jan Pappas
Keyword(s):  
Structural Integrity ◽  
Safety Issue ◽  
Cold Climate ◽  
Working Environment ◽  
Ignition Source ◽  
The Arctic ◽  
Process Equipment ◽  
Mechanically Ventilated ◽  
Design Loads ◽  
Extensive Program

The harsh environment of the arctic requires specialized safety solutions. One main safety issue in the arctic is the need for more enclosed modules. Enclosed modules are used for two reasons; to prevent ice and snow to expose the process equipment; and to prevent the cold climate to impose an unduly harsh working environment for operators. The enclosed mechanically ventilated process modules are different from the open naturally ventilated process modules that are normally used in offshore facilities. The explosion safety performance of the non-standard mechanically ventilated process modules has therefore been studied in detail through an extensive program of CFD simulations. It is seen that mechanically ventilated modules has explosion risk drivers that are distinctly different from risk drivers in naturally ventilated modules. It is seen that the ignition source isolation efficiency is significantly more important for confined modules than for standard naturally ventilated modules. The explosion design loads are therefore strongly depending on the ignition source isolation efficiency. Isolation control, and its impact on the explosion design loads, is discussed in this paper. The presented conclusions are of high importance in future developments in arctic climate.

Explosion Safety Drivers for Arctic Platform Designs

2012 ◽  
Author(s):  
Joar Dalheim ◽  
Sverre Nodland ◽  
Jan Pappas
Keyword(s):  
Safety Issue ◽  
Arctic Region ◽  
Cold Climate ◽  
Working Environment ◽  
The Arctic ◽  
Process Equipment ◽  
Main Process ◽  
Explosion Safety ◽  
Mechanically Ventilated ◽  
Explosion Risk

The unique and harsh environment of the arctic region requires specialized process area designs and safety solutions. One main process safety issue in the arctic is the need for more enclosed modules. Enclosed modules are used for two reasons; to prevent ice and snow to expose the process equipment; and to prevent the cold climate to impose an unduly harsh working environment for operators. The enclosed mechanically ventilated process modules are different from the open naturally ventilated process modules that are normally used in offshore facilities. The explosion safety performance of the non-standard mechanically ventilated process modules has therefore been studied in detail through several extensive programs of CFD simulations; see [1], [2] and [3]. It is seen that confined and mechanically ventilated modules has explosion risk drivers that are distinctly different from open and naturally ventilated modules. The following is seen to have significant impact on the explosion risk levels on confined process modules; the module size; the HVAC philosophy; the ignition source isolation efficiency; and the use of pressure release panels. These factors, and their impact on the explosion risk, are discussed in this paper. The presented conclusions are of high importance in future developments in arctic climate.

Sea spray icing: The physical process, and review of prediction models and winterization techniques

2021 ◽  
pp. 1-26
Author(s):  
Sujay Deshpande ◽  
Ane Sæterdal ◽  
Per-Arne Sundsbø
Keyword(s):  
Prediction Models ◽  
Offshore Structures ◽  
Cold Climate ◽  
Working Environment ◽  
The Arctic ◽  
Design Stage ◽  
Sea Spray ◽  
Ice Accretion ◽  
Sea Wind ◽  
The Impact

Abstract Ice accretion on marine vessels and offshore structures is a severe hazard in the Polar Regions. There is increasing activities related to oil and gas exploration, tourism, cargo transport, and fishing in the Arctic. Ice accretion can cause vessel instability, excess load on marine structures and represents a safety risk for outdoor working environment and operations. Freezing sea spray is the main contributor to marine icing. For safe operations in cold climate, it is essential to have verified models for prediction of icing. Sea spray icing forecast models have improved. Empirical and theoretical models providing icing rates based may be useful as guidelines. For predicting the distribution of icing on a surface at the design stage, Computational Fluid Dynamics has to be applied along with a freezing module. State-of-the-art models for numerical simulation of sea spray icing are still not fully capable of modelling complex ship-sea-wind interactions with spray generation and impact of shipped water. Existing models include good understanding of spray flow effects and freezing. Further development should focus on developing models for dynamic ship-sea-wind interactions, in particular including spray generation, effects of shipped water and distribution of icing on the vessel surface. More experimental and full-scale data is needed for development and verification of new and improved models. Models that estimate ice distribution may improve the winterization design process and reduce effort required for de-icing. Improved methods for de-icing and anti-icing will reduce the impact of sea spray icing and increase safety for marine operations in cold waters.

scholarly journals Review of Icing Effects on Wind Turbine in Cold Regions

2018 ◽  
Vol 72 ◽  
pp. 01007 ◽  
Author(s):  
Faizan Afzal ◽  
Muhammad S. Virk
Keyword(s):  
Wind Turbine ◽  
Structural Integrity ◽  
Turbine Blades ◽  
Leading Edge ◽  
Added Mass ◽  
Cold Climate ◽  
Ice Accretion ◽  
Wind Turbine Blades ◽  
Turbine Performance ◽  
Ice Shedding

This paper describes a brief overview of main issues related to atmospheric ice accretion on wind turbines installed in cold climate region. Icing has significant effects on wind turbine performance particularly from aerodynamic and structural integrity perspective, as ice accumulates mainly on the leading edge of the blades that change its aerodynamic profile shape and effects its structural dynamics due to added mass effects of ice. This research aims to provide an overview and develop further understanding of the effects of atmospheric ice accretion on wind turbine blades. One of the operational challenges of the wind turbine blade operation in icing condition is also to overcome the process of ice shedding, which may happen due to vibrations or bending of the blades. Ice shedding is dangerous phenomenon, hazardous for equipment and personnel in the immediate area.

Pipeline Visualization, Simulation and Monitoring in Unstable Areas Affected by Soil Movements at Serra do Mar – Brazil

2002 ◽  
Author(s):  
Jacqueline V. R. Musman ◽  
Alvaro M. Costa ◽  
Claudio Amaral ◽  
Robson C. Santos ◽  
Maria Tereza Carnevale ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Interaction Model ◽  
Simulation Software ◽  
Serra Do Mar ◽  
Knowing That ◽  
Extensive Program ◽  
Complete Set ◽  
The Times ◽  
Soil Movements ◽  
Visualization Simulation

In this work we discuss the importance of visualization, simulation and monitoring pipelines constructed in areas geologically unstable. In particular it is of great concern pipelines crossing Serra do Mar, in Brazil, where there are colluvium deposits subject to slow movements not traceable by a simple visual inspection most of the times. In order to guarantee the structural integrity of the pipeline it is necessary to measure the tensions transmitted by the ground to the pipeline. Knowing that the soil-pipeline interaction is extremely complex the implementation of an extensive program involving visualization, simulation and monitoring that includes not only the slope but also the pipeline becomes mandatory. This program seeks the collection of information that allows the establishment of a reliable interaction model. This model must be capable of providing operational control parameters and subsidize the decision of an intervention in the pipeline. Therefore the safety of pipeline operations can be maximized through instruction of operators and establishment of monitoring and inspection routines. Right now, in a joint effort of CENPES and TRANSPETRO, a complete set of visualization and numerical simulation software platform is available and it is being used to build a 3D model of all the geotechnical risky areas in Serra do Mar. Also the installation and operation of a pilot monitoring system, including piezometers and inclinometers on the slope and strain gauges on the pipeline, at three different pipelines crossing Serra do Mar, with data acquisition in real time is being undertaken.

scholarly journals Fracture and its Role in Determining Ice Forces on Offshore Structures

1983 ◽  
Vol 4 ◽  
pp. 216-221 ◽  
Author(s):  
A.C. Palmer ◽  
D. J. Goodman ◽  
M. F. Ashby ◽  
A. G. Evans ◽  
J.W. Hutchinson ◽  
...  
Keyword(s):  
Deformation Mode ◽  
Theoretical Models ◽  
Offshore Structures ◽  
The Arctic ◽  
Theoretical Treatment ◽  
Strain Rates ◽  
Natural Processes ◽  
Design Loads ◽  
Ice Forces ◽  
Fracture Processes

One of the most conspicuous phenomena in the Arctic Is the fracture of sea ice. It is scarcely possible to travel far without seeing a variety of fracture forms, produced both by natural processes and by human activity.At strain-rates below about 10−4s−1, deformation is dominated by creep, but at higher strain-rates fracture is much more important. One of the reasons for this is the very low fracture toughness of ice. The movements of ice in contact with offshore structures often induce strain-rates well beyond the level at which fracture begins, and so offshore structures will often operate in the fracture regime, and it is fracture processes which will determine the design loads. We consider the different modes of repeated fracture that will occur, and classify them into distinct mechanisms of crushing, spalling, and radial and circumferential cracking. Experimental and field observations are plotted on a deformation mode map. A theoretical treatment of radial cracking confirms that very low loads can propagate cracks to long distances; these loads are small by comparison with those calculated from theoretical models that treat ice as a plastically-deforming continuum.

scholarly journals Investigating the relationship between indoor environment and workplace productivity in naturally and mechanically ventilated office environments

2019 ◽  
Vol 41 (3) ◽  
pp. 280-304
Author(s):  
Rajat Gupta ◽  
Alastair Howard ◽  
Sahar Zahiri
Keyword(s):  
Environmental Conditions ◽  
Indoor Environment ◽  
Low Cost ◽  
Environmental Parameters ◽  
Working Environment ◽  
The Other ◽  
Mechanically Ventilated ◽  
Workplace Productivity ◽  
Office Environments ◽  
The Relationship

This paper uses a case study-based approach to empirically investigate the relationship between indoor environment and workplace productivity in two contrasting office environments: one naturally ventilated, the other mechanically ventilated. Environmental parameters were continuously monitored over 19 months. Transverse and longitudinal surveys recorded occupants’ perception of their working environment and self-reported productivity, while performance tasks (numerical and proofreading) measured cognitive capability as proxy for measured productivity. Indoor temperatures and CO2 concentrations were found to be higher and more variable in the naturally ventilated office. However, the correlation between occupant perception of their indoor environment and perceived productivity was stronger in the mechanically ventilated office. Occupants of the naturally ventilated office were found to be more tolerant of their environment than their counterparts in the mechanically ventilated office. Task performance was affected by indoor environmental conditions such as indoor temperature and CO2 concentration. Interestingly in the naturally ventilated office, the median scores were up to 12% higher for tests conducted at CO2 concentrations <1400 ppm, compared to those conducted above 1400 ppm, whereas in the mechanically ventilated office, this threshold was only 1000 ppm. The study showed that higher concentrations of CO2 were associated with lower task scores and longer task durations, reinforcing the need for good levels of ventilation in workspaces. It was found that occupants in NV workspaces were able to adapt to a broader range of environmental conditions. Therefore, controlling the indoor environment within narrow ranges (expending significant amounts of energy in the process) may not always be necessary to improve comfort and productivity. On the other hand, controlling indoor environment within a narrow range – as is common in MV workspaces – may be counterproductive, creating occupants who are less tolerant of small changes in their environmental conditions. The study also demonstrates occupant surveys can provide useful feedback on perceived comfort and productivity at relatively low cost. Insights from such surveys can be used to improve indoor environment in workspaces.

scholarly journals Numerical Simulation of Reactive Flows in Overexpanded Supersonic Nozzle with Film Cooling

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Mohamed Sellam ◽  
Amer Chpoun
Keyword(s):  
Film Cooling ◽  
Structural Integrity ◽  
Safety Issue ◽  
Rocket Engine ◽  
Supersonic Nozzle ◽  
Nozzle Geometry ◽  
Nozzle Flow ◽  
Rocket Engines ◽  
Flow Conditions ◽  
Reactive Flows

Reignition phenomena occurring in a supersonic nozzle flow may present a crucial safety issue for rocket propulsion systems. These phenomena concern mainly rocket engines which use H2gas (GH2) in the film cooling device, particularly when the nozzle operates under over expanded flow conditions at sea level or at low altitudes. Consequently, the induced wall thermal loads can lead to the nozzle geometry alteration, which in turn, leads to the appearance of strong side loads that may be detrimental to the rocket engine structural integrity. It is therefore necessary to understand both aerodynamic and chemical mechanisms that are at the origin of these processes. This paper is a numerical contribution which reports results from CFD analysis carried out for supersonic reactive flows in a planar nozzle cooled with GH2film. Like the experimental observations, CFD simulations showed their ability to highlight these phenomena for the same nozzle flow conditions. Induced thermal load are also analyzed in terms of cooling efficiency and the results already give an idea on their magnitude. It was also shown that slightly increasing the film injection pressure can avoid the reignition phenomena by moving the separation shock towards the nozzle exit section.

Refined Modeling of Projectile Impact Onto Submerged Structure

2008 ◽  
Author(s):  
Justin Onisoru ◽  
Ovidiu Coman ◽  
Paul Wilson ◽  
George Thomas
Keyword(s):  
Strain Rate ◽  
Structural Integrity ◽  
Initial Conditions ◽  
Safety Issue ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Material Behavior ◽  
Spent Fuel ◽  
The Impact

Structural integrity of spent fuel racks is a critical safety issue in nuclear power stations. The standard approach of evaluating the effects of an impact projectile on a submerged structure, which constitute the start point of the current study, involves three main steps: determination of the conditions just prior to the impact (that are considered as initial conditions for the analysis), setting the mechanism of transferring energy from the projectile to the target structure, and determining how that energy is absorbed by the impacted structure. Usually, the dynamics of the projectile are ideally considered, the influence of the fluid presence is restricted to the determination of the impact velocity and strain rate dependency is limited to choosing a true stress vs. strain curve corresponding to some constant strain rate. Starting from the standard engineering approach, the authors have refined the model considering more realistic dynamics of the projectile, extending the influence of the fluid to the entire analysis and using a more accurate strain rate dependant material behavior. Explicit Finite Element analyses are used in order to incorporate the desired effects.

Negative changes in permafrost due to waste storage

2020 ◽  
Author(s):  
Valery Grebenets ◽  
Fedor Iurov ◽  
Vasily Tolmanov
Keyword(s):  
Chemical Reactions ◽  
Frozen Soil ◽  
Cold Climate ◽  
The Arctic ◽  
Chemical Pollution ◽  
Drilling Fluids ◽  
Waste Storage ◽  
Frozen State ◽  
The Impact ◽  
Cryogenic Processes

&lt;p&gt;Keywords: permafrost, waste, hazardous cryogenic processes&lt;/p&gt;&lt;p&gt;The problem of waste storage is particularly acute in Arctic. This is due to the vulnerability of northern ecosystems, the existence of permafrost, especially vulnerable to anthropogenic impact, the water-resistant properties of frozen rocks and the effect of destructive cryogenic processes. In addition, the causes of concern are the trends in air and frozen soil temperatures reported for the northern regions: pollutants stored in relatively stable frozen state can be released into the environment as a result of thawing. This is especially true for industrial regions, where billions of cubic meters of waste from the mining and beneficiation of ores and coal, form timber processing, mine water spills and drilling fluids, etc. are stored in a frozen state.&lt;/p&gt;&lt;p&gt;Field investigations were carried out in number of settlements in cryolithozone of Russia (Norilsk, Vorkuta, Igarka, settlements in the lower Ob, national villages of Taimyr, etc.). The observations involved remote sensing methods and included estimation of the area of littering and the types of waste. In many cases sampling for chemical analyzes, thermometry, and mapping of hazardous processes were made.&lt;/p&gt;&lt;p&gt;The impact of stored wastes on permafrost was divided into three main types: a) mechanical (changing the relief and the flow paths of surface and ground waters); b) physical and chemical (pollution by the waste itself and by its decomposition products); c) thermal (heating of frozen soils by high-temperature waste or heat generation during various chemical reactions).&lt;/p&gt;&lt;p&gt;During the research, 6 main types of waste storage were identified, each of which had a destructive effect on permafrost soils and northern ecosystems:&lt;/p&gt;&lt;p&gt;1) dumps of municipal solid waste (inherent in all settlements);&lt;/p&gt;&lt;p&gt;2) storages of industrial waste, tailing storage facilities in the industrial centers of the north;&lt;/p&gt;&lt;p&gt;3) abandoned and cluttered territories;&lt;/p&gt;&lt;p&gt;4) landfills of timber processing waste in the centers of the timber industry;&lt;/p&gt;&lt;p&gt;5) rock dumps in open-cast mining sites, which in the cold climate can transform into rock glaciers;&lt;/p&gt;&lt;p&gt;6) storage areas for polluted snow tranfered from built-up areas.&lt;/p&gt;&lt;p&gt;Particular attention was paid to the accumulation of chemical pollutants in industrial centers (with Norilsk industrial region as an example). This problem in conditions of permafrost is exacerbated by the low self-purification of northern biogeocenoses; slowdown of oxidation and some other chemical reactions in cold climates; drainage and unloading of groundwater of seasonally thawed layer, intra-permafrost and under-permafrost taliks into the water bodies.&lt;/p&gt;&lt;p&gt;The use of imperfect technologies for the extraction and processing the raw materials, remains of past years practices with neglected environmental situation, the lack of special standards for the storage of waste and industrial by-products, the lack of development of waste disposal methods for severe climatic conditions led to the pollution of vast territories and to destruction of many ecosystems.&lt;/p&gt;&lt;p&gt;This work was supported by the RFBR grant 18-05-60080 &amp;#8220;Dangerous nival-glacial and cryogenic processes and their impact on infrastructure in the Arctic&amp;#8221;.&lt;/p&gt;

Analysis of Sodium Fire in the Containment Building of Prototype Fast Breeder Reactor Under the Scenario of Core Disruptive Accident

2006 ◽  
Author(s):  
P. M. Rao ◽  
N. Kasinathan ◽  
S. E. Kannan
Keyword(s):  
Structural Integrity ◽  
Peak Pressure ◽  
Safety Issue ◽  
Pressure Rise ◽  
Pool Fire ◽  
Mode Analysis ◽  
Fast Breeder Reactor ◽  
Reactor Assembly ◽  
Computer Codes ◽  
Breeder Reactors

The potential for sodium release to reactor containment building from reactor assembly during Core Disruptive Accident (CDA) in Fast Breeder Reactors (FBR) is an important safety issue with reference to the structural integrity of Reactor Containment Building (RCB). For Prototype Fast Breeder Reactor (PFBR), the estimated sodium release under a CDA of 100 MJ energy release is 350 kg. The ejected sodium reacts easily with air in RCB and causes temperature and pressure rise in the RCB. For estimating the severe thermal consequences in RCB, different modes of sodium fires like pool and spray fires were analyzed by using SOFIRE–II and NACOM sodium fire computer codes. Effects of important parameters like amount of sodium, area of pool, containment air volume and oxygen concentration have been investigated. A peak pressure rise of 7.32 kPa is predicted by SOFIRE II code for 350 kg sodium pool fire in 86,000 m3 RCB volume. Under sodium release as spray followed by unburnt sodium as pool fire mode analysis, the estimated pressure rise is 5.85 kPa in the RCB. In the mode of instantaneous combustion of sodium, the estimated peak pressure rise is 13 kPa.

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