Fretting Corrosion Analysis on Packings of Hypercompressors

2009 ◽  
Author(s):  
Jun-Xia Shi ◽  
Enzo Giacomelli
Keyword(s):  
High Pressures ◽  
Great Influence ◽  
Operating Conditions ◽  
Fretting Corrosion ◽  
Economic Operation ◽  
High Fatigue ◽  
Poly Ethylene ◽  
Critical Machines ◽  
Local Defects ◽  
Sealing Elements

Secondary compressors for Low Density Poly-Ethylene are very critical machines. Safety aspects and reliability expectations determine a thorough evaluation of the service and the parameters involved. The solution used for the machine requires a long experience of positive results in these applications. Cylinder performance is strongly influenced by the design and also related to the combination of operation and maintenance activities. The capability to withstand the high fatigue stresses and the need to avoid any leakage of gas around the compressor area involves due considerations and design solutions to minimize such occurrences also during abnormal operations and emergencies. In addition to the cylinder valves, packings represent important components with great influence on the availability of machine and plant. The operating conditions of the packing, due to the high pressures involved, and the geometry of the components, create the condition for a relative movement of the cups mating surfaces. In general at disassembly, when maintenance and reconditioning activities are carried out wear, pitting, corrosion and local defects can be detected on the cups and sealing elements, as a function of the life of the cylinders. The condition of the cups may also evidence some damages, with evident deposit of polymers, oil and wear of the components. Fretting corrosion phenomena may be sometime the reason of failure of packing in hyper-compressors for LDPE production. In some cases the repeated occurrence of various abnormalities on the packing life and particular wear pattern on the cups bring to need to discover the reason of the problems and require an accurate investigation, by using advanced laboratory analyses. The results evidence that the origin of such phenomena can be found on the surfaces of the components and on the organic acids, as in such conditions they are able to originate and develop the corrosion reactions. There is a strong connection with process parameters and operating conditions. These situations and particular applications have to be evaluated to put in place adequate actions to improve or have more chances of a reliable and economic operation.

Autofrettaging Procedures on LDPE Hyper-Compressor Components

2006 ◽  
Author(s):  
Enzo Giacomelli ◽  
Paolo Battagli ◽  
Nicola Campo ◽  
Franco Graziani
Keyword(s):  
High Pressures ◽  
Safe Operation ◽  
Extensive Experience ◽  
Tubular Reactors ◽  
Complex Shapes ◽  
Fitting Procedures ◽  
High Fatigue ◽  
Shrink Fitting ◽  
Sealing Elements ◽  
Very High

Hyper-compressors operating in plants with both vessel and tubular reactors are subject to very high pressures. Many cylinder components are exposed to pressures fluctuating between suction and discharge and therefore to high fatigue loads. To reach high endurance capabilities, the cylinder components have to be pre-compressed in order to keep them operating under compressive stress whenever possible. Special materials and shrink fitting procedures are usually required. In other cases or for complex shapes, other technological processes, like autofrettage, are also applied to further improve the pre-stress level. The application of autofrettage requires special rigs to withstand the severe processing conditions and an intensifier to reach final pressures up to 1.4 GPa. Suitable sealing elements, identified through extensive experience, allow to reach very high pressures required to adequately strain the material. The pressure transmitting fluid must also have specific characteristics to avoid solidification. The autofrettage process requires special conditions to increase, maintain and remove the pressure on the system in order to achieve the desired deformation when the plastic strain region is reached. This produces an optimum autofrettage result for enhanced reliability and safe operation of the components.

scholarly journals Estudo do efeito da tensão sobre a permeação por Hidrogênio em Aços API 5L X60 e API 5L X65

2017 ◽  
Vol 1 (37) ◽  
pp. 18
Author(s):  
Bruno Araújo Araújo ◽  
Reginaldo Florêncio De Paiva Filho ◽  
Eudésio Oliveira Vilar ◽  
Misael Souto De Oliveira ◽  
Antonio Almeida Silva
Keyword(s):  
Strong Influence ◽  
Oil And Gas ◽  
High Pressures ◽  
Great Influence ◽  
Operating Conditions ◽  
Lattice Deformation ◽  
X65 Steel ◽  
Properties Of Materials ◽  
Api 5L X65 Steel ◽  
Diffusion Properties

<p>Under operating conditions, the oil and gas transmission pipelines can be subjected to high pressures and, at the same time, suffer the effect of acidic substances in the transported hydrocarbons such as H2S, whose action alone or combined with stresses acting in the structure can cause degradation processes of the mechanical properties of the material. Given the importance of the phenomenon, this work has as main objective the realization of hydrogen electrochemical permeation tests in API 5L X60 and API 5L X65 steels under mechanical loading conditions. A device for performing electrochemical permeation tests of hydrogen in the specimens subjected to stress was used for the tests. Thus, it was possible to observe experimentally the influence of stress on the diffusion properties during the experiment. By applying stress on the order of 20% of the yield strength, it was possible to verify the increase of diffusivity of API 5L X60 steel. Furthermore, there was a strong influence of the stress level of permeability, because a large increase of permeability of API 5L X65 steel. The results indicate that the lattice deformation due to imposed mechanical stress has a great influence on the diffusion properties of materials</p>

Flow Coefficient Evaluation of Poppet Valves Used in Reciprocating Compressors for LDPE

2008 ◽  
Author(s):  
Enzo Giacomelli ◽  
Massimo Schiavone ◽  
Fabio Manfrone ◽  
Andrea Raggi
Keyword(s):  
Pressure Drop ◽  
Time Pressure ◽  
Experimental Tests ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Operating Life ◽  
High Fatigue ◽  
Strongly Connected ◽  
And Performance ◽  
Poppet Valves

Poppet valves have been used for a long time for very high pressure reciprocating compressors, as for example in the case of Low Density Polyethylene. These applications are very critical because the final pressure can reach 350 MPa and the evaluation of the performance of the machines is strongly connected to the proper operation and performance of the valve itself. The arrangement of cylinders requires generally a certain compactness of valve to withstand high fatigue stresses, but at the same time pressure drop and operating life are very important. In recent years the reliability of the machines has been improving over and over and the customers’ needs are very stringent. Therefore the use of poppet valves has been extended to other cases. In general the mentioned applications are heavy duty services and the simulation of the valves require some coefficients to be used in the differential equations, able to describe the movement of plate/disk or poppet and the flow and related pressure drop through the valves. Such coefficients are often determined in an experimental way in order to have a simulation closer to the real operating conditions. For the flow coefficients it is also possible today to use theoretical programs capable of determining the needed values in a quick and economical way. Some investigations have been carried out to determine the values for certain geometries of poppet valves. The results of the theory have been compared with some experimental tests. The good agreement between the various methods indicates the most suitable procedure to be applied in order to have reliable data. The advantage is evident as the time necessary for the theoretical procedure is faster and less expensive. This is of significant importance at the time of the design and also in case of a need to provide timely technical support for the operating behavior of the valves. Particularly for LDPE, the optimization of all the parameters is strongly necessary. The fatigue stresses of cylinder heads and valve bodies have to match in fact with gas passage turbulence and pressure drop, added to the mechanical behavior of the poppet valve components.

scholarly journals Inner Damping of Water in Conduit of Hydraulic Power Plant

2021 ◽  
Vol 13 (13) ◽  
pp. 7125
Author(s):  
Daniel Himr ◽  
Vladimír Habán ◽  
David Štefan
Keyword(s):  
Power Plant ◽  
Operating Conditions ◽  
Mathematical Apparatus ◽  
Pressure Pulsations ◽  
Hydraulic Power ◽  
Economic Operation ◽  
Compression And Expansion ◽  
Rotor Stator Interaction ◽  
Start Ups

The operation of any hydraulic power plant is accompanied by pressure pulsations that are caused by vortex rope under the runner, rotor–stator interaction and various transitions during changes in operating conditions or start-ups and shut-downs. Water in the conduit undergoes volumetric changes due to these pulsations. Compression and expansion of the water are among the mechanisms by which energy is dissipated in the system, and this corresponds to the second viscosity of water. The better our knowledge of energy dissipation, the greater the possibility of a safer and more economic operation of the hydraulic power plant. This paper focuses on the determination of the second viscosity of water in a conduit. The mathematical apparatus, which is described in the article, is applied to data obtained during commissioning tests in a water storage power plant. The second viscosity is determined using measurements of pressure pulsations in the conduit induced with a ball valve. The result shows a dependency of second viscosity on the frequency of pulsations.

scholarly journals Quantifying the Effect of Kinetic Uncertainties on NO Predictions at Engine-Relevant Pressures in Premixed Methane-Air Flames

2019 ◽  
Author(s):  
Antoine Durocher ◽  
Gilles Bourque ◽  
Jeffrey M. Bergthorson
Keyword(s):  
Gas Turbine ◽  
High Pressures ◽  
Reaction Pathway ◽  
Methane Combustion ◽  
Operating Conditions ◽  
Combustion Model ◽  
Atmospheric Conditions ◽  
N2o Production ◽  
Large Variability ◽  
Kinetic Rates

Abstract Accurate and robust thermochemical models are required to identify future low-NOx technologies that can meet the increasingly stringent emissions regulations in the gas turbine industry. These mechanisms are generally optimized and validated for specific ranges of operating conditions, which result in an abundance of models offering accurate nominal solutions over different parameter ranges. At atmospheric conditions, and for methane combustion, a relatively good agreement between models and experiments is currently observed. At engine-relevant pressures, however, a large variability in predictions is obtained as the models are often used outside their validation region. The high levels of uncertainty found in chemical kinetic rates enable such discrepancies between models, even as the reactions are within recommended rate values. The current work investigates the effect of such kinetic uncertainties in NO predictions by propagating the uncertainties of 30 reactions, that are both uncertain and important to NO formation, through the combustion model at engine-relevant pressures. Understanding the uncertainty sources in model predictions and their effect on emissions at these pressures is key in developing accurate thermochemical models to design future combustion chambers with any confidence. Lean adiabatic, freely-propagating, laminar flames are therefore chosen to study the effect of parametric kinetic uncertainties. A non-intrusive, level 2, nested sparse-grid approach is used to obtain accurate surrogate models to quantify NO prediction intervals at various pressures. The forward analysis is carried up to 32 atm to quantify the uncertainty in emissions predictions to pressures relevant to the gas turbine community, which reveals that the NO prediction uncertainty decreases with pressure. After performing a Reaction Pathway Analysis, this reduction is attributed to the decreasing contribution of the prompt-NO pathway to total emissions, as the peak CH concentration and the CH layer thickness decrease with pressure. In the studied lean condition, the contribution of the pressure-dependent N2O production route increases rapidly up to 10 atm before stabilizing towards engine-relevant pressures. The uncertain prediction ranges provide insight into the accuracy and precision of simulations at high pressures and warrant further research to constrain the uncertainty limits of kinetic rates to capture NO concentrations with confidence in early design phases.

Thermoeconomic Analysis of a Solar MVC Desalination System

2018 ◽  
Author(s):  
Lei Gao ◽  
Yunho Hwang ◽  
Gyeong Sung Kim
Keyword(s):  
Water Supply ◽  
Fresh Water ◽  
Great Influence ◽  
Operating Conditions ◽  
Specific Power ◽  
World Population ◽  
Vapor Compression ◽  
Solar Pv ◽  
Pump System ◽  
Fresh Water Supply

Globally, about 10% of the world population does not have access to enough fresh water. In many hot-and-dry coastal regions and islands, the desalination of seawater might be the only practical option to have a fresh water supply. Therefore, low-cost desalination system is critical for freshwater demands. To address this issue, a desalination system consisting of solar photovoltaic (PV) and mechanical vapor compression subsystem is proposed in this study. The entire desalination system was modeled and designed to produce 10,000 m3 of fresh water per day at the coast of San Francisco, California. Key components such as water vapor compressor, solar PV panel, and three-stream heat recovery unit were designed, and their performances were analyzed. The effects of design variables and operating conditions on the system performance were investigated through a parametric study. Finally, an economic analysis was conducted and compared with current desalination technologies. The analysis results show that the specific power consumption of desalination system can reach 14.4 kWh/m3 when the evaporation temperature is 70°C. It is found that the evaporating temperature has a great influence on the heat pump system efficiency and evaporator design. The levelized cost of the proposed system is $0.76 per m3 of fresh water which is lower than current grid-powered vapor compression desalination system and other thermal desalination systems. The proposed solar PV driven desalination improves thermoeconomics of desalination system by applying low-lift operating condition to the vapor compression cycle so that it can contribute to solving the fresh water supply challenges.

scholarly journals Improvement of Intake Structures in a Two-Way Pumping Station with Experimental Analysis

2020 ◽  
Vol 10 (19) ◽  
pp. 6842
Author(s):  
Yanjun Li ◽  
Rong Lu ◽  
Huiyan Zhang ◽  
Fanjie Deng ◽  
Jianping Yuan
Keyword(s):  
Frequency Domain ◽  
Great Influence ◽  
Operating Conditions ◽  
Stable Operation ◽  
Pressure Pulsations ◽  
Pump Unit ◽  
Measuring Point ◽  
Time Frequency ◽  
Pumping Station ◽  
Bell Mouth

Pumping stations are important regulation facilities in a water distribution system. Intake structures can generally have a great influence on the operational state of the pumping station. To analyze the effects of the bell mouth height of the two-way intake on the performance characteristics and the pressure pulsations of a two-way pumping station, the laboratory-sized model pump units with three different intakes were experimentally investigated. To facilitate parameterized control, ellipse and straight lines were used to construct the profile of the bell mouth. The frequency domain and time-frequency domain of the pressure pulsations on the wall of intakes were analyzed by the Welch’s power spectral density estimate and the continuous wavelet transform (CWT) methods, respectively. The results showed that the bell mouth height (H) has significant influences on the uniformity of the impeller inflow and the operation stability of the pump unit. When H = 204 mm, the data fluctuated greatly throughout the test process and the performance curves are slightly lower than the other two schemes. As the bell mouth height gradually decreases, the average pressure difference of each measuring point began to decrease, more homogeneous velocity distribution of impeller inflow can be ensured. The amplitude of blade passing frequency is obvious in the spectrum. While when (H) is more than 164 mm, the main frequency of pressure pulsations at three points fluctuates with the rotation of the impeller. When H decreases to 142 mm, pressure pulsations will be independent of the operating conditions and positions which contributes to the long-term stable operation of the pump unit.

scholarly journals Usage of the influence coefficient during calculation of a nominal error of gas counters

2019 ◽  
Vol 298 ◽  
pp. 00009
Author(s):  
M.S. Ostapenko ◽  
M.A. Popova ◽  
A.M. Tveryakov
Keyword(s):  
Relative Error ◽  
Gas Flow ◽  
Oil And Gas ◽  
Great Influence ◽  
Operating Conditions ◽  
Effect Of Temperature ◽  
Influence Coefficient ◽  
Technical Documentation ◽  
Flow Meters ◽  
Influence Coefficients

In this paper, we evaluate the method of finding the relative error of gas flow meters taking into account the influence coefficients. A literature analysis was carried out, which showed that flow meters are used at oil and gas enterprises, which show its metrological characteristic, showing specific values of gas flow in operating conditions. Various types of gas flow meters are considered, with a description of the quality indicators of the devices. An additional error was investigated depending on changes in operating conditions. The calculations of the relative error of the meter taking into account the limiting values of the additional errors indicated in the technical documentation, as well as calculations taking into account the coefficients of influence under operating conditions. Based on the obtained values of the influence coefficients, graphs were constructed on which the effect of temperature and pressure on the error was determined. The article provides tabular values of the influence coefficients for petroleum gas, a conclusion is drawn on the applicability of this method.Oil and gas industry have a great influence on development of national economy in our country. Oil and gas have a leading position in energy industry and they are more effective and energy-intense in comparison with other natural substances.

Description of Typical Flow Instabilities in the Natural Circulation System

2002 ◽  
Author(s):  
Shengyao Jiang ◽  
Xingtuan Yang ◽  
Youjie Zhang
Keyword(s):  
Natural Circulation ◽  
Great Influence ◽  
Operating Conditions ◽  
Boiling Water ◽  
Flow Instabilities ◽  
Circulation System ◽  
Boiling Water Reactor ◽  
Primary Loop ◽  
Water Reactor ◽  
Test Loop

The experiments were performed on the test loop HRTL-5, which simulates geometry and system design of the 5-MW Nuclear Heating Reactor developed by the Institute of Nuclear Energy Technology, Tsinghua University. Because of the difference of the geometry design and operating conditions between the heating reactor and the boiling water reactor, the flow behavior presents great differences too, some of which haven’t been deeply studied so far. Results show that in heating reactor, sub-cooled boiling, condensation and flashing play an important role on the flow instabilities of the natural circulation system. Correspondingly, geysering instability, flashing instability, and flow excursion are the very typical instabilities occurring in the primary loop of HRTL-5, which are different from those in boiling water reactor conditions. The compressibility of the steam space on the top of the primary loop has also great influence on the instability of the natural circulation system.

Coupling ultrafiltration and adsorption onto activated carbon cloth: application to the treatment of highly coloured wastewaters

2000 ◽  
Vol 42 (5-6) ◽  
pp. 355-362 ◽  
Author(s):  
H. Pignon ◽  
C. Brasquet ◽  
P. Le Cloirec
Keyword(s):  
Molecular Weight ◽  
Activated Carbon ◽  
Adsorption Capacity ◽  
Membrane Filtration ◽  
Flow Reactor ◽  
Great Influence ◽  
Dye Adsorption ◽  
Operating Conditions ◽  
Carbon Cloth ◽  
Kinetics And Isotherms

The aim of this work is to evaluate the efficiency of Activated Carbon Cloths (ACCs) as a refining treatment of membrane filtration in the case of effluent streams containing both dyes and suspended solids (SS) or colloids responsible for turbidity. It is divided into two parts. First, dye adsorption experiments are carried out. Kinetics and isotherms enable us to show the feasibility of the adsorption and to study the influence of different operating conditions. The results demonstrate that adsorption is enhanced under acidic conditions, the adsorption capacity being increased by 40% in some cases. Moreover, microscopic characteristics of ACCs have a great influence on the adsorption process: there is a relationship between the adsorbent porosity and the adsorbate molecular weight, the mesoporous adsorbent being more efficious to remove the larger molecular weight dyes. In the case of low molecular weight compounds, the adsorbent with the higher specific surface area provides the greater adsorption capacity. Molecular connectivity indexes were used to confirm the correlation of the molecular structure of the adsorbates with their adsorbability. The second part consists of an estimation of the efficiency of the coupling of ultrafiltration and adsorption onto ACC. Tests performed on a laboratory-scale coupling show that a molecular weight cut-off of 3,000 D gives rise to a 98% removal of turbidity whereas dyes are not much retained. Furthermore, ultrafiltration is useful in improving the adsorption capacities of ACC in a continuous flow reactor (up to 50%).

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