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Pressure Vessels (pressure + vessel)

Distribution by Scientific Domains

Polymers and Materials Science	42%
Chemistry	28%

Selected Abstracts

Fire exposure of liquid-filled vessels

PROCESS SAFETY PROGRESS, Issue 1 2003
Larry L. Simpson
Pressure vessels in the chemical industry generally have top-mounted pressure relief valves (PRVs) sized to handle fire exposure and other possible scenarios. Designers usually assume that the fire scenario causes liquid to boil and vapor to vent, regardless of the initial liquid level. Under some circumstances, however, a high liquid level, together with thermal expansion, can result in a vessel being full of liquid when the PRV opens. If so, the initial fluid discharged through the PRV would be a two-phase gas-liquid stream. This paper analyzes non-reactive phenomena occurring during the heat-up and venting process in non-agitated liquid-filled pressure vessels. A new criterion is developed to determine if the vapor-venting sizing assumption is justified. Results from several cases show that pressures in most liquid-filled vessels sized for vapor-only flow will be below the ASME Code-allowable values during fire exposure. Hence, the common industry practice of ignoring two-phase flow when sizing fire cases is usually justified. [source]

Pool boiling heat transfer in binary mixtures of ammonia/water: Effect of heat of dilution and dissolution on heat transfer coefficient

HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 4 2002
Toshiaki Inoue
Abstract Nucleate boiling heat transfer coefficients were measured on a horizontal heated wire during the pool boiling of non-azeotropic mixtures of ammonia/water. The experiment was carried out at pressures of 0.4 and 0.7 MPa, at heat fluxes below 2.0 × 106 W/m2, and over a range of mass fraction. The heat transfer coefficients in the mixtures were smaller than those in single-component substances. No existing correlation is found to predict boiling heat transfer coefficients over the range of mass fraction of interest. In the mixtures of the ammonia/water, the heats of dilution and dissolution were generated near a liquid surface while vapor with a rich concentration of ammonia was condensed and then was diffused into the bulk liquid; while in most other mixtures, little heat was generated during any dilution and dissolution. In relation to the heat generated, the effect of the heats of dilution and dissolution on pressure and temperature in a system (pressure vessel) is shown herein. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(4): 272,283, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10034 [source]

Polymer plasticization using supercritical carbon dioxide,

JOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 4 2008
Febe Kusmanto
The plasticizing effect of supercritical CO2 (scCO2) during the extrusion of polymers was investigated. A modified extrusion system was used to demonstrate the viscosity-reducing effect of scCO2 together with a capability to produce foam-free extrudate with selected polymers, including poly(vinyl chloride). Samples of extrudate and materials prepared off-line by using a pressure vessel were characterized by thermal, mechanical, and X-ray techniques. After gas diffusion from the polymer, there was no long-term effect on polymer structure and properties. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers. [source]

Artificial intelligence advancements applied in off-the-shelf controllers

PROCESS SAFETY PROGRESS, Issue 2 2002
Edward M. Marszal P.E.
Since the earliest process units were built, CPI engineers have employed artificial intelligence to prevent losses. The expanding use of computer-based systems for process control has allowed the amount of intelligence applied in these expert systems to drastically increase. Standard methods for performing Expert System tasks are being formalized by numerous researchers in industry and academia. Work products from these groups include designs that present process hazards knowledge in a structured, hierarchical, and modular manner. Advancements in programmable logic controller (PLC) technology have created systems with substantial computing power that are robust and fault tolerant enough to be used in safety critical applications. In addition, IEC 1131-3 standardized the programming languages available in virtually every new controller. The function block language defined in IEC 1131-3 is particularly well suited to performing modular tasks, which makes it an ideal platform for representing knowledge. This paper begins by describing some of the advancements in knowledge-based systems for loss prevention applications. It then explores how standard IEC 1131-3 programming techniques can be used to build function blocks that represent knowledge of the hazards posed by equipment items. The paper goes on to develop a sample function block that represents the hazards of a pressure vessel, using knowledge developed in the API 14-C standard. [source]

Effect of Nano-Aluminum and Fumed Silica Particles on Deflagration and Detonation of Nitromethane

PROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 5 2009
Justin
Abstract The heterogeneous interaction between nitromethane (NM), particles of nanoscale aluminum (38 and 80,nm diameter), and fumed silica is examined in terms of the deflagration and detonation characteristics. Burning rates are quantified as functions of pressure using an optical pressure vessel up to 14.2,MPa, while detonation structure is characterized in terms of failure diameter. Nitromethane is gelled using fumed silica (CAB-O-SIL®), as well as by the nanoaluminum particles themselves. Use of nanoaluminum particles with fumed silica slightly increases burning rates compared to the use of larger diameter Al particles; however distinct increases in burning rates are found when CAB-O-SIL is removed and replaced with more energetic aluminum nanoparticles, whose high surface area allows them to also act as the gellant. Mixtures including fumed silica yield a reduced burning rate pressure exponent compared to neat NM, while mixtures of aluminum particles alone show a significant increase. Failure diameters of mixture detonations are found to vary significantly as a function of 38,nm aluminum particle loading, reducing more than 50% from that of neat nitromethane with 12.5% (by mass) aluminum loading. Failure diameter results indicate a relative minimum with respect to particle separation (% loading) which is not observed in other heterogeneous mixtures. [source]

Prediction of ice content in biological model solutions when frozen under high pressure

BIOTECHNOLOGY PROGRESS, Issue 2 2009
B. Guignon
Abstract High pressure is, at least, as effective as cryoprotective agents (CPAs) and are used for decreasing both homogenous nucleation and freezing temperatures. This fact gives rise to a great variety of possible cryopreservation processes under high pressure. They have not been optimized yet, since they are relatively recent and are mainly based on the pressure,temperature phase diagram of pure water. Very few phase diagrams of biological material are available under pressure. This is owing to the lack of suitable equipment and to the difficulties encountered in carrying out the measurements. Different aqueous solutions of salt and CPAs as biological models are studied in the range of 0°C down to -35°C, 0.1 up to 250 MPa, and 0,20% w/w total solute concentration. The phase transition curves of glycerol and of sodium chloride with either glycerol or sucrose in aqueous solutions are determined in a high hydrostatic pressure vessel. The experimental phase diagrams of binary solutions were well described by a third-degree polynomial equation. It was also shown that Robinson and Stokes' equation at high pressure succeeds in predicting the phase diagrams of both binary and ternary solutions. The solute cryoconcentration and the ice content were calculated as a function of temperature and pressure conditions during the freezing of a binary solution. This information should provide a basis upon which high-pressure cryopreservation processes may be performed and the damages derived from ice formation evaluated. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]

C. botulinum inactivation kinetics implemented in a computational model of a high-pressure sterilization process

BIOTECHNOLOGY PROGRESS, Issue 1 2009
Pablo Juliano
Abstract High-pressure, high-temperature (HPHT) processing is effective for microbial spore inactivation using mild preheating, followed by rapid volumetric compression heating and cooling on pressure release, enabling much shorter processing times than conventional thermal processing for many food products. A computational thermal fluid dynamic (CTFD) model has been developed to model all processing steps, including the vertical pressure vessel, an internal polymeric carrier, and food packages in an axis-symmetric geometry. Heat transfer and fluid dynamic equations were coupled to four selected kinetic models for the inactivation of C. botulinum; the traditional first-order kinetic model, the Weibull model, an nth-order model, and a combined discrete log-linear nth-order model. The models were solved to compare the resulting microbial inactivation distributions. The initial temperature of the system was set to 90°C and pressure was selected at 600 MPa, holding for 220 s, with a target temperature of 121°C. A representation of the extent of microbial inactivation throughout all processing steps was obtained for each microbial model. Comparison of the models showed that the conventional thermal processing kinetics (not accounting for pressure) required shorter holding times to achieve a 12D reduction of C. botulinum spores than the other models. The temperature distribution inside the vessel resulted in a more uniform inactivation distribution when using a Weibull or an nth-order kinetics model than when using log-linear kinetics. The CTFD platform could illustrate the inactivation extent and uniformity provided by the microbial models. The platform is expected to be useful to evaluate models fitted into new C. botulinum inactivation data at varying conditions of pressure and temperature, as an aid for regulatory filing of the technology as well as in process and equipment design. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]

Cleavage fracture of RPV steel following warm pre-stressing: micromechanical analysis and interpretation through a new model

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 9-10 2006
S. R. BORDET
ABSTRACT In this paper, the warm pre-stress (WPS) effect on the cleavage fracture of an 18MND5 (A533B) RPV steel is investigated. This effect, which describes the effective enhancement of the cleavage fracture toughness at low temperature following a prior loading at high temperature, has received great interest in light of its significance in the integrity assessment of structures, such as nuclear pressure vessels, subjected to thermal transients. Several loading cycles between room temperature (RT) and ,150 °C are considered: Load-Unload-Cool-Fracture (LUCF), Load-Cool-Fracture (LCF) and Load-Cool with Increasing K-Fracture (LCIKF). All experiments complied with the conservative principle, which states that no fracture will occur if the applied stress intensity factor (SIF) decreases (or is held constant) while the temperature at the crack-tip decreases, even if the fracture toughness of the virgin material is exceeded. The experimental results indicate that an effective WPS effect is present even at small pre-load (Kwps= 40 MPa,m), and that a minimum critical slope (,,K/,T) in the LCIKF cycle has to be exceeded to induce cleavage fracture between RT and ,150 °C. Numerical modelling was performed using mixed isotropic and kinematic hardening laws identified on notched tensile (NT) specimens, tested in tension to large strains (up to 40%), followed by large compressive strains. Detailed microstructural investigations on compact tensile (CT) and NT fracture test specimens were performed so as to determine the nature of the cleavage initiation sites, as well as the local mechanical conditions at fracture. Based on this local information, a new cleavage model was calibrated and applied to predict the probability of cleavage fracture after WPS: it is shown that the predictions are in good agreement with the experimental results. [source]

Fracture behaviour of maraging steel tensile specimens and pressurized cylindrical vessels

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 3 2004
T. CHRISTOPHER
ABSTRACT A three-parameter fracture criterion is applied for the development of a failure assessment diagram to maraging steels and its validity verified by considering the maraging steel fracture data of surface crack tension specimens (SCT) and pressure vessels having axial surface cracks. Fracture-strength/failure-pressure estimates based on this criterion are found to be in reasonably good agreement with test results. [source]

A probabilistic simulation of fluid leakage in multiple cracks situation

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 11 2002
L. XIE
ABSTRACT In pressure vessels and piping the leak-before-break (LBB) assessment method is employed to avoid any catastrophic failure prior to a detectable leakage. One of the most important parameter, the leak rate, is investigated in the present paper by means of the Monte Carlo method. A brief review is carried out with emphasis on aspects such as crack growth, crack size with detectable leakage, crack opening area and leak rate. Issues concerning the property and behaviour of multiple cracks are also covered along with a review of the characteristics of leak rate through distributed multiple cracks using a statistical simulation method. The simulation results show that the effect of multiple cracks is quite significant to the LBB concept. Both the relationship between leak rate and crack length (or time) and the statistical characteristics of the leak rate are considerably different for different initial crack conditions. [source]

On the Fracture Toughness of Advanced Materials

ADVANCED MATERIALS, Issue 20 2009
Maximilien E. Launey
Abstract Few engineering materials are limited by their strength; rather they are limited by their resistance to fracture or fracture toughness. It is not by accident that most critical structures, such as bridges, ships, nuclear pressure vessels and so forth, are manufactured from materials that are comparatively low in strength but high in toughness. Indeed, in many classes of materials, strength and toughness are almost mutually exclusive. From a fracture-mechanics perspective, the ability of a microstructure to develop toughening mechanisms acting either ahead or behind the crack tip can result in resistance-curve (R-curve) behavior where the fracture resistance actually increases with crack extension; the implication here is that toughness is often developed primarily during crack growth and not for crack initiation. Biological materials are perfect examples of this; moreover, they offer microstructural design strategies for the development of new materials for structural applications demanding combinations of both strength and toughness. [source]

Residual stress analysis of an autofrettaged compound cylinder under machining process

MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 3 2009
E.-Y. Lee
Autofrettage; Schrumpfpassung; Verbundzylinder; Bearbeitungsprozess Abstract The autofrettage process is used to manufacture pressure vessels and cylinders that can withstand high internal pressure. A multi-layered cylinder was assembled by a shrink fit. Autofrettaged compound cylinder can resist higher internal pressure than a thick cylinder having the same dimension and extend its life time. Inner and outer surfaces of the autofrettaged compound cylinder have to be manufactured into exact dimensions. The distribution of residual stress can change after the machining process. The machining procedure of inner and outer surfaces also affects the distribution of residual stress as a function of the machining procedure. In this study, the distribution of residual stresses of an autofrettaged compound cylinder as machining procedure was investigated using analytical and numerical analyses. [source]

Fire exposure of liquid-filled vessels

Cation Leaching from the Basalt JB,1a by 2M NaCl Hydrothermal Solutions

RESOURCE GEOLOGY, Issue 2 2000
Etsuo UCHIDA
The experiments were carried out using standard cold-seal pressure vessels in the temperature range from 300 to 800C under the constant pressure of 1000 bars and also in the pressure range from 500 to 1000 bars at 600°C. The concentrations of Fe, Mn, Zn and Co in the hydrothermal solutions increased significantly with increasing temperature and with decreasing pressure. The thermodynamic analysis of the experimental results suggests that this is due to the formation of trichloro-complexes and also partly due to the temperature dependence of ion exchange between augite and aqueous chloride solution. The Na concentration in the aqueous solution decreases with increasing temperature and with decreasing pressure. On the other hand, the behavior of K, Ca and Mg is complex and their concentrations seem to be controlled by the coexisting minerals. Judging from the experimental results, it is concluded that the transition elements are effectively leached from the basalt under higher temperatures and lower pressures. This means that higher temperature and lower pressure conditions are preferable for the production of ore-forming hydrothermal solutions. [source]