Analysis of the Flange Seal Groove Cracking in a Hydrocracking Reactor

2020 ◽  
Author(s):  
Fakun Zhuang ◽  
Wen Liu ◽  
Guoshan Xie ◽  
Shanshan Shao ◽  
Zhiyuan Han
Keyword(s):  
High Temperature ◽  
High Stress ◽  
Metallographic Analysis ◽  
Operational Conditions ◽  
Σ Phase ◽  
Term Operation ◽  
Brittle Phase ◽  
Series Of Experiments ◽  
Cracking Tendency

Abstract The hydrocracking reactor, serving at the high temperature and pressure and containing S and N elements in medium, are the key equipment in the hydrocracking plant. Due to the severe operational conditions, flange and nozzle cracking commonly occurs, especially for the seal groove between the flange and gasket. A cracked stainless flange is found in a hydrocracking reactor during parking and maintenance. Through a series of experiments including chemical composition, metallographic analysis, SEM and fracture analysis, the flange seal groove is analyzed. Under the long term operation at high temperature and high pressure, the σ phase is found in the flange material which will increase the cracking tendency. The hydrogen content measurement also proves that the material has the hydrogen embrittlement tendency. Hence, the combination of σ brittle phase and high stress causes the flange seal groove cracking. After cracking, hydrogen element enters the fracture, thus accelerating the crack growth. Therefore, in order to prevent the flange cracking, the assembly stress should be controlled in an appropriate range. If necessary, periodical inspection must be performed.

Analysis of the Gasket Damage and Sealing Performance for the Thread Ring Block Heat Exchanger

2019 ◽  
Author(s):  
Fakun Zhuang ◽  
Wen Sui ◽  
Guoshan Xie ◽  
Shanshan Shao ◽  
Zhiyuan Han ◽  
...  
Keyword(s):  
High Temperature ◽  
Heat Exchanger ◽  
Metallographic Analysis ◽  
Tube Sheet ◽  
Operational Conditions ◽  
Term Operation ◽  
High Temperature And Pressure ◽  
Sealing Performance ◽  
Temperature And Pressure ◽  
Gasket Material

Abstract The thread ring block heat exchangers, served at the high temperature and pressure, are the key equipment in the petrochemical industry. Due to the severe operational conditions and unsuitable assemble, internal leakage problem commonly occurs, especially for the seal gasket between the tube sheet and shell. Many failed gaskets are collected. Through a series of experiments including chemical composition, metallographic analysis, SEM and fracture analysis, the gasket damage and leakage causes are analyzed. For further interpretation, the gasket stress analysis is completed by the finite element method. It shows that the gasket stress is a main factor that affects the sealing performance for the thread ring block heat exchanger. Under long term operation at high temperature and pressure, the gasket stress between the tube sheet and shell becomes loose and creep. The gasket material also deteriorates with increasing time. Therefore, in order to prevent the internal leakage, the stress should be controlled in an appropriate range. And periodical inspection must be performed.

The Analyses for the Casing Improvements of the MPM-20 Engine

2015 ◽  
Author(s):  
K. Ratkovská ◽  
J. Čerňan ◽  
M. Cúttová ◽  
K. Semrád
Keyword(s):  
Emission Spectra ◽  
Infrared Emission ◽  
Point Of View ◽  
Thermally Induced ◽  
Operational Conditions ◽  
Term Operation ◽  
Structural Modifications ◽  
Operational Issues ◽  
Combustor Liner

The operational issues of a small turbojet engine MPM – 20 are discussed. The engine was created by modifying the Soviet turbostarter TS – 20B/21 designed for short-term operation. It is necessary to make structural modifications that allow for the long-term operational premise of the engine. For this purpose, several analyses were focused on the thermally stressed parts. The first, a material analysis carried out on the outer casing of the combustion chamber and on the combustor liner reveals information about the mechanical properties of these structural nodes. It was necessary since there is no documentation of the engine with this information. Another analysis of the infrared emission spectra is important for monitoring operational conditions, especially from the temperature point of view. Subsequent stress analysis of the casing is based on results from previous analyses. It was used to observe the behaviour of the casing as operational conditions changed. This revealed a dangerous increase of thermally induced stress levels as temperature increased up to 150°C. Various structural modifications can be made in the future with these results, such as an application of a protective coating on the casing and combustor liner of the engine.

Influence of Creep on Low-Cycle Fatigue Life Assessment of Ultra-Supercritical Steam Turbine Rotor

2014 ◽  
Author(s):  
W. Z. Wang ◽  
J. H. Zhang ◽  
H. F. Liu ◽  
Y. Z. Liu
Keyword(s):  
High Temperature ◽  
Steam Turbine ◽  
Fatigue Damage ◽  
Low Cycle Fatigue ◽  
Turbine Rotor ◽  
High Temperature Creep ◽  
Cycle Fatigue ◽  
Term Operation ◽  
Start Up

Linear damage method is widely used to calculate low-cycle fatigue damage of turbine rotor in the long-term operation without fully considering the interaction between creep and low cycle fatigue. However, with the increase of steam turbine pressure and temperature, the influence of high-temperature creep on the strain distribution of turbine rotor becomes significant. Accordingly, the strain for each start-up or shut-down process is different. In the present study, the stress and strain during 21 iterations of continuous start-up, running and shut-down processes was numerically investigated by using the finite element analysis. The influence of high-temperature creep on low cycle fatigue was analyzed in terms of equivalent strain, Mises stress and low cycle fatigue damage. The results demonstrated that the life consumption of turbine rotor due to low cycle fatigue in the long-term operation of startup, running and shutdown should be determined from the full-time coverage of the load of turbine rotor.

Analysis of the Cause of Damage to the Steam Generator Cold Collector’s Dissimilar Weld Joint at Slovak Nuclear Power Plant

2020 ◽  
Vol 405 ◽  
pp. 165-170
Author(s):  
Michal Kapusňák ◽  
Michal Hajas ◽  
Marek Adamech
Keyword(s):  
Steam Generator ◽  
Weld Joint ◽  
Nuclear Power ◽  
Metallographic Analysis ◽  
Destructive Testing ◽  
Term Operation ◽  
Dissimilar Weld ◽  
Root Position ◽  
Non Destructive

By the non-destructive testing of a dissimilar weld joint (DWJ) of cold collector DN 1100 (CC) on a steam generator, indications were found on inner-side cold collector’s surface at the root position of the examined weld. All the identified indications were very similar in shape and form, therefore, it was decided to cut out a part of the damaged site from this type of DWJ DN 1100 and get the obtained ring (real piece of material) for complex metallographic analysis. This paper briefly describes the results and recommendations found for the future reference during the next long‑term operation induced ageing and degradation of critical steam generator parts in NPP Bohunice Unit 4. There are summarized the results obtained from evaluation of original DWJ material.

High Temperature Behavior of Candidate VHTR Heat Exchanger Alloys

2008 ◽  
Author(s):  
Richard Wright ◽  
Joel Simpson ◽  
Alan Wertsching ◽  
W. David Swank
Keyword(s):  
High Temperature ◽  
Good Deal ◽  
Carbon Activity ◽  
Haynes 230 ◽  
Environmental Resistance ◽  
Principal Candidates ◽  
Inconel 617 ◽  
Series Of Experiments ◽  
Term Response

Several nickel based solid solution alloys are under consideration for application in heat exchangers for very high temperature gas cooled reactors. The principal candidates being considered for this application by the Next Generation Nuclear Plant (NGNP) project are Inconel 617 and Haynes 230. While both of these alloys have an attractive combination of creep strength, fabricability, and oxidation resistance a good deal remains to be determined about their environmental resistance in the expected NGNP helium chemistry and their long term response to thermal aging. A series of experiments has been carried out in a He loop with controlled impurity chemistries within the range expected for the NGNP. The influence of oxygen partial pressure and carbon activity on the microstructure and mechanical properties of Alloys 617 and 230 has been characterized. A relatively simple phenomenological model of the environmental interaction for these alloys has been developed.

Elevated temperature creep properties of NiAl eryomilled with and without Y2O3

1995 ◽  
Vol 10 (5) ◽  
pp. 1171-1186 ◽  
Author(s):  
J. Daniel Whittenberger ◽  
Michael J. Luton
Keyword(s):  
High Temperature ◽  
Elevated Temperature ◽  
Stress Exponent ◽  
Tensile Testing ◽  
High Stress ◽  
Tensile Creep ◽  
High Temperature Strength ◽  
Compression Tests ◽  
Creep Properties

The creep properties of lots of NiAl eryomilled with and without Y2O3 have been determined in compression and tension. Although identical cryomilling procedures were used, differences in composition were found between the lot ground with 0.5 vol % yttria and the lot ground without Y2O3. Compression testing between 1000 and 1300 K yielded similar crecp strengths for both materials, while tensile creep rupture testing indicated that the yttria-containing alloy was slightly stronger than the Y2O3-free version. Both compression and tensile testing showed two deformation regimes; whereas the stress state did not affect the high stress exponent (n ≍ 10) mechanism, the low stress exponent regime n was ∼6 in tension and ∼2 in compression. The strengths in tension were somewhat less than those measured in compression, but the estimated activation energies (Q) of ∼600 kJ/mol for tensile testing were closer to the previously measured values (∼700 kJ/mol) for NiAl-AlN and very different from the Q's of 400 and 200 kJ/mol for compression tests in the high and low stress exponent regimes, respectively. A Larson-Miller comparison indicated that cyromilling can produce an alloy with long-term, high-temperature strength at least equal to conventional superalloys.

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