Generator Retaining Rings: In Situ Inspection and Life Assessment

2009 ◽  
Author(s):  
Jan Willem Noteboom
Keyword(s):  
Life Assessment ◽  
Inspection System ◽  
Non Destructive Testing ◽  
Detection Capability ◽  
Destructive Testing ◽  
New Developments ◽  
Retaining Ring ◽  
The Common ◽  
Non Destructive

Stress corrosion cracking (SCC) in retaining rings of generators has been a major issue since large generator manufactures started to advise generator owners to replace and inspect retaining rings made from certain materials in the mid 1990’s. KEMA has been inspecting generator retaining rings with automated systems from the seventies on. Since 1995 new developments led to the possibility of also testing rings in situ, eliminating the need of removing the rotor from the stator and thus saving considerable down-time. Over the years, step by step improvements to the system and its application to generator retaining ring inspections have been implemented, one of which is the use of smaller probes and manipulators. Another improvement is the implementation of eddy current testing (ECT) to increase the detection capability for cracking at the outside surface in parallel to the automated ultrasonic testing (AUT). Experience obtained with this method contradicts some of the common ideas about reliability of other Non-destructive testing (NDT) methods, in particular the application of Dye Penetrant inspection (DPI) which appears to be less reliable. By performing fracture mechanics calculations to evaluate detected and sized flaw indications, predictions of remaining life of the rings can be made (Fitness-for-Purpose analysis). This paper presents results of applying the in situ retaining ring inspection system in the last 14 years and gives an overview of cases — some of those from recent inspections — where defect indications were detected, sized and evaluated. In some cases this resulted in recommendations to replace the retaining rings.

scholarly journals HIGH RISE FRAME BUILDING CONSTRUCTION WITH REGARD TO DEFECTS IN MONOLITHIC BASE SLAB

2020 ◽  
Vol 22 (5) ◽  
pp. 160-172
Author(s):  
S. V. Yushchube ◽  
I. I. Podshivalov ◽  
G. I. Tayukin
Keyword(s):  
Defect Formation ◽  
Strength Properties ◽  
Building Construction ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
High Rise ◽  
Frame Building ◽  
Concrete Layer ◽  
Non Destructive

The paper analyzes the influence of defects detected in a monolithic base slab on the possibility of its further application in the construction of a 25-storey high-rise frame building. Non destructive testing and vertical core sampling techniques are used for the detailed analysis of the monolithic base slab. It is found that irregularities in the procedure during winter concreting of the base slab decreases the strength properties of concrete and provides the defect formation in the slab structure, namely delamination of the lower protective concrete layer and uncovering of working reinforcement. For the safe use of the 25-storey high-rise building, the base slab is proposed to be strengthened by adding in-situ reinforced concrete layer 100 cm thick.

Defect Types and Ultrasonic Nondestructive Testing for Fiber-Reinforced Composites

2013 ◽  
Vol 834-836 ◽  
pp. 233-236
Author(s):  
Lin Dong Liu ◽  
Xiao Qing Wu
Keyword(s):  
Failure Modes ◽  
Fiber Reinforced Composites ◽  
Fracture Mechanisms ◽  
Reinforced Composites ◽  
Non Destructive Testing ◽  
Fiber Reinforced ◽  
Destructive Testing ◽  
The Common ◽  
Non Destructive ◽  
Ultrasonic Ndt

In this paper, an attempt is made to introduce the defect types relevant to ultrasonic non-destructive testing, and then, we explain how these defects generate in fiber-reinforced composites. The common failure modes which occur are described and discussed. The significance of each of the fracture mechanisms, in terms of their effects on the residual load-bearing properties, is considered. The second part describes briefly the main relevant ultrasonic NDT methods used to identify these defects and indicates the sensitivity to the different types of defect.

scholarly journals The De-Noising of Sonic Echo Test Data through Wavelet Transform Reconstruction

1999 ◽  
Vol 6 (5-6) ◽  
pp. 267-272 ◽  
Author(s):  
J.N. Watson ◽  
P.S. Addison ◽  
A. Sibbald
Keyword(s):  
Wavelet Transform ◽  
Test Data ◽  
Discrete Wavelet ◽  
Non Destructive Testing ◽  
Destructive Testing ◽  
Transform Method ◽  
Mexican Hat Wavelet ◽  
Mexican Hat ◽  
Non Destructive

This paper presents the results of feasibility study into the application of the wavelet transform signal processing method to sonic based non-destructive testing techniques. Finite element generated data from cast in situ foundation piles were collated and processed using both continuous and discrete wavelet transform techniques. Results were compared with conventional Fourier based methods. The discrete Daubechies wavelets and the continuous Mexican hat wavelet were used and their relative merits investigated. It was found that both the continuous Mexican hat and discrete Daubechies D8 wavelets were significantly better at locating the pile toe compared than the Fourier filtered case. The wavelet transform method was then applied to field test data and found to be successful in facilitating the detection of the pile toe.

Influence of Water Content on Fundamental Frequency of Mortar Sample

2015 ◽  
Vol 1124 ◽  
pp. 273-279 ◽  
Author(s):  
Ladislav Carbol ◽  
Jan Martinek ◽  
Ivo Kusák
Keyword(s):  
Water Content ◽  
Fundamental Frequency ◽  
Non Destructive Testing ◽  
In Situ Testing ◽  
Mortar Sample ◽  
Destructive Testing ◽  
Impact Echo ◽  
Influence Of Water ◽  
Non Destructive

Ultrasonic non-destructive testing methods such as Impact-echo are often conducted under different conditions. Such results might be distorted by ambient temperature or by water content of the tested sample. Tested mortar sample displayed shift of the fundamental frequency by 3.7 %. This article confirms necessity of standardized conditions during ultrasonic testing for both laboratory and in-situ testing.

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