Failure Investigation on Reheater Pendent Tubes Due to External Scale Exfoliation and Internal Scale Formation

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
J. Ahmad ◽  
J. Purbolaksono ◽  
A. K. Kadir ◽  
M. M. Rahman
Keyword(s):  
Tube Wall ◽  
High Temperature Corrosion ◽  
Scale Formation ◽  
Boiler Unit ◽  
External Scale ◽  
Failure Investigation ◽  
Tube Wall Thickness ◽  
Creep Analysis ◽  
Thickness Measurements ◽  
Internal Scale

This paper presents failure investigation on reheater pendent SA213-T22 tubes through visual inspections, steam-side scale and tube wall thickness measurements, metallurgical examinations, and creep analysis. The investigations were carried out following subsequent tube failures of the reheater pendent region of a boiler unit. Interaction event of significant internal scale formation causing the higher metal temperature and external scale exfoliation as a result of high-temperature corrosion is identified to cause the failure of the reheater pendent tube. Prevention actions are recommended to avoid similar failures in the future.

Structural Integrity Assessment of Steam Generator Tubes Using a New EPRI Statistical Approach

2002 ◽  
Author(s):  
Carlos Alexandre de Jesus Miranda ◽  
Miguel Mattar Neto
Keyword(s):  
Steam Generator ◽  
Wall Thickness ◽  
Nuclear Power ◽  
Structural Integrity ◽  
Tube Wall ◽  
New Approach ◽  
Inconel 600 ◽  
Integrity Assessment ◽  
Tube Wall Thickness ◽  
Uniform Tube

A fundamental step in tube plugging management of a Steam Generator (SG), in a Nuclear Power Plant (NPP), is the tube structural integrity evaluation. The degradation of SG tubes may be considered one of the most serious problems found in PWRs operation, mainly when the tube material is the Inconel 600. The first repair criterion was based on the degradation mode where a uniform tube wall thickness corrosion thinning occurred. Thus, a requirement of a maximum depth of 40% of the tube wall thickness was imposed for any type of tube damage. A new approach considers different defects arising from different degradation modes, which comes from the in-service inspections (NDE) and how to consider the involved uncertainties. It is based on experimental results, using statistics to consider the involved uncertainties, to assess structural limits of PWR SG tubes. In any case, the obtained results, critical defect dimensions, are within the regulatory limits. In this paper this new approach will be discussed and it will be applied to two cases (two defects) using typical data of SG tubes of one Westinghouse NPP. The obtained results are compared with ‘historical’ approaches and some comments are addressed from the results and their comparison.

The Formation of Tracheae and Tracheoles in Rhodnius prolixus

1958 ◽  
Vol s3-99 (45) ◽  
pp. 29-46
Author(s):  
M. LOCKE
Keyword(s):  
Axial Compression ◽  
Wall Thickness ◽  
Tube Wall ◽  
Rhodnius Prolixus ◽  
Axial Orientation ◽  
Tube Wall Thickness ◽  
Walled Cylinder ◽  
Tangential Orientation

The formation of tracheae in Rhodnius is described by the hypothesis of expansion and buckling. The cuticulin lining is at first a smooth-walled cylinder. Later it expands equally in each direction, increasing in diameter but buckling in the axis. An engineering expression describing symmetrical buckling in a cylinder under uniform axial compression has been applied to this process. Agreement was obtained between the expected and observed values for buckling frequency and tube-wall thickness. The taenidia are formed within the buckles, their amplitude being proportional to the increase in diameter. The axial orientation of the chitin micelles in the lining membrane and the tangential orientation in the taenidia are consistent with their being oriented by the stresses expected during expansion and buckling. The formation of tracheoles may also be described by the expansion and buckling hypothesis.

Experimental and Numerical Studies on Flexural Behavior of Casing Joint of Square Steel Tube

2010 ◽  
Vol 163-167 ◽  
pp. 417-420
Author(s):  
Min Ding ◽  
Zhen Hua Hou ◽  
Xiu Gen Jiang ◽  
Yu Zhi He ◽  
Guang Kui Zhang ◽  
...  
Keyword(s):  
Wall Thickness ◽  
Failure Modes ◽  
Shear Failure ◽  
Tube Wall ◽  
Edge Length ◽  
Steel Tube ◽  
Flexural Behavior ◽  
Flexural Capacity ◽  
Tube Wall Thickness ◽  
Square Steel Tube

The tests on thirteen specimens of casing joints of square steel tube were conducted to investigate the flexural behavior of the joints. And numerical simulation studies on that were carried out by ANSYS/LS-DYNA. On this basis, effects of tube wall thickness, tube edge length, and inserting depth on failure mode, ultimate flexural capacity and deformation of the joints were discussed. The results show that there are two types of failure modes, i.e., inside tube yield failure and outside tube shear failure. Ultimate flexural capacity and rigidity of the joints increased with the inserting depth increasing. The ultimate flexural capacity is proportional to tube shear strength, tube wall thickness, inserting depth, and tube edge length.

Effect of High-Temperature Corrosion on the Service Life of P91 Piping in Biomass Co-firing

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
C. P. O'Hagan ◽  
R. A. Barrett ◽  
S. B. Leen ◽  
R. F. D. Monaghan
Keyword(s):  
Tube Wall ◽  
Thermal Power ◽  
Creep Damage ◽  
High Temperature Corrosion ◽  
Corrosion Mechanism ◽  
Creep Life ◽  
Sem Images ◽  
X Ray ◽  
Superheater Tube ◽  
Wall Loss

Co-firing biomass with traditional fuels is becoming increasingly relevant to thermal power plant operators due to increasingly stringent regulations on greenhouse gas emissions. It has been found that when biomass is co-fired, an altered ash composition is formed, which leads to increased levels of corrosion of the superheater tube walls. Synthetic salt, which is representative of the ash formed in the co-firing of a 70% peat and 30% biomass mixture, has been produced and applied to samples of P91 at 540 °C for up to 28 days. This paper presents results for oxide layer thickness and loss of substrate from testing. Scanning electron microscopy (SEM) images and energy-dispersive X-ray spectroscopy (EDX) element maps are obtained and presented in order to gain an understanding of the complex corrosion mechanism which occurs. A finite-element (FE) methodology is presented which combines corrosion effects with creep damage in pressurized tubes. The effects of corrosion tube wall loss and creep damage on tube stresses and creep life are investigated.

Viewing the world through Lucy Corin’s “Eyes of Dogs”

2020 ◽  
Vol 6 (2) ◽  
pp. 191-212
Author(s):  
Nathan D. Frank
Keyword(s):  
Short Story ◽  
Narrative Text ◽  
The Other ◽  
External Scale ◽  
Spatial Metaphor ◽  
The World ◽  
Internal Scale ◽  
The Way

Abstract Marie-Laure Ryan, Kenneth Foote, and Maoz Azaryahu pave the way, in Narrating Space/Spatializing Narrative (2016), to think of space in narrative as well as narrative in space. I steer their approach through nonhuman space by examining a narrative traversal of “the mesh,” which is Timothy Morton’s spatial metaphor for human and nonhuman interconnection. “A narrative traversal of the mesh” indicates two distinct aspects of narrative motion, which can be thought of as the motion that occurs within a narrative’s fictional spaces (internal), and as the movement of a narrative through the non-fictional spaces of the mesh (external). A narrative’s internal and external motions suggest that a narrative text is itself an enmeshed pocket of nonhuman space that emulates the meshiness of the space that envelops it. The outcome of each “narrative traversal” is that the text purports to become the mesh, but this outcome registers on two scales – that of the storyworld containing a fictional mesh (the internal scale), and that of the actual, non-fictional mesh containing the storyworld (the external scale). Remarkably, each type of traversal relies on and influences the other, so that the tandem dynamism that obtains between them emerges as my object of inquiry more so than either of them individually. Since a narrative’s spatial situation is precisely that of one nonhuman space within the larger mesh, my reading of Lucy Corin’s short story, “Eyes of Dogs,” engages ultimately with the scalar discrepancy between text and world and concludes that narrative may serve as an extramental shelter from correlationism.

Joining by Forming of Tubes to Sheets with Counterbored Holes

2018 ◽  
Vol 767 ◽  
pp. 421-428 ◽  
Author(s):  
Luis M. Alves ◽  
Rafael M. Afonso ◽  
Carlos M.A. Silva ◽  
Paulo A.F. Martins
Keyword(s):  
Analytical Model ◽  
Cross Section ◽  
Room Temperature ◽  
Tube Wall ◽  
Rectangular Cross Section ◽  
Dissimilar Materials ◽  
Forming Process ◽  
Element Analysis ◽  
Joining By Forming ◽  
Tube Wall Thickness

This paper presents a new joining by forming process for connecting tubes to sheets. The process consists of forming an annular flange with rectangular cross section by partial sheet-bulk of the tube wall thickness and performing the mechanical interlock by upsetting the free tube end against a flat-bottomed (counterbored) sheet hole. The presentation identifies the variables and the workability limits of the process and includes an analytical model to assist readers in the design of the new joints. The new proposed joining by forming process and the corresponding analytical model are validated by experimentation and numerical simulation using finite element analysis. The process allows connecting tubes to sheets made from dissimilar materials at room temperature, avoids the utilization of addition materials or adhesives and produces joints that are easy to disassembly at the end of live, allowing recyclability of the tubes and sheets.

Third element control of external scale formation

1986 ◽  
Vol 20 (10) ◽  
pp. 1355-1358 ◽  
Author(s):  
J.E. Morral ◽  
M.S. Thompson ◽  
O.F. Devereux
Keyword(s):  
Scale Formation ◽  
External Scale
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