Burnthrough Prediction for In-Service Welding: Past, Present and Future

2012 ◽  
Author(s):  
Matthew A. Boring
Keyword(s):  
Surface Temperature ◽  
Numerical Solutions ◽  
Computer Models ◽  
Operating Conditions ◽  
Inside Surface ◽  
Welding Parameters ◽  
Mechanical Approach ◽  
Alternative Approaches ◽  
Analysis Models ◽  
Determining Factor

The methods of determining burnthrough risk have changed over the years. The first burnthrough limits were developed experimentally and then, with the development of computers, came computer models. The first major advancement in computer models came at Battelle, in the early 1980s, with the development of the “Hot-Tap Thermal-Analysis Models.” The Battelle models use two-dimensional numerical solutions to predict the inside surface temperature as a function of the welding parameters, pipe parameters, and the operating conditions. The Battelle model considers an inside surface temperature of less than 1800°F (982°C) when using low-hydrogen electrodes, [1400°F (760°C) when using cellulosic-coated electrodes] to be safe. Since the release of the Battelle model, introduction other models have been developed which are based on Battelle’s logic as well as other approaches. PRCI, as well as others, has funded research to develop an alternative burnthrough prediction model which is based on a thermo-mechanical approach taking into account the stress associated with pressurized pipe. These alternative approaches differ from Battelle’s criteria which only uses the inside surface temperature as the lonely determining factor of safe welding practices.

Porous exponential slider bearings lubricated with MHD-couple stress fluid

2018 ◽  
Vol 70 (5) ◽  
pp. 838-845 ◽  
Author(s):  
N.B. Naduvinamani ◽  
Shridevi S. Hosmani
Keyword(s):  
Couple Stress ◽  
Numerical Solutions ◽  
Transverse Magnetic ◽  
Operating Conditions ◽  
Couple Stress Fluid ◽  
Content Type ◽  
Electrically Conducting ◽  
Slider Bearings ◽  
Load Carrying ◽  
First Time

Purpose The purpose of this study is to examine the magneto-hydrodynamic (MHD) effect on porous exponential slider bearings lubricated with couple stress fluid and to derive the modified Reynolds’s equation for non-Newtonian fluid under various operating conditions to obtain the optimum bearing parameters. Design/methodology/approach Based upon the MHD theory and Stokes theory for couple stress fluid, the governing equations relevant to the problem under consideration are derived. This paper analyzes the effect on porous exponential slider bearings with an electrically conducting fluid in the presence of a transverse magnetic field. Semi-numerical solutions are obtained and discussed. Findings It is found that there is an increase in the load carrying capacity, frictional force and decrease in the co-efficient of friction in porous bearings due to the presence of magnetic effects with couple stress fluid. Originality/value This study is relatively original and gives the MHD effect on porous exponential slider bearings lubricated with couple stress fluid. The author believes that the paper presents these results for the first time.

Analytical Modeling and Performance Study of a Cross Flow Air Dehumidifier Using Liquid Desiccant

2014 ◽  
Vol 875-877 ◽  
pp. 1205-1213 ◽  
Author(s):  
Mohamed M. Bassuoni
Keyword(s):  
Numerical Solutions ◽  
Removal Rate ◽  
Cross Flow ◽  
Operating Conditions ◽  
Maximum Deviation ◽  
Performance Study ◽  
Liquid Desiccant ◽  
Mass Transfer Processes ◽  
And Performance ◽  
Air Conditioning Systems

The dehumidifier is a key component in liquid desiccant air conditioning systems. Various mathematical models of heat and mass transfer processes inside the dehumidifier are introduced and numerically solved in the literature. Analytical solutions have more advantages than numerical solutions in studying the dehumidifier performance parameters. This paper presents the results from an analytical model for the performance of an adiabatic cross flow liquid desiccant air dehumidifier. Calcium chloride is used as desiccant material in this investigation. Both humidity and temperature effectiveness of the dehumidifier are used to predict the performance of the device under various operating conditions. Good accuracy has been found between analytical solution and reliable experimental results with a maximum deviation of +6.63% and -5.65% in the moisture removal rate. The method developed here can be used in the quick prediction of the dehumidifier performance. The exit parameters from the dehumidifier are evaluated under the effects of variables such as air temperature and humidity, desiccant temperature and concentration and air to desiccant flow rates. The results show that hot humid air and desiccant concentration have the greatest impact on the performance of the dehumidifier.

A Natural Convection Fin with a Solution-Determined Nonmonotonically Varying Heat Transfer Coefficient

1981 ◽  
Vol 103 (2) ◽  
pp. 218-225 ◽  
Author(s):  
E. M. Sparrow ◽  
S. Acharya
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Natural Convection ◽  
Transfer Coefficient ◽  
First Principles ◽  
Numerical Solutions ◽  
Flow Direction ◽  
Operating Conditions ◽  
Fluid Temperature ◽  
Wide Range

A conjugate conduction-convection analysis has been made for a vertical plate fin which exchanges heat with its fluid environment by natural convection. The analysis is based on a first-principles approach whereby the heat conduction equation for the fin is solved simultaneously with the conservation equations for mass, momentum, and energy in the fluid boundary layer adjacent to the fin. The natural convection heat transfer coefficient is not specified in advance but is one of the results of the numerical solutions. For a wide range of operating conditions, the local heat transfer coefficients were found not to decrease monotonically in the flow direction, as is usual. Rather, the coefficient decreased at first, attained a minimum, and then increased with increasing downstream distance. This behavior was attributed to an enhanced buoyancy resulting from an increase in the wall-to-fluid temperature difference along the streamwise direction. To supplement the first-principles analysis, results were also obtained from a simple adaptation of the conventional fin model.

Integrity Assessment of HP/HT Infield Pipelines: Experiences With a New Methodology Applied in the Norwegian Sea

2008 ◽  
Author(s):  
Birger Etterdal ◽  
Hroar Nes ◽  
Stig Olav Kvarme ◽  
Stian Svardal
Keyword(s):  
Hot Spot ◽  
Operating Conditions ◽  
Pipeline System ◽  
Operating Pressure ◽  
Assessment Methodology ◽  
Long Term Conditions ◽  
Norwegian Sea ◽  
Integrity Assessment ◽  
Analysis Models

The subsea pipeline development for the A˚sgard and Midgard fields in the Norwegian Sea has been challenging due to high operating pressure and temperature (HP/HT pipelines), uneven seabed conditions and the potential for trawl gear interference. A general experience from the first years of operation is that it is not easy to use design information as basis for an integrity assessment of the lines. This is mainly due to the complexity of the global buckling process and the significant load fluctuations applied to the lines. As a consequence of this, analysis models established during design may not represent the actual pipeline behaviour properly, and established design limits do not fit intermediate operational load conditions and configurations observed during surveys. StatoilHydro has developed an integrity assessment methodology where analysis models are calibrated according to the as-surveyed condition, and then exposed to operational cyclic loads in order to predict both intermediate long term conditions and a final design condition. In the assessment of long term fatigue accumulation, process parameters monitored during pipeline operation are used as input. The integrity condition of the HP/HT pipelines is assessed based on a staged approach, depending on the criticality of the considered failure mode. The first level is used for screening and initial ranking. At level two the risk of integrity failure is quantified based on general design criteria, covering relevant operating conditions and the most important input parameters. If the uncertainty related to the assessment of an individual hot-spot location is assumed too high, a detail level three assessment may be specified. The operating condition of the pipeline system is expressed as the risk of failure defined by a limited number of hot-spot locations. The risk matrix concept used for the HP/HT pipelines, provides for a consistent comparison between individual failure modes, between different locations and sections, and between different pipeline systems. StatoilHydro has worked in close cooperation with DNV to develop software tools required to implement this integrity assessment methodology. These tools are now used for integrity assessment and follow-up of all HP/HT pipelines operated by StatoilHydro in the Norwegian Sea. The objective of this paper is to show how the methodology is used in practice, discuss major results and findings, and give general recommendations with respect to operational integrity assessment of HP/HT pipelines.

scholarly journals Determining the maximum surface temperature for non-electrical equipment aiming at explosion prevention at protection

2020 ◽  
Vol 305 ◽  
pp. 00026
Author(s):  
Adrian Marius Jurca ◽  
Niculina Vătavu ◽  
Leonard Lupu ◽  
Mihai Popa
Keyword(s):  
Surface Temperature ◽  
Hazard Assessment ◽  
Electrical Equipment ◽  
Operating Conditions ◽  
Laboratory Research ◽  
Safety Level ◽  
Protective Measures ◽  
Protection Measures ◽  
Maximum Surface ◽  
Maximum Surface Temperature

Non-electrical equipment has been used for over 150 years in industries with potentially explosive atmospheres and great experience has been gained with regard to the application of protective measures to reduce the risk of ignition down to an acceptable safety level. The use of non-electrical equipment in explosive atmospheres required the development of specific requirements with regard to the concept of protection against the ignition of explosive atmospheres, which to clearly define protection measures and to include the experience gained and extended over the years. The practical studies, laboratory research and methods for assessing and testing the hazard of ignition by hot surfaces presented within the paper have as main purpose the improvement of ignition hazard assessment in different operating conditions.

Size Effect on the Behavior of Thermal Elastohydrodynamic Lubrication of Roller Pairs

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
Xiaoling Liu ◽  
Jinlei Cui ◽  
Peiran Yang
Keyword(s):  
Size Effect ◽  
Newtonian Fluid ◽  
Effective Viscosity ◽  
Numerical Solutions ◽  
Elastohydrodynamic Lubrication ◽  
Operating Conditions ◽  
Load Parameter ◽  
Performance Results ◽  
Thermal Ehl ◽  
Strong Size Effect

In order to investigate the size effect on elastohydrodynamic lubrication (EHL) of roller pairs, complete numerical solutions for both the Newtonian fluid and the Eyring fluid thermal EHL problems of roller pairs under steady state conditions have been achieved. It can be seen that there is no size effect on the isothermal EHL performance; however, there is a very strong size effect on the thermal EHL performance. Results show that the term of shearing heat is the most important factor for the film temperature when the size of a contact changes. Comparison between the Newtonian solution and the Eyring solution has been made under some operating conditions. It is interesting to see that the effective viscosity of the Eyring fluid is nearly the same as that of the Newtonian fluid when the size of a contact is large enough. The non-Newtonian effect, therefore, can be ignored when the size of a contact is very large. It is equally interesting to see that the thermal effect can be ignored when the size of a contact is very small. In addition, the influence of the velocity parameter, the load parameter, and the slide-roll ratio on the lubricating performance for various sizes of contacts has been investigated.

A Mixed-Lubrication Study of Journal Bearing Conformal Contacts

1997 ◽  
Vol 119 (3) ◽  
pp. 456-461 ◽  
Author(s):  
Qian (Jane) Wang ◽  
Fanghui Shi ◽  
Si C. Lee
Keyword(s):  
Film Thickness ◽  
Contact Pressure ◽  
Contact Area ◽  
Numerical Solutions ◽  
Mixed Lubrication ◽  
Lubricant Film ◽  
Operating Conditions ◽  
Asperity Contact ◽  
Lubricant Film Thickness ◽  
Asperity Contacts

Numerical analyses of finite journal bearings operating with large eccentricity ratios were conducted to better understand the mixed lubrication phenomena in conformal contacts. The average Reynolds equation derived by Patir and Cheng was utilized in the lubrication analysis. The influence function, calculated numerically using the finite element method, was employed to compute the bearing deformation. The effects of bearing surface roughness were incorporated in the present analysis for the calculations of the asperity contact pressure and the asperity contact area. The numerical solutions of the hydrodynamic and asperity contact pressures, lubricant film thickness, and asperity contact area were evaluated based on a simulated bearing-journal geometry. The calculations revealed that the asperity contact pressure may vary significantly along both the width and the circumferential directions. It was also shown that the asperity contacts and the lubricant film thickness were strongly dependent on the bearing width, asperity orientation, and operating conditions.

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