Here is our collection of papers, articles, and posters that were presented at various conferences and published in NDT magazines.
Capabilities of Modern Tank Floor Scanning with Magnetic-Flux Leakage
Presented at the WCNDT conference 2016 by Jim Costain
This paper focuses on state-of-the-art magnetic-flux leakage (MFL) technology for the inspection of storage tank floors. The primary advantage of the MFL approach is the ability to locate and estimate the size of defects over large areas in a quick and efficient manner. As with any inspection approach, there are limitations which can influence the consistency and reliability of reported defects.
Efficient Inspection from Measurement Collection to Report
Presented at the WCNDT conference 2016
Ascertaining the integrity of large steel structures such as storage tanks, pipes and vessels is a complex task. Silverwing (UK) Ltd has developed an inspection solution that can inspect, manage, present and generate reports. The inspection data generated from these large assets can be large, requiring gigabytes to even terabytes of storage and meticulous analysis. While it is normally accepted that more data is always better, the ability to handle, analyse and report findings with vast amounts of information efficiently becomes a challenge.
Bandwidth of MFL in Steel Plate Inspection
Presented at the WCNDT conference 2016 by Dr. Neil Pearson
Magnetic-flux leakage (MFL) continues to be a widely used approach to detect defects caused by corrosion in applications with large areas. The principal merit of MFL is that large areas can be covered relatively quickly making it beneficial for example in the inspection of asset components that are costly to expose and in large area; two good examples are the floor of above ground storage tanks or exceedingly large surface areas such as pipelines.
Factors that Affect the Defect Sizing capabilities of Magnetic-Flux Leakage
This paper is concerned with investigating inherent MFL technology variables that affect the reliability, repeatability and accurate sizing of defects. External defect sizing factors such as a clean inspection environment are not considered. With such extraneous variables removed the effects on the MFL signal due to magnetic saturation, the calibration process and of defect geometry can be investigated.
Improving Confidence in Tank Inspection
Tank inspection is an important part of effective asset management, from both regulatory and operating efficiency perspectives. A failure of a tank can be catastrophic, but probably more likely is degradation resulting in slow loss of stored product and possibly contamination of the environment.
Discrimination of Top and Bottom Discontinuities with MFL STARS Technology
Discontinuities due to corrosion can occur on the top and bottom surface of above-ground storage tank (AST) floors and can, if unknown increase the likelihood of a leak as inadequate repair strategies may be applied. Although surface discrimination can in some cases be achieved visually, low lighting conditions and in particular ASTs with opaque coatings on the top surface of the floor make the task of identifying top surface discontinuities difficult.
Tank Assessment Depends on the Accuracy of Measurements and the Probability of Detection
Storage tank corrosion inspection is an essential part of asset management, being used not only to certify safe operation, but also to predict expected lifetime, devise a repair strategy and assess the impact of different stored contents.
The Challenge to Asset Owners and Operators is to Use New Systems to Reduce Out-of-Service Time
Storage tanks are an essential part of the distribution network and are vital in buffering the varying demands of end users. They are most commonly built from steel with thickness from 5–15 mm (0.2–0.6 in). Steel is a relatively cheap and strong material that can easily fabricated on site, but has inherent problems of corrosion over time.
The Influence of Maintenance on the Life Cycle of Above-Ground Storage Tanks
In supply chains such as those in the petrochemical industry, the AST plays an important role in ensuring a continuous flow of product and these like other components must undergo regular maintenance. While maintenance on the majority of surfaces of the typical AST can be conducted when in its normal operational condition, the AST floor presents a particular challenge because of its inaccessibility. As a consequence the tank has to be periodically emptied and made out-of-service to conduct inspections and repair work deemed necessary. This is a costly activity both in terms of loss of earnings and the maintenance operation itself.
Practical Limits of MFL in Steel Plate Inspection
MFL is a widely used approach to detect corrosion in applications where large areas are to be inspected in short time scales. A particularly good example is in ASTs in the petrochemical industry where tank floors are inspected periodically, calling for ASTs to be taken out of service and emptied. This makes maintenance times that much more expensive and calls for techniques that are both reliable and fast.
A Study of MFL Signals from a Spectrum of Defect Geometries
Presented by Neil Pearson at the 18th World Conference for Non-Destructive Testing.
What Preparations are Required Before an MFL Tank Inspection Takes Place?
General questions and answers about tank preparation before MFL inspections.
Magnetic-Flux Leakage Technology
MFL technology has been used in the monitoring of underfloor and far-side corrosion for some time. Silverwing (UK) Ltd entered the field years ago, in 1991. As with all NDT methods, MFL has advantages and disadvantages, as well as pitfalls for the unwary. This paper attempts to explain the underlying principles of the method and highlights the advantages, disadvantages, and pitfalls.
Comparing MFL and Ultrasonic Testing
MFL and manual ultrasonic testing (UT) have been used extensively for the detection and sizing of corrosion pits in ferrous plates and pipes. Users and inspection service providers may have different perceptions and expectations of the sensitivity and accuracy of the methods. This paper discusses the underlying principles of the methods and their effects on the probability of detection and accuracy. It addresses the limitations on accuracy of UT due to pit shape and reflectivity, and also, for the first time, takes a quantitative look at the effect of pit volume on MFL results.
Corrosion Monitoring and Thickness Measurement: What are we Doing Wrong?
During the last three years, curiosity as the use of UT to detect corrosion and measure remaining wall thickness was rekindled. The method is extensively used to verify and quantify MFL results. Discrepancies between UT and MFL results have usually been put down to “another MFL false call”. However, having watched many UT inspections carried out, We believe that the boot is often on the other foot and that we place too much faith in UT for corrosion monitoring.