scholarly journals Heavy Loaded Parts of Petrochemical Equipment Destruction Cause Investigation

2022 ◽  
Vol 17 ◽  
pp. 1-7
Author(s):  
A. B. Laptev ◽  
S. A. , Naprienko ◽  
R. ZH. Akhiyarov ◽  
A. V. Golubev
Keyword(s):  
Mechanical Stress ◽  
Phase Inversion ◽  
Sequential Analysis ◽  
Narrow Range ◽  
Metals And Alloys ◽  
Operating Conditions ◽  
Corrosion Products ◽  
Local Corrosion ◽  
Film Performance ◽  
Petrochemical Equipment

The problem of using specialized passivating metals and alloys lies in a rather narrow range of the protecting film performance. With a slight change in operating conditions, the film is destroyed and an avalanche-like process of local corrosion begins at the place of film breakdown. A sequence has been developed for determining parts destruction causes, including a sequential analysis of operating conditions; nature of the part destruction; corrosion products composition; phase inversion in the alloy during overheating or mechanical stress in the part.

scholarly journals A Numerical Model for Bubble Size Distribution in Turbulent Gas-Liquid Dispersion

2010 ◽  
pp. 25-34 ◽  
Author(s):  
MAK Azad ◽  
Sultana R Syeda
Keyword(s):  
Numerical Model ◽  
Size Distribution ◽  
Bubble Size ◽  
Chemical Engineering ◽  
Narrow Range ◽  
Collision Frequency ◽  
Bubble Size Distribution ◽  
Operating Conditions ◽  
Liquid Dispersion ◽  
Bubble Collision

In present study a numerical model for bubble size distribution is developed that considers bothbreakage and coalescence in turbulent gas liquid dispersion. Two-step mechanisms are considered forboth breakage and coalescence of bubbles. The bubble breakage is structured as the product of thebubble-eddy collision frequency and breakage efficiency in gas-liquid dispersions. The coalescencefunction considers the product of bubble-bubble collision frequency and coalescence efficiency. Themodel overcomes several limitations observed in previous efforts such as empirical parameters,narrow range of operating conditions, and narrow range of geometries. Favorable agreement is foundbetween the predicted bubble size distribution and the experimental data reported in the literature. Thepercentage of error obtained for the average bubble size was found within ± 17%.Journal of Chemical Engineering Vol.ChE 24 2006 25-34

Localized Electrochemical Corrosion Characteristics of Carbon Steel in Seawater

2013 ◽  
Vol 842 ◽  
pp. 104-109
Author(s):  
Yan Zou ◽  
Qiang Bai ◽  
Jia Wang ◽  
Wei Wang ◽  
Xiang Feng Kong
Keyword(s):  
Carbon Steel ◽  
Water Surface ◽  
Immersion Time ◽  
Electrochemical Corrosion ◽  
Corrosion Products ◽  
Local Corrosion ◽  
Immersion Period ◽  
Wire Beam Electrode

The galvanic and potential distributions of carbon steel immersed in seawater were studied by wire beam electrode (WBE) technique. Results indicated that the corrosion of carbon steel in seawater tended to local corrosion. With immersion time increasing, local corrosion was more and more serious. During the initial immersion period, the top of the coupon near the water surface was main cathode. With the corrosion extended, corrosion products gradually gathered on the surface of the carbon steel. Potential differences between cathode and anode gradually became small. Cathode and anode redistributed on the surface of carbon steel. At last, the top and the bottom were cathode while the middle was anode. The areas of anode first increased and then decreased. The areas of cathode were in contrast.

Integrity Assessment of Spherical Pressure Components With Local Corrosion and Hot Spots

2006 ◽  
Author(s):  
Pattaramon Tantichattanont ◽  
Seshu Adluri ◽  
Rangaswamy Seshadri
Keyword(s):  
Lower Bound ◽  
Hot Spots ◽  
Structural Integrity ◽  
Hot Spot ◽  
Corrosion Damage ◽  
Pressure Vessels ◽  
Operating Conditions ◽  
Local Corrosion ◽  
Integrity Assessment ◽  
Spherical Pressure

Corrosion damage and hot spots are typical of damages that can occur in ageing pressure vessels and pipelines used in industrial processes. Internal and external corrosion could be the result of corrosive products stored inside or harsh environmental conditions on the outside. Hot spots are caused by damage due to loss of refractory lining on the inside wall of pressure components or due to maldistribution of flow containing catalyst and reactive fluids. The structural integrity of such ageing components needs to be evaluated periodically to establish the continued suitability of the vessels under operating conditions. The present paper develops a method for Level 2 (as categorized by API 579) structural integrity evaluations of spherical pressure vessels containing local corrosion damage or hot spot. The decay lengths for spherical shells subject to local damages have been studied based on stretching and bending effects using elastic shell theories so as to identify the reference volume participating in plastic action. A limit for “local” corroded spot or hot spot is defined by the size of damage that an onset of pure membrane action occurs inside the damaged area. The size of damage indicating the crossover from dominance of stretching effects on the damage behavior to that of bending effects is also presented. The lower bound recommended “remaining strength factors” for spherical pressure vessels containing corrosion or hot spot are formulated by application of Mura’s integral mean of yield criterion and the improved lower bound mα-multiplier. Three alternative recommendations are proposed. The effectiveness of the proposed methods is evaluated and demonstrated through illustrative examples and comparison with inelastic finite element analyses.

Buildup and Decay Analysis of Corrosion Products Activity in Primary Coolant Loop of AP-1000

2018 ◽  
Author(s):  
Fiaz Mahmood ◽  
Huasi Hu ◽  
Liangzhi Cao
Keyword(s):  
Radiation Exposure ◽  
Operating Conditions ◽  
Corrosion Products ◽  
Normal Operation ◽  
Reactor Operation ◽  
Primary Coolant ◽  
Reactor Control ◽  
Power Regulation ◽  
Coolant Loop ◽  
Control Regime

The broad half-life range of Activated Corrosion Products (ACPs) results in major radiation exposure throughout reactor operation and shutdown. The movement of unpredicted activity hot spots in coolant loop can bring about huge financial and dosimetric impacts. The PWR operating experience depicts that activity released during reactor operation and shutdown cannot be estimated through a simple correlation. This paper seeks to analyze buildup and decay behavior of ACPs in primary coolant loop of AP-1000 under normal operation, power regulation and shutdown modes. The application of a well-tested mathematical model is extended in an in-house developed code CPA-AP1000, to simulate the behavior of dominant Corrosion Products (CPs), by programing in MATLAB. The MCNP code is used as a subroutine of the program to model the reactor core and execute energy dependent neutron flux calculations. It is observed that short-lived CPs (56Mn, 24Na) build up rapidly under normal operation mode and decay quickly after the reactor is shutdown. The long-lived CPs (59Fe, 60Co, 99Mo) have exhibited slow buildup under normal operating conditions and likewise sluggish decay after the shutdown. To analyze activity response during reactor control regime, operating power level is promptly decreased and in response specific activity of CPs also followed decreasing trend. It is noticed that activity of CPs drops slowly during reactor control regime in comparison to emergency scram. The results are helpful in estimating radiation exposure caused by ACPs during accessibility of the equipment in coolant loop, under normal operation, power regulation and shutdown modes. Moreover, current analyses provide baseline data for further investigations on ACPs in AP-1000, being a new reactor design.

Improving Refractories for Waste to Energy Challenges

2011 ◽  
Author(s):  
Patrick M. Stephan ◽  
William H. Burak
Keyword(s):  
Water Content ◽  
Narrow Range ◽  
Operating Conditions ◽  
Waste To Energy ◽  
Energy Market ◽  
Thermal Gradients ◽  
Wide Range ◽  
Refractory Life ◽  
Materials Used ◽  
Harmful Effects

Operating conditions in steam generating units (boilers) in the waste-to-energy market present a wide range of operating conditions which challenge materials used throughout the units. While operators attempt to operate within a narrow range of conditions, the variability of fuel types, heating values and water content specifically affect refractory life throughout the units. In recent years, many operators have modified combustion conditions in order to reduce controlled emissions, resulting in higher temperatures, larger thermal gradients and different gas chemistries, with potentially harmful effects on refractory performance. Refractory manufacturers have responded through material developments and installation improvements which are meeting the new operating challenges.

Model for Estimation of Metallization Lifetime Including Electromigration and Thermo-Mechanical Stress Relaxation

1998 ◽  
Vol 516 ◽  
Author(s):  
Herbert F. Roloff ◽  
Johannes Fellinger
Keyword(s):  
Stress Relaxation ◽  
Mechanical Stress ◽  
Operating Conditions ◽  
Structural Dimensions

AbstractFuture semiconductor technologies with structural dimensions less than 0.35 µm and four or more metallization layers impede the realization of the reliability requirements due to their complexity and increasing operating conditions (>5 mA/µm2). Therefore it is necessary to provide reliability appraisal methods which ensure the operation lifetimes (up to 30 years) required by the market.

scholarly journals CO2 Absorption with NaOH Solution through the Porous PVDF Hollow Fibre Membrane Contactor

2017 ◽  
Vol 12 (1) ◽  
Author(s):  
A. Mansourizadeh ◽  
A. F. Ismail
Keyword(s):  
Flow Rate ◽  
Hollow Fiber ◽  
Phase Inversion ◽  
Co2 Flux ◽  
Operating Conditions ◽  
Co2 Absorption ◽  
Membrane Contactor ◽  
Hydrophobic Membrane ◽  
Transfer Resistance ◽  
Naoh Solution

In this study, porous hydrophobic polyvinylidene fluoride (PVDF) hollow fiber membranes were fabricated via a wet phase inversion process. In order to improve the phase inversion rate and provide porous membranes, 4 wt.% lithium chloride (LiCl) was used in the spinning dope. The prepared membrane morphology was studied using field emission scanning electron microscopy (FESEM). Chemical CO2absorption by NaOH solution (1M) was conducted through the PVDF hollow fiber membrane contactor. The effect of the main operating condition such as absorbent temperature, CO2 pressure and absorbent flow rate on the performance of CO2 absorption was investigated. From FESEM examination, the membrane possesses an almost sponge–like structure with ultra thin skin layer. Results of CO2absorption test showed that by increasing the absorbent flow rate the CO2 flux increased which confirmed the existence of liquid side mass transfer resistance. It was found that by increasing the absorbent temperature the CO2 flux considerably improved. Meanwhile, the effect of CO2 pressure on the absorption rate was insignificant. Therefore, it can be concluded that by applying a porous hydrophobic membrane with improved structure and optimizing the operating conditions, high CO2 removal efficiency can be achieved through gas–liquid membrane contactors

scholarly journals Simplified calculation method for coupled thermal--mechanical stress of drum using beam elements

2021 ◽  
Author(s):  
yanjun Li ◽  
zhenhua Zhang ◽  
qingpeng Zeng ◽  
chenshuo Li ◽  
jianxin Shi ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Mechanical Stress ◽  
Low Cycle Fatigue ◽  
Complex Structure ◽  
Operating Conditions ◽  
Life Assessment ◽  
Systematic Evaluation ◽  
Beam Elements ◽  
Simplified Method ◽  
Dual Action

The drum is the core part of a supercharged boiler that is prone to fatigue damage due to the dual action of thermal and mechanical stress. However, owing to its complex structure, complete modeling calculation of the drum requires considerable computational resources. Therefore, based on the basic theory of beam elements, we propose a simplified method using beam elements in place of solid tubes and evaluate the feasibility of this method. The results demonstrate that the simplified method reduced the overall mesh number of the model by 67.19% and the calculation time by 68.08%. Moreover, compared to the solid model, the maximum relative errors of stress and displacement were only 3.44% and 5.16%. Considering the dispersion of low-cycle fatigue life, we applied a statistical approach to the fatigue life assessment of the drum, and obtained the probability of failure corresponding to the fatigue life of the drum under the given operating conditions. This method provides an important basis for the systematic evaluation of fatigue life under various operating conditions and the prediction of failure occurrence.

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